Requirement about leveling and contact area about the skid ?

[spybreak]

Hello.
I have questions regarding when installing a pump skid without grouting, by just bolting on structural beams)

1. Is there a leveling requirement/recommendation/procedure about the skid, not about the pedestal pad where the pump is actually sit?
(I studied API 686, but I think it only tells you how to measure the level at the pedestal pads, not at the skids)

2. Is there a requirement about the contact area between the skid and the foundation just below? How should I deal with the gaps between them? (No grouting is allowed in my offshore projects.)
After a few times of lifting the skid during transportation, it’s been deformed and when it’s laid down on the foundation, there are always gaps. Although the deformation is within the acceptable region of the structural calculation, I don’t know whether I can just leave the gaps as they are.

 

[Artisi]

Nothing special here, bolt the skid to the structural steelwork as you have no other option open to you. BUT you must consider the pump / driver relationship and alignment (sounds like a problem waiting to happen)

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[nickelkid]

Take a look at API610. 7.3.20 /21 for baseplate criteria without grouting

 

[BigInch]

Actually it depends on the skid design itself. I've seen many skids (most of them) that were unsuitable to allow spanning beneath them, especially during startup torque loads. Many more skids were not suitable for lifting at four corners, requiring the equipment to be winched and dragged into place. It also might depend on the power of the motor, larger machines (over 250HP) should be grouted. Those over 1000HP would perform better if the contact area of the skid were made as large as possible and finely leveled with epoxy grout. Many manufacturers recommend the same, assuming that the skid will be continuously supported. Check the mfgr's installation instructions.

The skid design should be checked for static and vibratory deflections. Supporting structure should also be checked for dynamic action and the skid, or supporting beams, be strengthened when vibratory amplitudes are above limits. Faster equipment speeds require lower vibratory deflection limits. The speed of the machine should be well outside the range of natural vibration frequencies of the skid and supports. If in doubt, have a qualified structural engineer with dynamic equipment design experience check the skid and support design.

 

[Tmoose]

Oh man.

Is this a first of a kind installation?
What is the wording in the contract about responsibility for nonconformance of the equipment you are providing?

I anticipate difficulties passing vibration acceptance tests. Even IF the pump base itself is (as others were concerned) adequate to maintain motor/pump alignment under operating conditions.

There needs to be an excellent, continuous load path between the equipment feet and the machinery deck etc. The pump base needs to be stiff enough to keep the equipment well aligned and 100% self supporting and on any 3 of the 6 or 8 anchor points.

Which the typical pump base is not. Even before the flappy flanged interface at the foundation hold-down bolts is considered.
And, too often, after "grouting" as well.
A stiff load path is determined by geometry, not material name, or weight/mass.

If grouting is forbidden, I think I'd plan on shimming the contact points at the anchor bolts individually with pre-cut commercial stainless steel shims, and being darned sure my anchor bolt locations were not sprinkled arbitrarily on steel decking.


Or, as is apparently common for machinery mounted in and on ships, call the grout "chocking."

http://www.chockfast.com/