Piping Design Centrifugal Pump Piping

[Boghi1990]

Hi,

I do not have too much experience in piping design.I would appreciate if there is anyone out there who could give some advice on the following questions.

Regards,

One Point

"When the centrifugal pump is supported by piping, pipe supports should be installed on both sides of the pump as close to nozzles as possible..."

Question : If the pump is supported by piping, why we do need to use those resting type supports close to the nozzles ?

Question : Why these supports should be resting types supports and not anchor type supports?

"Provide a pressure connection in the discharge line as close to the nozzle as possible."

Question: What is a " pressure connection " and why does it need to placed close to the discharge nozzle ?

" Locate all block valves as close to the pump nozzle as possible".

Question: Why a block valve should be installed close to the pump nozzle?

" The use of the chain operated valves should be kept to a minimum."

Question: Why the use of these type of valves should be kept to a minimum ?

Question :Why the suction pump nozzles are one or two sizes smaller then the suction line size. "

Question :Why the discharge pump nozzles are one or two sizes smaller then the discharge line size ?

Question : Why the nozzles have to be installed as close as possible to the pump nozzles ?

" If the pump has a suction nozzle at the side (is a double suction pump), a straight run of 5 pipe diameters is required between the suction nozzle and an elbow which is not installed at 90 degree to the drive shaft."

Questions: Why do we need this straight run of 5 pipe diameter length at that location ? What happens when the elbow is installed at 90 degree to the drive shaft ? Why this elbow has to be in a vertical position to the drive shaft center line ? What would happen if the elbow is installed in a horizontal position ?

" Discharge piping might affect pump starting, stopping or priming."

Question : How the discharge piping line could affect the pump priming, stopping or starting ?

Question: Why and how the discharge piping configuration might alter the discharge flow recirculation line ?

 

[SNORGY]

Boghi1990:

Good questions to ask. However, in my opinion, they cannot be adequately answered by anything short of reading two books: one on pumps, and one on piping design, and then understanding how one affects the other.

You really should invest in two books:

(1) The Pump Handbook - Karassik, Messina, Cooper, Heald
(2) Pipe Stress Engineering - Peng and Peng

A third book that I think is pretty good is:

(3) Know And Understand Centrifugal Pumps - Bachus & Custodio


Regards,

SNORGY.

 

[pennpiper]

Your questions sound like they are from a piping design training class.

I think you need to check your text book and your notes then ask your instructor.

 

[saplanti]

If the pump operation is not effected by the piping loads, and the piping loads at the pump connections are under the pump allowables I do not see why you can not try it.

But, my guess is that you never achieve those. In the piping systems there are some weak points, pump connection is one of the important ones. Therefore, you need to be carefull at and around the pump connections. You can check API 610 for the API pumps on allowables, or you can get the values from the manufacturer.

You can see this after a stress analysis of the piping with pumps. When the pump connections have smaller pipe sizes than the line sizes this becomes even more problem than you can imagine ( I am saying this because you have asked the question and not aware of the problems).

There are some piping items which are designed to take the assigned flange loading given by the standard. Their bodies are designed to take the flange loading and their operation is not effected by the loading. So we do use them without hesitation, but still need to check the flange load to keep flange loads under the allowable. We can categorise valves, some filter equipment etc... under this items. However pumps are different. Their operation, especially shaft and its sealing effected by the external loads.

Regards,

Ibrahim Demir

 

[StressGuy]

Actually it sounds like a client piping design spec. Not uncommon when dealing with a reasonably sized refiner.

The answer to most of the questions is that experience has shown that not following those requirements decreases pump reliability.

Excessive imposed loads from the piping system, non-uniform flow patterns into the suction, etc, can can excessive shaft deflection leading to early bearing and seal failures.

Block valves should be close to the pump to minimize the trapped fluid to be drained out when the pump is taken out of service and blocked in.

I believe the "pressure connection" means a connection point for either a gauge or element that feeds back to the control room. You want to be able to see what pressure your pump is putting out.

Edward L. Klein
Pipe Stress Engineer
Houston, Texas

"All the world is a Spring"

All opinions expressed here are my own and not my company's.

 

[MechEngNCPE]

These are all basic design questions, which you will not get adequate answers here. I suggest finding a mentor where you work and letting him go over this with you.