【Daily Question 20090216】What items should be checked for thermal instruments before they are put into official use?

(1) Visual inspection. (2) Start-up test. (3) Submersion test. (4) Determination of the basic error. (5) Insulation strength test. (6) Running test (for installed electric energy meters). (7) Demand indicator test (for maximum demand meters).

Answer: Before being put into formal use, the thermal instruments should undergo the following inspections: (1) The labels and numbers of each thermal instrument must be correct, clear, and complete; (2) The fuse capacity of each fuse must meet the requirements of the instrument or equipment, and their on/off status should be checked, with all power switches in the “off” position； (3) The electrical wiring of the instruments is correct; measurement systems equipped with circuit adjustment resistors shall be assembled in accordance with the regulations ； (4) Before powering on the thermal instruments, the insulation of the circuits and related equipment should be checked; it should generally be no less than 1 MΩ. When checking insulation with a megohmmeter, the terminals on the transistor-based equipment should be removed ； (5) When powered by two circuits, check whether the phase sequence of the electricity is correct before paralleling ； (6) After connecting various power sources, check them to ensure that they meet the requirements of the respective devices being used ； (7) The gaskets at instruments, valves, pipe fittings, and pipeline joints should be appropriate and undamaged, with the joints being secure. If there are isolation containers, isolation fluid should be added properly. All primary and secondary valves are in the closed position (the intermediate balance valve of the differential pressure gauge should be in the open position)

Before being put into official use, the thermal instruments should undergo the following inspections: (1) The labels and numbers of each thermal instrument must be correct, clear, and complete； (2) The fuse capacity of each fuse should meet the requirements of the instruments or equipment, and their on/off status should be checked; all power switches should be in the “off” position ； (3) The electrical wiring of the instruments is correct; measurement systems equipped with circuit adjustment resistors shall be assembled in accordance with the regulations ； (4) Before powering on the thermal instruments, the insulation of the circuits and related equipment should be checked; it should generally be no less than 1 MΩ. When checking insulation with a megohmmeter, the terminals on the transistor-based equipment should be removed ； (5) When powered by two circuits, check whether the phase sequence of the electricity is correct before paralleling ； (6) After connecting various power sources, check them to ensure that they meet the requirements of the respective devices being used ； (7) The gaskets at instruments, valves, pipe fittings, and pipeline joints should be appropriate and undamaged, with the joints being secure. If there are isolation containers, isolation fluid should be added properly. All primary and secondary valves are in the closed position (the intermediate balance valve of the differential pressure gauge should be in the open position).

After reviewing relevant information, my answer is as follows: Before being put into official use, thermal instruments generally need to undergo inspections in the following seven steps. (1) The labels and numbers of each thermal instrument should be correct, clear, and complete. (2) The fuse ratings of each fuse should meet the requirements of the instrument or equipment, and their operation status should be checked; all power switches should be in the “off” position； (3) The electrical wiring of the instruments is correct; measurement systems equipped with circuit adjustment resistors shall be assembled in accordance with the regulations ； (4) Before powering on the thermal instruments, the insulation of the circuits and related equipment should be checked; it should generally be no less than 1 MΩ. When checking insulation with a megohmmeter, the terminals on the transistor-based equipment should be removed ； (5) When powered by two circuits, check whether the phase sequence of the electricity is correct before paralleling ； (6) After connecting various power sources, check them to ensure that they meet the requirements of the respective devices being used ； (7) The gaskets at instruments, valves, pipe fittings, and pipeline joints should be appropriate and undamaged, with the joints being secure. If there are isolation containers, isolation fluid should be added properly. All primary and secondary valves are in the closed position (the intermediate balance valve of the differential pressure gauge should be in the open position)

