Operating procedures for the three large compressors in our factory

Thread Content

(K6601, K6201, K6101) Compressor Operation Procedure Compilation: Liu Guangqing, Chen Peng; Review: Chen Wei; Approval: He Zhongsi. Chemical Engineering Department 2, Yingshan Petrochemical Plant, January 1998. Chapter 1: Introduction 1. Classification of compressors: Centrifugal compressors, reciprocating compressors (piston compressors), screw compressors. 2. Basic information on the compressors in Chemical Engineering Department 2: There are three compressors in our department, with model numbers K-6101, K-6201, and K-6601 respectively. (1) K-6101 (Hydrogen compressor): This is a single-stage, single-cylinder, balanced reciprocating compressor manufactured by Cooper Company in the United States. The hydrogen gas supplied from the hydrogen production facility, with a pressure of 2.0 Mpa and a temperature of 40°C, is compressed by this machine, resulting in a pressure of 3.0 Mpa (gauge pressure) and a temperature of 70–90°C. Then, after passing through several heat exchangers, it is sent to R-6101. (2) K-6201 (Circulating gas compressor): This unit is imported from the German company Atlas Copco; it is driven by a steam turbine and is a single-stage centrifugal compressor. The main function of this machine is to circulate the gas in the R-6201, in order to create a higher gas-phase load during the hydroxylamine reaction. (3) K-6601 (air compressor): This unit is imported from the German company Atlas Copco. It is driven by a back-pressure steam turbine K-6602 and a two-stage exhaust expansion turbine K-6603; air from the atmosphere is compressed to 0.66–0.7 Mpa (absolute pressure) through three stages of compression, and this compressed air is supplied to devices such as C-6602, C-6702, X-6801, and R-6601. Chapter 2: Working Principle of Compressors Section 1: Working Principle of Reciprocating Compressors Reciprocating compressors utilize a crank-slider mechanism to convert the rotational motion of the prime mover into the reciprocating motion of the piston. Through the control of intake and exhaust valves, they enable the intake, compression, and exhaust of gas, thereby increasing the gas pressure. Section 2: Working Principle of Centrifugal Compressors. A centrifugal compressor is a rotary vane-type gas compression machine. Its characteristic is that the intake, compression, and discharge of gas occur as a continuous flow process. Since the gas flow moves radially away from the axis within the impeller, it is called a centrifugal compressor. A centrifugal compressor consists of one or more cylinders, with the machine body contained within each casing representing one cylinder. The cylinder can be divided into sections; each stage between intermediate cooling, evacuation, and filling constitutes a section. A stage consists of one or more stages, with each impeller and its corresponding stationary component forming a stage of the centrifugal compressor. Chapter 3: Basic Structure of Compressors Section 1: Basic Structure of Reciprocating Compressors 1. The crank-and-connecting rod mechanism that converts the rotational motion of the drive unit into the reciprocating motion of the piston. 2. The piston-cylinder components that form the compression volume; the main unit. 3. The inlet and exhaust valves for transferring gas. 4. The packing components that prevent gas leakage. Basic structure: Buffers, auxiliary equipment, coolers, liquid-gas separators, lubrication system. I. Types of Compressors 1. Symmetrically balanced type (M-type, H-type): The cylinders are located on either side of the crankshaft, with the cranks of the opposite cylinders being 180° apart. Symmetrically balanced compressors are currently widely used in large and medium-sized compressors in petrochemical plants; the K-6101 belongs to this type (with one end being the balanced end). In opposed-compressor designs, the crankshafts of adjacent rows are not aligned at 180° angles, and the centerlines of the cylinders may or may not be on the same straight line; such compressors are generally used in ultra-high pressure applications. 3. Horizontal compressors: The cylinders are located on one side of the crankshaft, and there are single-row and double-row types; they are used in small high-pressure compressors for testing purposes. 4. Vertical compressors 5. Angular compressors (L-type, V-type, W-type): The angle between the cylinder centerlines is not 180°. II. Structure of main components 1. Cylinders and cylinder liners: Generally made of cast iron (steel); it is here that the gas is compressed. 2. Valve: Divided into intake valves and exhaust valves. 3. Piston and piston rod: The piston moves back and forth within the cylinder, and together with the cylinder it forms the compression volume ； The piston rod connects the crosshead to the piston and bears alternating loads. 4. Packing: The packing is a sealing component that prevents gas from leaking out. 5. Crankshaft: It receives the power supplied by the prime mover in the form of torque, and converts it into the reciprocating force of the pistons, thereby compressing the gas to perform work. 6. Connecting rod: The large and small ends of the connecting rod are connected to the crank pin and the crosshead, respectively, converting the rotational motion of the crankshaft into the reciprocating motion of the crosshead. 7. Crosshead: The crosshead connects the connecting rod and the piston rod through the crosshead pin. Section 2: Basic Structure of Centrifugal Compressors
