This may not be the correct forum for this question, but i'll try anyway as the replies are always highly valuable. Situation: We are preparing to hydrostatic test approx. 1000' of 10" sdr26 ASTM2241 force main. The line is a new location and we will have it completely isolated from the active system that we will tie in to after testing is completed. At this time we intend to have both ends of the 10" FM capped off with DI plugs. All bends and end caps are installed with MegaLugs for joint restraint. Our plan is to have a 2" air relief valve that we can close off on the high elevation end and feed water via service saddle/corporation stop on the low end. The elevation difference isn't great (maybe 2' vertical difference) between high and low ends so placing our pressure gauge on the low end shouldn't make much difference in the final analysis. Any experiences out there on how much water i'll need to pump (we'll be using industry standard hydrostatic test pumps) at the system to reach the 150 PSI mark? This is based on the assumption that i've bled the air from the line and the line is now completely full of water but at 0 psig. Additionally, if my calculations are correct, the end caps might have 4 or 5 tons of force on them!!! Manufacturer rates these megalugs for such pressure, but has anybody had experience of testing against dead end plugs that are exposed? My gut tells me to go ahead brace these ends (one end daylights into a manhole so we can't backfill it with earth per se, but could provide some timber blocking. The proposed testing saddle will rely on 1" Type K copper using compression fittings. Any problems with leaving that portion of the trench open during testing based on previous experiences?
The only part of this I can comment on is the part I'm quoting. Follow your gut, do the extra bracing. That gut feeling is there for a reason. :yup Good luck with the test. :thumbsup
definitely brace/block the ends. you've got a gasketed joint in the bank 20', right? not blocking those caps even mega lugged is nothing but a recipe for disaster. we just use a 5 hp gas driven pressure washer to test our lines, it's mounted on a trailer with a 250 gallon poly tank. how many actual gallons, i guess i don't know. my primary concern would be those end caps. i'd block the ends to the virgin soil bank with good concrete blocking. why can't you pipe your test equipment into your air release saddle?
thanks for the replies Gentlemen- Dayexco- I think we're gonna use your idea for blocking. One end outfalls into an existing wastewater manhole (mh currently not in use). Do you think that we could get away with making a timber bracing system in the manhole (say, 4"x4" timbers or 4"x6" timbers) to help block the end cap/megalugs? We decided to put the air release on the high end of the line (the part that daylights into the existing manhole and charge from the low end because: 1. seemed like an easier location to purge air 2. closer to our source of water , in this case a nearby fire hydrant. Would you recommend that we backfill the corporation stop/tapping saddle during the test as well as our 6' or 8' gooseneck extension of copper? Additionally, we've tried to be super careful with our DI fittings and plugs to keep fittings/gaskets square to pipe, alternate bolts during torqueing sequence, etc. Should we expect problems? Have you had to go back in on backfilled water/force main due to leaking joints on any previous projects? Since we're mostly gravity wastewater in our workload (air testing), i'm just wondering how well those MJ fittings and gasketed joint hold up. Our guys are pretty darn conscientious, but should i expect to fail more hydrostatic tests than we pass? thanks for the help Dayexco! ps (edit)- I love the idea of the pressure washer technique in lieu of the industry pumps. I expect that would save a lot of $$$$. Please provide details. Do you simply hook up your pressure washer and pipe in a pressure gauge?
yes, make sure you put a gate valve and check valve on your test pump side of your tee where you install the gauge to make sure you don't lose any of the pressure you've built up
We always just leave our test saddle/corp open, havent had any problems so far and we test waterline at ~230PSI for 2 hours. we connect our pump directly to the corp using a hose with some slick quick connect fittings. we have never had any problems with our fitting/joints leaking. we always torque them down in sequence, and to the proper spec. You can actually get a lot of deflection out of the fittings without them leaking if you have to. Biggest problem we have is that most of the time if we get a leak its at a saddle, corp, or somewhere on the pump.
It was not a case of running a test, but here's a story of what can happen if you don't block the ends. Post 34 and 35 of this thread: It's been a while since I put any waterline in, but my recollection is that we were required to test at something like 2 1/2 times the static pressure of the line, and I'd be lying if I claimed to remember for how long, but I'm pretty sure it wasn't as long as two hours.