Information found online, used for daily maintenance; I thought it was useful, so I’m sharing it with everyone: It’s quite common for manufacturing enterprises to start and stop their machinery. Short-term shutdowns have little impact on the instruments; process operators carry out shutdown or startup operations based on these instruments, with little need for assistance from instrument technicians, and the instruments themselves also do not require much handling. The start-up and shutdown processes discussed in this article are mainly due to major overhauls of the entire plant, which result in shutdowns and restarts across the whole facility; or they occur when a certain product needs to be shut down for an extended period because of poor sales or shortages of raw materials, before it can be restarted. The commissioning of newly established projects is not included in this scope. 1. Instrument shutdown: The instrument shutdown process is relatively simple, and the following points should be noted: ① Work closely with the process engineers. ② Understand the process shutdown time and the maintenance schedule for chemical equipment. ③ According to the maintenance schedule of chemical processing equipment, the instruments or sensing elements installed on such equipment, such as thermocouples, thermal resistors, flanged differential pressure transmitters, float level gauges, capacitive level gauges, pressure gauges, etc., are removed to prevent damage to these instruments during the maintenance of the chemical processing equipment. Before removing the instrument, turn off its power or gas supply first. ④ Remove the instruments in a timely manner in accordance with the instrument maintenance plan. When removing the differential pressure transmitter from the flange on the storage tank, it is essential to make sure that the tank is empty before proceeding. If it is difficult to empty the material, it is necessary to ensure that the liquid level is below the flange where the instrument is installed; once the instrument has been removed, a blind flange should be installed promptly. ⑤ After removing instruments such as thermocouples, thermal resistors, and electric transmitters, the connectors of the power cables and signal cables should be wrapped with insulating tape or adhesive tape respectively, and stored properly. ⑥ When removing pressure gauges and pressure transmitters, be careful as the pressure tapping ports may become blocked, resulting in localized pressure buildup ； Materials (liquid and gas) burst out and injure instrument technicians. The correct procedure is to first loosen the mounting bolts, vent the gas, and remove any residual liquid; only after all gas and liquid have been removed should the instrument be taken off. ⑦ For pneumatic instruments, electrical valve positioners, etc., turn off the air supply and loosen the connector of the filter pressure regulator. ⑧ When removing the ring chamber orifice plate, pay attention to its orientation: first, to check whether it was installed backwards previously, and second, to ensure correct installation afterward. Due to the requirements for straight pipe sections, there may be fewer supports for the process pipes; it is necessary to prevent one end of these pipes from sinking, as this could cause difficulties in installing the orifice plate ring chamber. ⑨ The tag numbers of the removed instruments should be placed in a visible location; when reinstalling them, they should be placed in their corresponding positions to prevent confusion among instruments of the same type due to different measurement ranges, which could lead to instrument failures. ⑩ For instruments with interlocks, switch it to manual mode before removing them. 2. Instrument startup – A successful or smooth startup of the instrument indicates high quality in its maintenance as well as proper preparation for startup. Conversely, the instrument technicians will be overwhelmed during the process startup, finding it difficult to cope, which can even directly affect the production process. Process shutdowns or production halts caused by instrumentation issues are something that should be avoided in instrumentation operations. Precautions for operating with instruments are as follows: ① Operating with instruments requires close coordination with the process. According to the requirements for pressure testing and leak detection of process equipment and pipelines, instruments should be installed in a timely manner, so as not to delay the start-up of the process due to these instruments. ② Due to the plant-wide overhaul, a large number of instruments need to be removed; when installing them, it is essential to pay attention to the instrument tag numbers and ensure they are placed in the correct positions. Otherwise, if the instruments are not installed correctly, it is difficult to detect faults (usually, instrument technicians do not consider this aspect when trying to determine the cause or origin of a fault). ③ Instrument power supply. The total power outage for the instruments will not last long. By \"power supply to the instruments,\" it is meant that after the wiring of the instruments in the field and those in the control room has been completed and verified to be correct, the automatic switches in the power supply cabinets as well as the individual power switches for each instrument are turned on in order to supply power to them. When using a 24VDC power supply, special attention must be paid to the output voltage level to prevent it from being too high or too low. ④ Gas source waste discharge. Gas supply pipes are generally made of carbon steel pipes, and rust may occur after they have been in use for a while. Due to start-up and shutdown processes, this rust can flake off. Over time, dry silica gel used in instrument air treatment units can turn into powder, which can also enter the air supply pipes. Some other impurities must also be removed before starting up the instrument. During