Hydrogenation Unit Equipment Science * Materials

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1. Working principle of centrifugal pumps: Before starting a centrifugal pump, the pump must first be filled with liquid. During operation, the liquid inside the pump impeller rotates along with the impeller, generating centrifugal force; under this force, the liquid is ejected from the impeller. The liquid passes through the pumping chamber and diffuser tube of the pump, and flows from the pump’s discharge port into the piping outside the pump. At the same time, as the liquid inside the impeller is thrown out, a low pressure is created at the suction port in the center of the impeller; as a result, the liquid in the suction tank, driven by the atmospheric pressure at the liquid surface, enters the impeller through the suction pipe and the pump’s suction chamber. In this way, as the impeller rotates, it continuously draws in liquid while simultaneously imparting energy to that liquid, pushing it into the pressure chamber and causing it to flow out of the pump through the diffuser tube. 2. Parameters of centrifugal pumps The parameters of centrifugal pumps are defined as follows: Rated flow rate: The amount of liquid that the pump can deliver per unit of time under optimal operating conditions; this is the value indicated on the pump’s nameplate, and it is denoted by Q. Rated head: The energy increase per unit mass of liquid as it passes through the pump at optimal efficiency, denoted by H, with units of meters. Efficiency: The ratio of the energy obtained by the liquid through the pump to the energy supplied to the pump by the drive mechanism, expressed as Ef or η. Power: The energy supplied to the pump by the drive motor is collectively referred to as shaft power. The power actually obtained by the fluid through the pump. Net positive suction head: The amount of energy per unit mass of liquid that must be present at the inlet of the pump’s impeller in order to prevent cavitation, beyond the vaporization pressure. It is expressed in NPSH, with the unit being meters; it is further divided into NPSHr (required net positive suction head, related to the pump) and NPSHa (related to the suction pipeline, unrelated to the pump). 3. The components of a single-stage centrifugal pump mainly include the impeller, shaft, suction chamber, pump body, pump cover, discharge chamber, shaft sleeve, wear ring, bearing coupling, etc. 4. What are the devices used to balance the axial force of centrifugal pumps? Balance holes, balance pipes, symmetric arrangement of impellers, balance disc 5; the cavitation principle and its hazards in centrifugal pumps. Principle: As liquid flows within the pump impeller, factors such as the shape of the blades and the sudden changes in flow direction determine the pressure distribution within the flow channels; local low-pressure areas exist on the non-working surfaces near the inlet of the blades. When the pressure of the liquid flow in the low-pressure area drops to the saturated vapor pressure corresponding to the temperature of the liquid, the liquid begins to vaporize and form bubbles ； The bubbles flow along with the liquid stream through the channel to areas of higher pressure, where they instantly collapse. At the moment of collapse, the liquid surrounding the bubble rushes into the cavity formed by its collapse, resulting in localized high temperatures and high-pressure water hammer effects. Harm: (1) Sudden decline in pump performance ； (2) Vibration and noise generated by the pump ； (3) Damage occurs in the flow-through part of the pump. 6. The proportional laws and specific speed of centrifugal pumps: For the same pump, Q1/Q2 = n1/n2, H1/H2 = (n1/n2), and N1/N2 = (n1/n2). In China, the specific speed is given by ns = 3.65 × n(Q)^(1/2) ÷ (H)^(3/4). 7. What is the cut-off law for centrifugal pumps? When the amount of impeller trimming is small, the trimming laws are as follows: (1) For pumps with medium and low specific speed: Q1/Q2 = D1/D2, H1/H2 = D1/D2, N1/N2 = D1/D2. (2) For pumps with high specific speed: Q1/Q2 = D1/D2, H1/H2 = (D1/D2)^2, N1/N2 = (D1/D2)^3. 8. Briefly describe the definition of mechanical seals. A device that prevents fluid leakage; it consists of at least one pair of end faces perpendicular to the rotation axis, which remain in contact and slide relative to each other under the action of fluid pressure and the elastic force (or magnetic force) from a compensation mechanism, with the assistance of auxiliary seals. 9. Basic structure of mechanical seals (1) Friction pair composed of the rotating ring and the stationary ring ； (2) Buffer and compensation mechanism primarily composed of elastic elements ； (3) Auxiliary sealing ring ； (4) A transmission mechanism that causes the driving ring to rotate with the shaft. 10. Several common flushing methods for mechanical seals: self-flushing, circulating flushing, and injection flushing. 11. Methods for detecting leaks in cascade sealing and double-end face sealing of tanks equipped with liquid seal tanks. Method for detecting leaks in cascade sealing: (1) If the liquid level in the liquid seal tank rises, the pressure in that tank increases, and there is no external leakage from the mechanical seal, then it indicates a leak in the first stage of the cascade sealing ； (2) External leakage of the cascade seal, leakage of the secondary seal in the cascade seal ； Double-end face seal leakage: (1) The liquid level in the liquid seal tank drops, and there is no external leakage from the mechanical seal; leakage occurs at the first stage of the double-end face seal ； (2) External leakage from the double mechanical seal; leakage from the secondary seal of the double mechanical seal ； 12. The purposes of mechanical seal flushing are sealing, cooling, flushing, and lubrication. 13. What are the “five fixed principles” for equipment lubrication? Fixed time, fixed place, fixed quality, fixed quantity, fixed person. 14. What is “three-stage filtering”? (1) From the oil receiving tank to the oil storage tank ； (2) From the station oil tank to the fuel filler cap ； (3) From the fuel can to the fueling point. 15. Key points for preventing freezing of pumps: (1) Keep the cooling water system unobstructed ； (2) Open the pump inlet and preheating valve; the flow rate should be set such that the medium does not freeze and the shaft does not rotate in the reverse direction ； (3) For equipment with insulation, its insulation layer must remain intact. 16. Pump turning standards: (1) Turn the pump once a day ； (2) Turn the shaft 180° each time ； (3) The turntable indicator is single white and red double. 17. What are the sealing leakage standards for pumps? (1) Packing seal: For heavy oil pumps, no more than 10 drops per minute; for light oil pumps, no more than 20 drops per minute. (2) Mechanical seal: For heavy oil pumps, no more than 5 drops per minute; for light oil pumps, no more than 10 drops per minute. 18. What are the common lubricating greases used for centrifugal pumps? Lubricants: N46 and N68 hydraulic oils, turbine oils. Greases: 2# and 3# extreme pressure composite lithium-based greases. 19. How to switch from a non-frequency-variable pump to a frequency-variable pump? (1) Change the outlet control valve of the non-frequency conversion pump to manual control; slowly close the outlet valve, and at the same time, while ensuring that the pump’s outlet flow rate remains constant, gradually increase the opening degree of the outlet control valve until it reaches 100% ； (2) Start the variable-frequency pump according to the centrifugal pump startup method, with the variable-frequency output at 100% ； (3) Slowly open the outlet valve of the variable-frequency pump; while ensuring that the flow rate at the pump’s outlet remains constant, slowly close the outlet valve of the non-variable-frequency pump until it is fully closed, and then shut down the non-variable-frequency pump ； (4) Slowly open the outlet valve of the variable-frequency pump; while ensuring that the flow rate at the pump’s outlet remains constant, gradually reduce the variable-frequency output until the outlet valve of the variable-frequency pump is fully open, and set the frequency output to automatic ； (5) Take proper measures to prevent freezing in non-voltage-variable pumps. 20. What are the requirements of “three abilities” and “four musts” for the proper use and maintenance of equipment? Three skills: knowing how to use it, knowing how to maintain it, and knowing how to troubleshoot faults. Four requirements to be met: the ditches should be bottomless, the shafts should be exposed to light, the equipment should show its true color, and the doors and window glass should be clean. 21. What are the temperature specifications for ordinary centrifugal pumps? The temperature of the motor bearings and the aircraft frame should not exceed 90°C; the temperature of the sliding bearings of the pump should not exceed 65°C, while the temperature of the rolling bearings should not exceed 70°C. 22. Inspection items before starting a centrifugal pump: (1) Wear the appropriate personal protective equipment, prepare the necessary tools, and clean the area around the pump ； (2) Check that the pumps, pressure gauges, coupling covers, coupling bolts, foundation bolts, valves, and pipeline flange gaskets are in good condition ； (3) Verify that the inlet and outlet processes as well as the fluid level meet the conditions for starting the pump ； (4) Open the inlet valve and slightly open the pump outlet vent valve; once oil is visible in the vent and no gas is present, close the vent valve ； (5) Check that the cooling water for the pump is functioning properly ； (6) Check that the quality of the lubricating oil is satisfactory and that the amount of lubricating oil is appropriate ； (7) Manually turn the crank two times; there is no unevenness in torque ； (8) Check that the hot oil pump is preheating properly; ensure all checks are completed before starting the pump. 23. Starting of the centrifugal pump (1) Perform the pre-startup inspections as specified ； (2) Close the preheating valve ； (3) Contact the operator on site to start the motor. Once the motor current drops from its maximum value to a stable level, check that the motor operates normally with no abnormal noises or vibrations, and that the pressure at the pump outlet is normal. Then slowly open the outlet valve, continuing to monitor the motor current and the pressure at the pump outlet to ensure they remain within normal ranges, until the outlet valve is fully open. Note that the pump should not operate for too long with the outlet valve closed ； (4) Check that the operating sound, vibration, bearing lubrication, seal leakage, and temperature rise of the pump are all normal. 