Air Testing of Water Lines

Define <...need...>, please.

This is the intension to save water. Thanks for quick response.

Please explain why there is a need to test the lines.

Leakage test for newly installed lines

What about structural test for newly installed lines, then?

And where does the need come from?

• A 200mm Ø line 10km long under test contains 314m³ of water, or 314m³ of compressed air, either at 50psig. Why choose the one over the other?

Keep going. Think it through.

Quite.

I'm going to throw in an opposing view from the crowd on this one, I say you can use air on certain applications.http://flexpvc.com/PVCPipeSize.shtml depends a lot on the schedule you use

If this is going to be a water line, why are you trying to conserve water?

Is the line buried? What schedule (wall thickness) is it?

One of the problems with compressed air in PVC is that small amounts of oil that might be present can soften and weaken the PVC, which can then burst into shards like shrapnel. A one-time leak test with clean air at well below the pipe's pressure rating would not have this problem.

The pipes are burried Schedule 80 uPVC. Intension is to save water in testing of water lines of a segment say 50 to100 meters.

100m of 80mm Ø pipe is about 0.5m³.

0.5m³ @ £0.60GBP per m³ delivered is about £0.30GBP or just over half the value of a 2nd class postage stamp. Go on. Explain further.

After the initial flurry of activity on this thread, it's all gone very quiet, for some reason.

OK. Consider these scenarios:

1. A Test Inspector is standing next to a 200mm Ø line some 10km long, clipboard, pencil and stopwatch in hand, while the line is being pressurised to 50psig with water. Owing to an unseen fabrication defect, when the line reaches 50psig, there is a sudden catastrophic failure and the pipe ruptures violently. What happens to the Inspector?
2. A Test Inspector is standing next to a 200mm Ø line some 10km long, clipboard, pencil and stopwatch in hand, while the line is being pressurised to 50psig with air. Owing to an unseen fabrication defect, when the line reaches 50psig, there is a sudden catastrophic failure and the pipe ruptures violently. What happens to the Inspector?

Awaiting response.

LOL, well who cares, he got what he deserved for standing so close....

15 minutes seems light, but it depends on who specified that and why, most leak tests are longer but it could easily be 15 minutes, why don't you just ask the person who spec'd that number??

As Tornado said, are the lines buried, or above ground?

If they are buried, and the above ground portion is wrapped with some blankets or protective material, for the test, I say go ahead and use air.

If the pipe is above ground, then I'd say maybe not.

Is there an echo in the room?

Is this the first echo you've ever heard here?

Here's a true story.

A long, long time ago, in the last century in fact, a much younger PWSlack was despatched to test a new-build diesel fire pump at a factory somewhere in Europe (names and locations have been altered to protect the innocent). Before the test, the three booster pumps servicing the water mains were just ticking along at about 25A on each ammeter with a mains pressure of about 55-60psig, and the Works' Chief Fire Officer, the Fire Prevention Manager and the Shift Fire Team Leader were all in attendance. All individuals donned ear defenders, as the pump was in a small building.

Said individual switched the electric pumps off and fired-up the diesel fire pump. Vrooooooooooooooooooooom! Off it went. Conversation in the building, even through ear defenders, became impossible. Pressure went up to 135psig. After a few minutes, all three got a call on their radios, which they were unable to address as the background noise was so high. After a couple of minutes more, the diesel was shut down and the electrics turned on again. Except there was a change. Current was up to 55A and the pressure was way down.

There was quite a commotion on the way back to the office, with fire appliances and other vehicles in attendance at one spot, with people running about turning valves off and running-out fire hoses to couple hydrants together.

A piece of reinforced roadway the size of a barn door had lifted and cocked itself to one side. There was water, mud, stones and all sorts of other mess everywhere from the cast iron main underneath it that couldn't handle it any more. A colleague remarked, "It was great to watch - just like in Thunderbirds when The Mole breaks through!"

Not finished yet.

In the distance, the Works Maintenance Manager is approaching, and his normally-cheerful face is bright scarlet. Uh-oh, serious uh-oh.

He approaches.

"Did you do that?", he asked, with a calmness that was unnervingly out-of-keeping with the colour of his face.

