Air separation and air tightness issues

Facecat has discussed this kind of problem, and the post tid--356801 can solve the original poster's problem.

Thank you. The main reason is that using nitrogen is too expensive. We plan to use steam to airtight first, and then use nitrogen to increase the pressure to save consumption. However, we are afraid that thermal expansion and contraction will affect the airtight effect.

Just use steam to test the pressure, and then use liquefied gas to catch up with the steam while keeping the air tight at 0.6MPa, 1.0MPa, and 1.6MPa. This is more cost-effective than using nitrogen.

I tried using steam to get 3.0MPa, but it doesn’t work. I don’t know how you made it airtight and how can you guarantee it’s qualified?

No, it’s better to use nitrogen. You can use medium-pressure nitrogen to test the pressure.

The air tightness test is mainly to check whether there is leakage in each connection part of the container. Pressure vessels whose medium toxicity is extremely or highly hazardous or whose design does not allow for trace leakage must undergo an air tightness test. 　　Pressure vessels should undergo air tightness tests according to the following requirements: 　　(1) The air tightness test should be carried out after passing the hydraulic test. For pressure vessels whose design requires air pressure testing, the air tightness test can be conducted simultaneously with the air pressure test, and the test pressure should be the pressure of the air pressure test. 　　(2) For pressure vessels made of carbon steel and low alloy steel, the temperature of the test gas should not be lower than 5°C. For pressure vessels made of other materials, the temperature should be as specified in the design drawing. 　　(3) The gas used in the air tightness test should be dry, clean air, nitrogen or other inert gases. 　　(4) When conducting air tightness tests, safety accessories should be fully installed. 　　(5) The pressure should rise slowly during the test. After reaching the specified test pressure, the pressure should be maintained for 10 minutes, and then reduced to the design pressure. All welds and connection parts should be inspected by applying soapy water. No leakage is considered qualified. If there is a leak, perform the hydraulic test and air tightness test again after repair. 　　The air tightness test is different from the air pressure test. First of all, their purposes are different. The air tightness test is to test the tightness of the pressure vessel, and the air pressure test is to test the pressure strength of the pressure vessel. Secondly, the test pressures are different. The air tightness test pressure is the design pressure of the container, and the air pressure test pressure is 1.15 times the design pressure.

The air tightness test of our company's gas separation device uses an air compressor to test the air tightness, and the pressure is the operating pressure.

Small devices can use steam, but large devices are recommended to use nitrogen.

We use medium-pressure nitrogen test pressure of 3.0MPa, which meets the requirements.