24. Inspection items for centrifugal pumps: (1) Check the lubricant level and quality of the pump ； (2) Check for leaks in the mechanical seal ； (3) Check the motor current ； (4) Check the outlet pressure and seal oil pressure of the pump ； (5) Check the temperature and vibration of the bearing housing and motor; the equipment should make no abnormal noises ； (6) Check whether the pump’s cooling water is functioning properly ； (7) Check the preheating status of the standby pump ； (8) Carry out the turning operation for the standby pump as well as the pump that is not in use ； (9) Keep proper records of the pump’s turning and operation. 25. Operating procedures for switching centrifugal pumps: (1) Carry out the preparatory work before starting the standby pump, such as preheating the pump ； (2) Start the standby pump; once all components are operating normally, slowly open the outlet valve while simultaneously closing the outlet valve of the pump being switched out. During this switching process, efforts should be made to minimize fluctuations in parameters such as flow rate caused by the switch, until the outlet valve of the pump being switched out is fully closed. (3) Stop the switching pump and fully open the outlet valve of the standby pump ； (4) Ensure proper anti-freezing measures for the pump used for switching. 26. What are the reasons for vacuum formation in centrifugal pumps and how to address them? Reason: (1) Air entrainment in the pump inlet pipe ； (2) Motor reversal ； (3) Insufficient pump inlet pressure ； (4) Gas inside the pump ； (5) High temperature of the medium at the pump inlet ； (6) Inlet pipe blockage ； (7) Sealing oil with water ； (8) When starting the backup pump, the two pumps compete for flow rate ； (9) Damage to the impeller and inner grinding ring. Solution: (1) Check and eliminate air leakage ； (2) Contact the electrician for adjustment ； (3) Increase inlet pressure ； (4) Refill the pump ； (5) Coordinate with relevant departments for adjustments ； (6) ； Clean the inlet pipeline; (7) Enhance oil sealing and dehydration ； (8) First close the outlet valve of the operating pump, then gradually open the outlet valve of the standby pump ； (9) Contact the fitter for handling. 27. What does the model IS50－32－200B centrifugal pump mean? Single-stage, single-suction clean water centrifugal pump; the diameter of the pump inlet is 50 mm, while that of the outlet is 32 mm. The nominal diameter of the impeller is 200 mm, and the outer diameter of the impeller has been subjected to secondary cutting. 28. What are the causes of high pump vibration and how to address them? Reason: (1) Rotor imbalance ； (2) Bearing damage ； (3) The flow rate is too low ； (4) Low inlet pressure, (5) Bent coupling ； (6) Loose foundation or anchor bolts ； (7) Contact between the pump’s rotor and stator ； (8) Debris enters the pump. Solution: (1) Switch the pump and contact a blacksmith for repair ； (2) Increase throughput ； (3) Increase the inlet pressure. 29. Given that the pump’s flow rate is 5.68 m3/h, its head is 58 m, the density of the fluid is 990.3 Kg/m3, and its efficiency is 34%, calculate the power required for this pump using the formula N = QHρg/η. Where Q is the flow rate, H is the head, ρg is the density, η is the efficiency, and g = 9.8 N/Kg. N-axis = QHρg/η = 5.683583990.339.8 ÷ (0.3433600) = 2.61 KW. 30. Assuming that the suction inlet of a pump is located 10 meters below the suction tank, and the resistance in the suction pipeline is ∑h1 = 0.5 meters of oil column, the allowable cavitation head for this pump is △h = 4.4 meters of oil column. The temperature of the oil is 50°C, its saturated vapor pressure is Pt=120 KN/m (absolute pressure), and its density is 640 Kg/m3. Assuming that the suction tank is in communication with the atmosphere, is this pump installed correctly? H = P0/ρg – P1/ρg – △h – ∑h1 = (101.3 – 120) × 3103 / (64039.81) – 4.4 – 0.5 = -7.88 (m of oil column). Since H is negative, it indicates that the oil pump should be installed at least 7.88 meters below the suction tank; currently, the pump is located 10 meters below the suction tank, so its installation is correct. 31. It is known that a hydrogenation reaction feed pump uses three-phase alternating current, with an operating current of 60A, a voltage of 6000V, a power factor of cosφ equal to 0.95, and a rated power of 340KW. The actual power of this pump is 500KW. What is the efficiency of this pump? The power consumed by the motor is N = 31/2 * UI * cosφ = 31/2 * 6000 * 60 * 0.95 = 592.8 kW. The efficiency of the pump is η = N_efficient / N = 500 / 592.8 = 84.3%. 32. What are the causes of overheating in the bearings of a centrifugal pump and what are the solutions? (1) The motor and pump shaft are not aligned ； (2) Insufficient lubricating oil ； (3) The lubricating oil is emulsified, deteriorated, or contains impurities; it is not up to standard ； (4) Excessive lubricating oil ； (5) Cooling water interruption ； (6) The oil slinger jumps out of its fixed position ； (7) Bearing damage ； (8) Shaft bending, rotor imbalance. Solution: (1) Contact a blacksmith for repair ； (2) Add sufficient lubricant ； (3) Replace with qualified lubricating oil or add new grease ； (4) Adjust the lubricant level to an appropriate level ； (5) Adjust the cooling water to ensure smooth flow ； (6) Switch to the backup pump and contact a fitter for repairs. 33. What is the preheating method for the hydrogenation refined diesel pump? (1) Check the operation of the cooling water supply ； (2) Turn the crank 2–3 times and check that there is no unevenness ； (3) Slightly open the vent valve and the inlet valve; once all the air in the pump has been removed and oil is visible in the vent, close the vent valve and fully open the pump’s inlet valve. Slowly open the first preheating valve, being careful to prevent the operating pump from running dry or the preheating pump from reversing; adjust the opening degree of the preheating valve so that the temperature rise does not exceed 50°C per hour. 34. What are the causes of shaft misalignment in pumps, and what are the solutions? Reason: (1) Unstable traffic ； (2) The thrust bearing clearance is large. Treatment method: (1) Adjust to a stable flow rate ； (2) Contact a fitter for repairs. 35. What are the causes of motor overheating and how to deal with it? Reason: (1) Low voltage ； (2) Overload operation ； (3) The motor is damp. Solution: (1) Contact an electrician to handle it ； (2) Reduce the load. 36. What are the reasons for a centrifugal pump’s shaft seizure and how to deal with it? Reason: (1) Insufficient lubricating oil ； (2) The lubricating oil is deteriorated, emulsified, or contains impurities ； (3) Cooling water interruption ； (4) Bearing damage ； (5) Water leakage in the bearing housing. Handling method: Stop the pump immediately, switch to the backup pump, and contact a mechanic for handling. 37. What are the causes of motor overload and how to deal with it? Reason: (1) Excessive export traffic ； (2) Debris enters the pump ； (3) The motor and pump shafts are not aligned ； (4) Improper installation of the mechanical seal ； (5) Bearing damage ； The specific gravity and viscosity of the liquid are higher than designed. Solution: (1) Adjust the flow rate to an appropriate value ； (2) Contact the fitter to handle it ； (3) Check the specific gravity and viscosity of the liquid, and reduce the flow rate. 38. Preparations before starting the hydrogenation reaction feed pump: (1) Wear appropriate personal protective equipment and prepare the necessary tools ； (2) Check that the inlet and outlet flow of the reaction feed pump, as well as the liquid level in the raw material tank, meet the requirements for starting the pump ； (3) Open the inlet valve and slightly open the pump outlet vent valve; once oil is visible in the vent and no gas is present, close the vent valve ； (4) Check that the oil level in the lubricating oil station is appropriate, that the lubricating oil samples meet the required quality standards, that instruments such as the filter differential pressure, pressure switches, and pressure transmitters are functioning properly, that the oil cooler operates normally, and that it is in use ； (5) Manually start the auxiliary oil pump; adjust the lubricating oil pressure to above 0.25 MPa, and set the lubricating oil pressure for the high-pressure motor at 0.01–0.05 MPa. The return flow of lubricating oil in all branches is normal ； (6) Check that the pumps, pressure gauges, coupling covers, coupling bolts, anchor bolts, valves, and pipeline flange gaskets are in good condition ； (7) Manually turn the crank two times; there is no unevenness in torque ； (8) Establish the flow path from the reaction feed pump back to the raw material tank. Inform the internal operator to set the opening of the return-tank control valve to no less than 40% (to ensure that the minimum flow rate of the pump remains at least 80 tons/hour). The field operator should then verify on-site that the valve opening is normal ； (9) The external operation report indicates that the conditions for starting the pump on the internal operation side are met; the interlock on the internal operation side has been reset, and it can be seen from the DCS that the conditions for starting the reaction feed pump are also met. 39. Interlock settings for the hydrogenation reaction feed pump: If the lubricating oil pressure drops below 0.15 MPa, the auxiliary oil pump starts automatically ； 2) When the lubricating oil pressure drops below 0.1 MPa, the two-out-of-three interlock pressure switch for lubricating oil pressure activates, causing the hydrogenation reaction feed pump to stop automatically. 