Safe Distance for Pressure Testing?

Yah, Pharaoh,..... AWAY. !!! :)

Use the old formula, if you are not involved with the test, be gone. Out of the building, area or compound. Do the math, Force= Presssure X Area, plus a dash of volume.

Cheers

how is it possible

pressure x area x volume will give you the answer in unit Kgm^3, that is not the unit of the distance, it should be in M

This question was asked once before... Pneumatic, you can't get far enough away in my opinion, but Hydrostatic? about 6" or 150mm. We use hydrostatic testing for our components, when we hit the test pressure, we hold for 1 min. This over stress the material so it can't be trusted for use after the test, so we turn the pump back on and run it to burst. This tell us exactly where the weak point is and exactly what pressure is required to burst. All good information to have.

When burst occurred in a hydrostatic test, we heard a small pop, then water flowed across our shoes...

I am having my valves pressure and fire tested in a few weeks. I can ask the lab for your info. I know this much we can witness the testing and these guys test day in and day out . I will get the info, I am also curious.

There is no any formular for calculating safe distance.

But you can use hydrostatic test for burst testing or over pressure testing; and pneumatic check for leak detecting.

there must be some formula for it.

Yes its called common sense, something which seems to be in short supply in our enlightened age of OH&S.

Please teach me some formula if you can.

But we can built some procedure test with the best safty e.g. must to use hydrostatic pressure test or use camera if there is any dangerous place for vision,.....

by our CR4 knowdlege and experience.

I said "there must be". It did not mean that I have it in hand. If I have it, I will teach you. where are you from guy?

Here is a formula I found in a Norwegian Specification. . The only thing on the top of the page is T0240|72-12| and in the footer "Rules, issue 96-02".

Anyway the formula is:

safe distance = (0.15) x (D) x (a)^0.4 x (p)^0.6

where D - internal diameter (m)
a - length / diameter of piece (m)
p - test pressure (bar)

Hope this helps,

Pharoah,

You've been right before but this formula somehow isn't working out.

Hi guest,

We do fluid and gas pressure testing where possible in custom designed test cells. In calculating the wall thickness for the materials of the cell we use formulae supplied by the (UK) HSE "Safety in pressure systems".

You should be able to obtain the guifance note (GS4) from http://www.open.gov.uk/hse/hsehome.htm

As has been stated earlier, fluid tests are less hazardous than gas (pnuematic) but all tests should be done inside a safe area.

Find the thickness of material and use a PLC with a safety switch to shut of the system when doors are open and testing fails. Hydostatic test is safer I think.

When testing pneumatically you might use the safe stand-off distance for a grenade or a bomb, because that, in effect, is what you are testing. When hydrostatic testing, we often pressurize the item with a fluid and place the whole test in a tank of fluid. This is how hydro-testing of pressure tanks is performed. This test is not only relatively safe, but by plotting internal pressure against external fluid displacement, you can create a stress/strain curve for the unit under test (UUT). This provides valuable information about yield pressure that can't be obtained by measuring ultimate burst pressure only. In fact much testing stops at yield pressure.

Could also suggest that you do your gas (Pnuematic) testing in water tank. Release of gas /air bubbles make it easier to trace the source of any leaks.

I saw several replies that assumed burst testing. In reading the original question, I don't believe that that was the intent.

For pressure testing of a component that will be used in service, the pressure is usually 1.3 ~ 1.5 x design pressure, which keeps the material from yielding, but subjects it to more stress that it will see in service (hopefully). Pressure testing with water is quite safe as the volume change for a full pressure release is small. Inspectors crawl all over the unit to look for drips. Pneumatic testing is done at a smaller pressure ~ 1.1 ~ 1.25 x design pressure out of consideration for the danger. However, inspectors still have to crawl over the unit to look for leaks.

If you are burst testing to prove the ultimate strength of a prototype or design, never use air - it is a shrapnel bomb, as others have said. With water, you don't have to be close to inspect it, the pressure will drop nearly instantly and then you can go see where the rupture happened. Unless you are above 1000 psi, 10 feet ought to be sufficient. You could put up temporary plywood walls or shields if the part is small enough.