Don’t make a big deal just to save trouble! Picture of explosion at Shanghai Yangshan Port LNG project site At around 12 o'clock today, an explosion occurred at the Yangshan Deepwater Port LNG project site, resulting in the death of 1 worker and 16 injuries. At around 12 o'clock, a violent explosion suddenly occurred at the Yangshan Deepwater Port LNG project construction site. The isolation pier 30 meters away was blown away, and the thick pipes on the construction site were twisted into a ball. It is understood that the intermediate medium gasifier exploded during the debugging process. According to the person in charge of the construction site, according to the statements of many injured people, there were more than 90 workers working at the construction site, most of them from Puyang, Henan Province. The gasifier was filled with air at that time, and it suddenly exploded for unknown reasons. The accident resulted in the death of one worker and injuries to 16 others, two of whom suffered serious fractures. Worker Qu Yongchong was only more than ten meters away from the burst LNG pipeline. He also saw gas filling the top of the pipeline. “Bang, bang, bang... like a mortar. ”Then dust and smoke rushed in, and the steel pipes on the scaffolding came crashing down one after another. 　　A worker said that the pipe network began to conduct air pressure tests a few days before the Spring Festival, but no problems such as gas leakage have ever occurred. But this time they did not know that the pipeline was undergoing gas pressure testing, and the construction site did not notify them to evacuate. The injured worker was sent to Nanhui Central Hospital for treatment. Picture of Morning News reporter Zhao Jing and Wang Haoran of this page. At about 11:20 yesterday morning, the Ximentang LNG project site in Xiaoyangshan emitted continuous loud bangs. The explosion lasted for about three or four minutes. The isolation pier 30 meters away was blown away, and the thick pipes on the construction site were twisted into a ball. The accident resulted in the death of one worker and injuries to 27 others, including three with serious fractures. 　　It is understood that the Xiaoyangshan LNG pipeline of Shanghai Liquefied Natural Gas Company where the pipeline burst occurred was undergoing a gas tightness pressure test. The diameter of the pressure test pipeline was 36 inches. The person responsible for the construction was China Chemical Engineering No. 14 Construction Co., Ltd. Currently, the cause of the accident is under investigation. 　　on site: 　　The 36-inch diameter pipe is twisted into a twist. The Xiaoyangshan Ximentang LNG project site is about five or six kilometers away from the Donghai Bridge. Reporters rushed to the scene of the incident yesterday, but the scene had been cordoned off. Looking from a distance, there are two huge gas storage tanks tens of meters high on the construction site, surrounded by a thick network of gas pipelines. 　　After the explosion, some gas pipelines were broken and some were twisted into twists. ； Cement bricks and scaffolding steel pipes can be seen everywhere. According to a safety personnel at the construction site, pipes burst in many places, and the explosion lasted for at least three to four minutes. 　　Worker: 　　The gas leak occurred around 11:20 a.m. yesterday, only a few minutes before the workers took their lunch break. Construction workers were building scaffolding near the pipeline, worker Qu Yongchong told reporters: “According to the project arrangement, we need to carry out heat insulation and cold-proof construction on the pipeline, which means multi-layer wrapping of the gas pipeline. ” 　　The pipeline is about 7 meters high from the ground, and the construction relies entirely on scaffolding. The worker, Master Xin, had just gotten off the scaffolding and was going to have lunch. He saw smoke filling the pipe more than 10 meters away from him. “I was wondering at the time, how could the pipes be so good that they were smoking? ”Before he could figure out what was going on, he heard an explosion. “Now that I think about it, the smoke at that time may have been a small amount of gas leaking from the pipe. ” 　　Worker Qu Yongchong was only more than 10 meters away from the burst LNG pipeline. He also saw gas filling the top of the pipeline. “Bang, bang, bang... like a mortar. ”He clearly heard the loud sound of the explosion, then dust and smoke rushed towards him, and steel pipes and other materials on the scaffolding came crashing down. 　　After the explosion, the scene was chaotic, and people instinctively ran away to survive. 　　Ding Li (pseudonym) lying on the hospital bed said: “After a loud noise, I subconsciously ran away from the pipe, but a burst of soot obscured my vision. ” Ding Li still remembers that during the escape process, the workers around him screamed in pain from time to time. Ding Li said that the power of the air wave not only tore apart pipes, but also rolled up building materials on the ground, such as bricks and other items into the air. Subsequently, these objects hit him and some co-workers as they fell. "A co-worker who was already eating lunch was also hit by a brick and his face was covered with blood. ”Ding Li said. 　　The reporter noticed that Ding Li had scratches on his head and forehead. Another injured worker, Pang Hong (pseudonym), whose face and clothes were covered with mud, said that the scene at the time of the incident was like a "sandstorm". He always felt that something was sticking to his back and chest, pressing on his chest, and it was difficult to breathe. Pang Hong said that he was hit by something in his left leg while running and suddenly fell to the ground. 　　