40. Startup process of the hydrogenation reaction feed pump: (1) The operator calls the dispatcher to instruct the main transformer to start the hydrogenation reaction feed pump ； (2) Once the conditions are met, notify the operator to start the high-pressure motor ； (3) After starting the high-pressure motor, ensure that the flow rate at the pump inlet, as controlled by the operator, is not less than 80 tons per hour; check that all temperature measurement points of the pump are within normal ranges ； (4) Outside the unit, check that the sounds of the motors and pumps are normal; observe that the lubricating oil pressure rises (if the pressure does not change, open the vent valve on the shaft pump and close it once oil appears). One person should stop the motor of the auxiliary oil pump and set the switch to the automatic position, while another person adjusts the lubricating oil pressure to ensure it is at least 0.2 MPa ； (5) The operator on site reports that everything is normal; the operator inside checks and shuts off the feed control valve, then informs the operator outside to restore the feed flow ； (6) Once the process is connected, the operator adjusts the opening degree of the feed control valve according to production requirements, slowly closes the return tank control valve, ensures that the flow rate at the pump inlet remains at least 80 tons per hour, and keeps the motor current within the rated value ； (7) Change the tank control valve to automatic mode, and set the pump inlet flow rate to not less than 80 tons per hour. (8) Internal checks show that the lubrication oil pressure and temperatures at all points are normal. 41. Switching process of the oil cooler for the hydrogenation reaction feed pump (1) Slightly open the vent valve of the oil circuit of the standby oil cooler ； (2) Slightly open the oil filling valve of the standby oil cooler; once oil is seen coming out of the drain valve in the oil circuit of the standby oil cooler, close both the drain valve and the oil filling valve ； (3) The operator on duty inside should pay close attention to changes in the lubricating oil pressure, while the operator on duty outside should slowly switch the lubricating oil circuit to the backup oil cooler ； (4) Switch the circulating water three-way ball valve to the standby oil cooler. 42. Switching process of the oil filter for the hydrogenation reaction feed pump: (1) Slightly open the vent valve of the oil circuit of the spare oil filter ； (2) Slightly open the filling valve for the spare oil filter; once oil is seen coming out of the drain valve in the oil circuit of the spare oil filter, close both the drain valve and the filling valve ； (3) The operator on duty inside should pay close attention to changes in the lubricating oil pressure, while the operator on duty outside should slowly switch the lubricating oil circuit to the backup oil filter. 43. Switching process of the hydrogenation reaction feed pump: (1) After the standby reaction feed pump is started according to the standard procedure and is operating normally, the operator on duty activates the pump operation sequence; meanwhile, the operator inside the control room slowly opens the return tank control valve of the pump in use. Depending on the amount of reaction feed required, the return tank control valve of the standby pump is slowly closed, so as to maintain a constant total reaction feed volume and ensure that the flow rates at the inlets of both the standby pump and the pump in use are not less than 80 tons per hour ； (2) When the opening degree of the return tank control valve for the pump in use is 40%, set the return tank control valve for the standby pump to automatic mode, and ensure that the pump inlet flow rate is not less than 80 tons per hour ； (3) Outside the plant, close the outlet valve of the pump in use, stop the main motor, verify that the auxiliary oil pump starts automatically as intended, and adjust the lubricating oil pressure to be no less than 0.2 MPa ； (4) Stop the auxiliary oil pump when the temperature at all points of the operating pump is not greater than 40°C. 44. Preparations before starting the high-pressure hydrogen injection pump: (1) Wear appropriate personal protective equipment and prepare the necessary tools ； (2) Check that the flow at the inlet and outlet of the high-pressure injection pump, as well as the liquid level in the inlet tank, meet the requirements for starting the pump ； (3) Open the inlet valve and slightly open the pump outlet vent valve; once oil is visible in the vent and no gas is present, close the vent valve ； (4) Check that the lubricating oil level is appropriate, that instruments such as pressure switches and pressure transmitters are functioning properly, and that the circulating water for the oil cooler is in operation ； (5) Manually start the auxiliary oil pump and check that the lubricating oil pressure is greater than 0.25 MPa ； (6) Check that the pumps, pressure gauges, coupling covers, coupling bolts, anchor bolts, valves, and pipeline flange gaskets are in good condition ； (7) Manually turn the crank two times; there is no unevenness in torque ； (8) Ensure the return-to-tank process for the high-pressure injection pump is operational; inform the operator inside the plant to set the opening degree of the return-regulation valve to at least 40% (to ensure a minimum flow rate of 3.5 tons per hour for the pump), and have the operator on site verify that the opening degree is correct ； (9) The external operation report indicates that the conditions for starting the pump on the internal side are met; the interlocks on the internal side have been reset, and it can be seen on the DCS that the conditions for starting the high-pressure water injection pump are also met. 45. Interlock functions of the high-pressure hydrogen injection pump: 1) When the lubricating oil pressure drops below 0.2 MPa, the auxiliary oil pump starts automatically ； 2) When the lubricating oil pressure drops below 0.15 MPa, the high-pressure injection pump shuts down via interlock. 46. Startup process of the hydrogenation high-pressure injection pump: (1) Once the conditions for starting the high-pressure injection pump are met, notify the operator to start the motor ； (2) After starting the motor, the operator shall ensure that the flow rate at the pump inlet is not less than 3.5 tons per hour ； (3) For outdoor operations, check that the sounds of the motors and pumps are normal; monitor the increase in lubricating oil pressure, then stop the auxiliary oil pump motor and set the switch to the automatic position. For indoor operations, ensure that the lubricating oil pressure is at least 0.25 MPa ； (4) The operator on site reports that everything is normal; the operator inside checks and shuts down the feed control valve, then informs the operator outside to restore the feed flow ； (5) Once the process is connected, the operator adjusts the opening degree of the outlet control valve according to production requirements, slowly closes the return tank control valve, ensures that the flow rate at the pump inlet is not less than 3.5 tons per hour, and keeps the motor current within the rated value ； (6) Change the tank control valve to automatic mode, and set the pump inlet flow rate to not less than 3.5 tons per hour. 47. Switching process of the high-pressure hydrogenation injection pump: (1) After the standby injection pump is started according to the normal procedure and is operating properly, the operator on duty activates the pump operation sequence; meanwhile, the operator inside the control room slowly opens the return tank control valve of the pump in use. Depending on the amount of water to be injected, the return tank control valve of the standby pump is slowly closed, so as to maintain a constant total amount of water injected, with the inlet flow rates of both the standby pump and the pump in use being no less than 3.5 tons per hour ； (2) When the opening degree of the return tank control valve for the pump in use is 40%, set the return tank control valve for the standby pump to automatic mode, and ensure that the pump inlet flow rate is not less than 3.5 tons per hour ； (3) Outside the plant, close the outlet valve of the pump in use, stop the main motor, and verify that the auxiliary oil pump starts automatically properly, with the lubricating oil pressure being no less than 0.2 MPa ； (4) Stop the auxiliary oil pump when the temperature of the pump gearbox in use is not greater than 40°C. 48. What are the precautions for using the pump for transporting sulfur-containing wastewater (magnetic pump)? (1) The temperature of the fluid should not exceed 80°C℃ ； (2) Open the return tank valve before starting the pump to prevent vaporization of the medium inside the pump, which could cause demagnetization of the drum ； (3) Pumping to vacuum can easily cause demagnetization of the drum ； (4) Open the return tank valve before stopping the pump to prevent vaporization of the medium inside the pump from causing demagnetization of the drum. (5) Closely monitor the condition of the inlet filter to prevent demagnetization of the drum due to pump cavitation ； (6) The solid particles in the medium should not be too large, to prevent blockage of the self-cleaning tubes, which could lead to demagnetization of the drum or wear of the isolation sleeve. 