1. Do not mix the signal cable and the power cable with a multi-core cable!
2. Oxygen pipeline instrumentation equipment maintenance do not stick to oil, oil transmitters and pressure gauges do not mix with ordinary tables.
3. When disassembling the maintenance instrument, we must pay attention to wrap the wire well to prevent short circuit!
4. Cables should not have intermediate connectors.
5. The shielding ground of the point is generally shielded and grounded on the side of the control room.
6. The protective hose must be lower than the instrument inlet to prevent water from the instrument.
7. Leaky instruments should be added to the instrument protection box or wrapped in nylon plastic bags.
8. When cables are laid in the trough, separate the intrinsic safety cables, power cables, and signal cables with partitions.
9. When wiring, the compensation wire can not use the wiring nose (piece) to avoid contact between two different conductors, causing measurement errors.
10. During production, if the instrument is to deal with problems, including indoor and outdoor, it must be handled according to procedures or regulations, especially to notify the operator, and sometimes it must be signed in person.
11. In the case of a surge protection area, the field instrument is connected to the safety grid through the surge protector and then connected to the DCS, SIS and other control systems. To avoid redundant indirect cabinet lines, the surge protector in the field cabinet and the safety grid in the corresponding loop are installed on the same side of the cabinet as possible.
12. The control room must take measures to prevent small animals, because the mouse urinates on the ESD card, causing the entire device to stop, and the loss is large.
13. The instrument must complete the monomer debugging before installation, and the loop debugging must be completed after installation.
14. When the device is running, the technician must be present for the maintenance of the instrument. Remember that when something goes wrong, it's not a small thing.
15. The on-site maintenance of the instrument must contact the technician, ask the process status of the instrument with power supply must be turned off first when disassembling the power supply, and then use the multimeter to confirm whether the power supply is turned off, and know that life is its own.
16 Flow meter design, we must choose the right type of flow meter according to the measurement medium, temperature, pressure, and do a good job of flow compensation. The installation should pay attention to the special requirements of the flow meter.
17. When the instrument is designed into the groove plate of the control room, in order to prevent rain from entering the control room, it must be considered to bend up and down and do a good sealing treatment.
18. When the instrument air is introduced from the main pipe, the valve must be above the center of the pipeline, preferably at a position of 90 degrees above the pipeline, to avoid the stolen goods in the wind line: into the instrument valve.
19. The shielding layer shall not be grounded at both ends; Rainproof measures should be taken at the mouth of outdoor cable protection pipes; Explosion-proof environment pay attention to the sealing of the pipe mouth.
20 Alarm instruments, audio equipment must be maintained and normally put into use, otherwise once the process accident, the instrument professional not dead also have to delamination, the reason is because the alarm is broken, the operator did not find.
21. Where ammonia is involved, copper and copper alloys are prohibited; DCS system power supply, should design two power supply into!
22. Thermal resistance temperature measurement, long-distance transmission can not be used two-wire system.
23. The insulation resistance of the cable should be greater than 5 megohm; The turning radius of the cable should generally be greater than 10 times the cable diameter, and the optical cable should be 15 times. Instrument cables should be laid in parallel with electrical cables at a certain distance (greater than 0.8 m), and the distance between equipment and pipelines should be greater than 150 mm.
24. Instrument pipeline hydraulic test, for the austenitic stainless steel pipeline experiment, the chloride ion content in the water shall not exceed 25PPM(parts per million) instrument working ground should be less than 1 ohms, other grounding is less than 4 ohms.
25. The protection of the instrument should be made of fire-proof cloth "asbestos cloth". Plastic bags shouldn't be used.
26. The instrument used in the hydrogen unit must meet the requirements of explosion-proof grade and protection grade, which are indispensable. Intrinsic safety signal (cable) and flameproof signal (cable) can not enter the same field intermediate junction box.
27. The insulation resistance of the cable should be greater than 5 megohm; The turning radius of the cable should generally be greater than 10 times the cable diameter, and the optical cable should be 15 times. Instrument cables should be laid in parallel with electrical cables at a certain distance (greater than 0.8 m), and the distance between equipment and pipelines should be greater than 150 mm.
28. Instrument pipeline hydraulic test, for the austenitic stainless steel pipeline experiment, the chloride ion content in the water shall not exceed 25PPM(parts per million) instrument working ground should be less than 1 ohms, other grounding is less than 4 ohms.
29. The instrument used in the hydrogen unit must meet the requirements of explosion-proof grade and protection grade, which are indispensable. Intrinsic safety signal (cable) and flameproof signal (cable) can not enter the same field intermediate junction box.
30. When designing the FF bus, a terminal (resistor and capacitor connected in series) should be installed at the terminal of the power regulator and the fieldbus junction box.
31. The interlocking valve should be fail-safe, live under normal circumstances, and power off when interlocked.
32. When the instrument is designed and installed, if the temperature instrument is installed in the pipeline below DN80, the thermometer expansion pipe should be used to expand the pipeline to more than 80.
33. The flow measuring element does not participate in the power plant hydraulic test.
34. To measure the steam flow, when the condenser is used in the positive and negative pressure guide pipeline, the installation height of the two condensing tanks should be consistent.
