Can anyone guide me on Equipment Supports in CAESAR?

1. Many Equipments are bolted, so whether I should provide Anchor or Y REST, X STOP, Z STOP with no gap, and RX and RZ with some nominal free movement like 0.2 degree or something.

2. Is there some general guideline... Like Heat Exchangers are One Side Anchored and One Side Y Rest and Lateral Stop...

I’m new to this forum with very little experience. My view on above topic is as below. Senior Stress guys please correct me if I’m wrong.

In the models I’ve analyzed so far, equipments are much stiffer than connecting piping; therefore it is the equipment that governs thermal movement of nozzle/pipe. In such cases defining anchor for fixed point of equipment should be correct. In above case only lateral movement of support for equipment is restrained.
I do not understand (due to lack of experience/knowledge) as to why should we take advantage of free RY and 0.2 deg rotations in RX and RZ unless it is clear from equipment drg ?? This would result in lesser stress, nozzle loads and displacements.

If pipe and equipments have comparable stiffness, then in order to minimize thermal loads and stresses some equipments are generally kept sliding (e.g. small filters, sliding pumps). In such cases each restraint (X, Y, and Z) should be defined separately with appropriate friction factor and appropriate gaps with appropriate rotations to be defined by looking at supporting arrangement of equipment. Wt of equipment is important in such cases (for checking nozzle loads)

Vyanky,
Please make sure that you are defining correct support conditions (i.e. 6 DOF are properly restrained) in C-II without undue risk.

Thanks Sigma,

I am facing main problem in Small Filters.
Due to Anchoring it, the Nozzle Loads and Moments are going very high.

But, if we don't define Rx, Ry and Rz in Equipment support, then CAESAR'll consider it as completly free...

"vyanky", have someone there review your work. A mistake defining a boundary condition can completely change the outcome of an analysis.

Typically a bolt type connection would be defined as an "X" restraint, and a "Y" restraint, and a "Z" restraint. If there is a slot in one direction, that direction needs a gap defined. However, do not model construction tolerances. You mentioned 0.2 deg above - this is a construction tolerance, ignore this in your CAESAR II analysis.

You are correct, that if you define the "XYZ" restraints as described above, the rotations are free. However, your equipment is not going to rotation because you (probably) have four bolts at the corners. So these translational restraints will prevent the equipment from rotating.

If you're having trouble with your model due to the anchorage of your equipment, talk to the vendor. Perhaps they can offer additional advice on how to model the boundary conditions that you are unaware of.

There is a useful tool in CAESAR II for estimating nozzle stiffnesses. But you should ALWAYS have someone competent review your work. I have been doing this stuff for 30 years, and wouldn't dream of considering something final without having it reviewed. Richard Ay is clearly right - once you use COADE's little tool, you should talk to an engineer at the vendor's office and discuss the results with him. He will have a better insight into the vessel. Sometimes, there are internals that make thinga a lot stiffer than you would think from the shell dimensions.

It's best to consider equipment as truly rigid if you can. Then, if your piping passes the code and the equipment allowable forces and moments are within limits, you KNOW the system is OK (barring metallurgical screw-ups). Displacements of nozzles should always be included. And your first, second, and maybe even third option to reducing the piping stresses, or terminal point forces and moments, should be to make the pipe more flexible.

But, as I have posted before, NOTHING is really and truly rigid. If a Kenmore diesel rig is rolling down the highway at 75 mph and hits a bug, the Kenmore deflects. Not very much, though, in relation to the bug.

If you absolutely have to consider the flexibility of the equipment, then do it. But be very aware when you step into that swamp, there are creepy-crawlies and nasties with sharp teeth below the surcface. You are getting away from your own expertise, and from the expertise of generations of good pipers as documented in the Codes.

If something goes wrong with a piece of equipment that you have modeled as flexible without getting some good advice and competent review, YOU and YOU ALONE are responsible for the problem. This is usually not a pleasant situation to find yourself in.

Is not modelling construction tolerances typical practice. I have always modelled them in (perhaps mostly because I can), but I'm typically not tremendously comfortable near pumps if the tolerance makes a difference between passing and failing. (However when that is the case I always mutter about how the loads aren't meant for computer analysis) Away from equipment I usually model gaps as well, but will eliminate them if my solution is not converging.

Thanks all for your thoughts.
Shannon

I don't recommend construction tolerances, because you can't control them. On the other hand, if you call for a 1/2" gap someplace, then that is what you want, and that is what you model.

I once had a client laugh at me for specifying a gap. Apparently, they had no faith in their construction crew.

BTW, I haven't been to the "new" forum much. Looks nice.

There are good ways for design people to set up a job so that field people will be able to fit up piping to alleviate construction tolerances. It all has to do with the placement of field welds, purchase of some spools in strategic locations with extra length to allow for field cuts, etc.

If you have a 400' run of pipe with loops and such that connects to a sensitive nozzle on each end, you do not have to allow for 1/4" and 0/2 degrees of fit-up error in every direction at each weld joint and drive yourself nuts trying to allow for it. Statistical process control concepts in general do not apply to piping installation.

In general, most piping designers with 20+ years of experience are pretty good at this sort of thing. Tell your designer for your project about your concern and he will likely be able to help you.

You may also have a good piping installation spec available that you can read through to see how it's done. In general, there are two valid methods. You can build the piping from critical nozzles outward and use field adjustment spools to close the middle. Or, you can build from one nozzle to the other, and then use torches with rosebud tips to heat the piping and allow it to be pulled into alignment with the final connection. This second method is not valid for alloys or components that require PWHT in the field!!!!

As to Richard Havard's comment, if you need a gap, specify it. Put it somewhere where the field crew can "build out" from both ends and allow for field adjustment spools in all three axes at the gap location. It will happen, and pretty accurately. Clients occasionally get seduced by their labor contracts into believing that their maintenance crews are construction crews. They aren't, not by a long shot.