49. Preparations before starting the hydrogenation stabilization reflux pump (model: SHP-FG50-32-16/190): (1) Wear appropriate personal protective equipment and prepare the necessary tools ； (2) Check that the flow at the inlet and outlet of the stable reflux pump, as well as the liquid level in the inlet tank, meet the requirements for starting the pump ； (3) Open the inlet valve, slightly open the pump outlet flare valve, and close the vent valve after a short time ； (4) Check that the lubricating oil level is appropriate, and start using the cooling water for the gearbox lubricating oil ； (5) Check that the pumps, pressure gauges, coupling covers, coupling bolts, foundation bolts, valves, and pipeline flange gaskets are in good condition ； (6) Manually turn the crank two times; there is no unevenness in the torque ； (7) After slightly opening the pump outlet valve, inform the operator on site to prepare to start the pump. 50. The flow rate range of the hydrogenation stabilization reflux pump (model: SHP-FG50-32-16/190) is normally 11.2–19.2 m3/h, with the optimal flow rate being 12.8–17.6 m3/h. 51. How to determine whether the hydrogenation furnace tubes are coked? What are the causes of coking? What preventive measures exist? How should it be dealt with? Coking in the furnace tubes can be identified through the following aspects: (1) With the feed amount remaining constant, check whether the pressure difference between the inlet and outlet of the furnace tubes increases; if there is such a change, the cause should be analyzed promptly. (2) The furnace outlet temperature drops, and it is difficult to raise the temperature even by increasing the fuel supply. (3) Check whether the surface of the furnace tube is reddened; due to coking inside the tube, the thermal resistance increases, preventing heat from spreading, which leads to a local increase in temperature of the tube wall and thus reddening of it. The reasons for coking of the furnace tubes include: (1) poor combustion at the burner, with the flame hitting the furnace tubes directly, causing localized overheating of these tubes. (2) Dry burning is caused by too low oil flow rate inside the furnace tube, excessive residence time of the medium, or interruption in feed. (3) Malfunctioning instruments fail to reflect the temperature at various points in a timely and accurate manner, resulting in overheating of the pipe walls. Preventive measures: (1) Maintain uniform furnace temperature to prevent localized overheating of the furnace tubes; a combustion method with multiple burners, uniform flame heights, short flames, and a bright furnace interior should be employed. (2) During operation, strengthen the monitoring, analysis, and adjustment of parameters such as the feed rate to the furnace, pressure, and furnace temperature. (3) Prevent material deviation. 52. What are the causes and symptoms of flashback in hydrogenation heaters? How can it be prevented? Symptoms: Positive pressure is generated inside the furnace, causing the explosion vent to open; flames are ejected from the furnace, which can injure people or lead to an explosion inside the furnace, resulting in equipment damage. Reason: (1) A large amount of fuel is injected into the furnace, or the gas contains a high amount of oil. (2) The opening degree of the flue baffle is too small, reducing the furnace’s suction force and preventing the smoke from being expelled. (3) The furnace is operating beyond its capacity; flue gas cannot be discharged in time. (4) Backfire during startup is mainly caused by a faulty gas valve, which allows gas to enter the furnace, or by incomplete purging of the furnace before a second attempt at ignition, resulting in an explosion and backfire inside the furnace. Prevention: (1) It is strictly prohibited to allow large amounts of fuel oil and gas to enter the furnace before ignition; gas must not contain oil. (2) Determine the actual position of the flue baffle, and promptly replace or repair any valves that are not functioning properly; the flashback arrester should also be checked regularly, and replaced if it stops working. (3) It must not be operated under overload conditions; a negative pressure should always be maintained inside the furnace. (4) Strengthen equipment management; gas valves that are not airtight should be replaced or repaired promptly. The tempering device also needs to be checked regularly, and it should be replaced promptly if it malfunctions. (5) Before starting up and igniting, it is necessary to check whether the valves for gas and fuel are airtight; before each ignition, the combustible gases in the furnace must be purged with steam. 53. What precautions should be taken when using heat exchangers, especially high-pressure heat exchangers in hydrogenation units? Precautions to be observed during the operation of heat exchangers include: (1) After being newly installed or repaired, a heat exchanger must undergo a pressure test before it can be put into use. (2) When starting up the heat exchanger, the cold flow should be introduced first, followed by the hot flow; when shutting it down, the hot flow should be stopped first, followed by the cold flow. To prevent leaks or damage caused by uneven thermal expansion and contraction. (3) Fixed-tube-sheet heat exchangers are not allowed to be heated in one direction, and excessive temperature differences are also not permitted on either side of the tubes and shell in floating-type heat exchangers. (4) During startup, the exhaust valve should remain open to allow all air to be expelled, and it should be closed after startup is complete. (5) If hydrocarbons are used, the air in the heat exchanger must be purged with an inert gas before filling it with hydrocarbons to prevent explosions. (6) During shutdown purging, the condensate must be completely drained before introducing steam, and ventilation should be carried out slowly to prevent water hammer. When ventilating one side of the heat exchanger, it is necessary to open the drain valve on the other side to prevent damage due to excessive pressure. When shutting down the heat exchanger, the exhaust valve and the drain valve should be opened to avoid damage to the equipment caused by a vacuum forming as a result of cooling. (7) When using the air cooler, ensure that the flow is evenly distributed to guarantee effective cooling. (8) Regularly pay attention to monitoring to prevent leaks. High-pressure heat exchangers in hydrogenation units: There are mainly three structural types: 1. The first type is a flanged heat exchanger. 2. The second type is a heat exchanger with sealed cover plates by seal welding (this structure is also known as the “Ω”-shaped seal). 3. The third type is a heat exchanger with a threaded locking ring seal structure. However, the main bolts of flanged heat exchangers and seal-plate welding heat exchangers have to withstand both internal pressure and compressive forces; as a result, the bolts and nuts used in such heat exchangers, designed for the same pressure levels, are very large, and the flange surfaces are extremely thick. This not only makes them much larger in size than threaded locking rings but also makes it difficult to tighten them in case of a leak. The biggest feature of the heat exchanger with a threaded locking ring seal structure is that it transfers the enormous pressure exerted on the tube sheet side to the threaded locking rings; the compression bolts only need to provide the force required for sealing via the gaskets. In the event of a leak, it is sufficient to adjust the compression bolts in order to tighten the gaskets. 54. What are the main components of hydrogenation catalysts and the reasons for their deactivation? (1) The catalyst used in hydrogenation units is of the RN-10B grade, with the main active metal components being WO3 and NiO. The protective agent has the grade RG-1, with the main active metal components being MoO3 and NiO. The function of loading a protective agent at the top of the catalyst bed is to prevent dienes and monoenes in the feed oil from undergoing intense reactions upon contact with the catalyst due to its high activity, which could lead to a sharp rise in temperature and accelerate catalyst coking and deactivation. During the pressurization process at the start of hydrogenation, it should be ensured that the system pressure does not exceed 2.375 Mpa until the reactor wall temperature reaches 93 degrees. (2) The deactivation of catalysts can be summarized into two situations. One type is temporary inactivation, which can regain its activity through regeneration ； The other is permanent inactivation, after which its activity cannot be restored. The carbon deposition that forms during the operation of hydrogenation refining catalysts, also known as coking, is a major cause of temporary catalyst deactivation. During the hydrorefining process, due to the high reaction temperature, side reactions such as polymerization and condensation also occur. As operation time increases, the carbon deposits formed as a result of these side reactions gradually accumulate on the catalyst, covering its active sites and thereby causing a continuous decline in the catalyst’s activity. Generally speaking, the catalyst needs to be regenerated when the carbon deposit on it reaches 10–15%. The deposition of metal elements on the catalyst is the cause of its permanent deactivation. Common metals include nickel vanadium, arsenic, iron, copper, zinc, etc. The deposition of these metals blocks the micropores of the catalyst, resulting in a loss of its activity. 55. What are the common problems in hydrogenation units such as hydrogen bubbling, hydrogen embrittlement, and hydrogen corrosion? Hydrogen bubbling occurs because atomic hydrogen diffuses into the metal, where it forms molecular hydrogen in the pores within the metal. Since hydrogen molecules cannot diffuse, they accumulate in the micropores, creating high internal pressures that cause the metal to bubble and even rupture. Hydrogen embrittlement occurs when atomic hydrogen enters the metal, causing severe deformation of the metal’s crystal lattice, which in turn reduces the metal’s toughness and ductility, leading to its embrittlement. Hydrogen corrosion occurs when atomic hydrogen penetrates into the metal and reacts with its components or elements; for example, hydrogen infiltrates carbon steel and reacts with the carbon in the steel to form methane, which reduces the toughness of the steel. Meanwhile, the removal of carbon from the steel leads to a decrease in its strength. 