TLHS
Structural
- Jan 14, 2011
- 1,600
Hi all,
Does anyone have good references regarding vibration design of rotating equipment skids? I have done a fair number of them, but it's generally from first principles, and I also generally have the option to lay things out in a way that makes things easy (i.e. I can keep equipment low, load paths really direct and grout things that worry me). On the rare time I am worried about vibration on a numeric level due to equipment size or service I'll run what I think it necessary regarding dynamics looking for resonance or occassionally doing a detailed time history. I'm trying to evaluate someone else's layout that I don't really find ideal, so I'd like to have better documentation on the standard of care.
Are there any design guides out there, preferably that have things like "Do X level of evaluation of Y types of equipment at Z RPM". The GMRC has some documents about reciprocating compressors, but the one I want is $500 USD and it's hard to justify that when I don't really know what the contents are (although their compressor pipe support document that I have is pretty good).
The most I've tended to see are things that say if power or RPM are over a certain size, do a 'dynamic analysis' without any thoughts on the level of care. That isn't all that helpful. Lots of specifications just say something like "steel shall be sufficiently rigid." The level of care can be anything from a really quick frequency analysis on a stick frame FEA to a time history analysis including the equipment housings and plate or solid models of the structural members that you'll see for complex reciprocating equipment. It's that continuum that I'd really like more solid ground to stand on. The extremes are easy to decide on. Low speed, low power, low mass is an easy eyeball, high speed, high power, high mass is easy to justify a lot of steel and a lot of analysis. Mid-range stuff is where you see all sorts of skids on the market that look really flimsy but work fine and it's hard to sell or deliver something too fancy to a client. The standard of care seems to be typically a resonance check (maybe / maybe not), a conservative deflection check and best practice detailing wherever possible (fully welded cross members at equipment anchor bolts, full depth stiffeners at any bolt location, carry through loads directly into the foundation bolts wherever possible, pretension with stretch length at connection points, don't do hangers style flange welds, stiffeners anywhere load could conceivably otherwise try to transfer by weak axis bending in the flange or web, etc).
Basically, I have a pretty good feel for reasonable engineering judgement on this kind of thing, I'd just really like to be able to point at more authoritative documents when justifying decisions sometimes.
Does anyone have good references regarding vibration design of rotating equipment skids? I have done a fair number of them, but it's generally from first principles, and I also generally have the option to lay things out in a way that makes things easy (i.e. I can keep equipment low, load paths really direct and grout things that worry me). On the rare time I am worried about vibration on a numeric level due to equipment size or service I'll run what I think it necessary regarding dynamics looking for resonance or occassionally doing a detailed time history. I'm trying to evaluate someone else's layout that I don't really find ideal, so I'd like to have better documentation on the standard of care.
Are there any design guides out there, preferably that have things like "Do X level of evaluation of Y types of equipment at Z RPM". The GMRC has some documents about reciprocating compressors, but the one I want is $500 USD and it's hard to justify that when I don't really know what the contents are (although their compressor pipe support document that I have is pretty good).
The most I've tended to see are things that say if power or RPM are over a certain size, do a 'dynamic analysis' without any thoughts on the level of care. That isn't all that helpful. Lots of specifications just say something like "steel shall be sufficiently rigid." The level of care can be anything from a really quick frequency analysis on a stick frame FEA to a time history analysis including the equipment housings and plate or solid models of the structural members that you'll see for complex reciprocating equipment. It's that continuum that I'd really like more solid ground to stand on. The extremes are easy to decide on. Low speed, low power, low mass is an easy eyeball, high speed, high power, high mass is easy to justify a lot of steel and a lot of analysis. Mid-range stuff is where you see all sorts of skids on the market that look really flimsy but work fine and it's hard to sell or deliver something too fancy to a client. The standard of care seems to be typically a resonance check (maybe / maybe not), a conservative deflection check and best practice detailing wherever possible (fully welded cross members at equipment anchor bolts, full depth stiffeners at any bolt location, carry through loads directly into the foundation bolts wherever possible, pretension with stretch length at connection points, don't do hangers style flange welds, stiffeners anywhere load could conceivably otherwise try to transfer by weak axis bending in the flange or web, etc).
Basically, I have a pretty good feel for reasonable engineering judgement on this kind of thing, I'd just really like to be able to point at more authoritative documents when justifying decisions sometimes.