drainage, the main air supply pipeline must be drained first, followed by the branch air supply pipelines, until the filter-reducing valves installed in the electrical valve positioners, as well as those installed in other pneumatic instruments and pneumatic cut-off ball valves, have been drained. The main air supply pipeline equipped with pneumatic instruments in the control room also needs to be drained. Supply air only after the waste fluid has been discharged, to prevent issues such as blockages in the constant-throttle orifice caused by dirty air supply, which could lead to malfunctions in the instruments. ⑤ When installing throttling devices such as orifice plates, attention must be paid to the direction to prevent them from being installed backwards. Check whether the inner walls of the straight sections at both ends are smooth and clean; any dirt should be removed promptly. If the inner walls are not smooth, use a file or sandpaper to smooth them out. In the annular chamber, attention must be paid to the thickness of the pipe center, orifice plate gasket, and annular chamber gasket; the materials used must be appropriate and the dimensions must be correct. Once the throttling device is installed, the pressure tapping valve should be opened promptly to prevent the absence of a pressure signal during startup. It is recommended to fully open the pressure tap valve using the handwheel and then turn it back half a turn. ⑥ When installing the control valve, ensure that the arrow on the valve body is in line with the flow direction. If the material is quite dirty, it can be cleaned by opening the inlet and outlet shut-off valves before installation (be careful to avoid material contamination or environmental pollution). The shut-off valves should be fully opened first and then turned back half a turn. ⑦ When using a single-flange differential pressure transmitter to measure the liquid level in a sealed container, a negative-pressure connecting tube is employed to transfer the pressure of the gas phase. This measurement method involves filling the negative pressure connection tube with liquid; therefore, after reinstallation, it is necessary to add liquid to this connection tube, and the product of the liquid level and the liquid density is equal to the negative migration amount of the flange transmitter. The liquid added is generally the same as the medium being tested, that is, the material inside the container. ⑧ For differential pressure transmitters and pressure transmitters protected with isolation fluid, when restarting the equipment, make sure to fill the pressure guiding tubes with isolation fluid. ⑨ All joints on the pneumatic instrument signal pipelines should be tested for leaks using soapy water, in order to prevent air signal leakage that could cause measurement errors. ⑩ When measuring steam flow with a differential pressure transmitter, first close the pressure-taking valves for positive and negative pressures in the three-valve assembly, open the balance valve, and check the zero position. Open the gauge only after all the steam in the pressure guiding tube has condensed into water. To prevent oscillations in the instrument when steam finally condenses, which can sometimes damage the instrument, there is another installation method: a separate tank is placed after the pressure-taking valve in the ring chamber. Before starting the measurement, cold water is poured into the pressure guide tube through this tank, allowing the instrument to be used immediately for measuring steam flow without any oscillations occurring. ⑾ When connecting the compensation wires of thermocouples, care must be taken to ensure that the positive and negative poles are connected correctly; they must not be reversed. Be careful not to confuse the three levels of thermal resistors A, B, and B. ⑿ After maintenance, prior to starting up the instrument, coordinated calibration should be carried out, so that the readings from the field primary instruments (transmitters, sensing elements, etc.) match those of the control secondary instruments (panel-mounted, rack-mounted, computer interfaces, etc.), or so that the output values from the primary instruments are consistent with those from the instruments mounted in the control room (distribution units, protectors, DCS input interfaces). Check that the regulator output, DCS output, operator panel output, and the valve position indication are consistent (or consistent with the input of the electrical valve positioner). ⒀ For instruments with interlocks, switch them to the automatic (interlock) mode only after the instruments are operating properly and the process is functioning normally. ⒁ When starting up a metal tube rotameter, due to the long downtime for maintenance, as well as activities such as welding flanges during process operations, there may be debris such as weld slag, rust, and small particles inside the process pipes. It is necessary to first open the bypass valve; after some time, the inlet valve of the metal tube rotameter should be opened, followed by the outlet valve. Finally, the bypass valve should be closed, in order to prevent the newly installed metal tube rotameter from suffering from blockages shortly after it is put into use. Additionally, attention should be paid to the sequence of opening and closing valves; for process routes in which centrifugal pumps are used to transport materials, the requirements regarding the order of operation are not strict ； When a piston-type metering pump is used to transport materials, the sequence of opening and closing the valves should be reversed (first close the bypass valve, then open the inlet and outlet valves). Furthermore, when the time interval between opening and closing the valves is larger – that is, when the bypass valve is closed without immediately opening the outlet valve of the metal tube rotameter – it often leads to an increase in pipeline pressure, damage to the instrument, and other types of failures.