56. What is the specific relationship between sulfide corrosion of equipment and temperature (t)? (1) When t<120°C, the sulfides do not decompose; there is no corrosion to the equipment in an anhydrous environment, but low-temperature sulfide corrosion occurs in the presence of water. (2) 120℃＜t＜240℃: The sulfides in the crude oil remain unbroken, causing no corrosion to the equipment. (3) At 240℃ < t < 340℃, sulfides begin to decompose, producing H2S, which causes corrosion of the equipment; moreover, the corrosion intensifies as the temperature rises. (4) For 340℃＜t＜400℃, H2S begins to decompose into H2 and S; the reaction equations for corrosion of the equipment at this stage are: H2S → H2 + S, Fe + S → FeS, R–SH (thiol) + Fe → FeS + unsaturated hydrocarbons. (5) When t > 480°C, hydrogen sulfide is nearly completely decomposed, and corrosion decreases. (6) When t＞500℃, it is not within the corrosion range of sulfides; rather, it is high-temperature oxidative corrosion. 57. The filtration precision of the backwash filter SR301 is 25 μm. Gum and mechanical impurities in the hydrogenation feed are the main reasons for frequent backwashing. 58. How to determine when hydrogen pre-sulfidation is complete? (1) The H2S concentration is ≤10,000 ppm before the end of the constant-temperature phase at 360°C. (2) High scores fail to produce water twice in a row. (3) The highest temperature of the bed layer has shifted to the bottom layer of the reactor. (4) The calculated amount of sulfur injection has been fully injected. 59. What are the hazards of water in hydrogenation feedstock? Whether it is hydrorefining or hydrocracking, hydrogenation processes have strict requirements regarding the moisture content of the feed oil. The moisture present in the feed oil has a significant impact on both the catalyst and the system pressure drop, as reflected in the following aspects: (1) The moisture in the feed oil affects the strength of the catalyst carrier; when the moisture content is too high, it can lead to a decrease in the catalyst’s surface area, as well as damage or pulverization of the catalyst carrier, resulting in an increase in system pressure drop and loss of active components. (2) When the moisture content in the crude oil is low, it has little effect on the active metal components of the catalyst; however, when the moisture content is high, metal agglomeration occurs among these active metal components, resulting in a decrease or even loss of their catalytic activity. (3) The moisture in the feed oil also affects the system pressure drop; when the moisture content is high, the system pressure drop increases, which raises the energy consumption of the plant. In severe cases, this can cause the cycle hydrogen compressor to become overloaded and force it to shut down. (4) The water content in the crude oil can also cause low-temperature corrosion due to petroleum naphthenic acids and active sulfides, leading to corrosion and thinning of equipment and pipelines. Moreover, when these corrosion products enter the hydrogenation reactor, they increase the pressure drop in the reactor, affecting the long-term operation of the facility. For general hydrogenation feedstocks, the moisture content is required to be no more than 300 ppm. 60. The hydrogenation water injection points are the A-301 inlet, in front of E303/A, and the R-301 outlet. The purpose of water injection is to prevent ammonium salts from forming during the cooling process and thus blocking pipes and equipment. 61. In the event of an accident in a hydrogenation unit, which areas are prone to high-pressure air leaking into low-pressure areas? (1) The oil phase between the high-grade and low-grade streams, as well as the acidic water from both grades, is sent to the acidic water tank; the level of the high-grade liquid must be maintained at a certain height to prevent the gas phase from entering the low-grade stream ； During shutdown, do not allow the high-level cut-off to go empty to prevent gas phase from entering the acidic water tank. During startup, the cut-off control valve manual valve can be opened only after establishing the high-level cut-off. (2) For the cross-line between the separator tank at the recycle hydrogen inlet and the separator tank at the fresh hydrogen compressor inlet, care should be taken during startup, shutdown, and operation to prevent sudden failures of the fresh hydrogen compressor, which could lead to high pressure flowing into the low-pressure system. During normal operation, all the cross-line valves at the top of the separator tank at the recycle hydrogen inlet should be closed, while the inlet valve of the separator tank at the fresh hydrogen compressor inlet should be kept fully open. (3) When the reaction feed pump, fresh hydrogen compressor, and feed water pump stop operating due to a fault, their outlet valves should be closed promptly to prevent high-pressure hydrogen from flowing back into the low-pressure system due to a faulty check valve. Additionally, care should be taken to close the two-way and manual valves of the fresh hydrogen compressor in a timely manner. (4) From the low-pressure tank to the distillation system, to prevent gas phase from entering the distillation system due to an excessively low level of liquid in the low-pressure tank. (5) Corrosion inhibitor injection lines at the top of the fractionation tower and stabilizer tower to prevent the backflow of toxic substances. 62. Treatment of \"three wastes\" (1) Waste gases: The hydrogen sulfide-containing gases generated during the production process are mainly found in areas such as high and low pressure separators and the reflux tank at the top of the stripping tower. All such sulfur-containing gases are sent to the gas desulfurization unit within the coking plant, where they are absorbed using N-methyldiethanolamine solution to remove H2S. The desulfurized dry gas is then used as a raw material for hydrogen production in the hydrogen generation unit, while the acidic gases produced in the desulfurization process are sent to the sulfur recovery unit for sulfur recovery. The hydrocarbon-containing gases discharged from the safety valves and venting systems within the unit are all sent to a sealed flare system. The gas seal gas from the crude oil buffer tank and the water injection tank is also discharged into a sealed flare system. The flue gases emitted by the heating furnace are discharged at high heights through chimneys, ensuring that the emitted gases meet the relevant environmental protection standards. (2) Wastewater and liquid waste: Acidic water: Sulfur- and ammonia-containing wastewater discharged from the high-pressure separator, low-pressure separator, and the reflux tank at the top of the stripping tower is pumped to an acidic water treatment facility for centralized treatment. Oily wastewater: The oily wastewater from the crude oil buffer tanks, as well as groundwater and gutter water, are all sent to the wastewater treatment plant. Rainwater drainage is separated into clean and polluted streams, reducing the amount of oily wastewater discharged from the facilities and thereby lowering the load on wastewater treatment plants. (3) Waste residues: No waste residues are generated during the normal operation of the facility. The deactivated catalysts and toxic chemicals are removed from the reactor, then disposed of by deep burial in barrels or sent to catalyst recycling plants for recovery. 63. What are the reasons for a large temperature difference between the cylinders of a turbine? What are the consequences? The reasons for a large temperature difference between the upper and lower cylinders of a turbine are as follows: (1) Poor insulation of the unit, such as inappropriate materials or the detachment of the insulation layer on the lower cylinder. (2) Abnormal startup conditions, such as steam parameters entering the turbine not meeting requirements, too short a startup time, incorrect warm-up speed, poor drainage from the cylinders, and insufficient warm-up time. (3) The shutdown method is abnormal, such as the shaft seal stopping steam supply prematurely. (4) During normal operation, air convection on both sides of the machine room causes one side of the cylinder to cool down. The hazards of large temperature differences are as follows: (1) Cylinder deformation and misalignment of the center. (2) Bolt fracture. (3) Friction between the moving and stationary parts. (4) Cause vibration in the unit. 64. Why must a condensing steam turbine maintain a certain level of vacuum when shut down? What are the causes of a decrease in the vacuum of a turbine condenser? The reason for maintaining a certain level of vacuum is as follows: (1) When steam supply to the turbine is just stopped, the rotor’s speed is still very high; by maintaining vacuum, the amount of residual steam in the cylinder can be reduced, thereby preventing the friction caused by air ingress from reheating the components inside the cylinder and affecting their service life. (2) It can keep the inside of the cylinder dry, as water accumulated within the cylinder can evaporate fully at lower pressures. (3) Maintaining a certain vacuum level and reducing the turbine speed allows the coasting time during each shutdown to be compared under the same conditions. The reasons for a drop in the vacuum of the turbine condenser include (1) an interruption in the circulating water or insufficient water volume. (2) The condenser is full of water. (3) The extraction pump is not operating properly. (4) Scaling on the cooling surface of the condenser. (5) The air leakage rate of the vacuum system increases. 65. What is surge in a centrifugal compressor? What are the hazards of \"surge\"? (1) When a centrifugal compressor operates at low flow rates, vortices are generated within the flow channels of the impeller and diffuser. The formation and disappearance of these vortices cause intermittent blockages and openings in the liquid flow channels, leading to periodic vibrations in the airflow and blades. This results in severe periodic vibrations and roaring noises within the compressor; this phenomenon is known as \"surge\" in centrifugal compressors. (2) Surge phenomenon is very harmful to compressors. Intense pulsations and periodic oscillations of the airflow cause severe vibration of the blades, which increases the stress on the impeller and raises noise levels. This leads to intense vibrations throughout the entire unit, and it may damage the bearings and seals, resulting in shutdown or serious accidents. 