02-08-2012 11:33 AM - edited 02-08-2012 11:34 AM
A helpful publication is LEBV0915, Engine Installation and Service Handbook, page 98 has a quick discussion of this topic. Since I'm in the US and you didn't say where you are I'll do this in US units because it easier for me.
Cast iron has a thermal growth rate of 0.0000066 inches per inch per degree F. The formula is Expansion Coefficient X Linear Distance X Differential Temperature = Thermal Growth
Linear distance is the distance from the mounting point to the reference point, so for alignment it would be from the bottom of the mounting foot to the crankshaft centerline, off top of my head it's about 20 inches, but you need to measure to be sure.
Differential temperature is the difference in temp between when you do the actual alignment or measurement and the normal running condition of the equipment. So if you are working and the engine is off and cold and at 60 degrees F, and the normal engine operating temp is 195 degrees F, your differential temp is 135 degrees.
So from example you have 0.0000066 X 135 X 20 = .0178", total thermal growth for this example, you have to calculate for both prime mover and driven machine, the difference in the two thermal growths is the thermal offset you apply for a cold alignment.
In actual practise, I use 0.012" engine low for most alignments on 3600 products for a starting point, but depending on your equipment, actual ambient conditions and operating conditions that number will vary slightly. The vertical thermal growth should be the same for both the 3612 and 3616 because they likely have the same mounting foot the crank centerline measurement, unless you have some kind of custom mounting arrangement.
Hope that helps, Mike L.
02-08-2012 07:01 AM
I'm new to this forum. Can anyone tell me the thermal growth rate for CAT 3616G and 3612G engines?
We are using these with Ariel reciprocating compressors and Thomas Rexnord disc pack couplings.
Thanks in advance.
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