Polyethylene (PE) Gas pipe job

By TRC

Date 01-24-2009 00:16

Hey SW, I've done lots of high density( HDPE) poly but no medium density (MDPE) which most of the time is called yellow pipe. High density is black on the inside with a thin yellow coating on the outside. MDPE is rated for a 60 psi system and HDPE is for 100 psi. Fusion is very simple just be sure every one follows the instruction as trained. A certified fuser usually doesn't make any extra pay because it's so simple. Talk with the gas company ASAP because everything that will done on this job will require OQ training. Operator Qualification is extensive and can eat up a lot of time. No one on the job site will be able to perform any task unless they have training- this is DOT requirements. I hope you are getting a coil trailer with straightner. Coiled plastic has taken out more front teeth than bar fights.
If you don't have a straightner, it can still be installed but it's a pain. Testing is done with air and is typical i.e. 1-1/2 times MOP. Trenching is trenching and back filling is done with a layer of sand usally at least 12" over the pipe. Also a tracer wire is installed with the pipe so it can be located after installation. Some gas companies have the warning tape and tracer wire made as a unit. If it's for a gas company they will have specs for installation just like any other pipe job. Hope this helps- Ted

By swsweld (****)

Date 01-24-2009 18:48

Thanks for the info Ted, it was helpful.

We will be getting a coil trailer.
The straightener was mentioned and since we still have our teeth we will get one.
This job is on a military base and there is a little confusion as to who the responsible oversight will be, the Army Core Of Engineers or the Gas Company since we tie into there existing line. We are 10'-20' off of the road and bore under the road many times so DOT has a role in this even though it is on base.

Our specs are from the ACOE and are vague in some areas such as TTCP (temp traffic control plan),welding procedures and qualifications but it does fall under B31.8.
Tracer wire and marking tape are detailed. Wire after six inches of back fill and detectable marking tape (6" wide 0.004 thk) 12" below grade.

http://www.jmeagle.com/pdfs/2008%20Installation%20Guides/YellowGasDistTechIG_June%202008.pdf
http://www.cpchem.com/hb/getdocanon.asp?doc=127&lib=CPC-Portal

These were two helpful web sites.

Did you always have to bring in sand for the initial back fill?

This is a sandy area (Sandhills)
I did not see that requirement in our specs.
It does specify that rock or debris must be removed.

By spgtti

Date 01-24-2009 22:47

I spent 2 years welding for the local gas co in NE GA and we never had any requirements for backfill material, just don't chuck big rocks in on it. We used to unroll 2" spools by hand and that was bad enough trying to get it to line up in the McElroy machine. We recieved our training and certs from a rep for the welding "machines". This is a very easy process and requires little training.

By swsweld (****)

Date 01-25-2009 01:52

That's good to hear because I didn't put any money in the job for sand. I should have seen it in the specs but didn't.

As it stands we will get the procedure, trained and certified by the supplier. They also have the machines. I hope that's all we have to do.

The spec requires us to do a destructive test everyday before any production weld is made.

By pipehead (***)

Date 01-25-2009 04:39

The last few I worked alot with HDPE and MDPE for the pipeline company I worked for, even though you are on a military base you will still be governed by the DOT specs along with the additional specs from the COE. Also you should find out who the gas company is because even though the work is for the corp, the gas is coming from some one else and will probably involve another set of specs.

As far as backfill I am in Colo and only one gas company here requires sand. So unless specified I wouldn't worry about it. I do believe Dot spec does call out that no rocks greater than 4" can be within the 6"under and 12" over the pipe.

Make sure you rent a wheel or track mounted unit for your fusion welding because anything over 2" is a pain with hand held Irons!

Hope that helps

By Robert Turney (*)

Date 01-25-2009 22:43

I work for CenterPoint Energy in Arkansas and I have put in alot of PE pipe from 1/2 inch cts to 8 inch. Just follow the specs and proper heating times and you will be fine. As far as testing if the MAOP is 60 lbs we have to test it at 1 and a half times the maop. Do you know if its butt fusion? If so, make sure you get all the proper heating times and facing pressure as well as the proper fusion temp. Alot of the tie ins could be electrofusion.

By swsweld (****)

Date 02-12-2009 03:22

Robert, it is butt fusion.

We will get training and test this Friday. We are going to use a McElroy machine in the field.

My question is do they make a fitting for a hot tie in for a 4" tee on 4" pipe without a valve installation that is made of PE?

