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I. Lessons Learned and Improvements from a Certain Gasification Plant Project 1. Due to the overly long design of the pipe connection stubs, the insertion depth of certain thermal resistors and thermocouples in the plant was insufficient; these components have been repurchased, and better communication between the instrumentation and piping teams should be established during the design review phase； 2. For the large-diameter instrument air supply pipes of the equipment (1/2 inch and above), flexible connections should be used to prevent the air supply from becoming loose or breaking due to excessive vibration of the valves ； 3. For domestic unpolished gas supply pipes with a diameter of 8mm or more, it is not recommended to use ferrule connections. The irregular outer surface of low-quality unpolished stainless steel pipes prevents the ferrule from gripping properly; thus, under excessive vibration, the gas supply pipe may come loose ； 4. For the pneumatic clutch of the gasified coal mill, a small air compressor is used to draw air directly from the atmosphere; during the compression of air, a large amount of liquid water is formed, which can affect the service life of the air bags and pipelines. Therefore, instrument air should be used ； 5. The selection of radar level gauges for the gasified coal silo and limestone silo is unreasonable. Given the high level of dust inside the silos, a pneumatic high-frequency radar should be used to prevent dust accumulation on the PTFE tips ； 6. The feed rate control circuit for gasified calcite uses a low-end secondary meter, whose control performance is poor; therefore it should be designed within the DCS control system, with the DCS sending a 4-20mA variable-frequency speed control signal to the inverter ； 7. Switch valves with an actuator weight of over 100 KG do not have brackets designed for them, resulting in excessive vibration of the valve during operation ； 8. Using the same feedback rod for the three valve-position sensors that provide feedback for the gasification on/off valve’s three possible positions does not enable true redundancy; once the feedback rod fails, all three valve-position sensors cease to function simultaneously ； 9. In the gasification black ash water wedge-shaped flow meter, only the throttling element (the wedge portion) is coated with tungsten carbide; since the area of this coating is too small, it tends to peel off. Therefore, the entire component should be coated with tungsten carbide, and the coating thickness must be no less than 3 mm ； 10. The temperature-sensing end of the thermocouple on the turntable of the gasification furnace does not have a fixing device; this can lead to displacement of the temperature sensing point during startup/shutdown and high-pressure cleaning processes, so a fixing device should be added ； 11. The flange spacing and the location of the pressure tapping points for the dual-flange level transmitters of the three gasification furnaces are not consistent; these parameters should be standardized ； 12. The lower flange of the double-flange level transmitter in the gasifier scrubber tower is designed to be at a 45° angle upward horizontally; when establishing a liquid level in the gasifier, pressure measurement at this lower flange tends to result in air accumulation, so the horizontal angle should be reduced to 10–20° ； 13. One of the double-flange level transmitters for the gasification furnace is designed to be installed on the manway; this manway tends to get clogged easily during operation, so the three level gauges should be installed directly on the body of the gasification furnace ； 14. After unboxing the oxygen valve of the gasification unit, it should be properly protected; it should be stored in its original wooden box, sealed, and kept in a closed warehouse ； 15. Before putting the instrument air pipeline into service, it is necessary to ensure the quality of purging. The purging time at each point must be no less than two hours, and the purging pressure must be no less than 0.5 MPa ； 16. Party A and the supervisor shall jointly supervise the construction unit to conduct valve leakage tests, valve body strength tests, actuator airtightness tests, and valve stroke tests; the valves can be put into use only after passing these tests ； 17. For complete sets of equipment and DCS contacts (pure display), it is recommended to use Moubus communication as much as possible, in order to reduce the utilization of DCS channels, save cables, and decrease the workload ； 18. During the valve procurement process, lifting points must be designed for valves weighing over 100 KG to facilitate their lifting and installation ； 19. The flow control valve for the gasification quench water is designed in a sleeve format; the reduced gap between the valve element, which is prone to scaling due to gray water, and the sleeve can cause the valve to stick, so another design should be used ； II. Case analysis of an engineering construction project related to instruments in a certain plant 1. The configuration developed by the design institute for that plant was directly copied from other power plants, resulting in numerous errors; through continuous improvements, it has become more adequate. 