Principles and practical methods for draining waste gas from instrument air supplies
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The specifications for instrument air supply drainage state that drain valves should be installed at the lowest point, at the ends of the lines, and at the liquid collection points. In my case, a drain valve was installed on the first floor; the main pipe is 1 inch in diameter, but no drain valves were installed on the second and third floors. A 1-inch stainless steel pipe runs from the first floor to the upper floors, where the main pipe remains 1 inch in diameter, while the pipes leading to the second and third floors are 1/2 inch in diameter. So, should drain valves be installed on the second and third floors? I think they should be. What do you think? Because every floor has a lowest point, there will always be areas where water accumulates. My suggestion is to add a sewage outlet on each floor.
I don’t agree with you; I’m not sure if there’s any standard for this. Generally, for the drainage of instrument air, I install it at the bottom of the buffer tank and simply carry out regular drainage.
We don’t have any buffer tanks here; the instrument air coming from the process goes directly into the control valve.
Our facility has a buffer tank; there is a filter screen before the fluid enters the tank, and waste liquid is discharged from the bottom of the buffer tank
This post was last edited by sgq1313 on 2012-4-1 09:16. Another approach is to install a drying and filtering device on the main instrument air pipeline (I’m sorry, I still can’t remember what that device is called). Regularly draining waste fluid is also an option; I’ve never seen such devices installed on each floor – it’s not necessary. The instrument air itself meets the requirements.
During the equipment installation and commissioning phase, if the gas source used for instrument installation and commissioning comes from equipment installed in Phase 2 or later, the gas supplied by equipment from earlier phases can be utilized. Such gas has generally undergone processes such as filtering, oil removal, and water removal. For the entire instrument gas supply system, what needs to be done is to clean and purge the gas supply pipelines. Installing blow-off valves on the gas supply pipelines will meet the usage requirements. The gas supply system is powered by a separate instrument air compressor; however, this instrument air is not thoroughly filtered or dehydrated and degreased. As a result, strict requirements exist for waste removal from the other gas supply pipelines – not only must waste and drain valves be installed on the buffer tanks, but such valves are also needed on the gas pipelines themselves.
1. What is the meaning of the first letter in the alphabetical code used in instrument tag numbers? A: Analysis C: Conductivity D: Density F: Flow rate H: Manual L: Level M: Moisture or humidity P: Pressure, vacuum Q: Quantity or number of units R: Nuclear radiation S: Speed, frequency T: Temperature W: Weight, force Z: Position 2. What is the meaning of the master tag number as a subsequent letter in instrument tag numbers? A: Alarm C: Control E: Sensing element G: View mirror, observation H: High I: Indicator L: Light (low) M: Medium R: Recording or printing S: Switch, interlock (e.g., PI: Pressure gauge, PS: Pressure switch) 3. What are the reasons for large fluctuations in measurement values or a large static error during the operation of a pneumatic regulator? How to handle it? Answer: Reason: a) Improper adjustment of PID parameters. b) The static error of the regulator has not been set properly. c) Blockage or leakage in the external signal piping of the instrument. d) Transmitter and control valve failures. Treatment: a) Re-adjust the PID parameters. b) Readjust the static error. c) Check the signal piping. d) Check and address faults in transmitters and control valves. 4. What is the working principle of a diaphragm pneumatic control valve? Answer: When signal pressure is applied to the diaphragm chamber, it generates a force that causes the push rod to move; the spring is compressed, and the resulting reaction force balances the thrust exerted by the signal pressure on the diaphragm (dynamically). The displacement of the push rod is the stroke of the pneumatic actuator. 5. How to choose a on/off control valve? Answer: It is mainly considered from the perspectives of production safety and process requirements; when the signal pressure is interrupted, it is necessary to prevent equipment damage and harm to operators. If the valve poses little hazard when in the open position, a air-shut type should be chosen; otherwise, an air-open type should be selected. 6. Why doesn’t the locator move even though there is an air supply control valve? Answer: 1. The constant-throttle orifice of the amplifier in the positioner is blocked. 2. Moisture in the compressed air accumulates at the amplifier ball valve. 7. Describe the daily maintenance tasks for pneumatic instruments Answer: 1. Check whether the instrument output is normal. 2. Check whether the instrument air supply is normal. 3. Check the instrument connection pipelines and valves for leaks, damage, and corrosion. 8. What aspects should be considered when repairing interlocked instruments that are in operation? Answer: 1. Inspection and maintenance should be carried out by two or more persons. 2. Before maintenance, the consent of the operator on duty must be obtained, and a work order must be issued. 3. Maintenance must be carried out after the interlock is disconnected (released). 4. After the maintenance is completed, the on-duty operator should be notified to be present for verification and to restore the interlock. 9. What problems can occur with control valves at low opening degrees? Answer: 1. When the valve is opened to a small degree, the throttling gap is small and the fluid velocity is high, making it easy for the liquid medium to flash. As a result, mechanical erosion or cavitation occurs on the throttle device, thereby shortening the valve’s service life. 2. When the valve is opened to a small degree, the unbalanced forces acting on it are large, resulting in poor stability of the valve and a tendency to oscillate. 【Nuoding Instrument Information Network】
Oh, it’s the manager who adds them; the branches depend on the situation. Got it! Thanks to the moderator!