Production Technology [Weekly Topic]: How to Make a Negative Pressure Tower Airtight (2011-02-14~02-20)

This post was last edited and replied to by Benbenxuan on 2011-2-14 16:47. Reply 1# shmily327: The airtightness test for negative-pressure towers is the same as that for positive-pressure towers. After pressurizing with positive pressure, check the sealing points using soapy water to identify any leakage points and their locations. If pressure is maintained after applying negative pressure, any leakage points cannot be detected. Therefore, it is better to use positive pressure airtightness. However, attention must be paid to the test pressure to avoid damaging the equipment. Oxidation can be avoided by using airtight low-pressure nitrogen.

Could we use the positive-pressure tower method, fill it with air to reach the pressure allowed by the system, and then use soapy water to check for leaks?

Generally, a pressure test is conducted first, followed by a vacuum pumping test

The last edit to this post was made by Refinery Operator on 2011-6-8 at 12:10. After the installation or maintenance of the vacuum tower, it is necessary to first conduct a pressure test to detect leaks, and then fix any such issues； Next, evacuate the system and maintain that vacuum state for a period of time to check whether there is any change in the system pressure. If the vacuum level cannot be maintained, break the vacuum and conduct a pressure test to identify any leaks or internal leakage in the valves, then address those issues ； Finally, the system was evacuated once more in a systematic manner and the vacuum was maintained for a period of time; since the system pressure did not change, it was confirmed to be airtight.

This post was last edited by Refinery Operator on 2011-6-8 at 12:10. Airtightness procedures: 1. Close the system isolation valves, as well as the vent valves and drain valves; open the internal valves of each system; close the safety valves of each tower; close the pressure relief and vent valves for instruments; open the valves for pressure gauges; close the valves for vacuum instruments. 2. The system must be airtight; check each sealing point using soapy water. For negative-pressure systems, a pressure drop of less than 0.005 MPa/h during the positive-pressure test is considered acceptable. Airtight operation 1. Inspection items: (1) All flange and valve connections (including valve packings), the joints of various level gauges and pressure gauges, drain valves, vent valves, etc. (2) All removed piping, fittings, valves, and instrument components ； (3) All parts that have not undergone strength testing. (4) All repaired parts. (5) The inlets, outlets, and manhole areas of all pump equipment. (6) Check for internal leakage in the main valves, such as control valves, system vents to the flare, and connection valves for raw material and product pipelines to the boundary area. (7) Check for leaks at the location where the blind flange is installed. 2. Handling of leakage points: (1) Mark or label the areas where there is a leak, and keep a record of them. After maintenance, conduct tests until it is eliminated. (2) The treatment of the leak site should be carried out after depressurization or venting. Negative pressure: Create negative pressure in the system and maintain it. Check the voltage drop.

Freshwater pressure testing, pressure 0-----2 kilograms.

This post was last edited by Refinery Operator on 2011-6-8 at 12:10, using a nitrogen pressure test and a soapy water test to identify possible leak points.

We still use positive pressure testing, with the test pressure determined according to the equipment’s design specifications. After inflating using the conventional method, check each connection with soapy water

The last edit to this post was made by Refinery Operator on 2011-6-8 at 12:11. Reply to 1# shmily327: First perform a leak test under positive pressure using soapy water; once there are no issues under positive pressure, then conduct the leak test under vacuum