Customerally we find in many P&IDs bellow shown in pump suction line only for ambient water piping - why ? Is it for vibration isolation ?
If it is provided for construction dimensional mismatch or vibration isolation, why it is not provided at discharge side of pump ? Or, it is just a copy of the previous projects's P&ID, where it was provided for some other purpose, say for meeting allowable load at pump nozzle ?

What could be the possible reason ?

regards,

sam

Sam,

Your answer is yes.... often times expansion joints are shown in P&IDs by people who really have no idea whether they are needed or not.

Centrifugal pumps do not vibrate much if at all really but I heard justifications based on vibration which is usually nonsense...

Sir,

Thanks for your bold reply.

But, most of the engineers never question; they silently follow the traditional path.

regards,

sam

But if the EJ was put in for vibration, why not also in the disch.? I think Sam's comment, "most engineers never question," has it precisely. I have worked with a small number of process engineers who think all pumps should have EJ's at all nozzles.

Also, many engineers are unaware that a well-trained piping designer (regretably, a rapidly-retiring breed today) can almost always design the piping such that loads on the pump nozzles fall well within limits. Almost all the overstressed pumps I have analyzed recently were designed by pipers whose design experience was mostly CAD school or who came from industries where EJ's are used everywhere. Stress-sketches from the "old-school," usually petrochem-trained pipers were generally inside API limits.

Sam,
Another possible reason for EJ on pump suction might be settlement of the tank foundation, causing initial displacement of the suction piping to pump.
This would not be a thermal expansion load with multiple cycles. It would have added loads to consider on a pump.
Since pump suction pipng is usually of larger diameter, and installation requirements might dictate straight run inlet piping to the pump suction, there could be more challenges to designing adequate flexibility into pump suction piping. Pump discharge pipipng has fewer constraints. The discharge pressure also has more concerns for EJ thrust loads, leaks, or failures.

Hi Richard Yee,
Hope you are keeping well. Remember me? IOF...
Very good comment! I have also used bellows recently on big cooling water pumps suction to allow for 15mm settlement between the towers and pump bases.
Regards
Ranka

Hi Ranka,

Your example of cooling water pumps shows that the weight or thermal cases don't always result in the largest loads on a pump. Soft soil condition and big tank size can combine for settlement greater than 50 mm. Just another item to keep in mind. I like the vertical submerged pumps more more than horizontal pumps on cooling tower sump applications partly for that reason. Maybe if the foundations were tied together the differential settlement could be zero...

Good to hear that piping stress is in good hands for RSA. The IOF steam piping model has provided addition benefit in the beta testing of ver 5.0 , uncovering incomplete items in 5.0 report outputs.

Richard, I did learn a lot from you on that job, for which I am very grateful. You were the only REAL LIVE teacher in my carrier apart from the literature and this forum.
It is good to hear that there was a "life after life" for our steam model.
I wish you all the best and always looking forward to see you comments on this forum.
Ranka

If you have a settlement issue to contend with here are my suggested solutions and the order of preferred remediation...

1)Common foundation for pump, supports and tank.

2)Spring cans and added piping flexibility (offsets, loops etc.).

3)Expansion Joint...

Expansion Joints should usually be selected as last choice, they are very good when all goes well between design, installation, and operation... but when they are bad they are very bad.

If you have a joint attached to a tank nozzle with no shutoff valve and it fails you would de-inventory the entire tank.

If we select a EJ in the suction line of cooling water pump,how to consider the thrust force act on the pump?
Thanks!

Pressure thrust is not that important for suction lines.The usually used EJ on suction line is the untied bellow.Apart from the vertical settlement the use of expansion joint(untied) also allows for rotation and misalignments which can be critical for small lengths large dia suction piping.
I feel expansion joint is better to use in place of springs(specially in such examples as suction piping of cooling tower pumps)in non hazardous fluids
Best regards

Dear pipe_engbangalore,
Can u pl. eleborate on what you are trying to say by the statement"Pressure thrust is not that important for suction lines.The usually used EJ on suction line is the untied bellow".

I would like to know the technical reasons for you saying so.Also I would like to know what your views are on the pressure thrust loads on nozzles in case of untied bellows and the effect on pump foundation.Anywaything you say should be supported with solid technical justification.

Pl. also elaborate the statement" I feel expansion joint is better to use in place of springs(specially in such examples as suction piping of cooling tower pumps)in non hazardous fluids".This statement also requires a technical justification.

Regards

Anindya,
I feel what i wrote was quite clear. Can you please elaborate.Maybe what I feel I have written clearly is misunderstood by others. Anyway I may not have that much reference at hand as you have in your company.
Thanks

Dear pipe_engbangalore,

I think you are an engineer; if so, please don't 'feel', but 'understand by logic'.