66. How to determine the \"surge\" in a centrifugal compressor? What actions should be taken when surge is detected? Determining compressor \"surge\" (1) Listen to the noise of the airflow in the compressor outlet pipe. Under stable operating conditions, centrifugal compressors produce low-level, continuous noise. However, as they approach the surge condition, periodic oscillations of the airflow within the entire system cause the noise generated by the airflow in the outlet pipe to vary in intensity, showing periodic fluctuations. Once surge conditions are reached, the noise level increases sharply, and even explosive noises may occur. (2) Observe the changes in the compressor outlet pressure and inlet flow rate. When a centrifugal compressor operates under stable conditions, the changes in its outlet pressure and inlet flow rate are minimal, with very small variations in the measured data. When approaching or entering the surge condition, both of them experience significant changes, with periodic large-amplitude fluctuations; sometimes it is even possible to observe gas being pushed back out from the compressor inlet. (3) Observe the vibration of the machine body and bearings. Measures to be taken: When approaching or entering the surge condition, both the machine body and the bearings experience severe vibrations, with amplitudes that are **higher** than during normal operation. (1) A backflow device is installed between the exhaust pipe and the intake pipe of the compressor; when the air supply volume of this device drops to a specified value, the backflow amount is appropriately increased in a timely manner, causing some of the gas from the exhaust pipe to return to the compressor inlet – this phenomenon is known as backflow. This allows the centrifugal compressor to maintain its normal operating flow rate, keeping it within a stable operating range and thus preventing surging. (2) When the air intake volume is low, in order to prevent surge and keep the compressor operating normally, a portion of the gas from the compressor outlet can be directed to a flare to reduce the back pressure, or the counter-rotational momentum can be increased. (3) Pressurization in the compressor outlet pipeline is prohibited; when instability occurs in the hydrogen-rich gas recovery unit, causing an increase in pressure within the pipeline, pressure should be reduced promptly to prevent surging. (4) If the unit still experiences surge even after taking the above measures, it can be shut down immediately for inspection and repair. 67. What is the basic principle of a dry gas seal? A dry gas seal is essentially a type of mechanical seal that consists of an O-ring as the primary sealing element, located within a stainless steel ring. This primary ring is pressed against a tungsten carbide alloy ring (the moving ring) by spring force; the moving ring is fixed to and seals the compressor shaft. Sealing is achieved through the only path for fluid to pass between the radial mating surfaces of the rotating ring and the stationary ring; these sealing surfaces are polished to a high degree of smoothness. The rotating tungsten carbide ring has a series of spiral grooves formed in its rotating plane, and it is at these points that annular sealing walls are created. These sealing walls exert resistance against the flow of air, thereby increasing pressure. This increased pressure keeps the surface of the carbon ring separated from the tungsten carbide ring, preventing contact (with a gap size of approximately 0.001–0.002 inches). The gap between the sealing surfaces is established when the closing force equals the force generated by the flow within the film. 68. Startup procedures for reciprocating hydrogen compressors (1) Lubrication system ① Check that the local indicating instruments such as pressure gauges and thermometers are complete and in good condition. ②Check the condition of the lubricating oil in the engine’s oil reservoir; if the quality of the oil is unsatisfactory, it should be replaced with fresh oil. The oil level should be maintained at 1/2 to 2/3 of the mark on the oil sight gauge. ③Activate the lubricant flow and place the filter switch handle in the correct position. ④Open the inlet and outlet valves of the auxiliary pump, open the outlet valve of the main shaft pump, start the auxiliary lubricating oil pump. Once the oil pump is running steadily, check whether the oil temperature and pressure are within the specified ranges. The oil cooler circulating water is put into use as appropriate. ⑤Fill the spare filter and the spare oil cooler with oil slowly. (2) Airtightness check and nitrogen purging before driving: *A nitrogen seal should be applied before ensuring airtightness; the injection pressure for this nitrogen seal is generally 0.1~0.2 MPa. ①Check whether the compressor inlet valve, outlet valve, and vent valve are closed; ensure that any valves not properly closed are closed. At the same time, put the safety valve into service. ②Open the pressure gauge valves for each line. ③Open all the vent valves and bottom drain valves of the unit, and put the oil collector into operation. ④Slightly open the nitrogen valve at the inlet, slowly introduce nitrogen into the compressor until the airtight pressure is reached, and then close it. ⑤Check the compressor, auxiliary equipment, and pipelines for leaks. ⑥Open the vent valve on the outlet pipeline to release the gas inside the machine, and then close it. ⑦After passing the airtightness test, replace the air with nitrogen following the airtight nitrogen filling procedure. ⑧During nitrogen purging, open each drain valve to drain the condensate and then close them. (3) Hydrogen displacement: ① After nitrogen displacement is successful, displace it with hydrogen once (it is strictly prohibited to directly displace air with hydrogen). ②Slightly open the inlet valve to introduce hydrogen into the system, and close the inlet valve once its pressure equals the system pressure. ③Open the outlet pipeline vent valve to release the gas. ④Finally, adjust the valve to its pre-start condition: the inlet and outlet valves are closed, while the outlet vent valve is open. (4) Cooling system (including systems with on-site cooling water stations): ① Check that the local indicating instruments of the cooling system, such as pressure gauges and thermometers, are complete and in good condition. ②Ensure the proper operation of the compressor cooling water system; check the level in the soft water tank; fill the water pumps with oil and rotate their shafts. Start the water pumps and maintain an outlet pressure of around 0.35 MPa. Drain any air from the return lines of the compressor to ensure smooth flow of water back to all cooling areas. ③Supply cooling water to the cooler, and be careful to vent to eliminate air blockages. ④Introduce the oil cooler gradually depending on the lubricating oil temperature. (5) Driving: ① Start the oil injector about 10 minutes in advance to supply oil to all lubrication points, ensuring that they are properly lubricated. ②Notify the electricians, mechanics, and technicians to go to the site; the electrician will supply power. ③Turn the crank 2–3 times; there should be no abnormal resistance or noises, after which the crank operator can be removed. Be careful to turn the shaft only when there is no pressure inside the machine, otherwise accidents can easily occur. ④Turn the load adjustment knob to the “0” position to fully open all the intake valves. The outlet valve or outlet vent valve is opened to prevent pressure buildup. ⑤The comprehensive inspection and preparation work are complete; the unit meets the startup conditions, and the dispatching department and relevant teams are notified. ⑥Press the on-site start button; immediately after startup, conduct a thorough inspection of the unit, checking the oil pressure, oil temperature, current, and cooling conditions, as well as whether the temperatures of various components and the operating sounds are normal. If any abnormalities are detected, the unit should be stopped immediately to resolve the issue. When the pressure in the lubricating oil main pipe is ≥ 0.6 MPa, manually stop the auxiliary oil pump and set it to the “automatic” position. ⑦After confirming normal operation, proceed with loading according to the following procedure: a. Open the compressor outlet valve, close the vent valve, and open the compressor inlet valve. b. Turn the load handle from “0” to “50%”, wait for a moment, and then turn it to “100%”. c. After the unit is connected to the system, a comprehensive inspection should be carried out promptly, with proper records kept. 69. Inspection and maintenance of reciprocating units during operation: (1) Pay attention to the quality and level of the lubricating oil in the unit; the lubricating oil should be tested once a month, and its level should be within the range of 1/2 to 2/3 of the mark on the gauge. The lubricating oil pressure, temperature, and filter differential pressure are adjusted and switched in a timely manner to ensure that the auxiliary pump remains in auto-start mode. (2) Regularly check the pressure and temperature values indicated by the unit’s instruments; these values should meet the various technical specifications of the compressor. (3) Regularly pay attention to the sounds emitted by the unit during operation, and check whether there is any overheating of the suction valve cover. (4) Make sure that the liquid level in each separation tank does not rise too high; drain condensate regularly, and avoid having oil remaining inside the tank. (5) The current, voltage, and temperature values of the motor shall comply with the relevant specifications stated in the motor’s manual. (6) Safety valves should be regularly calibrated as specified. (7) In winter, if the compressor is shut down for an extended period, the water in the compressor system and the cooling water station system should be drained completely to prevent freezing. (8) Regularly