Before being put into official use, the thermal instruments should undergo the following inspections: (1) The labels and numbers of each thermal instrument must be correct, clear, and complete； (2) The fuse capacity of each fuse should meet the requirements of the instruments or equipment, and their on/off status should be checked; all power switches should be in the “off” position ； (3) The fuse capacity of each fuse should meet the requirements of the instruments or equipment, and their on/off status should be checked; all power switches should be in the “off” position ； (4) Before powering on the thermal instruments, the insulation of the circuits and their associated equipment should be checked; it should generally be no less than 1 MΩ. When checking insulation with a megohmmeter, the terminals on the transistor-based equipment should be removed ； (5) When operating with dual-circuit power supply, check whether the phase sequence of the electricity is correct before paralleling ； (6) After connecting various power sources, check them to ensure they meet the requirements of the devices being used ； (7) The gaskets at instruments, valves, pipe fittings, and pipeline joints shall be appropriate and undamaged, with the joints being secure. If there are isolation containers, isolation fluid should be added properly. All primary and secondary valves are in the closed position (the intermediate balance valve of the differential pressure gauge should be in the open position).

After reviewing relevant information, my answer is as follows: Before being put into official use, thermal instruments generally need to undergo inspections in the following seven steps. (1) The labels and numbers of each thermal instrument should be correct, clear, and complete. (2) The fuse ratings of each fuse should meet the requirements of the instrument or equipment, and their operation status should be checked; all power switches should be in the “off” position； (3) The electrical wiring of the instruments is correct; measurement systems equipped with circuit adjustment resistors shall be assembled in accordance with the regulations ； (4) Before powering on the thermal instruments, the insulation of the circuits and related equipment should be checked; it should generally be no less than 1 MΩ. When checking insulation with a megohmmeter, the terminals on the transistor-based equipment should be removed ； (5) When powered by two circuits, check whether the phase sequence of the electricity is correct before paralleling ； (6) After connecting various power sources, check them to ensure that they meet the requirements of the respective devices being used ； (7) The gaskets at instruments, valves, pipe fittings, and pipeline joints should be appropriate and undamaged, with the joints being secure. If there are isolation containers, isolation fluid should be added properly. All primary and secondary valves are in the closed position (the intermediate balance valve of the differential pressure gauge should be in the open position)

For details, see \"Technical Specifications for the Construction of Petrochemical Instrumentation Projects\" SH/T3521-2007

Answer: Before being put into official use, the thermal instruments should be inspected as follows: (1) The labels and numbers of each thermal instrument should be correct, clear, and complete； (2) The fuse capacity of each fuse should meet the requirements of the instruments or equipment, and their on/off status should be checked; all power switches should be in the “off” position ； (3) The electrical wiring of the instruments is correct; measurement systems equipped with circuit adjustment resistors shall be assembled in accordance with the regulations ； (4) Before powering on the thermal instruments, the insulation of the circuits and related equipment should be checked; it should generally be no less than 1 MΩ. When checking insulation with a megohmmeter, the terminals on the transistor-based equipment should be removed ； (5) When powered by two circuits, check whether the phase sequence of the electricity is correct before paralleling ； (6) After connecting various power sources, check them to ensure that they meet the requirements of the respective devices being used ； (7) The gaskets at instruments, valves, pipe fittings, and pipeline joints should be appropriate and undamaged, with the joints being secure. If there are isolation containers, isolation fluid should be added properly. All primary and secondary valves are in the closed position (the intermediate balance valve of the differential pressure gauge should be in the open position).