I. Basic Structure
1. Drive unit (electric motor, steam turbine, or gas turbine)
2. Compressor (single-cylinder or multi-cylinder)
3. Speed increaser
4. Gas system (coolers, separators, etc.)
5. Oil system
6. Control and safety systems
7. Other rotating machinery such as expanders and generators

II. Structure of Major Components
1. Rotor: Includes shaft, impeller, balance disk, thrust disk, coupling, sleeve, etc.
2. Housing: Available in horizontal split type and vertical split type.
3. Bearings: The radial and thrust bearings used in centrifugal compressors are usually sliding bearings based on the hydrodynamic pressure principle. 4. Sealing: labyrinth seal, liquid film seal, mechanical seal, damping ring seal, dry gas seal. Section 2: Basic Structure of the Three Compressors in Our Department I. K-6101 (I) Compressor Frame Components 1. Frame: The frame is made of cast iron, featuring a robust structure; it is completely sealed and also serves as an oil tank. 2. Connecting rod 3. Crosshead guide rail 4. Crosshead and crosshead pin 5. Crankshaft and main bearings (II) Compressor cylinder (lubrication-free): 1. Cylinder and cylinder liner 2. Piston reinforcement ring: It bears the weight of the piston; the piston is supported within the cylinder bore by two split reinforcement rings mounted at its central portion, and these reinforcement rings are made of Teflon compound. 3. Piston rings: The piston rings are made of Teflon compounds; they are single-piece components with beveled joints, and there are four of them in total. 4. Piston rod packing: A set of packing consists of a radial ring, a tangential ring, and a support ring. (III) The air valve K-6101 has four sets of intake valves and exhaust valves, which are installed on the cylinder. (IV) The mounting units of the compressors in the lubrication system are all pressurized for lubrication. The gear pump is driven by the compressor crankshaft. Low oil pressure alarm switch: 0.172 Mpa (gauge). Low oil pressure shutdown switch: 0.124 Mpa (gauge). High oil temperature alarm switch: 60°C. Water system: Low water pressure shutdown switch: 0.207 Mpa; normal water pressure: 449 Kpa. Inlet water temperature: 33°C; outlet water temperature: 38.3°C. II. K-6201: This machine is a single-stage centrifugal compressor driven by a steam turbine; it is a radial compressor with integral gear transmission. The gear mechanism is of the monoclinic spur gear type, featuring two shafts and a horizontally mounted gearbox. The impeller features an extended design, which is aerodynamically advantageous for the axial entry of the compressed gas. The inhaled gas accelerates in the inlet and impeller, where the kinetic energy generated in the impeller is converted into potential energy in this area as well as in the diffuser that follows; the resulting pressure increase is achieved within the impeller, diffuser, and spiral casing. (1) Housing (2) The rotor consists of an impeller and two shafts (large and small gear shafts). (3) Shaft seal: The shaft seal is used to seal the space between the back of the impeller and the gearbox; the K-6201 shaft seal utilizes a double-acting dry face mechanical gas seal. (IV) Diffuser guide vanes (V) The bearings of the gear box are of the horizontal assembly type. (VI) Drive unit: Steam turbine K-6202. (VII) Support structure. (VIII) Lubrication system: The lubrication circuit starts from the oil tank; the oil pump draws oil from the tank, and then the oil is pumped to the lubrication points via oil coolers and filters. The heated lubricating oil returns to