Supporting a small pipe off the side of larger pipe

[KevinNZ]

Does anyone have good idea on how to support a small pipe off the side of a large pipe?

We have an overhead loop made from a large steam pipe and need to run a small pipe over the same loop. Both pipes are for steam and have different hot and cold expansion requirements. The larger pipe is insulated carbon steel and the smaller is stainless.

We could weld support steel to the side of the larger pipe but the client wants to avoid welding on site.

 

[mk3223]

Not a good practice to support a pipe from another pipe, especially from the process, steam, or insulated pipe.
However, instead of welding the support directly to the pipe, may consider the support steel welded to a pipe clamp which bolted on the larger pipe.

 

[FormerAIS]

As mk3223 stated, not a good idea to support one from the other. This holds especially true being they are different materials and different expansion/contraction rates.

The hanging mechanism(s) to support the steam pipe should be able to support a smaller diameter pipe run (such as you're describing) with ease. Possibly re-configuring the mechanism to have the pipes stacked on top of one another (with adequate separation).

Quality is not an act, it is a habit - Aristotle

 

[RVAmeche]

I definitely don't recommend it like others have said, but I have seen pipes supported from other pipes using cable loops and a trapeze/roller type support (smaller pipe sitting below the larger pipe).

 

[danschwind]

How is the larger pipe currently supported? There is no way to expand this support to hold the smaller pipe too?

 

[KevinNZ]

The large pipe is self supporting and fully designed and stress checked. We also add the smaller pipe into the stress model so have no concerns about stress in either pipe, even when one is hot and the other cold.

 

[LittleInch]

I would go for a subsea piggyback type clamp over the insulation.

Search "subsea piggyback clamp" like this

https://www.subseacableprotection.com/products/piggyback-clamps-guides-and-saddles.cfm

and choose a size slightly bigger than your small pipe to allow for differential expansion.

what type of insulation do you have?
You might need something like PU foam collar to allow the clamp something to grip onto.

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

 

[Dhurjati Sen]

Dear KevinNZ,

This is a serious issue. Do not go for it. I have faced issues when there is external corrosion on the bigger pipe due to the support. Very difficult to evaluate the extent of damage even offline.

Regards.

DHURJATI SEN

https://www.nace.org/people/dhurjatisen

 

[1503-44]

They are not going to like penetrating the insulation and corrosion protection coating on the big line.
If it wasn't a hot insulated line and the small pipe was 1 or 2" diameter and the big one was 8" or above, I would U-bolt it to the larger pipe, but not that one.

 

[KevinNZ]

Thanks for your input.

We have decided to go with a bolted clamp around the large pipe and weld the support bracket, for the small pipe, to the clamp. We will have to put up with a penetration in the insulation.

 

[davefitz]

The possibility of failing the small pipe is significant if the stress caused by E*a*DT is in excess of yield stress of the small pipe, where E= youngs mod, a= thermal expansion coefficient, and DT is the max differential temperature that can occur between the 2 pipes under the the worst combination of operating scenarios. If you are talking about supporting a water pipe off a sewer pipe, then it is not a problem. If you are talking about 2 different steam pipes, then it is a big problem. If you must proceed, then use supporgts tha allow differntial movement and add a few extra flex loops in the msall pipe

"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick

 

[1503-44]

Surprising that client will let you cut back insulation for ubolt.

 

[LittleInch]

What sort of insulation?

If you use solid PU and glue the insulation on, you can clamp the clamp on the outside.

Far far better than having holes in your insulation.

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