another incident
From: J Sriram [mailto:----------@gmail.com]
Sent: Friday, May 27, 2011 6:53 AM
Subject: : potential hazards of pneumatic testing.
This failure happened last weekend. A GE compressor package was under nitrogen pressure test. You can see the pipe had a brittle fracture failure. I have no other details at this time. This is another illustration of the potential hazards of pneumatic testing.
This is for the expansion of the West-East Gas Pipeline project for PetroChina. It is China's longest natural gas pipeline at 2500 miles (4000 km).
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Bathula Raghuram (Mumbai - PIPING)
Sent: Thursday, February 10, 2011 12:29 PM
To: 'materials-welding@googlegroups.com'
Subject: [MW:9797] Criticality of Pneumatic pressure test vs Hydrostatic onpiping system
The following info is from various sources.
ONE worker was killed and 15 injured in an explosion on a construction site at Shanghai's Yangshan Deep Water Port.
The man who died was pierced by a flying steel rod while lying in his dormitory bed. He was pronounced dead at the scene, his co-workers told reporters.
The injured were having lunch when they were hit by flying cement, stone and metal fragments from the blast, which occurred just after noon.
"There was a big bang that sounded like an explosion," said a worker who declined to be named.
The worker who died was employed by China National Chemical Engineering No. 14 Construction Co Ltd.
Two men suffered fractures and were in stable condition last night, said Nanhui District Central Hospital. The others were released after treatment for bruises.
The accident happened at a Shanghai LNG Co Ltd work site on Ximentang Isle, north of the Yangshan Deep Water Port, an international shipping center about 45 kilometers from Pudong International Airport.
The explosion occurred when workers were adjusting equipment, according to a spokesman for the municipal work safety authority.
The men were working on a liquefied natural gas terminal that is expected to receive 3 million tons of the fuel annually after the first phase becomes operational this year.
When the facility is finished, LNG shipped by sea from Malaysia will be transformed into a gaseous state and sent to downtown Shanghai through pipes.
The explosion occurred during a pressure test of the equipment, according to the city government media office. Workers were pumping air into a gasifier when some 500 meters of the piping network burst into fragments, buckling cement crossbeams.
The cause of the rupture was still under investigation last night, the Shanghai Commission of Safety Production said.
The general contractor team includes Japan-based Ishikawajima-Harima Heavy Industries Co Ltd, Taiwan's CTCI Co and Wuhuan Engineering Co Ltd, said the media office.
A few more pieces of information about the explosion according to a report (in Chinese) issued by the owner and construction contractor a couple of days after the accident:
· The explosion was caused by a sudden flange failure while the workers were conducting pneumatic testing of a 36 inch diameter line, 600m long segment, laid out in an S shape.
· The testing pressure was 15.6MPa (2,262psi), and the explosion occurred when the system pressure reached 12.3 MPa (1,784psi).
· The explosion was caused by the rupture of a flange at the end of the test section. The 2nd and 3rd last pictures in the attachment show the face of rupture. The flange was for future connection.
· The rupture occurred in the flange body, 30 to 40 mm from the flange to pipe weld. It's a "clean" break, i.e., brittle failure. The cause of the flange failure was under investigation.
· The worker killed by a piece of flying scaffold pipe was outside the entrance door to the dorm (not lying in his bed according to news below), 350 m away from the explosion.
· The injured workers were about 100m away from the explosion (installing insulation).
· The explosion is likely to delay start up of the project by 6 months. The LNG terminal was to be ready to receive shipment in a couple of months.
· The accident was reported in the news media in China and Hong Kong the next day.
Pneumatic testing of such a large and long pipe at such a high pressure (the accumulated the energy is huge) should never be done.. In my opinion, the test should have never been allowed in the first place.
Please note that, due to the huge accumulated energy in the system the sudden failure of the flange not only causes a huge explosion at the rupture location but also will violently jerk the whole pipe line to cause extensive damage along the entire length. The crushing of concrete pipe supports shown in the pictures is the evidence.
From: kannan.sundaram@linde-le.com
Sent: Friday, February 29, 2008 3:43 PM
To: materials-welding@googlegroups.com
Subject: Criticality of Pneumatic pressure test vs Hydrostatic onpiping system
Just to add, apart from the material brittleness issue, this is also the fundamental reason why we find all heavy equipment's and construction machinery's are having hydraulically operated arms. And low power equipment's in the range of around 10barg, are pneumatically operated. The author's equations are different interpretation of Bernoulli's theorem known to every body, does say the same of the incompressability...and not zero.
But the site situations are different and as what happens in the engg. office lacks the visualisation of the site difficulties. So sometimes the project manager has to override certain technical theories to avoid 'over safety' requirements. There has been a situation in one of the LNG project where engg. office wanted hydraulic test in most of the lines and the site went ahead with pneumatic with client's concurrence violating the code. The plant is functioning without any problems for the past 5 years. The client was Shell.
It depends on the engg. as well as the construction team, not just alone by the engg. team.
With regards,
Kannan Sundaram.
| "Bathula Raghuram \(Mumbai - PIPING\)" <r.bathula@ticb.com> 29/02/2008 08:47
|
|
FYI!
Hereto attached the criteria for evaluating the potential dangerous of
pneumatic test vs hydrostatic test from safety point of view.
In this concern, we should always remember that is necessary to evaluate
the design aspects of material selection for piping lines to be
submitted to pneumatic test due to Process requirements: in these cases
ASME B 31.3 require that the materials be guaranteed against their
brittleness at the ambient temperature during pneumatic test.
Typical cases are the plants where the ambient temperature could reach
even minus 50^C (in particular to places like Azerbaijan, Kazakhstan or
Chinese plants on Mongolian border).
--
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