the oil tank without the need for pressure. (IX) Separator and process gas pipelines: The purpose of the separator S-6202 is to separate liquids from the circulating gas, thereby protecting the compressor. (10) Sealing system: The sealing system is designed to prevent contaminated process gases from entering the shaft seal and damaging it, as well as to prevent hazardous gases from escaping into the atmosphere or the gear mechanism. The sealing pressure is always set higher than the gas pressure downstream of the compressor impeller. (11) Instruments, control, and regulation systems. III. K-6601 (1) The steam turbine K-6602 is driven by high-pressure steam. (II) The expansion turbine K-6603 is driven by the C-6702 exhaust gas; it features a two-stage impeller structure, with the two impellers located at both ends of the same shaft. (III) Three-stage impeller structure of compressor K-6601. Stage 1 uses one shaft, while stages 2 and 3 share one shaft, each of which is connected to the large gear via a gear coupling. (IV) The gearbox connects the steam turbine to the compressor’s large gear shaft; through gear reduction, it lowers the rotational speed from 5200 rpm of the steam turbine to 1500 rpm of the large gear shaft. (5) The inter-stage cooler E-6601 is connected to the primary outlet and secondary inlet of K-6601, with the purpose of cooling the temperature of the gas coming from the primary outlet. (VI) Lubrication system (similar to K-6201) (VII) Process gas pipelines (VIII) Instrument control and regulation system Chapter 4: Basic operation of compressors Section 1: Operation of K-6101 I. Main design parameters 1.1 Compressor specifications: Model – 8-7/8×9-HOFPCP. Gas to be compressed: Hydrogen. Inlet pressure: 2.0 Mpa (gauge). Outlet pressure: 3.0 Mpa (gauge). Inlet gas temperature: 30–40°C. Outlet gas temperature: 70–90°C. Flow rate: 6730 Nm3/h. N2 pressure at the filler inlet: 0.172 Mpa. 1.2 Compressor motor: Model – F250AFKF3TO. Type: TIKE. Power: 187 KW. Voltage: 6000 V. Frequency: 50 Hz. Rotational speed: 492 rpm. Full-load current: 26 A. 1.3 Oil system: Lubricant type – Anti-wear hydraulic oil HM150. Oil pressure: 0.345 Mpa (gauge). Flow rate: 6.6 m3/h. Oil temperature: 48.9°C. 1.4 Flushing and cooling water systems: Inlet temperature of process water: 33°C. Inlet pressure of process water: 0.449 Mpa (gauge). Total flow rate of process water: 4.0 m3/h. Total outlet temperature of cooling water: <38.3°C. Pressure of N2 used for purging: 0.172 Mpa (gauge). 1.5 Alarm and shutdown interlocks: 1.5.1 Alarm values: Crankcase oil temperature: >60°C. High exhaust temperature: >104°C. Low flushing pressure at the control panel: <0.0076 Mpa (gauge). Alarm for low oil pressure and activation of the auxiliary oil pump: <0.172 Mpa (gauge). 1.5.2 Shutdown values: Oil pressure: <0.124 Mpa (gauge). Water pressure: <0.207 Mpa (gauge pressure). Shutdown due to low inlet pressure: Hydrogen pressure <1.65 Mpa (gauge). Shutdown due to low nitrogen protection pressure: Nitrogen pressure <0.103 Mpa (gauge). II. Preparations before starting up 2.1 Inspection of the lubrication system 2.1.1 Check whether the oil level and oil temperature are normal. The oil level must be above 1/2 of the sight glass, but not above the maximum level indicated by the sight glass. 2.1.2 Drain a small amount of oil from the lowest point of the tank to check for water content. 2.1.3 Set the auxiliary oil pump to manual mode and start it. 2.1.4 Check for leaks in the oil system; the oil pressure should be between 300~400 Kpa ； Oil filter (pressure difference