Concrete pipe trench
Concrete pipe trench
(OP)
We are designing a concrete pipe trench on an industrial site that will hold 2 24" Gas lines with 2 smaller gas lines running above them. 4 pipes total in concrete trench. One 24" gas line will be laid in the trench initially will the others to be installed with other phases. What would be the best design for this trench? I am thinking a grated top for the length of the trench (it will be partiall underground and above ground). If there is not a grated top and instead a fully enclosed trench it would be difficult to install the future lines. A grated top will pose some problems where the tench crosses the roadwAy with drainage considerations. Anyone have experience with this? Thanks.





RE: Concrete pipe trench
“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King
http://waterhammer.hopout.com.au/
RE: Concrete pipe trench
RE: Concrete pipe trench
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Concrete pipe trench
RE: Concrete pipe trench
Strongly recommend against any "covered" "solution" such as a precast pipe or culvert or the like except where road crossings are needed and planned. You really, really want to be able to lay the pipe in the ditch/trench with a simple crane and tools. Long runs of covered pipe are a slow nightmare of moving the pipe, welding, supporting it, cliimbing arond it, insulating/cleaning/painting it, etc. Did I mention "slow" very expensive as well?
Use a simple pre-cast or pre-fab'ed (poured-in-place only if absolutely necessary!) rectangular pipe trench with a cast lip and simple lift-off concrete covers and lifting plugs/lugs/wires. Or put the retaining lip on the pre-cast conc covers. Rate them for a pickup truck or forklift loads where needed, or best case, for full traffic: you will want the access later.
First pipe in the first one planned: 24 inch. Above is room for the next 24 inch, then the third and fourth. Now, this means you can't get to the first 24 inch for mods or repairs, so consider a shallower but wider: 2x 24 on the bottom, then the two smaller. The first option means you need a less expensive cover plate, but a deeper trench. Second option gives you more flexibility to add more pipes later.
RE: Concrete pipe trench
For the rest of the site why not install the pieps aboveground as in a refinery? Piperacks are invariably cheaper than trenches and much easier to maintain.
“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King
http://waterhammer.hopout.com.au/
RE: Concrete pipe trench
The only downsize I see is not being able to maintain the two 24" pipes at the bottom of the trench.
RE: Concrete pipe trench
RE: Concrete pipe trench
If installing in a casing, one would weld up a pipe string equal to the crossing length and then pull it through the casing.
Multiple strings would need specially fabricated spacers to hold the pipes in position inside the casing. For installing future lines, you may need guide trays between spacers. Supposedly you could weld and test the assembly, then pull through, if the length was not too long.
Now you know the reason that each gas pipeline is customarily placed in its own trench, or conduit.
If it ain't broke, don't fix it. If it's not safe ... make it that way.
RE: Concrete pipe trench
In light of all the above, I would be considering laying those lines above ground, above water level, on pipe racks, "T" type supports, or sleepers.
If it ain't broke, don't fix it. If it's not safe ... make it that way.
RE: Concrete pipe trench
Just a prcedural comment on your post --
You have two threads running on this question, each with a bunch or thoughtful answers. If you feel the need to post in more than one forum, put your question in one of them only, and post a link to that thread in the others. It's good to consolidate all responses so that the experienced folks can see what all the others have said. Read the forum policies, especially number 4. There's a link below under my name.
Good on ya,
Goober Dave
Haven't see the forum policies? Do so now: Forum Policies
RE: Concrete pipe trench
RE: Concrete pipe trench
For supports, assuming a pre-cast series of conc units are going to be used as the trench liner, I'd cast into both walls of the trench units support niches (slots) for WF members crossing the trench perpendicular to the pipe centerline. Then on each WF cross member, pre-fab a pipe support for BOTH 24 inch pipes. (It's easier to shop weld two supports at once in the shop on jigs waist high 240 times rather than a separate welded joint 240 times in the field inside the bottom of trench next to a filled and pressurized 24 inch gas pipeline.) In the field, drop in the pre-fab'ed WF members, drop in the first pipe, cover it with the blocks. Weld at each joint where needed before putting the cover on.
For floating, check total relative weights, check the results of the movement (it may be negligible (your plant is in dry gravel or rock or hard dirt, or major if in wet soil or crossing a quicksand/marsh environment) Add weight if needed.
RE: Concrete pipe trench
If it ain't broke, don't fix it. If it's not safe ... make it that way.
RE: Concrete pipe trench
Thank you.
RE: Concrete pipe trench
If it ain't broke, don't fix it. If it's not safe ... make it that way.