One equitment at company has low vibration (3.7mm/seg), the mechanic take the comparator on and the disaligment measurement is 0.015" radial (RIGID COUPLING). Why does not it show high vibration?. If anyone has have that kind of experience. Please comment me.

Regards,
Fabian

Fabian,

3.7 mm/sec, is that close to .15 in/sec?
Is this the overall value or 1X or what?

.15 in/sec is approaching a medium high level, in my opinion, depending on what type of equipment it is and what frequency it is.

So, by "rigid" coupling are you saying no "flex" at all between the driver and driven parts?

Are your readings 3.7 in all directions, horizontal, vertical and axial?

Only my opinion and I could be totally wrong.

What type machine and what type reading. How long in service? First time measurement and what type bearing - running on packing????!!!!?

Generally 0.15 IPS isn't too high in my opinion and is field acceptable. But, 15 mils misalignment on a rigid coupling and one would expect to find higher magnitudes of vibraton at 1X. How reliable is your alignment readings? Something doesn't add up!

Fabian,

Depending on what type of equipment this is, the 0.015" of radial misalignment may be acceptable. Turbine generators are often aligned cold with a vertical offset to account for thermal growth. These couplings have a rabbett fit so the coupling halves are in line when bolted up. The coupling faces may be open or closed at the top, again depending on the thermal growth.

My advice is to look in the instruction book for this equipment for the manufacturer's recommended coupling alignment specification. Judging by the vibration readings, the alignment is probably close to specification.

John