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1. Never use a single multi-core cable for both signal cables and power cables! 2. When maintaining instruments and equipment on oxygen pipelines, ensure no oil adheres to them. Oil-free transmitters and pressure gauges must not be installed together with ordinary gauges. 3. When disconnecting wires from the instrument for maintenance, be sure to wrap the wire ends properly to prevent short circuits! 4. Cables should not have intermediate joints. 5. Point shielding grounding is generally carried out on the control room side. 6. The protective hose must be placed below the instrument inlet to prevent water from entering the instruments. 7. Instruments exposed to the elements should be fitted with protective cases or wrapped in nylon plastic bags. 8. When cables are laid in cable trays, intrinsically safe cables, power cables, and signal cables should be separated using partitions. 9. When wiring, compensation wires must not be used with wire nuts (terminals); this prevents two different conductors from coming into contact, which could cause measurement errors. 10. During production, if instruments need to address any issues, both indoors and outdoors, the required procedures or protocols must be followed. In particular, operators must be notified; sometimes a written signature is also required. 11. In areas with lightning protection, where field instruments are connected to a safety barrier via surge protectors and then to control systems such as DCS and SIS, in order to avoid unnecessary wiring in additional cabinets, the surge protectors located in the field cabinet room should be installed on the same side of the cabinet as the safety barriers for the corresponding circuits. 12. Measures must be taken in the control room to prevent small animals from entering. It was precisely because rats urinated on the ESD cards that the entire plant had to be shut down, resulting in tremendous losses. 13. Single-unit testing must be completed before installing the instruments, and circuit testing must be finished after installation before conducting integrated testing. 14. During the operation of the equipment, process personnel must be present during any maintenance of the instruments. Keep this in mind: if a problem arises, it’s not a minor matter. 15. When performing on-site maintenance of instruments, it is essential to contact the process engineers to understand the current operating conditions. When removing instruments that are connected to power supplies, be sure to turn off the power first, and then use a multimeter to confirm that the power has indeed been turned off – after all, your life is your own. 16. When designing flow meters, it is essential to select the appropriate type of meter based on the medium being measured, as well as temperature and pressure factors, and to implement proper flow compensation. During installation, various special requirements of the flow meter should be observed. 17. When installing the instrument panel in the control room, to prevent rainwater from entering the control room, it is necessary to consider upward and downward bends as well as ensure proper sealing. 18. When instrument air is introduced from the main pipe, the valve must be positioned above the exact center of the pipeline; ideally at a 90-degree angle above the pipeline, to prevent contaminants in the air stream from entering the instrument valve. 19. The shielding layer shall not be grounded at both ends ； The outlets of outdoor cable protection pipes should have rainproof measures ； In explosion-proof environments, pay attention to the sealing of pipe openings. 20. Alarm instruments and audio equipment must be properly maintained and functioning normally; otherwise, in the event of a process accident, personnel specializing in instrumentation will suffer greatly—if not face fatal consequences—simply because the alarms failed to operate, and the operators failed to notice this. 21. In situations involving ammonia, copper and copper alloys are prohibited ； For power supply to the DCS system, dual power inputs should be designed! 22. For thermistor temperature measurement, two-wire wiring cannot be used for long-distance transmission. 23. The insulation resistance of the cable should be greater than 5 megohms ； The bending radius of cables should generally be more than 10 times the cable diameter, while for optical fibers it should be 15 times ； When instrument cables are laid parallel to electrical cables, a certain distance should be maintained between them (greater than 0.8 meters), and the distance from such cables to equipment and pipes should be more than 150 millimeters. 24. For the hydraulic testing of instrument pipelines, when testing austenitic stainless steel pipelines, the chloride content in water must not exceed 25 PPM. The working ground resistance of the instruments should be less than 1 ohm, while the resistance of other grounds should be less than 4 ohms. 25. The protection of instruments should be done using fire-resistant fabric, namely “asbestos cloth”. Plastic bags should not be used. 26. The instruments used in the hydrogen unit must meet both the explosion-proof rating requirements and the protection rating requirements; neither can be neglected. Intrinsic safety signals (cables) and flameproof signals (cables) cannot be fed into the same field intermediate junction box. 27. The insulation resistance of the cable should be greater than 5 megohms ； The bending radius of cables should generally be more than 10 times the cable diameter, while for optical fibers it should be 15 times ； When instrument cables are laid parallel to electrical cables, a certain distance should be maintained between them (greater than 0.8 meters), and the distance from such cables to equipment and pipes should be more than 150 millimeters. 28. For the hydraulic testing of instrument pipes, when conducting tests on austenitic stainless steel pipes, the chloride ion content in water must not exceed 25 PPM (parts per million). The grounding resistance for instrument circuits should be less than 1 ohm; for other grounds, it should be less than 4 ohms. 29. The instruments used in the hydrogen unit must meet both the explosion-proof rating requirements and the protection rating requirements; neither can be neglected. Intrinsic safety signals (cables) and flameproof signals (cables) cannot be fed into the same field intermediate junction box. 30. When designing the FF bus, terminators (series-connected resistors and capacitors) must be installed at the terminals of the power regulator and the fieldbus junction box. 31. The solenoid valves used for interlocking should be fail-safe type, remaining powered under normal conditions and de-energized during interlocking. 32. When designing and installing instruments, if the pipeline for the temperature instrument has a diameter of less than DN80, a thermometer expansion tube should be used to increase the pipeline diameter to over 80. 