Before being put into formal use, thermal instruments generally should undergo inspections in the following seven steps: (1) The labels and numbers of each thermal instrument must be correct, clear, and complete; (2) The fuse capacity of each fuse must meet the requirements of the instrument or equipment, and its on/off status should be checked, with all power switches in the “off” position； (3) The electrical wiring of the instruments is correct; measurement systems equipped with circuit adjustment resistors shall be assembled in accordance with the regulations ； (4) Before powering on the thermal instruments, the insulation of the circuits and related equipment should be checked; it should generally be no less than 1 MΩ. When checking insulation with a megohmmeter, the terminals on the transistor-based equipment should be removed ； (5) When powered by two circuits, check whether the phase sequence of the electricity is correct before paralleling ； (6) After connecting various power sources, check them to ensure that they meet the requirements of the respective devices being used ； (7) The gaskets at instruments, valves, pipe fittings, and pipeline joints should be appropriate and undamaged, with the joints being secure. If there are isolation containers, isolation fluid should be added properly. All primary and secondary valves are in the closed position (the intermediate balance valve of the differential pressure gauge should be in the open position)

Answer: Before being put into official use, thermal instruments generally need to undergo inspections in the following seven steps: (1) The labels and numbers of each thermal instrument should be correct, clear, and complete; (2) The fuse capacity of each fuse should meet the requirements of the instrument or equipment, and its on/off status should be checked, with all power switches in the “off” position； (3) The electrical wiring of the instruments is correct; measurement systems equipped with circuit adjustment resistors shall be assembled in accordance with the regulations ； (4) Before powering on the thermal instruments, the insulation of the circuits and related equipment should be checked; it should generally be no less than 1 MΩ. When checking insulation with a megohmmeter, the terminals on the transistor-based equipment should be removed ； (5) When powered by two circuits, check whether the phase sequence of the electricity is correct before paralleling ； (6) After connecting various power sources, check them to ensure that they meet the requirements of the respective devices being used ； (7) The gaskets at instruments, valves, pipe fittings, and pipeline joints should be appropriate and undamaged, with the joints being secure. If there are isolation containers, isolation fluid should be added properly. All primary and secondary valves are in the closed position (the intermediate balance valve of the differential pressure gauge should be in the open position)

Before being put into official use, the thermal instruments should undergo the following inspections: (1) The labels, numbers, and certificates of conformity for each thermal instrument must be correct, clear, and complete； (2) The fuse capacity of each fuse should meet the requirements of the instruments or equipment, and their on/off status should be checked; all power switches should be in the “off” position ； (3) The electrical wiring of the instruments is correct; measurement systems equipped with circuit adjustment resistors shall be assembled in accordance with the regulations ； (4) Before powering on the thermal instruments, the insulation of the circuits and related equipment should be checked; it should generally be no less than 1 MΩ. When checking insulation with a megohmmeter, the terminals on the transistor-based equipment should be removed ； (5) When powered by two circuits, check whether the phase sequence of the electricity is correct before paralleling ； (6) After connecting various power sources, check them to ensure that they meet the requirements of the respective devices being used ； (7) The gaskets at instruments, valves, pipe fittings, and pipeline joints should be appropriate and undamaged, with the joints being secure. If there are isolation containers, isolation fluid should be added properly. All primary and secondary valves are in the closed position (the intermediate balance valve of the differential pressure gauge should be in the open position).

