Steel Pipe Rack Design (mixing mechanical engineer loads with structural engineer loads)

[x5bulldog]

I am designing a steel structure that supports alot of mechanical piping. The main or the biggest pipes my structure supports are referred to as Main Steam and a Process Steam Piping. Unfortunately in the business I am involved-in requires my structure to be designed way before the mechanical engineers provide me any loads. So typically our structures are way over-designed. Then as the mech engineers begin their design and feed us structural enginners loads we check our structure to see if it is okay and often we are more than okay. But also we are required to reinforce our structure where the loads are greater than anticipated.

Loads I usually receive are hot (operating) loads, cold loads, hydro loads, restraint loads. I also receive movement of the pipes. There are so many pipe support locations throughout my structure. A single pipe can run horizontal than bend and go vertical & back to horizontal. Piping is constantly being re-routed and stressed. The loads & movements I receive are the worst load case scenarios.

Can someone reference me some literature on to better understand the loading from all the pipings in an industrial facility (as in a power plant). I am already conservative with my structural loads and with the conservative loads I get from mechanical I think sometimes my design is way overkill.

I guess I am trying to understand the mechanical load paths and how to check it with the structural load path. FOR Example I can have a strong wind or seismic event acting east-west direction. I would like to know if some of the pipe loads will always act in the north-south direction. Or if I get two loads from two diferent pipes, I would like to know if they will never occur at the same time. Just small stuff like that. Or another example; if I have a three story structure and a lot of the mechanical boiler feed pump piping is supported on the first level, will the load from a different piping on the third level be acting in opposite directions or do they occur at different times.


Thanks for your time

 

[x5bulldog]

No offense, but some mechanical engineers do not like being questioned about their design from other engineer outside their discipline(structural).

 

[BigInch]

The only sane way to design pipe racks is to put 40 lbs/ft2 on each rack level. At 20 Ft bent spacing that's 800 plf vertical load on the beams. Design the beams for lateral load of 10% of the tributary weight (pipe friction in a rack goes both ways and mostly will cancel out), making for about 80 plf of lateral load. If you have any large pipe loads from some big ones, or pipe anchors, or other special loads, superimpose those on a case by case basis.

Designing for each and every pipe load is next to insanity, if not the classic definition itself.

Independent events are seldomly independent.

 

[DSB123]

x5bulldog,
That's strange you say the mechanical engineers provide you with the piping loads. Normally it is the Pipe Stress Engineer or sometimes a Piping Engineer, with a bit of nouse, that provides piping loads. As for the combination of loadings there is a very good ASCE publication - cannot remember it name for the moment (i will get back) which proposes different scenarios to be designed for dependant upon the types of piping on the rack. The answer is you do not take all of the piping loads acting in the same direction at the same time. Normally 25% is taken- but the ASCE document goes into this more deeply. Also remember to place the larger lines over or close to the column uprights to minimise the beam bending. The piping engineers I know are very open to debate on application of piping loads - you must just have some obstinate ones on your project!!!!

 

[x5bulldog]

Thanks for the help,

I have the latest ASCE Wind loads on Petroleum Facilities and mentions Pipe Racks, and it discusses 10% of the tributary. Also I have seen the 40psf load from the Process Industry Standards PIP STC01015. This article is about thirty one pages and does not cover alot.