33. Flow measuring elements shall not be included in the plant’s hydraulic pressure test. 34. When measuring steam flow and condensers are used for the positive and negative pressure transfer lines, the installation heights of the two condenser tanks must be kept identical. 35. For bending the pressure guiding tubes of on-site instruments, cold bending should be used; hot bending methods such as gas welding are not permitted. 36. The occurrence of flashing must be fully considered in the design and selection of control valves, the design of pipelines, and the determination of pressure distribution. When looking at control valves, the following points should be noted. (1) Increase the hardness of the material. (2) Reduce the flow velocity of the fluid. (3) Select the appropriate type and flow direction of control valve. For example, for fluids that vaporize easily, ball valves and butterfly valves with high pressure recovery are not suitable; instead, single-seat valves with low pressure recovery can be used. Measures to eliminate and reduce what actually occurs: (1) Control the pressure drop to prevent cavitation. For example, a multi-stage pressure reduction method is employed to divide the pressure drop across the control valve into several stages. (2) Reduce the impact of cavitation. A similar method to that used to prevent flashing is employed. For example, by increasing the hardness of the material or reducing the flow rate, the impact caused by cavitation can be minimized. (3) Allocate pipeline pressure reasonably to increase downstream pressure. 38. Issues to note when laying cables and wires overhead to enter the control room: (1) Before entering the control room, provide a fixed support for the tray to prevent stress from weather changes from being applied to the equipment inside ； (2) There should be a slope of more than 1/100 before the trough plate reaches the control room, with the slope facing outward, to prevent rainwater from flowing into the control room along the trough plate ； (3) The openings through the walls leading to and from the control room should be sealed to prevent rats and insects from entering. 39. When selecting local pressure gauges, it is essential to determine the nature of the pressure source: whether it is a shock load or normal pressure. If there aren’t enough gauges available, replacing them can be a problem. The installation dimensions of on-site thermometers must be discussed with the process engineers. When measuring liquids that do not completely fill the pipe, it is essential to select appropriate dimensions ； When designing, the selection of materials for high temperature and high pressure must differ from those used under normal temperature and pressure conditions. Do not disassemble equipment while it is powered on; carry a voltage tester with you to avoid the risk of electric shock. 40. Do not disassemble or install equipment while it is energized. Carry a test pen with you to prevent the risk of electric shock. 41. DCS must implement proper anti-static measures to prevent accidents caused by static electricity. 42. To service the interlock equipment, a forced command from the DCS is required before any action can be taken. 43. The solenoid coil must not be removed while it is powered, otherwise the coil will be damaged. 44. When rotors and wheel flowmeters are installed vertically, it is essential to ensure that the fluid flows from bottom to top. 45. After installing a new control valve, the air supply pipeline must be purged for some time before being connected to the valve positioner, to prevent oil from entering and damaging the positioner. 46. Copper is also prohibited in instruments used for acetylene gas; therefore, in applications involving acetylene gas, in addition to meeting the requirements regarding explosion protection ratings, it is necessary to pay attention to the fact that some device labels may indicate “Not suitable for acetylene gas”. 47. Current signals between DCS and electrical systems. Since the electrical signals that are sent over are usually active, it is best to use an isolator for isolation. On one hand, this prevents the instrument’s I/O cards from being connected to the electrical circuit; on the other hand, without an isolator, it may be impossible to achieve proper synchronization between the two systems. 48. Provide steam tracing for the instrument piping; it is advisable to use tracing pipes with an outer diameter of 12 inches or more, as otherwise, if the pipeline length is large, it is easy for the steam to not be hot enough, resulting in poor tracing efficiency. 49. To correct a common error in design: some people install safety barriers regardless of the type of anti-riot system in use. In fact, safety barriers are used in intrinsically safe explosion-proof systems. Intrinsic safety explosion-proof system: (1) The field instruments must be intrinsic safety type instruments ； (2) A safety barrier must be present on the control room side. (3) The cable in the middle must be an intrinsically safe signal cable. 50. For intrinsically safe instruments and flameproof instruments, signal isolation can be achieved using isolators if necessary. 51. Attention must be paid to grounding issues with Zener-type safety barriers. 52. In fact, instruments and the manufacturing process are inseparable; when performing online maintenance on instruments, it is essential to minimize any disruption to the manufacturing process. 53. Selection of flow meters: When the conductivity of the process fluid being measured is low, electromagnetic flow meters cannot be used ； When high-level factory-level measurement is required, a mass flow meter should be used. 54. When measuring the pressure of a medium, a condenser or desiccant should be used if the temperature of the medium being measured is above 60 degrees. 55. After installing the pneumatic control valve, be sure to pay close attention not to get the operating settings for air-open and air-close types wrong in the DCS. 56. If the reading of the temperature instrument system suddenly reaches the maximum or minimum value, it is generally due to a fault in the instrument system. Because the temperature instrument system has a large measurement lag, no sudden changes occur. At this time, the causes of failure are usually broken thermocouples, thermal resistors, compensation wires, or a malfunctioning transmitter amplifier. 57. Be sure to label the wire numbers properly when wiring instruments! I made such a silly mistake while working before; it was very difficult to fix. If a component is installed at a bend in the pipe or at an inclined angle, it should be installed against the flow direction. 58. If both pressure primary points and temperature primary points are present on the same pipeline, the pressure primary point should be upstream of the temperature primary point. 59. The rotameter must be installed vertically on the pipeline, and the flow direction of the medium must be from bottom to top. 60. Straight pipes require 5DN on the upstream side and 3DN on the downstream side (DN is the pipe diameter).