Small reciprocating compressor foundation inside shipping container

[winflex]

We need to mount an identical pair of 11 kW shaft power oil-free reciprocating gas compressors inside a 20ft shipping container.

The manufacturer recommends a typical ACI-351 type 0.6 m thick steel reinforced concrete foundation weighing 5 times the skid weight. No specific information was provided for container mounting the units. No imbalance / vibration information is available.

My question is whether it is acceptable to mount both compressors on a single, reinforced concrete "foundation" that is anchored to the container floor (large lag screws cast into the concrete attach the foundation to the container).
Is epoxy grouting required for small machines like these? I'm considering Chockfast grey for both anchor bolts and the baseplate (2 separate pours).

Is all this effort required or am I completely over-complicating this install because small compressors don't require this level of foundation engineering?

Your feedback is much appreciated!

- Felix

Here is a more detailed description of the compressors, also a picture is attached showing one of the units.

The compressors each have four stages (arranged in a dual 90° V-twin configuration) and are driven by a 15 kW 4 pole motor. Belts and a flywheel drive the compressor input shaft at 450 RPM. The motor is VFD driven, skid weight is 950 kg.
CO2 is compressed from atmosphere to 160 bar at a flow rate of 35 Nm^3/hr. Only one compressor will operate at a time (100% standby).

 

[1503-44]

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[1503-44]

5x mass method is normally good up to 250 HP.
Epoxy grout not required.

Why 2 pours?

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[winflex]

Thank you for the reply!
Two pours, first to epoxy the anchor bolts into the foundation holes, the second to grout the machine baseplate to the foundation. I've read that anchor bolt nuts should be hand tight to prevent movement of the equipment during grouting, hence the need for two pours.
Would you recommend cementicious grout or no grout at all for a small compressor like this?

 

[1503-44]

No grout is probably fine. Use cement grout, if you do.
OK. I wasn't thinking of grouting as a pour.


--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[Rputvin]

All this work for a foundation and you're going to be bolting it to a 1/2" plywood floor that can have a fair amount of flex? Are you putting spacer blocks underneath to support the compressor foundation to the pad the container sits on, or are you keeping the exterior unmodified to retain its seaworthiness?

 

[winflex]

Hi Rputvin,

The container exterior can't be modified because, as you correctly pointed out, it needs to maintain seaworthiness.

The concrete will serve as a "Inertia block" type of foundation for the compressors.
I'm debating whehter to use lag screws to attach the foundation to the container plywood, or if the concrete should be poured on a vibration isolation pad like this one:

https://www.recip.org/wp-content/up...n-Anchor-Bolts-Grouting-October-19th-2017.pdf

One other question recently arose when reviweing API RP 686 regarding multiple rolling element bearing machines on a common foundation:

4.7 The design engineer should also consider incorporating the individual foundations of several machines in the
same vicinity into one common foundation mat. When multiple machines are placed on a single mat foundation, the
dynamic and static analysis shall consider all possible loading arrangements and combinations of the machines to
produce the most unfavorable effects on the supporting foundation, including partial foundation loading due to
removal of individual units for maintenance.
NOTE Consideration should be given to incorporating the foundations of several individual machines in the same vicinity into
one foundation. A large combined mat foundation may provide a more economical foundation than several closely spaced
individual foundations. This may not be applicable to machinery with rolling element bearings that may sit idle while adjacent to
operating machinery that may result in brinneling of the idle equipment bearings.

 

[Rputvin]

We've been doing 20ft container pump rooms for a little bit now, each one is a new learning experience. We're doing domestic shipping, so we've been cutting in doors and access hatches and things. We went down the road of shimming the underside to make the floor more stationary and to do a better job of distributing the load on the final concrete pad, it's not something I would recommend as the undersides are heavily coated in whatever they're using for corrosion protection, which we've also seen variations of.

Be aware the floor type and thickness can vary. We've seen 1/2" and 3/4" plywood floors. The entire floor is floated as the container only contacts the ground at the corners, we've seen some containers that will become fairly springy when loaded with equipment, and we've had to add center posts and other means to deal with the container bounce or flexing when picked up as it has a tendency to tear out anything hard piped (probably not an issue if you're not tied into the walls).