Crosshead's pin load in reciprocating compressors

[sinectica]

Hello guys,
I would like to know which reciprocating masses I should consider in order to calculate the inertia force (load) on the crosshead pin of a reciprocating compressor.

I have two different informations about this:

* piston + piston rod + crosshead = total weight
* piston + piston rod + 1/3(crosshead) = total weight

As the crosshead have an important weight the result is different in both cases, and it has to be added to the pressure forces acting on the piston.
My goal is to be sure that I have enough reversal rod load on that pin, in order to guarantee the lubrication.

Do you have a clear idea of which masses have to be considered or do you have any link where I could find further information?

Thanks a lot for your kind help,

Marc

 

[zdas04]

I can't believe that the difference matters for a reasonably loaded machine. If I'm going from 22 psia to 100 psia (4.5 ratios) the net compression force on a double acting 10-inch cylinder is over 6,000 lbf at TDC and 5800 lbf at BTC disregarding masses. The crosshead weight is different for each frame, but it is never anything like 3 tons. If it is 150 lbm then the difference between using the crosshead weight and 1/3 of it is 100 lbm--not in the same magnitude as the compression forces.

I'd use whichever equation gives you the most conservative result.

David

 

[sinectica]

Hello David, many thanks for your help.

In the case that I'm studying to consider a mass of 453 kg (which considers 1/3 crosshead) gives me a inertia force of 82 KN which leads into don't having reversal load on the pin.
On other hand, if I consider the complete weight of the crosshead (which is 375 kg), I have a total reciprocating weight of 703 kg which gives me a inertia force of 128 KN. Then it's enough to give some reversing load.
That's the reason why I would like to be sure which is the correct weight to consider and any available information in the net will be appreciated.

Thanks a lot
Marc

 

[nickelkid]

The crosshead is 100% reciprocating weight. You need to add 1/3 of the connecting rod weight to the reciprocating weight.