[Honesty is the best policy] "Er, yes, <first name withheld>, I did."

"Well, next time you do it, make sure I'm b...dy-well on holiday!"

There is a moral here:

• Imagine what would have happened if the barn-door-sized piece of road was being propelled by compressed air instead....

Nuff said?

I can tell you if a joint pops it sounds like a shotgun going off....If you happen to be standing next to it and the pipe hits you in the leg, you will be limping for a few days...at least that's what I've heard....

Is this is permissible in any standard.
I doubt it. However, the only standards that apply are those applicable to your jurisdiction.

...the location of which is unknown to the forum.

Ummm,

If the lines are to carrry water, why not hydrostatically test them with....

water ?

Hey - that's an idea.

Thought-provoking story. Thanks for sharing it.

If an air test at 50psi doesn't fail and blow the ears off of everyone besides other limbs and body parts, you will not be able to find any small leaks because it will not cause a noticeable pressure drop due to the compressibility of gases such as air. If you were to use water the only body parts in danger are wet feet. Since water is not compressible, any leak will cause an immediate loss of significant pressure. You will be able to notice this.

Also when the modulus of elasticity of air, plastic and water are considered, air will expand easily. When air is heated, depending what time of the day this pressure test is done, you could end up with a higher pressure after the test than at the beginning of the test.

As I, and others have preached, air in pvc is a claymore mine waiting to explode. Water is a pair of wet socks.

Good Luck, Old Salt

According to the OP, the pipe is buried.

#9

Thanks, I missed that.

Depending upon how deep he has them buried, the intensity of the sun and soil conditions it could have a minor effect, but not nearly as much as I had projected.

Thanks again!

Good Luck, Old Salt

"Is this is permissible in any standard."

NO! NO! NO! NO! NO! NO! NO! NO! NO! NO! NO! NO!

PVC pipe not to be used in compressed air systems

October 1990

The Department of Labor & Industries warned consumers and employers in May 1988 that plastic-polyvinyl- chloride (PVC) pipe cannot be used in compressed air piping systems without risk of explosion. By law, employers must protect their workers by avoiding the use of unapproved PVC pipe in such systems.

As Solar Eagle said!

Even buried I would not charge a line of several kilometers long with air.

Is this potable drinking water?

If this is a new install then you need to flush the pipe anyway!

Charge the piping with water and be done with it.

The piping should have been tested prior to burial with the intended fluid that it will transport.

I can see a problem using air @ 55psi, but normally a pressure of 5 psi is used to test a pressure vessel. It may take a longer time for leak down to occur, but it is a safe method. A typical air test, is 5psi; hold for 15 minutes; no leakage allowed. If leakage is detected, inspect, repair and retest. This is something we did on ships all the time where using water as a test medium is not practical.

Dear Mr.syedzaidi,

1 What is the working Pressure designed.? 2. On what basis 50 psig. air is decided.? 3. Is the pipe laid below ground.? 4. What is the class of pipe used.?

It is NOT CORRECT to use Air for testing. Only water is to be used for testing. As the pipe line is installed, the class of pipe will vary and towards the ens - the thickness will reduce and hence 50 psi Air Pressure IS NOT ADVISABLE.

I have experience of maintaining, for 14 years, 13400 Metres 250 MM AC Pipe for Water Pumping 1600 M^3 of water in 16 Hrs in a day.

Pipe laid for first 1/3 of total length was class C pipe - 15 MM thick, and second 1/3 is of B Class - 10 MM thick, and balance is A Class - 5 MM thick, where the Pressure is of 1/3 of Pressure at the delivery of the pump.

If compressed air is used - then, the presuure at the delivery end will be very near to 50 psig it will pose problem.

DHAYANANDHAN.S

DO NOT PRESSURE TEST A WATER MAIN WITH COMPRESSED AIR, UNLESS YOU WANT TO KILL YOURSELF OR SOMEONE ELSE!!!!!!!

Follow the AWWA C600 Standard for Hydrostatic Pressure Test, as follows:

http://in-valparaiso.civicplus.com/DocumentCenter/Home/View/917