Anindya & You, both are right in your own way.

Anindya is right, because it is incorrect to ignore pressure thrust on pump foundation.

You can claim to be right, as this pressure thrust is relatively small in cooling water pump suction piping, as mostly this piping remains in low vacuum below atmosphere pressure & gauge pressure used in pressure thrust expression becomes small & 'not that important' for you.

Your fight reminds me the recent duel between our "Infosys"'s Narayana Murthy and India's Ex. P.M. H.D. Deve Gowda. There, everyone knows who is right & why, but can't tell the no-so-plesant truth in a local democracy without the fear of getting beaten up. I am writing this here, because of the 'bangalore' in your nickname.

Is there any reason for us to quarallel here? When you know that Anindya has said correctly, where is the harm in acceptance ?

I didn't want to hurt you by this comment. But, if you follow a flexible approach instead of rigid one, you will not get stressed up easily, not becoming patient of high BP, which most of us are already due to various reasons.

regards,

sam

Dear Stressedguy,

My objective was not to hurt you as like you I am a professional and I keep out my personal emotions out of my profession.

But being a prefesional you should know :

1) This forum has experienced persons who knows what to take and what not to.

2) Newcomers who have not developed that ability and can accept things on a face value.

3)This is a forum for engineers and SAM in his response has clearly mentioned that engineers do not "feel" but "understand by logic".

For new comers who can take your statements on face value can design systems which can result in catastrophic failures ( I wish you would have seen photographs of failure of pump foundations in case of untied bellows).

Last but not the least , if you have to develop yourself in your profession learn the meaning of the word "humility" and delearn the meaning of the word "ego". There is no end to learning and we everyday learn something from somebody.

Only then you will succeed.

Regards

Dear Anindya/sam
Thanks for all the preaching, however both of you seem to act otherwise and are too much emotionally involved.
Anyway, the word feel was used to politely raise a point where I seemed to differ from some of the greater minds on the forum. I have no illusions of knowing it all like some people seem to have. Infact I admit my experience in stress analysis is very limited.
Having said that I will stand by what I said as this was in particular reference to cooling water pumps. If I am not wrong the topic was revolving around that point. And as Sam also agrees that pressure is suction lines is negligibly small. Calculations of pressure thrust will be only of academic interest. If you want to see such successful installations go to any fertilizer plant and look around cooling towers. I have not seen any failed foundations due to my designs. In hydrocarbons, who will prefer a bellow even if you have designed the foundation for pressure thrust?
Now some more points.
1. There are a lot of polite ways to correct somebody even if he is technically wrong.The aim of any forum shall be to bring correct technical facts for the benefit of all forum users. Pulling down somebody does not show true professionalism.
2. I don't think a newcomer shall apply something from this or any other forum without consulting his seniors (unless it is from people like John Breen or John Luf and he knows who they are).The final document shall be as decided by the lead engineer of the job as he is the person taking responsibility.
3. In technical discussions individual words/grammar doesn't matter much as long as intent is clear. (Unless it a document being sent to client or you are writing a code)

Regards
This forum is still worth a visit because of people like John Breen and Ed.

This topic is closed from my side.
Regards

Analysis and design of piping systems remains a difficult and somewhat subjective occupation.

The skills required take many years to accumulate and frankly some people never "get it". But we should all try to better ourselves and learn each day.

The most aggravating thing to me personally is a person who takes no responsibilty for doing some research and study on their own and yet present themself as competent in the field.


Often times people will post a question which can be answered simply by opening a book... when I see those types of questions I make no suggestions because if they are too damned lazy to do their homework I won't do it for them!

Luf Sir,

But, still you couldn't resist giving your sane comment after the closeout declared by our young friend.

You have rightly said that, 'we should all try to better ourselves and learn each day.' It is a simple message, but so true!

Just a couple of days ago, I got reaffirmation in this adage while attending a test myself, failing to answer many a question! Some of the answers to the questions I could find searching afterwords.

Let anyone call me emotional, I love to learn & visit this forum as I have need for it.

Even for a seeker, this lesson is worth sharing with fellow learners.

regards,
sam

I don't think I have ever tried to insult anybody in this forum in any way , in fact on several occasions I have protested against such actions.However I will always continue to raise points when something somebody says w/o giving adequate reason/justification/supporting data.I don't have any problem so long a person supports his statements with data/logic.In fact I never mentioned that some statement is correct or incorrect, I only wanted supporting document/engineering argument which is very rational.

Regards