I used to do hydrostatic pressure testing of aircraft tubing for a "very large and well known company" and we would routinely pressure test 1/4" tubing to over 9000 psi and check for leaks on the welded segments. The pressure was so great it would deform the bends in the tubing along its length (only temporarily), which would straighten the tube. All we were told was dont stand in front of the plugs on the end of the tube. Other then that, you could put your hand on the tube (in fact, we needed to in order to find leaks) without shields or PPE. It makes me wonder what the OSHA requirements, if any, are.

Avery Montembeault

I just talked to a fellow that is pipeline consultant. They are doing a 500km 36" line just down the way. I asked him of the hydro test proceedures and safe distances.

He said, "Everyone away, off the r/w and back to camp for the test." He even commented on how they would ask the farmers to stay out of the fields that the pipe line was running through, during the hydro test. He could not express the kind of damage a leak or burst would do. He just indicated that it would be rather severe. So you can take it from an expert (not me) STAY AWAY!!!!!

It depends upon the perceived danger.

Here's a little 2-part story for amusement purposes.

Many years ago, a young Engineer was 'persuaded' to venture forth and pressure-test a service water main at a pharmaceutical manufactory.

1) Now, it was well-known that the pipework within a particular building was as 'rotten as a peach', so to speak, and all held together with rubber patches and bits of string in a Heath Robinson fashion (http://en.wikipedia.org/wiki/W._Heath_Robinson). So along came PWSlack with the shiny-new works fire engine, which was puposefully coupled-up to a fire hydrant and, having isolated this particular building, raised the pressure in the main well above the normal 30psig. No-one had any maintenance information about the building isolating valve, until various people came running out, dripping wet, asking WTF was going on....

2) Same factory, same operation. Same personnel, even. This time it was a diesel-driven fire pump. All was well, until the electric circulating pumps, which had previously been nantling away at around 30A were switched off and this socking-great fire pump switched on. Vrrrrrrrooom! Lots of noise. After about three minutes the members of the fire team witnessing the test received a call on their hand-held radios. It was far too noisy to hear the content of the call. After a while the diesel was shut down and the electric pumps switched back on. Except this time they were pulling 65A instead of 30A, and the pressure was well down. Anyway, to cut a long story short, a colleague was walking along a roadway in the works when a huge lump of it suddenly swelled and burst, spewing water, mud, stones, everything across a wide area. "It was just like in 'Thunderbirds', you know, when The Mole breaks through!" (http://en.wikipedia.org/wiki/Thunderbirds_%28TV_series%29) Along came the works Maintenance Engineer, with a face that was beetroot red with displeasure. PWSlack's heart began to sink. "Did you do that?", he asked, forcefully. "Yes, Eric, I did." "Well next time, blummin-well make sure you do it while I am on holiday!"

Testing a push-cycle inner tube with hand-pumped compressed air, by looking for bubbles under water, can be done at close range.

One must be mindful that compressed air in a large volume has energy that can do a lot of personnel and equipment damage.

• 5psig is dangerous at any distance if it is propelling an unrestrained manhole cover....
• 3psig overpressure is enough to knock down a 2m high wall formed in 9in brickwork....

Let commonsense prevail.

Hi,

Just noticed your question while I was Googling something similar. Australian and New Zealand Standard AS/NZS 3788:2006 D16.2 has what you're after. I have cut and pasted it below but it isn't clear in this format. You can get the document from saiglobal.com or I can scan and E-mail the pages if you like (malcolm.stephen@ansto.gov.au).

The following is a guide to distances from the pressure equipment to the pressure control point and the limited access boundary for protection against general blast pressure:

Stored energy To control point To limited access boundary

MJ m m

≤13

13 to 34

34 to 270

>270

7

10

30

46

15

30

90

200

If stored energy exceeds 270 MJ, consideration shall be given to any extra safety measures required. Stored energy is calculated from the following equation:

101.3 +

3 . 1 10

1 101.3) + ( 2.5 =

0.286

 





 













−

P

V P E . . . D16.2

where

E = stored energy, in joules

P = gauge pressure, in kilopascals

V = volume of equipment, in litres

For combined hydrostatic/pneumatic testing, only the volume of gas in the equipment need be considered in calculating the stored energy.

check for Netherlands Stoomwezen Rules for pressure vessels

T0240|72-12(96-09)

Yes i Know

BACK DOWN THE CHAIN THERE WAS REFERENCE TO A FORMULAE FOUND IN A NORWEIGN DOCUMENT. THIS APPEARS TO HAVE BEEN TAKEN FROM LLOYDS REGISTER - CALCULATION OF MINIMUM SAFETY DISTANCE FOR PRESSURE TESTING (LLOYDS REGISTER 96-02) FORM T-0240 SECTIONS 3.3 (FLUID) AND 4.3 (GAS). I TRIED TO ATTACH THE WORKING ELECTRONIC VERSION, BUT IT WILL NOT LOAD, SO I ATTACH THE SPREAD SHEET, AND YOU WILL HAVE TO SET UP THE CALCULATION FORMULAE YOURSELVES.