check the water level in the water tank at the water station and the water temperature before it enters the unit. (9) Regularly check for any blockages in the packing cooling water filter. When the pressure difference exceeds 0.1 MPa, it should be switched promptly, and the standby filter should be cleaned. (10) Regularly check the operation of the water station, pay attention to the temperature of the pump bearings, and prevent the pump from operating under vacuum conditions. When the oil coolers, inter-stage coolers, and water station coolers are in standby mode, reduce their flow rate appropriately; in winter, take precautions against freezing by ensuring that the flow rate is not too high. 70. Normal shutdown of a reciprocating compressor: ① Upon receiving the shutdown command, first turn the load control knob to the “50%” and then to the “0” position, in order to open the suction valve. ②Press the shutdown button. ③After the compressor flywheel stops rotating, close the outlet valve, then close the inlet valve. Meanwhile, open the compressor outlet vent valve to relieve pressure and then close it. ④With the main oil pump shut down, special attention must be paid to whether the auxiliary oil pump starts automatically. If it fails to start on its own, it should be started promptly. Once the temperature of the bearing shells drops below 35°C, the auxiliary oil pump should be stopped and the cooling water turned off. In winter, the cooling water should either be drained completely or kept flowing to prevent damage to the equipment and pipelines due to freezing. ⑤After the compressor is shut down, if maintenance is required, nitrogen replacement should be carried out promptly and the nitrogen seal should be discontinued. 71. Switching operations for reciprocating compressors: ① Start the standby unit following the normal startup procedures. ②Once the standby unit is operating properly, reduce the load on the operating unit to “50%”, while increasing the load on the standby unit to “50%”. Once the operation of both units is stable, reduce the load on the operating unit from “50%” to “0%”, and increase the load on the standby unit from “50%” to “100%”. Then press the shutdown button for the operating unit, close its outlet valve and inlet valve, open the relief valve to release pressure, and then close it again. The switching process should try to avoid significant fluctuations in traffic. ③After shutting down, proceed with the normal shutdown procedures. 72. Emergency shutdown procedure for reciprocating compressors: (1) Conditions for emergency shutdown: ① The main motor catches fire suddenly. ②The transmission mechanism emitted a distinct metallic clanging sound. ③There is a metallic banging sound coming from the compressor cylinder. ④Severe gas leak. ⑤The feed gas contains a large amount of liquid. ⑥The bearing is smoking. ⑦Emergency situations such as a rupture in the lubricating oil pipeline that makes it impossible to gain control. (2) Emergency shutdown procedure: ① When the above conditions occur, the operator should immediately press the shutdown button, close the inlet and outlet valves promptly, open the vent valve to quickly release the pressure inside the machine, and adjust the load lever to the “0” position. ②If the machine cannot be stopped by pressing the stop button, contact an electrician immediately. Move the load control lever to the “0” position, open the outlet vent valve to quickly release the pressure inside the machine, and then close the outlet valve and the inlet valve in sequence. ③Others are handled as normal shutdowns. 73. What are the shutdown interlocks for a circulating hydrogen compressor equipped with a dry gas seal system? (1) Excessive vibration of the compressor shaft. (2) Excessive vibration of the turbine shaft. (3) Excessive displacement of the compressor shaft. (4) Excessive displacement of the turbine shaft. (5) Low pressure in the lubricating oil main line. (6) Low pressure of the emergency shutdown oil for the turbine. (7) High pressure of the primary exhaust air for the seal gas. (8) EBI ≥ 30% (from 505) and n ≤ n0 (from 505). (9) Emergency shutdown (from the auxiliary control panel) or emergency shutdown (from the turbine local panel). (10) Tripping of 505 or 203. 74. Startup procedure for the circulating hydrogen compressor. 74.1. Preparations before startup: (1) Clean the area and remove all items that are not related to startup. (2) Prepare the tools needed for driving, such as wrenches and tools for ensuring airtightness during turning. (3) Check the freezing points of each row and ensure that all pipelines are unobstructed. (4) Coordinate the supply of water, electricity, steam, air, etc. to the equipment to ensure that all specifications are met. (5) Cooperate with instrument inspections to adjust the automatic protection, automatic control, alarm systems, as well as various measuring and control instruments of the unit, to ensure their flexibility and effectiveness. (6) After cleaning the lubricating oil tank and the like, use an oil filter to add qualified N46# rust-proof turbine oil to the tank, ensuring that the oil level remains above 70%, and open the dehydration valve at the bottom of the tank to remove water. (7) Open each drain valve and vent valve before opening the turbine emergency shutdown valve to warm the pipes. Note that the pipe warming rate should be ≥ 200°C per hour; warming should be carried out gradually along the process. When approaching the quick-close valve, attention should be paid to any steam leakage into the turbine casing, and the turbine should be rotated accordingly based on the actual situation. (8) Draw circulating cooling water from the condenser and add desalinated water to 80% of the hot well, then start the condensate pump to initiate circulation. (9) Replace the air in all water cooler inlets, open the upper drain valve; once water is seen, close the drain valve and the inlet valve. (10) Check that the fire-fighting equipment is flexible and functional. 74.2 Preparation and startup of the lubricating oil system. Note: Before starting the lubricating oil system, the isolation gas system must be activated first to prevent lubricating oil from entering the dry gas seal chamber and damaging the dry gas seal. (1) Preparation work ① Thoroughly check whether there is any looseness at the system connections; if so, tighten them immediately. ②Improve the oil circuit flow. ③Install local display instruments as well as indoor display and control instruments. ④Guide the circulating water of the oil cooler to the front of the cooler. ⑤Activate the fuel tank heater to heat the fuel temperature to around 45°C. ⑥After the isolation gas system is activated, the main oil pump is started, and the lubricating oil system begins to circulate. ⑦Open the filling valve for the high-level fuel tank; once filling is complete, close the valve to prevent overflow. ⑧Charge the accumulator with nitrogen as appropriate, up to around 0.5 MPa. ⑨The sequence of commissioning of the isolation gas system, the lubricating oil system, and the sealing gas system is as follows: the isolation gas system is commissioned first, followed by the lubricating oil system, and finally the sealing gas system. (2) Oil system commissioning ① Adjust the lubricating oil pressure to above 0.25 MPa. ②Adjust the control oil pressure using the control oil pressure regulator to keep it at 0.85 MPa. ③ Put the cooler into operation, and use a self-regulating temperature control valve to maintain the temperature after cooling at 45±3°C. ④ Conduct tests on switching between the oil cooler and the oil filter, and observe the fluctuations in oil pressure. 74.3, Static tests: ① Test items: Include all alarms and interlocks related to the compressor. ② Preparations before testing: The quick-shut oil solenoid valve shall be energized. Start the lubricating oil pump to establish a normal oil circulation. Ensure that the isolation gas system is put into operation in advance. Check to confirm that the inlet and outlet valves of the compressor and turbine are closed. ③Test procedure A: The lubricating oil pumps are tested for self-starting capability against each other. This experiment is best carried out in conjunction with the oil pressure low interlock shutdown. B. Self-starting test of the condensate pumps: Switch to the condensate discharge circuit and set the condenser level proportional control to automatic mode. Make up demineralized water to the condenser to 325 mm; LS4976 gives an high alarm and the standby condensate pump starts automatically. Once the liquid level returns to normal, stop the main condensate pump. Make up brine to the condenser to 325 mm once again; LS4976 gives an high alarm and the main condensate pump starts automatically. Once the liquid level returns to normal, stop the standby condensate pump and restore the normal circulation process of the condensate. C. Interlock shutdown test: The mechanical, electrical, and instrumentation personnel should be notified to be present before conducting the test. Meet each of the compressor startup conditions one by one until startup is permitted. Interlocks such as shaft displacement and shaft vibration can only generate simulated signals with the assistance of instrumentation personnel, in order to check the closing status of the turbine emergency shutdown valve. During the simulation, each time an interlock shutdown occurs, the quick shut-off valve must be opened following the normal procedures before proceeding with the next simulation test. During the test, pay attention to recording the time it takes for all the lubricating oil in the high-level oil tank to flow into the bearings once the main engine stops; this time should be no less than 5 minutes. 