pipe installation

[par060]

We have a tunnel a little over 12’ in diameter in which 2 60” force mains are going to be run. The tunnel will be about 4000’ long. I believe the pipe is going to be rfp or possibly hdpe. I have little experience in this but I have to come up with some installation options to put on our bid drawings. I have been hearing about 2 methods that are probably going to be used….either sliding or carrying the pipe. The tunnel is fairly straight a slight vertical curve will be present. As of now the tunnel is about 40’ deep with 30’ shafts. Can someone give me a rundown of the 2 installation methods….if the sliding method is used do they just fill the invert and push the pipe along the concrete?….if the pipe is carried in there will not be a lot of room for the second pipe to be worked on…how will the connection be made?…….what kind of problem will I have grouting in the pipe after installation….is the grouting needed?

Any infomation on the pipe or installation would be helpful…thanks

 

[LHA]

I doubt you can push a fiberglass pipe on concrete, especially with a vertical curve.

Grouting will most likely be needed, for thrust resistance alone, but may also be required for lateral support at that vertical curve.

With small diameter pipes, connection is by fiberglass overlay, but I would guess there are couplings inside the overlay with 60" diameter.

Remember: The Chinese ideogram for “crisis” is comprised of the characters for “danger” and “opportunity.”
-Steve

 

[StephenA]

If I was doing the job, I would install a HDPE / HPPE welding machine at the bottom of one shaft and lower HDPE pipes down the shaft. I would fit appropriate skids to the pipes, a winch at the other end and pull the welded pipe along the tunnel. Maybe a light railtrack for the skids to run on. Grouting would have to be done carefully to avoid overpressurising the HDPE pipe and collapsing it by external pressure.

Fibreglass pipes could be pushed along with jacks from the back. Use side guides with lead-ins at intervals for each pipeline to avoid buckling. Again use skids and light railtrack to reduce pushing load and avoid damage.

I would leave the railtrack there.

 

[JedClampett]

A word of caution that has very little to do with your original question. HDPE has a very high coefficient of thermal expansion. Unless you're sure that the temperature is going to be constant from installation through operation, stay away from HDPE. If there was room, you could install it in a serpentine pattern, but with 60 inch pipe in a 12 ft. tunnel, that won't work.

 

[StephenA]

I agree with JedClampett that HDPE has a very high thermal expansion, but the Young's Modulus is much lower than steel and varies with time (it creeps), so with proper restraints it should be no problem. I would have thought that the temperature in a tunnel was fairly stable anyway.

 

[par060]

I believe they are leaning toward useing RFP rather than HDPE. That choice is not mine to make.

Once the pipe has been positioned they will grout around most of the pipe circumference I assume this will provide the restraint that would be required during operation.

Is there a particular type of grout typically used in this application?

 

[dicksewerrat]

Neat cement grout. see comments on your other post

 

[JeffSEAL]

as far as the grouting question goes, if you are using restrained joint pipe it would not be neccessary to grout the anulis. If you do make sure the pipe is tied down so it does not float. if you pump to much grout to fast you may float the pipe. 4000' is alot of twin 60's to thread into a tunnel. Normally you would either weld some angle iron on the bottom of the tunnel (if its liner plate) and push the pipe in or put skids on the pipe (band treated 4x4's around the pipe) for a tunnel this long you will have to bring the pipe in piece by piece on a loco and bell them up as you go. It would be alot easier if you have a horseshoe shaped tunnel 12'feet wide so you could put the twin 60's side by side. depending on whats going to be in the pipe i would use frp or dip. the advantage of the frp is you can get shorter joints but if you have room for a 30' shaft a 20' Ductile joint might be your best bet.

 

[stanier]

I would use HDPE and install by the push pull method.

Pipeline liners are installed routinely up to 500m long by pulling from one end after the liner has been compressed. It is run through rollers to reduce the outside diameter. The creeep relaxation properties allow it to regain its original dimension so it becomes a tight fit in the steel liner.

In your situation if you were to pull from one end and use rollers to push from the other the line could be readily installed. Just beware that the number of welds per day on a pipe this size would be about one very 2 hours. You need to allw the weld to cool to gain strength. So a strategy of welding lengths at the launch site and just make joining welds will speed things up.

The problem with the legacy materials of DI and FRP is what do you do with a leak at the rubber ring joint?

 

[dicksewerrat]

Either pipe will work but I'd go with the HDPE. weld together 1000 foot sections. Pull in 900 feet, weld next section and pull again. Repeat for the 4000 feet. Use rollers under the first pipe. Place rollers above first pipe anchored to the walls of the tunnel.Repeat welding, pulling. You should be able to send in people along the side of the pipe to tack weld the rollers so they don't move after installation. Bring in a slick line to blow sand into the annular space. Unless the liquid being transported is heated, there will be little temp. change from 55 degrees F. Wait at least 5 days for all the pulling stresses to be relieved before welding rollers.