35. The simmering of the field instrument pressure guide pipe is cold simmering, and can not be heated by gas welding.
36. The occurrence of flash should be fully considered in the process of designing and selecting control valves, designing pipelines, and determining pressure distribution. From the control valve point of view, should pay attention to the following matters.
(1) Improve the hardness of the material.
(2) Reduce the flow rate of the fluid.
(3) Select the appropriate control valve type and flow direction. For example, for fluids that are easy to vaporize, it is not appropriate to choose a ball with high pressure recovery
37. Valve and butterfly valve, can choose low pressure recovery of single-seat valve, etc. Measures to eliminate and reduce actual occurrence:
(1) Control the pressure drop so that cavitation does not occur. For example, the multi-stage pressure reduction method is used to divide the pressure drop of the control valve into several stages.
(2) Reduce the impact of cavitation. A similar method is used to prevent flash from occurring. For example, increase the hardness of the material, reduce the flow rate, etc., so that the impact of cavitation is reduced.
(3) Reasonable distribution of pipeline pressure to increase downstream pressure.
38. Cable and wire overhead laying into the control room should pay attention to the problems:
(1) Before entering the control room, a fixed fulcrum should be given to the slot plate to prevent climate change and generate stress for indoor equipment;
(2) Before the groove board enters the control room, there should be a slope of more than 1/100, and the slope is outdoor to prevent rain from flowing into the control room along the groove board;
(3) The access to the control room through the wall should be sealed to prevent rats and mosquitoes from entering.
39. The choice of local pressure gauge must be clear about the nature of the pressure source: what is the impact load or the general pressure, when there is no more meters, the replacement can be miserable. The installation size of the local thermometer must be communicated with the process, and the size must be selected when measuring the liquid in the dissatisfied pipe. When designing, the material selection of high temperature and high pressure must be different from normal temperature and normal pressure. Do not live demolition and construction equipment, carry a test pen with you to prevent the risk of electric shock.
40. Can not live demolition and construction equipment, carry the test pen with you to prevent the risk of electric shock.
41 DCS must do a good job of anti-static work, do not cause accidents due to static electricity.
42 maintenance chain equipment must DCS play compulsory action.
43. Solenoid valve coil should not be unplugged in the case of power, otherwise it will burn the coil.
44. When the rotor and wheel flow meter are installed vertically, be sure to pay attention to the fluid from the bottom up.
45. After the newly installed regulating valve, the air supply pipeline should be emptied for a period of time and then connected to the valve positioner to prevent oil from entering and causing damage to the positioner.
46. Acetylene gas instrument should also ban copper, so in addition to the requirements of explosion-proof grade when used in acetylene gas occasions, it should also be noted that some device nameplates will be marked with "not for acetylene gas".
47. Current signal between DCS and electrical. Because the electrical transmission is generally active, it is best to go through an isolator isolation, on the one hand, it is not necessary to string the instrument I/O card into the electrical circuit, on the other hand, if you do not use the isolator, the two sides may be debugged.
48. To the steam tracing of the instrument pipeline, the tracing pipe is best to use more than 12 O.D. Otherwise, once the route is long, it is easy to appear that the steam is not hot and the heat tracing effect is not good.
49. To correct a common mistake in the design, some people add security grids regardless of the type of riot control system. In fact, the safety grid is used for intrinsically safe explosion protection systems. Intrinsic safety explosion-proof system:
(1) On-site instruments must be intrinsically safe instruments;
(2) The control room side must have a safety fence.
(3) The middle cable must be a safety signal cable.
50. For increased safety instruments and flameproof instruments, isolators can be used for signal isolation if necessary.
51. Zener safety grid must pay attention to the grounding problem.
52. In fact, the instrument and the process are inseparable. The online maintenance of the instrument must pay attention to reducing the interference to the process as much as possible.
53. The selection of flow meters: When the conductivity of the measured process medium is low, electromagnetic flowmeters cannot be selected; The mass flowmeter should be used when the measurement requirements of factory level measurement are very high.
54. When measuring the pressure of the medium, add condensation tube or siphon gas when the temperature of the measured medium is greater than 60 degrees.
55. After the installation of the pneumatic control valve, pay attention to the role of the air open type and the air closed on the DCS do not reverse the setting.
56. The indicating value of the temperature instrument system suddenly changes to the maximum or minimum, which is generally a failure of the instrument system. Because the temperature instrument system measurement lag is large, there will be no sudden change. At this time, the fault is caused by thermocouple, thermal resistance, compensation wire break or transmitter amplifier failure.
57. When wiring the instrument, be sure to mark the line number! At the beginning of the work made such a low-level mistake, it is a good trouble to recover the temperature once the parts are installed in the corner of the pipeline or inclined installation, should be against the flow direction.
58. If there is a pressure primary point or a temperature primary point on the same pipe line, the pressure primary point should be upstream of the temperature primary point.
59. The rotameter must be mounted vertically on the pipe, and the flow of the medium must be from the bottom up.
60. The straight pipeline requires 5DN on the upstream side and 3DN on the downstream side (DN is the diameter of the pipeline).