Anchor support on a Riser 1

[nikolastrojman]

Hello everyone,

I’m currently working on a project that involves several piping lines of various sizes (starting from 2" and upwards) with long vertical segments (up to 10m). These segments are routed towards different types of equipment (heat exchangers, filters, etc.) located on a steel structure with platforms at different elevations.

One key challenge in this project is that the piping design within the steel structure is being handled by a sub-contractor. To perform the piping stress analysis for the lines in our scope, we need to establish proper boundary conditions. Specifically, we need to provide anchor points at the battery limit of the steel structure.

My initial approach is to use either:

• Fixed supports: Welded directly to the secondary steel, or
• Moment-free fixed supports: Using suitable steel hardware to restrain movement in both horizontal directions while allowing rotational freedom.

This method would allow us to split the piping stress models correctly, avoiding the need to model the entire piping routing and making the analysis more manageable.

However, an additional concern is ensuring the loads at these supports remain within allowable limits. I’m unsure whether standard piping support manufacturers (like Lisega) can provide guarantees for such specialized supports, particularly in terms of their load capacities for this application.

I´m looking forward to hearing your thoughts and experiences!

 

[RVAmeche]

To start with, when intentionally splitting the pipe stress design at anchors/fixed points, someone needs to be responsible for including both sides of the loads on the fixed point boundary support otherwise it may get under designed. I normally prefer to just use a real anchor for simplicity but the structural engineers sometimes hate moments; I would at least ensure your moment-free support includes axial/limit stops too; it should have no movement.

Everything else depends on information you haven't provided like system temps, expected movements, materials of construction, etc. Assuming your process isn't anything crazy standard pipe supports, including spring hangers, should be perfectly fine for this.

If this sub is doing the piping inside the structure, which includes the vessel/equipment connections, be sure to confirm they're actually reviewing nozzle loads and properly accounting for all temperature scenarios.

 

[nikolastrojman]

To start with, when intentionally splitting the pipe stress design at anchors/fixed points, someone needs to be responsible for including both sides of the loads on the fixed point boundary support otherwise it may get under designed. I normally prefer to just use a real anchor for simplicity but the structural engineers sometimes hate moments; I would at least ensure your moment-free support includes axial/limit stops too; it should have no movement.

Everything else depends on information you haven't provided like system temps, expected movements, materials of construction, etc. Assuming your process isn't anything crazy standard pipe supports, including spring hangers, should be perfectly fine for this.

If this sub is doing the piping inside the structure, which includes the vessel/equipment connections, be sure to confirm they're actually reviewing nozzle loads and properly accounting for all temperature scenarios.

To provide more context, the lines in this project are made of either carbon steel (ASTM A106 Gr. B) or alloy steel (ASTM A335 Gr. P5), with operating temperatures ranging from 280°C to 420°C.

The client also prefers to use pipe clamps instead of pipe shoes because this aligns with their standard practice.

Can you please share an example of a moment free support you're using in this kind of situations?

 

[KevinNZ]

The client also prefers to use pipe clamps instead of pipe shoes because this aligns with their standard practice.

Can you please share an example of a moment free support you're using in this kind of situations?

For an anchor you can use two pipe clamps and the tighten clamps to the support structure. But clamps can (and do) slip under axial loads. There should be a fixed/welded line stop incorporated into the pipe clamps.

Pipe clamps are a poor detail for large pipes and/or high loads.

• There will be high local stress and clamps are weak.
• Clamps do not have side gaps for thermal expansion.
• Thermal insulation and allowing for pipe movement is difficult with clamps.
• No hard axial restraint
• Open to installation errors, too tight, too loose

Engineered pipe shoes are much better.

An pipe anchor can be a section of pipe welded between the line pipe and support structure.

 

[RVAmeche]

The client prefers clamps because they're cheaper (and possibly no field welding). I agree with KevinNZ that carte blanche applying them for large bore/hot systems is not the best method, if you/the contractor are doing proper pipe stress you will see you need different types of supports than just clamps on threaded rod or spring hangers.

If not using PIP standard support details or other in-house specs, reach out to one of the vendors who can design custom shoes and attachments for your system.