Precautions for Instrument Installation to Prevent Leaks and Liquid Ingress (Revised Discussion Version)
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This post was last edited by Yongshi on 2023-9-7 09:34: Measures to Prevent Leaks and Fluid Ingress During Instrument Installation (Revised Discussion Version). After the instrument is installed, the following precautions should be taken to avoid leaks during operation (internal leaks, external leaks, water ingress): 1. Use qualified gaskets during installation: Select the appropriate type of gasket based on the physical and chemical properties of the medium (temperature, pressure, corrosiveness, structure), as well as the type of flange and the lining material of the pipeline. Materials available include rubber, asbestos, polytetrafluoroethylene, graphite paper, red copper, aluminum, 304L/316L. Types of gaskets include flat gaskets, gaskets without alignment rings, gaskets with (inner/outer) alignment rings, wound gaskets, graphite-reinforced composite gaskets (for integrated ball valves), and octagonal gaskets. Thickness: 3.5–5.5 mm; the thickness of the wound steel strip should be greater than that of the alignment ring. Sealing surface: The flange sealing surface must be smooth and even, with proper sealing ridges； Certain anti-corrosion coatings need to be smooth or padded ； The surface of the gasket is clean and smooth, without any axial scratches ； 2. Close the drain valve and tighten the drain plug ； 3. Ensure that the nuts at all joints of the pressure guide tubes are firmly tightened ； The insertion depth and deformation of the sampled ferrule connectors are normal ； 4. Fastener bolts: Use a small hammer to check the bolts; a dull sound indicates looseness ； Cloudy means tight ； (Generally, a hammer is used to check bolts; the correct method is to hold the handle and strike the side of the nut. If it is loose, a clear sound is produced and the hand feels vibration as well) ； If it is tightened, a muffled sound is produced and no vibration can be felt by hand.) 5. PTFE tape and sealant are used at the NPT thread connection, and it has been tightened properly ； Appropriate flat washers (PTFE, copper, etc.) are used at pipe thread connections such as those where local pressure gauges are installed, and the nuts have been tightened ； 6. Important valves must have completed pressure testing and been signed off ； 7. The spare electrical wiring holes for transmitters, junction boxes, positioners, etc. have been sealed with explosion-proof plugs ； 8. The explosion-proof flexible hose and explosion-proof gland sealing washer have been tightened, and the cable is not loose ； 9. The waterproof bend before the cable enters the instrument is correct ； 10. The outlet holes for the instruments’ wiring are located in the middle of the cable tray, and they are properly sealed (using plate connectors, sealant, and sealing putty). 11. At the bottom of the tubing used for instrument wiring, a drain tee is used; if necessary, holes are drilled in the tubing itself to ensure proper drainage ； 12. The rubber gasket at the instrument’s sealed end cover is in good condition, and the end cover has been tightened properly ； 13. The pretreatment system for gas analysis instruments is well-designed and operating properly: heaters, temperature controllers, cyclonic coolers, coolers, adsorbers, condensate separation tanks, etc., are all in good working condition ； 14. The combustible and toxic gas alarm should be installed at a height of 300–500 mm above the ground level (note: refer to the actual floor level where the device will be installed) ； 15. The necessary protective boxes and rain covers are in good condition. 2023.9.7
To ensure that there are no leaks or spills of liquid after the instrument is installed, please follow these guidelines: 1. Choose the appropriate gasket during installation: Select a suitable gasket material based on the physical and chemical properties of the medium (temperature, pressure, corrosiveness) as well as the structure of the pipeline, such as rubber, asbestos, polytetrafluoroethylene, etc. At the same time, select gaskets of different structures as needed, such as flat gaskets, centering rings, and wound gaskets. The thickness of the gasket should generally be between 3.5 and 5.5 mm. 2. Close the drain valve and tighten the drain plug. 3. Ensure that all the nut connections of the pressure guide tube are firmly tightened, and check randomly to confirm that the ferrule connections are properly inserted and not deformed. 4. Perform a spot check on the fastening bolts: Tap the bolts with a small hammer; a clear sound indicates that they are loose, while a muffled sound indicates that they are tightened. 5. Use appropriate sealing materials, such as PTFE tape or sealant, at the NPT threaded connections, and ensure they are properly tightened in place. For pipe thread connections, such as at local pressure gauges, use appropriate flat washers and tighten the nuts. 6. Ensure that the spare electrical wiring holes have been sealed with explosion-proof plug plugs. 7. Ensure that the explosion-proof flexible hose and explosion-proof gland gaskets are properly compressed, and that the cables are not loose. 8. A proper waterproof bend must be installed before the cable enters the instrument. 9. The outlet holes for the instrument cable trays should be located in the middle of the tray, and they must be sealed, using methods such as plate connectors and sealant. 10. Use a drain tee at the bottom of the instrument wiring conduit; if necessary, drill holes yourself to ensure proper drainage. 11. Ensure that the rubber gaskets at the sealed end caps of the instrument are intact and have been tightened properly. 12. Ensure that the pretreatment system of the gas analysis instruments is properly designed and operating correctly, including heaters, temperature controllers, cyclonic coolers, coolers, adsorbers, condensate separation tanks, etc. 13. The combustible and toxic gas alarm should be installed at a height of 300–500 mm above the ground (depending on specific conditions). 14. Install a protective box or rain cover as necessary to ensure the safety of the instruments. The precautions provided above should help you prevent leaks and the entry of liquids after the instrument has been installed. .
“Important valves must have completed the pressure testing and been signed off； ”This item is also necessary to confirm that there are no leaks in the valve packing, valve body, and actuator.
Thank you very much for your additional explanation. Indeed, when installing leak and fluid-intrusion prevention measures on instruments, for critical valves, it is necessary to ensure that pressure testing has been carried out and that this is documented with signatures, in order to confirm whether there are any leaks in the valve gaskets, valve body, or actuator. This is a very important step, as it ensures the proper operation of the valve and its sealing performance. .