Basic Question Regarding PIP STC01015

[TiCl4]

I have a (hopefully) easy question regarding the aforementioned PIP.

In the quoted section below, what exactly is the area referenced for pipe racks? Is the the area of the flange of the beam?

4.1.2.6 Pipe Rack Piping Loads

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1.Unless more determinate load information is available and requires otherwise, dead loads for piping on pipe racks shall be estimated as follows:

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a.Operating dead load (Do): A uniformly distributed load of 20 psf (1.0 kN/m2) to 60 psf (3.0kN/m2) as determined by engineering judgment for piping, product, valves, fittings, and insulation based on the average size of piping on each level.

 

[strucbells]

No, it would be the area in plan of the entire rack per framing level (ea level with supported pipes).

Do a load takeoff with some estimated pipe sizes and compare to an area load. It's usually appropriate to provide plenty of cushion for adding additional piping in the future for industrial sites, but talk to the owner to understand their anticipated use of this structure.

It's a fairly basic concept, I recommend consulting a structural engineer if this is not in your wheelhouse.

 

[JStephen]

From the way it's worded, I would interpret it like this, for the load on one panel/beam/pair of columns. If columns are not equally spaced, then center of one span to center of next.

 

[TiCl4]

Thanks. It’s certainly not in my arena, so I’ll be contacting some engineering firms. However, I still like understand the basics of the general design principles so I can understand the drivers for designs.

What is the purpose of this 20-60 psf stipulation?

To clarify, I am moving a a current process to a new building, and have created a Plant3D model using the building design (provided by a third party). Using the provided building design, I have run the pipe and located the equipment.This building is a PEMB, so most piping and equipment load is going to the floor. I have placeholder steel for the piperacks in the model right now, with placement driven by maximum allowable pipe span.

I’ll be going to a design firm to actually design the piperack, but was diving into general pipe routing principles that I should follow in order to avoid iterations on the design process. It’s a small application - the largest pipe is 3 NPS on the rack, and we only need two levels of a 5’ wide rack to hold all the pipe in the main rack.

 

[strucbells]

It's just a convenient way to represent the pipe loads for a pipe rack. Let's say you have (2) 16" DIA, (4) 8" DIA, and (6) 4" DIA pipes. You can easily tabulate the weight per foot of each pipe, sum them up, and divide by the minimum width to fit the pipes and any shoes/slides/etc. to get a representative area load. Usually some engineering judgement gets applied to bump this up a bit to cover potential eccentricities in the weight distribution (ie more heavy pipes concentrated towards one side of the rack). It is also common practice to allocate additional capacity for future piping. My experience with these structures is once they are built, industrial facilities owners tend to load them up with pipes, and a little foresight/planning can go a long ways. Can be very difficult to retrofit for additional capacity after a rack is full of pipes... many access issues, foundation issues, etc.

When it comes to actually supporting these area loads, they are obviously only supported where you have transverse framing members supporting the pipe. So you multiply the area load by the tributary length of pipe to each supporting member to get the load on each beam.

Make sure your maximum allowable pipe span is based on your smallest pipe, or that you have provisions for intermediate framing to support the smallest pipes if spacing all supports based on that span isn't efficient.

I'm assuming you are discussing routing this pipe rack inside of an existing PEMB on a new steel pipe rack independent of the PEMB framing. The PEMB will not have the capacity to support any significant pipe rack loads unless these were factored into the original PEMB design (unlikely).

Depending on the magnitude of pipe load and geometry of your pipe rack, it is likely that you will need supplemental footings beyond just the PEMB slab unless the PEMB slab is very thick. Be careful cutting out PEMB slabs, some designs rely on continuous reinforcement in the slab for stability that cannot be cut or will require retrofit if it is. Be sure to provide the PEMB foundation/slab drawings to the structural engineer designing your pipe rack.

 

[strucbells]

Just saw your edited post and that this rack is small and only supports small pipes. Now your request makes more sense.

Re-read the PIP section.."Unless more determinate load information is available and requires otherwise". Do a load takeoff of your 3" DIA and smaller pipes that need to be supported and come up with a representative area load. The 20-60 PSF is just a typical guideline for general pipe racks. You don't have to follow it.

 

[TiCl4]

Yes, this will be a new piperack, but the PEMB is not built yet. It will be supported off the floor of the PEMB, some grassy area, and a tankfarm pad nearby. We are in final design phases, so any modifications to the PEMB floor will be run by the contractors before final bid.

The application size is so small that I briefly considered just throwing some oversized steel (placeholder steel beams are W 8x13s) and anchoring on it and calling it a day. Only briefly, though.

 

[r13]

The estimated piping load is for preliminary design purpose, during which the exact pipe sizes are yet unknown, and the chose of 20 psf - 60 psf is put on the hand of the experienced engineer to conduct plant layout. Once the size of pipes are determined, the exact pipe load shall be calculated and compared with the estimated load.

 

[WARose]

Have to echo what the others said about "additional piping" in the future.....not just one one level, but what they'll try to hang off the rack once they've filled up the levels they have.