We are trying to avoid cathodic protection if there is an alternative. The tie in to the existing line is the only location in the 5 miles that I'm not sure PE material will be used.

Our sales rep is very helpful but also very inexperienced with PE gas pipe so I haven't asked him yet. You guys have hands on experience and are more qualified to answer that question.

Thanks for all the helpful replies.

By TRC

Date 02-12-2009 22:56

It's called a branch saddle. It is a 4X4 electrufusion branch that the tapping machine is fused to. Once the tap is made the branch is pinched off , the tapping machine is cut off and tie-in is by fusion in most cases.

By Robert Turney (*)

Date 02-13-2009 00:08

TRC is correct on the Branch hot tap, and Im pretty sure that Central Plastics makes the one we have at work. Is it going in the ditch by itself or is it joint trenched with anything else? Dont forget wire, markers, and locator balls! Is the tie in on plastic or steel pipe? I havent been paying attention. Who is the job for? I f you dont mind me asking. Have fun. Oh by the way, be glad its 4 inch and not eight inch 40 ft joints. That sucks.!!!!

By swsweld (****)

Date 02-13-2009 04:22

It is for the Army Corp of Engineers. Hopefully the existing pipe will be PE as well as everything we will be running. If the existing pipe is steel it wouldn't surprise me, but the prints say it's PE and no valve is specified which seems odd that they wouldn't call for one at the tie in.

We will be running parallel to a sanitary sewer line (new) and two goat stinking fiber optics (existing) that was not on the prints that we bid the job with. Funny how that works.
SS pipe is installed first by another contractor and back filled then we install the gas pipe approx 3' beside them and 1' deeper than them. 4" deep

Our specs call for tracer wire 6" above pipe and marking tape, not sure what the locate balls are. The prints called for electrostop fittings but they only apply to steel material if I understand it correctly.

There is a lot of up front cost for reel trailers, straighteners, re rounders if you use reeled pipe. We are considering using 40' joints to avoid the extra cost of equipment. Lots more welding and not as fast I presume.

Any idea how much faster it is using 600' reels as opposed to 40' joints? It's all 4" pipe. Easy trenching, no rock but lots of horizontal boring at roads and creeks. (12) We probably will have a lot of criss crossing of those stupid fiber optic cables, therefore causing extra welds. Total length is 5 miles and about 3 of them are straight runs with no foreseen problems except roads, creeks and fiber optic cables. The last two miles have many branch lines, tees, valves that feed the newly constructed buildings.

We have never installed PE gas pipe before and might never do another one so we are hesitant to spend 15K on a job for reel trailer etc and never use it again.

By swsweld (****)

Date 03-11-2009 12:52

We are ready to test our first run. Everything is going well. One big problem that I think will get resolved on its own.
The ACOE is requesting that we test 500' at a time and at the end of everyday. This is not acceptable to us and there is no contract documentation to support this requirement.
Not in the specs, B31.8 or the manufacturers installation recommendations. The only relevant code that I don't have is ASTM 2774 Underground Installation of Thermoplastic Pressure Piping.
We submitted a test plan that goes from point to point (road bore to creek etc) it is not restricted to linear feet.
My research has found nothing to restrict our test to 500'. Is there anything out there that I'm not aware of? They are leaning on SIP Standard Industry Practices to support them. I'm telling them that there is no SIP for 500' max test.
We are not wanting to start out with a knock down drag out but can't afford to be held to this unnecessary requirement.
If held to this we plan on asking for a change order but don't expect it to go that far.

By TRC

Date 03-13-2009 21:13 Edited 03-13-2009 21:37

Hey Tim, your right on track- Ted

P.S. make sure the drill dudes are usung a break-away link for 4" MD pipe. If the pipe hangs up while pulling back serious and permanet elongation of the piper will occur.

By Robert Turney (*)

Date 03-15-2009 18:28

Are ya'll putting your tracer wire in any kind of casing, I.E. smaller pipe? Just curious.

By swsweld (****)

Date 03-15-2009 18:54

Thanks Ted. I will ask them about the B A link. I asked if we need to remove the external beads for the bores and was told no. Hope they do our first bore this week.

Robert, our specs didn't require a casing or conduit for the tracer wire.
It's 12 ga single strand copper wire insulated installed one lift above the gas pipe.

By Robert Turney (*)

Date 03-16-2009 01:40

I didnt know if you were going to use it for any road bores or anything like that. Just make sure you put up plenty of locate points, locators will like that.