Before being put into official use, the thermal instruments should undergo the following inspections: (1) The labels, numbers, and certificates of conformity for each thermal instrument must be correct, clear, and complete； (2) The fuse capacity of each fuse should meet the requirements of the instruments or equipment, and their on/off status should be checked; all power switches should be in the “off” position ； (3) The electrical wiring of the instruments is correct; measurement systems equipped with circuit adjustment resistors shall be assembled in accordance with the regulations ； (4) Before powering on the thermal instruments, the insulation of the circuits and related equipment should be checked; it should generally be no less than 1 MΩ. When checking insulation with a megohmmeter, the terminals on the transistor-based equipment should be removed ； (5) When powered by two circuits, check whether the phase sequence of the electricity is correct before paralleling ； (6) After connecting various power sources, check them to ensure that they meet the requirements of the respective devices being used ； (7) The gaskets at instruments, valves, pipe fittings, and pipeline joints should be appropriate and undamaged, with the joints being secure. If there are isolation containers, isolation fluid should be added properly. All primary and secondary valves are in the closed position (the intermediate balance valve of the differential pressure gauge should be in the open position).

Before being put into formal use, thermal instruments generally should undergo inspections in the following seven steps: (1) The labels and numbers of each thermal instrument must be correct, clear, and complete; (2) The fuse capacity of each fuse must meet the requirements of the instrument or equipment, and its on/off status should be checked, with all power switches in the “off” position； (3) The electrical wiring of the instruments is correct; measurement systems equipped with circuit adjustment resistors shall be assembled in accordance with the regulations ； (4) Before powering on the thermal instruments, the insulation of the circuits and related equipment should be checked; it should generally be no less than 1 MΩ. When checking insulation with a megohmmeter, the terminals on the transistor-based equipment should be removed ； (5) When powered by two circuits, check whether the phase sequence of the electricity is correct before paralleling ； (6) After connecting various power sources, check them to ensure that they meet the requirements of the respective devices being used ； (7) The gaskets at instruments, valves, pipe fittings, and pipeline joints should be appropriate and undamaged, with the joints being secure. If there are isolation containers, isolation fluid should be added properly. All primary and secondary valves are in the closed position (the intermediate balance valve of the differential pressure gauge should be in the open position)

Answer: Before being put into formal use, the thermal instruments should undergo the following inspections: (1) The labels and numbers of each thermal instrument must be correct, clear, and complete; (2) The fuse capacity of each fuse must meet the requirements of the instrument or equipment, and their on/off status should be checked, with all power switches in the “off” position； (3) The electrical wiring of the instruments is correct; measurement systems equipped with circuit adjustment resistors shall be assembled in accordance with the regulations ； (4) Before powering on the thermal instruments, the insulation of the circuits and related equipment should be checked; it should generally be no less than 1 MΩ. When checking insulation with a megohmmeter, the terminals on the transistor-based equipment should be removed ； (5) When powered by two circuits, check whether the phase sequence of the electricity is correct before paralleling ； (6) After connecting various power sources, check them to ensure that they meet the requirements of the respective devices being used ； (7) The gaskets at instruments, valves, pipe fittings, and pipeline joints should be appropriate and undamaged, with the joints being secure. If there are isolation containers, isolation fluid should be added properly. All primary and secondary valves are in the closed position (the intermediate balance valve of the differential pressure gauge should be in the open position)

Before being put into formal use, thermal instruments generally should undergo inspections in the following seven steps: (1) The labels and numbers of each thermal instrument must be correct, clear, and complete; (2) The fuse capacity of each fuse must meet the requirements of the instrument or equipment, and its on/off status should be checked, with all power switches in the “off” position； (3) The electrical wiring of the instruments is correct; measurement systems equipped with circuit adjustment resistors shall be assembled in accordance with the regulations ； (4) Before powering on the thermal instruments, the insulation of the circuits and related equipment should be checked; it should generally be no less than 1 MΩ. When checking insulation with a megohmmeter, the terminals on the transistor-based equipment should be removed ； (5) When powered by two circuits, check whether the phase sequence of the electricity is correct before paralleling ； (6) After connecting various power sources, check them to ensure that they meet the requirements of the respective devices being used ； (7) The gaskets at instruments, valves, pipe fittings, and pipeline joints should be appropriate and undamaged, with the joints being secure. If there are isolation containers, isolation fluid should be added properly. All primary and secondary valves are in the closed position (the intermediate balance valve of the differential pressure gauge should be in the open position)