2. None of the control valves in a certain device are equipped with bypass lines; should a control valve fail, prompt action is required to address the issue, as such problems can directly affect the normal operation of the device. It is necessary to install bypass lines along with inlet and outlet shut-off valves to facilitate the maintenance of the control valves and ensure the proper functioning of the device. 3. The locations of some instrument air sampling points are not designed properly; the sampling method below the main duct makes it easy for water droplets to enter valves, positioners, and other air-controlled components when the instrument air contains water, thereby causing control failures. 4. The instrument measurement points for each device involved in the train derailment protection mechanism should adopt a two-out-of-three configuration, to prevent incorrect interlock reactions caused by a failure in one of the measurement points. 5. The valve actuators in various device components are too large and lack proper support; pipeline vibrations may cause the air supply and wiring connected to the valves to become loose, leading to unintended operations, which affects performance and poses safety risks. Changes have been added. 6. There are issues with the cable design process: the cable schedule was prepared before the DCS design, and the actual cable layout does not match the DCS wiring diagrams. The design institute compensated for this by adding intermediate terminal cabinets, which led to problems such as numerous failure points, heavy workload, and significant waste of equipment and materials. Ultimately, the intermediate terminal cabinet was canceled, and the cable schedule was redrafted. 7. For the design of the connection method for temperature instruments, it is preferable to use welded connections with protective sleeves, rather than threaded connections using straight connectors, in order to prevent the temperature sensing elements from being damaged due to excessive vibration. 8. The issue of the insertion depth of temperature instruments. The designed insertion depth should not be too long, as this will not affect the temperature measurement accuracy. Inserting it too deep can cause cantilever oscillations, often damaging the temperature sensor. 9. The instrument box for measuring gases should be placed above the measurement point ； The instrument box for measuring liquids should be placed below the measurement point. This helps to avoid problems with fluid accumulation and air buildup. 10. Choose ferrule connectors with caution; they require high precision in the pipes as well as specific standards for ferrules. Imported versions are expensive, while the performance of domestic alternatives cannot be guaranteed. Important systems have been changed to welded or threaded connections. 11. The impact of pipeline vibration on flow meters cannot be ignored. Support should be added for pipeline vibration. 12. The design institute is required to review the complete control system proposed by the manufacturer, with the aim of addressing interface issues as thoroughly as possible and meeting the technical requirements of the system supplier. Unless there are special requirements, it is advisable to ask the supplier to provide the necessary materials so that control functions can be implemented within the DCS and ESD systems, followed by joint testing to ensure everything works properly. The client should pay attention to the technical documentation provided by the manufacturer, and check for any items that do not meet the client’s requirements – such as issues related to redundancy, up-to-date hardware, genuine software, etc. – in order to avoid the manufacturer shirking responsibility later on. 13. Ensure consistent labeling of hardware, such as labels for DCS, ESD, PLC, and complete system cabinets; this should be carried out by the design institute. It helps to determine the number of cabinets, thereby facilitating issues such as cabinet placement, civil engineering openings, and installation preparations, and preventing the need for multiple civil engineering opening works. During the instrument review and FAT functional testing at the design institute, attention should be paid to the rationality of the control circuits and logical interlocks, and relevant personnel should be organized to conduct reviews. Avoid extensive logical changes and unnecessary costs in the future. 14. Issues with instrument ranges: In actual operation, the ranges of some instruments do not meet the process operating requirements. It is necessary to strengthen the review of equipment selection. 15. For DCS and ESD systems, select the latest models to ensure performance metrics such as a short historical data acquisition time (less than or equal to 1 second), fast SOE event recording speed (less than or equal to 10 milliseconds), and a historical data storage duration of 1 year. 16. For SIS systems, it is advisable to use the manufacturer’s proprietary software or third-party software that has proven successful in integration with suppliers’ systems. It is necessary to ensure that the SIS system can be updated quickly, conveniently, and easily, in order to avoid extensive manual modifications. 