(ALTERNATIVELY I CAN TRY TO E-MAIL IT SEPERATELY)

FOR FLUIDS (3.3) IT IS :

L = 0.15 X INTERNAL DIAMETER X ((ALPHA) ^ 0.4) X ((TEST PRESSURE / (CUBE ROOT OF DENSITY))^0.6

FOR GASES (4.3) IT IS :

L = 30; 3.6 X CUBE ROOT OF (VOLUME X ((TEST PRESSURE + LENGTH) - ((TEST PRESSURE + LENGTH) ^ 0.714)))

IF ANYBODY CAN ADVISE THE LOCATION OF AN ELECTRONIC COPY OF THIS COMPLETE DOCUMENT, THEN PLEASE LET ME KNOW.

MAXIMUM L APPEARS TO BE THE MINIMUM "L" SAFE DISTANCE PLUS 30 METERS. ALTERNATIVELY, IT COULD MEAN THAT YOU SHOULD ALWAYS BE AT LEAST 30 METERS AWAY - WHICH APPEARS TO BE EXCESSIVE FOR LOW PRESSURE SMALL SCALE PIPING SYSTEMS.

HOPE THIS HELPS THE DISCUSSION.

Dear Gents.

Pls send to me the documentation related to hydrotest safety distance, such as T-0240 SECTIONS 3.3 (FLUID) AND 4.3 (GAS)

Thanks so much.

Hello.

I saw your contribution to the forum and I want to know if you have any excell to calculate this distance.

If you have it, could you be so kind and send it to me?

Thank you very much and regards.

Victoria

Could you be kind enough to send the XL sheets to me greatly appircate you help

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Please email this excel sheet if you can. it would be greatly appreciated. <email removed>

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Pls send me the documentation related to hydrotest safety distance, such as T-0240 SECTIONS 3.3 (FLUID) AND 4.3 (GAS)via email:

Thanks

Madhusudanan

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BACK DOWN THIS E-MAIL CHAIN THERE IS REFERENCE TO A DOCUMENT LOCATED IN NORWAY. THIS IS INFACT TAKEN FROM A LLOYDS REGISTER DOCUMENT "RULES FOR PRESSURE TESTING LLOYDS REGISTER 96-02" FORM T-0240.

SECTION 3.3 IS FOR HYDRAULIC TESTING, AND THE FORMULAE GIVEN CORRECTLY CALCULATES THE MINIMUM SAFE DISTANCE.

SECTION 4.3 IS FOR GAS (PNEUMATIC) TESTING.

I CAN NOT PASTE THE FORMUALE HERE, BUT I CAN TRY TO E-MAIL AN XL WORKING DOCUMENT IF YOU SEND YOUR E-MAIL ADDRESS.

IF ANYBODY CAN ADVISE THE LOCATION OF AN ELECTRONIC COPY OF THIS TOTAL LLOYDS DOCUMENT, THEN PLEASE ADVISE.

please email me XL safe distance for pressure testing formula document

Dear Sir

Pls send to me the documentation related to hydrotest safety distance, such as T-0240 SECTIONS 3.3 (FLUID) AND 4.3 (GAS)

Thanks so much.

Dear colleague

can you kindly send excel sheet for calculation of safety distance for hydro test and pneumatic tests?

Many Thanks

J. Nunes

Hello,

please kindly email the excel sheet for calculation of safety distance for hydro test and pneumatic tests. Appreciated.

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Pipes, flanges & valve are identified as one unit only.

If any body is interested in getting the safe distance calculations for pneumatic testing in excel sheet, pl contact me on my email.

But someone knows how to calculate safe distance for hydrotesting please passon to me.

Rgds.