reason: 　　The investigation is still ongoing. According to the statements of many injured people, there are more than 90 workers working at the construction site, and most of them are from Puyang, Henan. Master Xin Hualei told reporters, “We came to the construction site years ago and did not go home during the Spring Festival. We have been working for more than a month. ” 　　According to a worker, the pipeline network began gas pressure testing a few days before the Spring Festival, but no problems such as gas leakage have ever occurred. But this time they did not know that the pipeline was undergoing gas pressure testing, and the construction site did not notify them to evacuate. 　　It is understood that the Xiaoyangshan LNG pipeline of Shanghai Liquefied Natural Gas Company was undergoing a gas tightness pressure test when the accident occurred. The diameter of the pressure test pipeline was 36 inches. The general contractor responsible for the construction was a consortium composed of Japan's Ishikawashima Harima Heavy Industries, Taiwan's Zhongding and Wuhuan Technology. The person responsible for the construction was China Chemical Engineering No. 14 Construction Co., Ltd. Currently, the cause of the accident is under investigation. 　　Hospital: 　　Opening a green channel to rescue the wounded Dr. Shi, director of the emergency department of Nanhui Central Hospital, said that after receiving notification of a large number of injured, the hospital immediately opened a green channel and mobilized experts from the hospital's surgery, neurology, orthopedics and other fields for consultation. 　　The injured Ding Li said that within about 40 minutes of the accident, the first ambulance arrived at the scene. At the same time, before the ambulance arrived, the construction site also mobilized its own vehicles to transport the injured to the hospital. 　　One person died in the accident and more than ten people were injured and sent to hospital. According to reports, the deceased’s surname was Li, his age was 37 years old, and he belonged to the 14th Chemical Construction Company. ； Among the injured, 3 suffered serious fractures and 5 were hospitalized for observation. The remaining injured left the hospital yesterday afternoon after examination and treatment. 　　Among the three workers with fractures, 36-year-old Yan Youjun was the most seriously injured and had to undergo surgery. Two other injured, one * * A leg was broken and another suffered a broken lumbar vertebra. According to Dr. Wu from the hospital's orthopedics department, he will be discharged from the hospital soon after receiving treatment. Screen shot of the accident scene, news attachment, Yangshan LNG project planned to be put into trial operation in February. As a major energy project and key project in Shanghai, the Yangshan Liquefied Natural Gas (LNG) project is planned to be put into trial operation in February 2009, with an annual receiving capacity of 3 million tons of LNG. 　　The Yangshan LNG project is constructed in two phases. The first phase includes an LNG receiving station and a submarine gas transmission trunk line. The construction scale is to meet the annual import of 3 million tons of LNG and supply about 4 billion cubic meters of LNG to Shanghai urban area every year. It has become a world-class clean energy supply base and the main gas source of Shanghai’s natural gas supply system. Together with the West-East Gas Transmission and East China Sea Natural Gas, it has formed a multi-gas source joint supply situation. 　　Among them, the LNG receiving station is located on Ximentang Island in Yangshan Deepwater Port Area. It mainly constructs three 160,000 cubic meter LNG storage tanks, three LNG unloading arms and other corresponding recovery, transportation, gasification facilities and public supporting projects. It covers an area of ​​39.6 hectares and has reserved a second-phase expansion site. ； The LNG special ship terminal includes a special LNG ship terminal of 80,000 to 200,000 cubic meters and supporting facilities for heavy cargo terminals. The submarine gas transmission pipeline completed this time is through the construction of a DN900 submarine gas transmission trunk line. After landing on the east side of the East China Sea Bridge, it is transported by the land gas transmission pipeline to the Lingang New City Gas Transmission Station, and then enters the Shanghai urban natural gas high-pressure trunk network system. Related topics of "Pictures of explosions at the Shanghai Yangshan Port LNG project site": Shanghai LNG project site explosion photos, Shanghai Yangshan Port, Shanghai Yangshan Port construction site explosion pictures, Shanghai Yangshan Port explosion "Shanghai Yangshan Port LNG project site explosion pictures" This article comes from Fly Information Group http://blog.ppzhe.cn , starting address: http://blog.ppzhe.cn/newsunion/1578.html

You can use steam first and then nitrogen. It’s best not to use air

Our company's 90,000 tons/year gas fractionation unit uses nitrogen for airtightness and replacement. Because it is easy to leak the floating head of the heat exchanger with steam, we have not used steam pressure testing.

If steam is used, it will be difficult to clean the condensed water from the system pipeline, and future operations will be very troublesome.

, steam is not good, if you don’t have nitrogen, you can use compressed air directly, just find a car to pressurize it. Generally, you don’t need to perform air sealing after testing the water pressure with a pump. Personal opinion.