Pump- motor alignment (overhung) doubts-reg.

Problem is between the prime mover and driven pump--RIGHT?

ANS: Introduce improved self-aligning couplings.

dear mr. sampath kumar,

thanks for your reply. i feel i am taking the alignment readings correctly, as it was not changing when i take 2 to 3 times (usually). your last statement should be agreed at any cost ( as long as there are no vibrations there is nothing to worry of alignment readings).

thanks,

regards,

r.babu

hi Mr. George,

thanks for your detailed mail. today (saturday) is my weekly off and tomorrow i will get the informations you need to know. whether you agree or not you are going to solve my company's great problem. i am also working as rotary equipment supervisor for your information.

regards,

r.babu

Hi Babu,

how do you measure and indicate misalignment?

As there is no bellows in both lines there are forces from these lines transmitted to the pump and distorting pump and its mounting. These forces are temperature dependant.

Additionally the pump to motor mounting may be not adequate: too compliant in the wrong way.

So as stated by others above it would be best to have a sketch and photos of the configuration.

Without having these I would guess that the platform where motor and pump is mounted is to be made more rigid: strengthen it by adding considerable more and screwed or welded supporting beams.

Then make the mounting of pump and motor isotropic with respect to its elasticity. If a flanged motor is not suitable for the pump then add an upper beam (above the pump and motor) to the lower supporting structure and screw this very reliably so that any forces (axially between pump and motor) will not bend anything.

This beam above is very likely to remove also most of the temperature-induces distortions.

If both recommendations do not work: send the sketch and the fotos.

Have success!

RHABE

Dear mr. rhabe,

sorry for the delayed reply. as i was fed up with my regular duties i could not send the pump photos promptly. now i am sending the photos of the problematic hot service pump (7304j). a brief discription of the pump 7304j may help you to pinpoint.

· the pump operates at 250 degree celcuis.

· so far, no coupling (not even the flexible membranes) damage happened.

· john crane TSKS series metalic flexible membrane coupling is used.

· pumping hydracarbon ( refined kerosence cut) at 30 bar discharge pressure.

· distance between shaft centerline and the motor base approx. 400mm

· pump type: simply supported and seal plan 21 used.

· distance between two bearings (antifriction bearings. drive side cylinderical brg and nondrive side angular contact ball brg set with back to back arrangement) is approx 1000 mm .

if you need more information please let me know. i am herewith sending four photos of 7304j pump. later i will send the other pump 7305j details which is cold service pump so that you will not get confused with this pump.

thanks,

regards,

r.babu.

Hi this is parbat,Jamnagar(india)

If pipe support is culprit

then u can check it by flange bolts of suction and discharge flange, putting dial in position,if during loosening reading of dial changes,then there is strain in piping ,it has to remove before alinment,

Second thing u should have cold alignment reading( U might have noted during maintenance)

Now when pump gets its max temp. stop it and take new readings immediately after stopwhich may be different U have noted earlier if hot expansion is problem there. Diff. of yours and this reading will be cold target readings for hot alignment,

Hi there,

what is your actual goal? If motor or pump shafts, bearings or seals are getting damaged then you need to use a coupling with better flexibility. It is perhaps more economical then anything else. Think of coupler as relatively inexpensive component wich is easy to replace without re-alignment...

The coupling will take all stress due to misalignment resulting from piping/base thermal movement and all you need is to develop a replacement strategy i.e. interval.

Cheers.

DEAR G.M.,

THANKS. YOUR ADVICE IS A APPRECIABLE ONE. SO FAR WE DIDN'T EXPERIENCE ANY COUPLING DAMAGE IN OUR SITE. THAT IS WHY I WORRIED ABOUT. MY QUESTION IS THAT COUPLING DIDN'T FAIL MEANS IT TRANSMITS THE STRESSES TO THE PUMP INTERNALS. ISN'T IT? SO I FEEL THIS MISALIGNMENT MAY DAMAGE THE PUMP INTERNALS IN THE NEAR FUTURE.

ANYHOW THANKS,

REGARDS,

R.BABU

dear mr ramanathan babu,

understood that for axial dial shoulnd not be rotated along with the motor or pump coupling since in some motor shaft there should be a allowable axial movement of .1 to.3 mm hence due to floate of motor shaft dial always shows different readings on different timings.so you keep either one of the coupling stationary which means you dont coupled the coupling by loose or single bolt.remember your readings on axial only were changing.am i correct?

sorry to say mr.guest, i am not using rim and face method for alignment which will give wrong axial readings because of axial movement of pump or motor shaft as you said. i am using reverse indicator method which will not get affected by the axial movement of any shaft, as the readings are taken only on the rims. anyhow thanks for your comment.

regards,

r.babu