#16284 - 02/26/08 11:08 PM
Roller bearing...
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Member
Registered: 06/23/07
Posts: 285
Loc: Manila, Philippines
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Hi all,
After running thru different adjustment of spring and vertical support near at pump, it seems like this problem dont quit. All flexibility are tried and failed. BUT... I have this option last option which my project engineer dont agree the use of "roller bearing"(simply because he dont have any experence with it). I am new to this practice so I would like to ask for your opinion of the credibility of this roller bearing in service and also economic aspect...
Thank you!
Regards!
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BOM
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#16311 - 02/27/08 09:01 AM
Re: Roller bearing...
[Re: bom]
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Member
Registered: 03/09/00
Posts: 482
Loc: Pittsburgh, PA (& Texas)
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Have you investigated spring mounted pump bases?
Roller bearings? Not something that I have ever seen.
John
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John Breen
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#16324 - 02/27/08 05:27 PM
Re: Roller bearing...
[Re: John Breen]
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Member
Registered: 06/23/07
Posts: 285
Loc: Manila, Philippines
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Sir Breen,
My suction configuration is almost and L(all segment are in horizontal), two of vertical supports are spring hanger(the only two) because of pump displacement of nozzle, one in the pump segment and one in other segment. I put close two guide in the long segment of L so ther will no rotaion at the vertical axis.
Now the problem is, when the segment(not in pump)experience thermal growth, the horizontal loading of both guide is very big that a friction reaction force of a teflon (mu=.1) would exceed pump allowables. When doing friction less, it probably drop to 50% w/r allowable. So I try to look at the vendor catalog where I find Roller bearings with mu(max)=4% to the reaction.
Thank you...
Regards!
_________________________
BOM
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#16327 - 02/27/08 11:47 PM
Re: Roller bearing...
[Re: bom]
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Member
Registered: 02/25/04
Posts: 643
Loc: Maharastra, India
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Dear,
Isn't it a too obvious solution! Also, will bearing vendor certify maximum friction coefficient not more than 0.04 ?
As you wrote that you are new to this practice, you need to develop higher order thinking skills, popularly known as HOTS (term borrowed from CBSE, India) to meet the demands of ever-changing tomorrow.
Breen-Sir has given us a lot of very useful links in this discussion forum to develop such thinking ability. Search & learn from these resources first.
regards
sam
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#16329 - 02/28/08 12:29 AM
Re: Roller bearing...
[Re: sam]
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Member
Registered: 06/23/07
Posts: 285
Loc: Manila, Philippines
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Isn't it a too obvious solution! Also, will bearing vendor certify maximum friction coefficient not more than 0.04 ? You know the credibility in aplication of this roller bearing and its physical change due to its inovation as per vendor is concern? That's my question Sir Sam. Regards!
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BOM
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#16346 - 02/28/08 12:13 PM
Re: Roller bearing...
[Re: bom]
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Member
Registered: 08/13/03
Posts: 405
Loc: Europe
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i would question your rationale.
I hate springs on pumps, but your situation seem to be a case of throwing everything in your arsenal to create a solution, rather than solving the cause.
Be VERY wary of gadgets and gizmos, in most cases a strong will should be enough to convince the design team to change the configuration to something more acceptable.
take a step back and look for the simple answer,
sure, the lead wont like his medicene but who does, and it (usually) makes you feel better.
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#16353 - 02/28/08 07:14 PM
Re: Roller bearing...
[Re: SUPERPIPER]
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Member
Registered: 06/23/07
Posts: 285
Loc: Manila, Philippines
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Thank you SUPERPIPER.. It really make's a flash back..  Well in my case this was prety low in flexibility, a 24" pipe with temperature of 85deg.C at start-up the transient force due to friction enough to distort the pump with 200%.(I attach some drawing) Regards! 
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BOM
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#16359 - 02/28/08 10:58 PM
Re: Roller bearing...
[Re: bom]
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Member
Registered: 02/25/04
Posts: 643
Loc: Maharastra, India
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Dear bom
'at start-up the transient force due to friction'
Is there anything 'transient' in this case ?
regards,
sam
Edited by sam (02/28/08 11:00 PM)
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#16366 - 02/29/08 01:40 AM
Re: Roller bearing...
