Pipe Stress of At Grade Piping

[TLHS]

Has anyone got a good reference on the design of at grade pipelines. I'm thinking about the rough systems that are typically used in mines for things like tailings and process water. I've seen a lot of different practices over the years that vary from basically completely unrestrained to giant directional stops all over the place. A lot of it comes down to different design basis philosophies by the engineers involved. Is anyone aware of material that addresses this specific type of system. I think some of the more costly restraint schemes have come from engineers that are trying to use process plant style design philosophies at a scale where it becomes cost prohibitive due to the pipe size, and potentially unnecessary due to the large amounts of space that is often available for growth.

In theory these are simple systems, but I've seen a huge amount of disagreement between practicing piping engineers.

I don't seem to have ever run across a great piece of literature about this sort of thing, though. Pipeline texts seem to mainly discuss buried lines, and aboveground texts tend to focus on process piping. It would be very nice to be able to point at actual references.

 

[1503-44]

There is a lot of pipe laid on the surface.
Usually reserved for remote areas, due to low population and land use activities, plus concerns of security, damage, theft of products inside, and bad visuals. It tends to interrupt vehicle traffic, farming, stop animal migrations and doesn't look nice. It also gets hotter and colder than buried pipelines. That can cause the pipeline to walk and/or snake around, if not restrained. It will easily move down slopes, so flat land is best. It's good to anchor occasionally. Plastic pipe expands/contracts about 10x steel pipe, so those tend to go on walk abouts. Sliding around isn't great for corrosion coatings either. The only advantage is cheap construction and it is easily moved around. Hydraulic mining ops like it because you can pick it up and move it to where water is needed as the excavation progresses.




--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[LittleInch]

It's basically pipe stress analysis.

Mines and other surface laid stuff can be pretty rough and ready and it helps if they actually just throw it in as this allows the small expansions to be accommodated. The ground often undulates as well.

Dead straight and level lines need more guidance and stress analysis.

Pipe connections also count. push fit joints common on water systems need anchors as do snap together type systems which have low axial strength.

Welded or flanged or screwed are much better at resisting axial forces without coming apart.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[KernOily]

There's No reference per se that I've ever seen. Most people use horse sense and past experience. The code permits that approach as long as the piping is laid out by a competent designer (the code defines exactly what that means) and the layout can be shown to be adequate by virtue of existing past successful installations of very similar conditions. You can't argue with past successful experience, and the code acknowledges that.

The disagreement between folks on the design and layout of these systems arises from what requirements the various owners have, what requirements their EPC contractor has, and what everybody's appetite is for liability.

If you decide you have to have documentation, remember the ASME B31.X piping code governs unless you are outside the US. Make a sketch of your layout, run it through flexibility analysis (don't forget the seismic case if that applies) and put some pipe guides here and there wherever the model tells you to; this will keep the stress under the allowable. If there are hydraulic thrust forces predicted, you will need anchors.

If sensitive equipment is connected at the ends of the line, e.g. rotating/reciprocating equipment or thin-walled tanks/pressure vessels, a flexibility model should be made to protect the equipment and to CYA.

 

[LittleInch]

" A lot of it comes down to different design basis philosophies by the engineers involved."

Yup. Piping design is one of those areas where design is not a prescriptive as others and as long a you don't break the pipe in service the are many ways to skin the same cat.

"I think some of the more costly restraint schemes have come from engineers that are trying to use process plant style design philosophies at a scale where it becomes cost prohibitive due to the pipe size, and potentially unnecessary due to the large amounts of space that is often available for growth"

Yup again. Some people just can't think outside the box they're used to or have created. The worst is when you get the response "The code says..." or "It MUST be done this way", without any explanation or detail.

Restraining pipe is sometimes required where movement or force could damage other equipment, but in general it just leads to more and bigger supports which serve little purpose.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[TLHS]

Thanks all, pretty much lines up with what I understand. I was hoping there might be some fun references I wasn't aware of, so figured it was worth an ask around!