Dayexco- per your question, we are using type K copper for our extension neck and compression fittings (basic parts that are city compliant in our area for service connections..) I really like your idea for a bonus per foot for crews that meet testing requirements. Is the $0.10/LF per man or crew total? Sounds like that might be a good new thread, discussion of bonuses/crew motivations! thanks
per man, and that's on a per job basis, if we pull onto a 200' job, it passes...they each get $20.00 bonus...if we have a job that is 2000', 4 manholes, 4-500' runs...if one fails out of the 4, they get none.
One thing I will add to this is the use of Megalugs to restrain the end caps is fine, but the entire end section of pipe will pull out of the next joint if not properly blocked. With it blocked securely you will be OK, but in the event you cann't block the end, you must use restrained joints for a distance back up the line. You pipe supplier can give you a spec book showing how many feet of joint restraint for a given pipe size. I have seen restrained joints on 10" pipe pull out 4 sticks, or 80 ft of pipe that was backfilled. Be sure to follow the table if you need to rely solely on the restraints. I have braced the end cap before by placing the excavator bucket in front of the cap, and firmly planting the teeth into the ground. just be sure there is no angle to cause the pipe to shoot up. Hope this helps
Hydro. Testing Forsythebros. I'm a construction manager for a large County Government. The "Architect/Engineer of Design" should have specification requirments detailing the exact method/means, pressure and time for hydro testing your lines. Someone mentioned 2 hours as being to long. We test minimum of three hours recording the drop as we go. Myassitis
Just a quick update on our project: Our test requirement was revised to 100 PSI for 1 hr with approx 2 gallons make-up water. Test required 150% of pump shutoff head. We used a local fire hydrant to fill the line via garden hose. Approx 4 hours to fill the line. For speed, i don't recommend the small hose, but for removal of air, maybe a good idea. We ended up putting a guage on the upstream end of the line as well, and charged the line to approx 60 psi based on the static head of the local fire hydrant pressure. Basically, we filled the line to 0 gauge and then let the pressure from the nearby hydrant do the rest. This took about 1 hour. At this point, we disconnected the hydrant line and connected the hurco hydrostatic pump. Went to 100 psi in about 2 seconds! Everything went pretty well at that point, no leaks, no visible drop in gauge reading. Definitely good ideas on blocking of end caps! Thanks Gentlemen!
bleeding the air What is the best procedure for purging all the air out of a line? Seems like about everytime we go to test we have a hell of a time getting all the air out of our lines. Like for instance the last short run of pipe we did was only about 100 feet of 4 inch. We had a blind at the low end with a 2" saddle and corp for testing. Straight run with 2 1" saddles for services and a 2" blow off at the very end. We filled the line with a 2" hose off the hydrant, then hooked up the pump and went around and cracked all the services and the blow off multiple times to bleed out any air. gave us hell trying to get it to stick at 230psi. We did end up having one very small leak on a compression fitting for the blow off, we actually ended up checking every single joint, MJ, saddle, corp, threaded fittings, everything and nothing was letting out any water. When we were testing it it held at 230 psi for an hour and a half then in about 10 minutes dropped to 215, we bumped it back to 230 and it stuck there. Although if you watched the gauge you would see it bounce around a little every so often.
Tyler- Man, This is my one experience thus far for water hydrostatic testing,so take that for what it's worth, but in talking to an old timer in my area, he really wanted us to keep flushing the pipe (slowly adding water) for a long time even after we thought all the air was out. We were fortunate in that we had an easy air relief on the high end of the line and our guys laid the pipe to grade (although only about 0.2% was called for!) to help reduce air pocket locations. We even let the thing sit overnight at 0 gauge to see if that would help eliminate air. My lessons learned: 1. good practice during the pipe laying regarding joint assembly and attention to details on the fittings is a must. 2. arbitrary laying of pipe creating hills and valleys may cause issues later during testing 3. good positive feeder line connections are important 4. per old timer, flush the crud out of the line. We preloaded the pipe to a lower than required pressure to perform some checks and then released the pressure back to zero before loading to the required values. Maybe that helps blow off some air? Regarding air, am i correct in stating that over a given time, any air pockets can be compressed to the correct pressure value, in your case 230 psi gauge? Maybe having some air is not such a bad thing, other than short term compressibility and safety issues regarding shrapnel if a pipe breaks? Obviously the last item is a very bad thing. I didn't really provide you anything more than you already know, i've got more questions than answers myself....