[Re: sam]
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Member
Registered: 06/23/07
Posts: 285
Loc: Manila, Philippines
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mmmhhh... I dont know. Maybe you know everything can you tell me please? 
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BOM
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#16369 - 02/29/08 03:02 AM
Re: Roller bearing...
[Re: bom]
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Member
Registered: 09/20/07
Posts: 39
Loc: Aberdeen
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Good morning all
bom,
Experts have given their knowledgeble opinions in previous posts.
I understand you must have tried many things, but thought of sharing my view of optimising the solution(keeping in mind the last pump I analysed was some 4 years back!).
IMHO,if I were to try optimising this situation, I would protect the relatively weak nozzle(pump) more in comparison than the relatively strong (vessel) as seems practical. At least you have the options open for reinforcing the vessel nozzle with higher allowables.
How about using the spring support #5 exactly below the nozzle #6. Instead of spring #4 I would try using hold-down support with guide at the place of spring #4 but very reasonably close to the elbow and to take out the moment I would try using +y and guide in between #3 and #4 as long as it helps.
The torsional moment passing onto pump nozzle may be brought within limits provided you have more CONTROL over the elbow below vessel nozzle dipping down. Replacing the spring #4 with a Y support and controlling the pipe movement in -y direction below the vessel nozzle can be of some help.
my two cents!!
regards,
Siddharth.
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#16370 - 02/29/08 03:58 AM
Re: Roller bearing...
[Re: Sid.]
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Member
Registered: 08/13/03
Posts: 405
Loc: Europe
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Good morning all
bom,
Experts have given their knowledgeble opinions in previous posts.
I understand you must have tried many things, but thought of sharing my view of optimising the solution(keeping in mind the last pump I analysed was some 4 years back!).
IMHO,if I were to try optimising this situation, I would protect the relatively weak nozzle(pump) more in comparison than the relatively strong (vessel) as seems practical. At least you have the options open for reinforcing the vessel nozzle with higher allowables.
How about using the spring support #5 exactly below the nozzle #6. Instead of spring #4 I would try using hold-down support with guide at the place of spring #4 but very reasonably close to the elbow and to take out the moment I would try using +y and guide in between #3 and #4 as long as it helps.
The torsional moment passing onto pump nozzle may be brought within limits provided you have more CONTROL over the elbow below vessel nozzle dipping down. Replacing the spring #4 with a Y support and controlling the pipe movement in -y direction below the vessel nozzle can be of some help.
my two cents!!
regards,
Siddharth.
Sage advice, Most pumps should be strong enough to bend an elbow 1 size larger than the nozzle, so in this case, the pump must be really weak (en5199?) I'd agree with removing the first spring. But friction cannot be your reason for failure, otherwise something is not right with the specified equipment. Changing the configuration will not matter if you equipment is not srong enough to flex the pipe. If that is the case, change the pump (API) or as a last resort, use expansion joint, although that in itself is another long question. best of luck
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#16371 - 02/29/08 04:14 AM
Re: Roller bearing...
[Re: SUPERPIPER]
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Member
Registered: 09/20/07
Posts: 39
Loc: Aberdeen
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SUPERPIPER
I agree without second thought that the most pumps should be strong enough. Rather I should have said in previous post with regards to the low allowable values for the pump nozzles for qualification in this case.
I remember one of the senior telling me that in such a last resort, the pump vendor can be requested to uprate the pump base plate/bolting so as to accept higher loading, provided the pump vendor confirms the acceptability.
Regards,
Siddharth.
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#16374 - 02/29/08 05:20 AM
Re: Roller bearing...
[Re: Sid.]
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Member
Registered: 06/23/07
Posts: 285
Loc: Manila, Philippines
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Thank you Sid..
My main purpose of spring would be reducing the friction load. But I had to admit this will call for pad.
Thanks everyone...
Regards!
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BOM
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#16376 - 02/29/08 05:35 AM
Re: Roller bearing...
[Re: SUPERPIPER]
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Member
Registered: 06/23/07
Posts: 285
Loc: Manila, Philippines
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Thank you Sir Superpiper,
The pump is already decided by the vendor but the vessel is on construction so, it would be my first option to place a pad in my nozzle. That should solve the case. About the spring in segment W/ pump.. This is use to compensate the thermal displacement of the nozzle.
Thank you again..
Regards!
Edited by bom (02/29/08 06:54 AM)
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BOM
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