74.4 Preparation and startup of the dry gas seal system: (1) Preparation work ① Check whether the fastening components of the isolation gas (seal gas) system are loose; if so, tighten them. ②The pressure reduction valve for the isolation gas (sealing gas) features accurate and flexible adjustment. ③Differential pressure control valve for isolation gas (sealing gas), differential pressure gauge for isolation gas (sealing gas) filter, sealing gas discharge flow meter, sealing gas discharge pressure switch, local pressure gauge in operation. (2) Commissioning process: ① Open the first valve at the N2 supply point for isolation gas and the drain valve to remove any liquid from the gas; close them once no liquid is present. ②For the isolation gas system, open each valve in reverse order of the process, adjust the differential pressure of the isolation gas, and observe its discharge situation. ③After the lubricating oil system is operating properly, the seal gas system opens the various valves in reverse order according to the specified procedure (hydrogen from the outlet of the new hydrogen compressor is used before startup, while the circulating hydrogen generated by the unit itself is used once the unit is operating normally). 74.5 Preparation and startup of the condensing system: ① Thoroughly check all connections in the system for any looseness; if there is any looseness, tighten them immediately. ② Open the demineralized water supply valve to inject 80% demineralized water into the hot well of the condenser. ③Refuel the condensate pump and ensure smooth cranking; once no issues are detected, start the condensate pump to establish the circulation process. 74.6, Compressor airtightness and purging ① Compressor airtightness: Note: Before checking for airtightness, the gas isolation, lubricating oil, and sealing gas systems are operating properly. Close all the inlet and outlet valves of the compressor, the anti-surge valve, and the vent valve. Open the manual valves of the pressure gauges on each pipeline. Slightly open the N2 valve on the inlet pipeline, and slowly fill the compressor with N2; once a gas-tight pressure of 2.5 MPa is reached, close the N2 valve. Use soapy water to check the compressor body, auxiliary equipment, and pipelines for leaks. If any leakage is detected, it must be dealt with promptly. Open the vent valve on the outlet pipeline to release the gas inside the machine, and then close the vent valve. ②N2 displacement: Open the N2 valve at the compressor inlet, and slowly fill the compressor with nitrogen until the pressure reaches 0.5 MPa, after which close the valve. Permute twice in a row. ③H2 displacement: Slightly open the compressor inlet valve, slowly introduce hydrogen into the compressor, and close it when the pressure reaches 0.5 MPa. Open the drain valve on the compressor housing and check that there is no liquid. Open the compressor outlet vent valve to release the hydrogen gas inside the machine. 74.7、Create a vacuum ①Establish and adjust the water seal of the condenser’s atmospheric safety valve to ensure it is in good condition. ②Before and after starting the turbine, supply steam to the steam seals, adjust the steam pressure, and observe the steam emerging from the steam seal tubes at a height of about one foot. ③Activate the start-up extraction steam turbine: First open the steam inlet valve, then slowly open the air inlet valve. Gradually adjust the steam pressure and monitor the vacuum level. ④After the warm-up is complete, proceed with the following steps: a. Activate the main steam extractors: first turn on the secondary main steam extractor, then the primary main steam extractor. Open the steam valve first, then the air valve. b. Open the primary drain valve of the main steam extractor, and open and adjust the secondary drain valve. c. Stop starting the extraction steam turbine: Close the air valve first, then the steam valve. Ensure that the main extraction steam turbine maintains a vacuum level of -0.09 MPa. 74.8, Host preparation: Adjust the valves to their positions before startup – the inlet valve and the anti-surge control valve should be open, while the outlet valve should be closed. The vent valve and the drain valve should also be closed. Rotate the manual adjustment knob for the start-up oil counterclockwise to gradually build up the pressure of the start-up oil in front of the quick-shut valve to 0.85 MPa (G). Rotate the manual adjustment knob for the quick-shut oil counterclockwise to gradually build up a quick-shut oil pressure of 0.85 MPa (G) behind the piston disc of the quick-shut valve; then rotate the oil supply knob clockwise until the oil pressure returns to zero, causing the quick-shut valve to open, after which a secondary oil pressure of 0.15 MPa (G) is automatically established. The DCS “operational conditions” are met, allowing the compressor to be started. 74.9: Increase the speed of the host – press RUN on 505, select Idle; the compressor’s speed will rise to 2100 rpm, and it will run at low temperature for 30 minutes ； Press F3 again; when the compressor speed reaches 9541 rpm, activate remote control for 505. Steps for remote control: (1) Align the DCS with the 505 speed; press Speed on the 505 and ensure that the Speed setpoint is as close as possible to the Actual Speed. (2) 505, press F4, select Remote. (3) Display “505 remote control activated” on the DCS. Thereafter, the compressor speed control was transferred to the DCS, with adjustment via FIC542 ； The compressor speed is adjusted to meet the process requirements. (4) Close the counterflow valve to adjust the compressor outlet pressure; when the outlet pressure is slightly higher than the system backpressure, slowly open the outlet valve to integrate the compressor into the system ； The anti-surge valve is set to automatic mode. 75. Normal shutdown of the compressor: (1) Switch the seal gas. (2) On the DCS, use FIC542 to gradually reduce the compressor’s speed; as appropriate, open the anti-surge valve and close the outlet valve to isolate the compressor from the system. (3) When the speed drops to 9541 rpm, press F4 on 505 to select Local, then continue to reduce the speed and smoothly pass through the critical speeds of the compressor and turbine. (4) Perform a manual emergency stop and record the coasting time. (5) Rotate the handwheel of the quick-shut assembly to the lowest position; close the steam inlet valve (to prevent steam from leaking into the unit), and open the main steam and turbine casing drain valves to drain all the liquid inside. (6) After shutting down the machine, immediately close the compressor inlet valve and the anti-surge valve; open the vent valve to relieve pressure and then close it. (7) Perform nitrogen purging inside the compressor housing; after completion, release the nitrogen from the housing and maintain a slight positive pressure (less than 0.15 MPa), then close all valves to isolate the system. (8) Shut down the exhaust pump (first stop the primary stage, then the secondary stage); when the vacuum level drops to zero, cease feeding steam to the turbine seal. (9) Stop the condensate pump and the cooling water for the condenser. (10) Shut down the compressor seal air system. (11) After shutdown, the lubricating oil system must remain in operation; cranking should continue for half an hour, with 1800 degrees of rotation per 5 minutes. After one hour, cranking should be carried out every 30 minutes at 1800 degrees of rotation, until the bearing temperature drops to normal levels. At that point, cranking should be stopped as well as the lubricating oil pump (the cooling water of the oil cooler should be stopped first before shutting down the pump). (12) After the lubricating oil system is shut down, disconnect the isolation gas system. 76. Hot start of the circulating hydrogen compressor: The compressor can usually be started hot when it is shut down, but immediate startup is not allowed if there is damage to any instruments or equipment. The specific steps for thermal startup are as follows: (1) The operator accesses the SOE system to determine what caused the shutdown and what the current status of that factor is, so that it can be checked and addressed promptly. The field crew immediately put the turbine warming pipeline (located on the second-floor platform for the cycle hydrogen compressor) into use to ensure that the inlet temperature of the turbine and the cycle hydrogen were ≥180°C; at the same time, they closed the compressor outlet valve and paid attention to rotating the turbine. Note: If the shutdown is caused by a leak in the dry gas seal, consult the workshop or the mechanical department as well as the maintenance team to determine whether it is possible to restart immediately; do not rush to start it. (2) Check whether the interlock can be reset, that is, to meet the startup conditions as soon as possible (the light in front of the startup conditions turns green to indicate that the conditions are met). If it is not possible to immediately identify the cause and eliminate it. Once the requirements are met, it can be brought to operation; note that starting up is prohibited if the steam temperature does not meet the specifications. (3) Before turning on the device, check the 505 panel for any alarm messages; remove the remote control and press reset to initialize it. Turbine warm-up: Press the RUN button to increase the speed to 2100 for warming up. (Note the sequence for removing remote control: DCS removes remote control – 505 panel F4+0). (4) Warm up for 5 minutes (if the time from shutdown to startup is short and the steam temperature is sufficient, acceleration can be carried out directly); after checking that there are no abnormalities, turn off the warming line and press F3+1 to increase the speed to the lower limit of the adjustable range. Special attention should be paid to the steam temperature. If any abnormalities occur during the acceleration process, you can use the F3+0 keys to temporarily stop the acceleration, and resume it once the issue is resolved. (5) Gradually close the backflow valve; once the outlet pressure rises to roughly equal the system pressure, open the compressor outlet manual valve and fully close the backflow valve. Set the rotation speed via remote control and adjust it to meet the process requirements. Pay attention to the sequence for sending remote controls: F4+1 (note that the light on the F4 key goes out at the same time), then send the remote control command for the rotation speed on the startup screen.