Hydrotest failure
Hydrotest failure
(OP)
Here is something from other company for lesson to be learned:
Quote:
"Every now and then you get reminded why you hydrotest and why you try to minimize how often you do NDE in lieu of hydro.
The fabrication, consisting of 24" sch. 30 (0.562 wall) pipe & fittings, was in the process of being hydro-tested when the failure occurred. There was approximately 80 linear feet of piping included in the test. The piping was to be pressurized to
2160 psi. When the test pressure reached 1740 psi, there was a loud noise, similar to a gunshot.
4 workers were impacted by the water pressure release. Two were thrown under a truck – One received a bad contusion on his head when he hit the under-carriage of the truck, and the other worker received a severe laceration to his cheek. A third worker lost several teeth when he was hit in the mouth by test equipment which was propelled by the rush of water. Luckily, the fourth worker was not injured.
This is a very sobering situation considering the number of hydro tests we administer during Construction. It is very easy to get lulled into a false sense of security after looking at hundreds of hydro & pneumatic tests. It is easy to begin thinking, “I've looked at a thousand tests - nothing's going to happen..." It is easy to become complacent with hazards you have in your job every day." unquote.
See attached photos:
Quote:
"Every now and then you get reminded why you hydrotest and why you try to minimize how often you do NDE in lieu of hydro.
The fabrication, consisting of 24" sch. 30 (0.562 wall) pipe & fittings, was in the process of being hydro-tested when the failure occurred. There was approximately 80 linear feet of piping included in the test. The piping was to be pressurized to
2160 psi. When the test pressure reached 1740 psi, there was a loud noise, similar to a gunshot.
4 workers were impacted by the water pressure release. Two were thrown under a truck – One received a bad contusion on his head when he hit the under-carriage of the truck, and the other worker received a severe laceration to his cheek. A third worker lost several teeth when he was hit in the mouth by test equipment which was propelled by the rush of water. Luckily, the fourth worker was not injured.
This is a very sobering situation considering the number of hydro tests we administer during Construction. It is very easy to get lulled into a false sense of security after looking at hundreds of hydro & pneumatic tests. It is easy to begin thinking, “I've looked at a thousand tests - nothing's going to happen..." It is easy to become complacent with hazards you have in your job every day." unquote.
See attached photos:





RE: Hydrotest failure
RE: Hydrotest failure
Based on 2160 psi test pressure, assume the design pressure is 1440 psi ....
Seems to me that if this were designed to B31.3 with no corrosion allowance or tolerance deducted and an allowable stress of 20ksi, the minimum wll would be 0.84 in. or 50% greater than stated above.
Maybe it was much stronger material ?
RE: Hydrotest failure
RE: Hydrotest failure
RE: Hydrotest failure
One really shouldn't be conducting hydrostatic tests unless one knows what one is doing.
RE: Hydrotest failure
RE: Hydrotest failure
Is there a mistake somehow with these numbers reported ?
A quick review of the allowable stress tables of B31.3 shows no material (to me) that would be acceptable for these conditions.
Please tell us the material of the piping system and the Piping Code of Record for the project
I believe that there also was a material failure on the Chinese elbow intrados....but this is co-incidental.
Anyone ?????
RE: Hydrotest failure
With regard to released energy, I performed a short calculation with Bernoulli using SI units:
speed = sqrt (2*1740/14.5*100000/1000) = 155 m/s
which seems to me fast enough to throw a man.
Regards,
Stefano
RE: Hydrotest failure
RE: Hydrotest failure
http://www.safteng.net/index.php?option=com_conten...
We're not the first people to be suspicious that something is wrong with this report- see the comments below the article.
The speed of the water is less relevant than the volume of water that must be lost in order to dissipate the energy stored in the elastic stretching of the pipe and the elastic compressibility of the water. In the absence of substantial trapped air, this volume is very small. By my rough calc, the amount of water necessary to take the steel all the way to the onset of yield would be about a cubic foot, with perhaps another whole cubic foot or two for the compressibility of the water itself. Propelled out of a crack, it will not be coming out in a nice coherent jet- it will definitely spray. The likelihood that this small amount of water hits several people directly or via "thrown testing equipment" with sufficient force to throw the people any distance would seem very low indeed- UNLESS there were a LOT of trapped air to propel a vastly larger amount of water.
RE: Hydrotest failure
RE: Hydrotest failure