[Sftyvlv]

A project the first yr welding apprentices completed.
1 1/2"pipe inside 2" pipe welded in the 2,5 and 6f positions. This mock up is used to simulate socket weld fittings. Welded with 3/32 6010 and 7018.
This pipe spool was then hyroed to 650 psi. All 14 apprentices passed with one project pumped to 840 psi with no leaks.
Proud of our Ua welding apprentices.

20170315_155429.jpg (39.22 KiB) Viewed 2173 times

[Otto Nobedder]

Nice work, Safety Valve!

Pneumatic and hydro testing are great skills to learn as you progress, as well.

Here's a pneumatic I did on my own work, sch. 160 304, 1/2" pipe (after 25% x-ray).

GEDC1506.JPG (183.44 KiB) Viewed 2158 times

Steve S

[exnailpounder]

Nice work, Safety Valve!

Pneumatic and hydro testing are great skills to learn as you progress, as well.

Here's a pneumatic I did on my own work, sch. 160 304, 1/2" pipe (after 25% x-ray).

GEDC1506.JPG

Steve S

It only got to 9675...what happened after that

[Otto Nobedder]

9680 was the goal. The Haskell pump I achieved this with was rated for 9000. I pushed it a bit...

The test was 110% of maximum working pressure (8800 psi).

It actually operates at 8000 PSI,

Steve

[exnailpounder]

That is some scary pressure. I used to get nervous filling SCUBA tanks, or should I say overfilling SCUBA tanks to 4000 psi. which reminds me of a question...If a 330cf bottle of air (or any gas) ruptured and suddenly released the whole volume of gas, what would it do to a building if all the doors and windows were shut? I always wondered that when I worked in a dive shop when I was alive.

[Farmwelding]

That is some scary pressure. I used to get nervous filling SCUBA tanks, or should I say overfilling SCUBA tanks to 4000 psi. which reminds me of a question...If a 330cf bottle of air (or any gas) ruptured and suddenly released the whole volume of gas, what would it do to a building if all the doors and windows were shut? I always wondered that when I worked in a dive shop when I was alive.

I don't know but I want to have a camera to film it quite a few yards(meters for those across the pond ) away from it. If you haven't seen the myth busters tank drop test video watch it. They take I beleive a 330 tank and knock the head off and it goes through cinder blocks a few times.

[electrode]

I always wondered that when I worked in a dive shop when I was alive.

You mean you are actually dead now?

[Farmwelding]

I always wondered that when I worked in a dive shop when I was alive.

You mean you are actually dead now?

I guess Jeff died and now his ghost has taken over him. Endless alcohol and can weld without gloves and a helmet and in any position with no problems. His wife is actually not happy though because Jeff has decided to use his ghost abilities to scare the living hell out of her all the time bu sneaking around unnoticed and then using a haunting voice. From now on he is phantom Jeff.

[electrode]

And she has to wear that gas mask looking welding hood after he stinks up the bathroom with a "Mr. Hankey".

[exnailpounder]

That is some scary pressure. I used to get nervous filling SCUBA tanks, or should I say overfilling SCUBA tanks to 4000 psi. which reminds me of a question...If a 330cf bottle of air (or any gas) ruptured and suddenly released the whole volume of gas, what would it do to a building if all the doors and windows were shut? I always wondered that when I worked in a dive shop when I was alive.

I don't know but I want to have a camera to film it quite a few yards(meters for those across the pond ) away from it. If you haven't seen the myth busters tank drop test video watch it. They take I beleive a 330 tank and knock the head off and it goes through cinder blocks a few times.

I saw the Mythbusters episode but I am talking about a tank rupture...I know it could never happen but I always wondered.

[Sftyvlv]

That's why water is used. Unlike a gas (compressed air, nitrogen etc) you can't compress water. Inside a vessel the water will act as a solid and when released to the atmosphere it sprays harmlessly for a split second and drops to atmospheric pressure. If the same was done with a gas...........well you saw Mythbusters.
Enuf said.