17. In cold regions, great attention must be paid to the selection of outdoor equipment designed to withstand low temperatures. Inspection upon delivery must be thorough; transmitters, control valves, cylinders, diaphragm heads, seals, positioners, solenoid valves, and air-controlled accessories are all items that require careful verification. 18. Care should be taken to avoid issues such as too many options when selecting valve and other instrument control equipment, poor versatility of spare parts, and large quantities of these parts. 19. For measuring the liquid level in tanks on the ground, a single-flange level gauge is a better choice; ultrasonic level gauges are not recommended, as water droplets tend to form on their sensors when the temperature is low, which can affect the measurement accuracy. 20. For wastewater flow, flow meters such as electromagnetic flowmeters are recommended; otherwise, debris in the water can easily get entangled around the measuring components, leading to inaccurate readings. 21. For level measurement in the torch water seal tank and the liquid separation tank, dual-flange transmitters are a better choice. If a differential pressure transmitter is used, care should be taken to ensure that the pressure sampling point on the positive-pressure side is not too low or located at the bottom of the tank; otherwise, debris at the bottom of the tank can easily block the pressure conduit. 22. There are many types of level gauge instruments, and a comprehensive consideration should be given when selecting equipment; factors such as safety of use and ease of maintenance come into play, and magnetostrictive level gauges are not recommended. 23. It is essential to ensure high quality for consumable analysis instruments such as PH and dissolved oxygen meters. The market is filled with various types of such instruments, and some manufacturers use probes with a short lifespan in order to win bids; this leads to inappropriate selection of equipment, resulting in inaccurate measurements and malfunctioning of the devices, causing numerous problems. Try to choose well-known manufacturers and brands. 24. Precautions for instrument heating, insulation, and anti-freezing in winter: In some areas, the lowest winter temperatures can reach minus 40 degrees, putting the system’s heating and insulation measures to a severe test. Excessively low temperatures can also affect the operation and indications of instruments, etc. All these factors can affect the stable operation of the device. Since the instrument heating pipelines are relatively thin and have high pressure resistance, it is not suitable for them to share a distribution panel with the process heating pipelines. The process heating pipelines are thicker and subject to higher pressures; as a result, poor backflow in the instrument heating pipelines can lead to freezing and blockages. It is recommended to design a separate distribution panel for the instrument heating pipelines. (1) For instrument heating pipelines, a stainless steel pipe with a diameter of Φ14 is generally sufficient; however, it should not be too long, ideally not exceeding 60 meters. Prevent several instruments from being connected in series using a single heating pipeline. (2) For the thickness of the insulation material, since the temperature here can drop as low as -38.5°C, it is recommended to use an aluminum silicate alumina spun fiber blanket insulation material with a thickness of 80 mm. For instruments that use differential pressure transmitters to measure liquid level or flow rate, especially those equipped with condensation tanks, vaporization of condensed water can occur. To prevent this, it is advisable to insert 50 mm thick insulation material between the measurement tube and the heating tube as a barrier, and then wrap them together; this approach yields good results. (3) The heat tracing for analytical instruments is rather special; using cable-based heat tracing does not yield good results. Moreover, such systems are usually quite long, with some exceeding 200 meters in length. Additionally, if the heat tracing tubes freeze and crack, it becomes difficult to deal with the situation. It is recommended to use segmented heat tracing, keeping the length within 50 meters, and to lay separate heat tracing pipes, which yields better results. 25. Precautions for instrument and control installation: (1) Water ingress was observed during the valve testing of the molecular sieve system in a certain unit; it is necessary to detail the plan and the steps involved in the testing process to prevent similar incidents from occurring. (2) In winter, when temperatures are low, the molecular sieve valve cannot function properly. Electric heat tracing and insulation have been added to all the valves and cylinders in the device’s molecular sieve system. (3) The instrument signal wire trunking should be kept away from heat sources or steam flange connections, to prevent damage to the instrument signal wires caused by steam leakage from the flanges.