[exnailpounder]

I always wondered that when I worked in a dive shop when I was alive.

You mean you are actually dead now?

I guess Jeff died and now his ghost has taken over him. Endless alcohol and can weld without gloves and a helmet and in any position with no problems. His wife is actually not happy though because Jeff has decided to use his ghost abilities to scare the living hell out of her all the time bu sneaking around unnoticed and then using a haunting voice. From now on he is phantom Jeff.

Gosh you guys are some serious thread-jackers ain't ya?

[Farmwelding]

Shut up Jeff, remember you're dead

On a more serious note-when you pressure test a vessel with water-how do you find the failure point? Does a small pinhole happen or is it a reading somewhere in the tubing.

[exnailpounder]

Shut up Jeff, remember you're dead

On a more serious note-when you pressure test a vessel with water-how do you find the failure point? Does a small pinhole happen or is it a reading somewhere in the tubing.

https://en.wikipedia.org/wiki/Hydrostatic_test
Very interesting science.

[Sftyvlv]

An engineer will decide the test pressure. He bases his calculations on code requirements from ASME (American Society of Mechanical Engineers). They are the regulatory body responsible for pressure vessel and piping (boilers, air receivers and the like as well as piping for steam, air, nitrogen, acidic fluids etc).
The results of an engineers calcs decide a given pressure test (max allowable, and service pressure and temp). The usual spec for testing is 1 1/2 times the working pressure held for a specific period of time. A failure is deemed if any part of the vessel/pipe including the weld leaks.

[Otto Nobedder]

An engineer will decide the test pressure. He bases his calculations on code requirements from ASME (American Society of Mechanical Engineers). They are the regulatory body responsible for pressure vessel and piping (boilers, air receivers and the like as well as piping for steam, air, nitrogen, acidic fluids etc).
The results of an engineers calcs decide a given pressure test (max allowable, and service pressure and temp). The usual spec for testing is 1 1/2 times the working pressure held for a specific period of time. A failure is deemed if any part of the vessel/pipe including the weld leaks.

Safety Valve, this may surprise you, then.

I do DOT required vessel retests for liquid hydrogen vessels. These tests are pneumatic (compressed nitrogen), not hydraulic. Every five years, I take the vessel to 125% of MAWP in controlled conditions.

The reason this is permissible is this is a vacuum jacketed vessel, and a catastrophic failure "should" be contained and vented through a relief port intended for that purpose.

We also retest CO2 trailers that are not jacketed, and these are hydro-tested for the reasons you explained.

The test for jacketed vessels at 125% MAWP is done with the jacket under full vacuum, so you can add another 14.7 PSI to the gauge pressure.

Steve

[Sftyvlv]

Yea Otto, I've been on a crew at a refinery that used nitrogen as the test medium. Because of the potential energy inside of the pipe we had to rope off a specific distance away from it.
The engineer equated the energy in the pipe to a certain amount of TNT.

[Otto Nobedder]

Yea Otto, I've been on a crew at a refinery that used nitrogen as the test medium. Because of the potential energy inside of the pipe we had to rope off a specific distance away from it.
The engineer equated the energy in the pipe to a certain amount of TNT.

I can see TNT as a good measure of the stored potential energy. I've taken 8' dia. vessels to 219 PSI in nitrogen, always done outdoors, and I get a bit more attentive once I'm above 185 PSI. Since it's a vacuum-jacket, I'm monitoring vacuum for any sign of a rise to warn me of an impending failure. I have yet to have one, though working outside for several hours, the sun on the vessel will cause the vacuum to creep a few microns. I know this is going to happen, but once I'm above MAWP, it gets my attention.

The highest pneumatic test pressure I've done was 9670 PSI, on 1/2" sch. 160 304SS pipe that I welded myself. 25% had been x-rayed, and those were all bench welds. None of my field welds were x-rayed. Let's say I was "alert" that day...

Steve