PUMP ANALYSIS

[odion]

HI
I HAVE THREE PUMPS WHICH I AM ANALYSIS AND THE PIPES PASS THE STRESS BUT USING API 610 TO ANALYSIS MY PUMPS IT FAILS AND I DONT HAVE SPACE FOR LOOP, PLS HOW CAN I SLOVE THIS PROBLEM.

 

[richay]

You need more flexibility. There are a number of ways to achieve that, depending on the system:

- expansion loop
- expansion joint
- spring hangers
- re-route the piping

Something has to be changed to resolve the over-load.

Richard Ay
COADE, Inc.

 

[odion]

thank Richard, but after runing my pump analysis, my 'x' force, 'y' moment and 'z' moment failed but the values that make it fails is not time two of the Table 4, and my resultant applied forces is less than two.am trying to juge the result from Annex F in API 610. can please trow more light on it and can i leave routing the way it is with this criteria.

 

[Sid7]

odion,

Have you discussed this with your senior experienced colleagues?

Richard has stated the good direction for your problem. Now its upto you how you go for it. If I were you I would discuss in my work place in the first place.

Good luck.

Siddharth
These are my personal views/opinions and not of my employer's.

 

[ApC2Kp]

odion,
It sounds like you need the help of your piping designer. The loads on the pumps are ideally zero for maximum life of pump bearings and mechanical seals - don't settle for just meeting the allowables or a factor 2x the allowables.
The arrangement of pumps must include sufficient space for the flexible routing of piping, along with the maintenance access areas. The flexible routing of piping and the wise choice of support location and type will prevent problems of pipe expansion loads between the 3 pumps, and also keep the pipe runs from pushing back onto the pumps. Plan on sufficient pipe lengths, offsets, and changes of direction to provide flexibility between pump connections. The valve weights need to be individually supported, and valves will be better located away from any vertical discharge line - if lift off occurs from a support, then valve weight is likely shifted to the pump connection. Guides and line stops could possibly be located at the neutral lines of shaft centerline or pump case mounting to minimize external loads of thermal expansion due to pipe runs to / from the pumps. The choice of well positioned spring supports will balance the weights to result in smaller moment loads on pump connections.
Take the piping loads to your piping designer, and explain the loads and directions to him. View the model to understand how the weights and piping expansion cause the forces and moments at each pump connection. Work with him to locate the supports needed to restrain the piping so that weights are balanced and piping growth is pushed away from the pump connections.
The piping stress analysis results will only show the low loads of a good piping design - analysis does not make it good or bad.

 

[LSThill]

Reference to COADE CAESAR II PIPING STRESS ANALYSIS:

Review VIDO on the COADE CAESAR II PIPING STRESS ANALYSIS: disk.

WRC Bulletin 449:

Guidelines For The Design And Installation Of Pump Piping Systems

Guidelines For The Design And Installation Of Pump Piping Systems

Vincent A. Carucci, James R. Payne

WRC Bulletin 449

Vincent A. Carucci
James R. Payne February 2000 (48pp)(ISBN#1-58145-456-2)
Where piping systems interact with load sensitive equipment it is likely that the allowed interface reactions will govern the pipe system design. Unrealistically low allowable reactions may increase piping system cost while excessively high reactions may increase equipment maintenance costs. The cooperative best efforts of pump and piping designers are needed to arrive at the most cost effective pump piping system on a life cycle basis. Excessive piping reactions at pumps cause high vibration, coupling failures, and pump shaft misalignment. In severe cases there are flanged joint leaks and the occasional occurrence of impeller rub or casing distortion. Excessive shaft misalignment in turn leads to premature seal and bearing failures. These difficulties are a costly maintenance item that can also result in plant shutdowns, and in severe cases, fires and extensive damage. This guide presents industry practices intended to minimize these difficulties while keeping capital and life cycle costs in perspective. A survey prompted by industry inquiries was conducted to establish an experience base about the effect of pipe reactions on centrifugal pumps, the nature of the problems experienced, the standards and criteria used to design and install pump piping systems, and industry attitudes on the issue. The survey concentrated on the experience and needs of piping and pump system designers, specifiers, manufacturers, and operators. It was designed to help the PVRC determine, among other things, its research priorities in these areas. The survey results confirmed that a pump nozzle load problem exists, and that it has significant cost impact on industry. This impact was in two broad areas: Operating and maintenance costs, such as: 1-shutdowns caused by excessive vibration, cracks or deformation to casings, flange leaks and coupling failures; 2-capital project costs, such as those accruing from a poor understanding of required pump strength and piping load criteria before pump purchase.
The purpose of this Guide is to: Establish recommended practices and guidelines for pump piping system design, layout, installation and alignment for the process and power industries; Provide consistent recommended allowable pipe reaction and pump strength criteria where none exist at present.
This Guide was developed mainly by assembling and documenting the most appropriate practices currently in use by the process and power industries for various services. The guidelines are mainly broad-based and consider standard engineering practice. Nevertheless, new tolerances are suggested for pipe to pump flange alignment of critical piping systems and new allowable pipe reaction and pump strength criteria for situations where none presently exist. Many of these guidelines apply with little modification to piping for other types of load sensitive equipment such as turbines, compressors and air fin heat exchangers. However, this Guide does not attempt to extend the information presented beyond centrifugal pumps.
************************
ISSN: 0043-2326
Library of Congress Catalog Card Number: 85-647116


Last Update: Thu, 10/30/2003 03:15:01 PM



L S THILL

 

[LSThill]

Technical Review: Example System from WRC-449

Mechanical Engineer New COADE JULY 2003, PAGE 11, 12.

http://coade.com/newsletters/jul03.pdf

Satisfying Expansion Load Case
Requirements
(by: Richard Ay)

Typical Power and Process piping codes evaluate the stresses of a piping system under in three different states; sustained (or primary), expansion (or secondary), and occasional. The focus of this article is on the proper evaluation of the expansion stresses, and the corresponding load case setup.

The B31.3 code in Paragraph 319.2.3.b states “While stresses
resulting from displacement strains diminish with time due to yielding or creep, the algebraic difference between strains in the extreme displacement condition and the original (as-installed) condition (or any anticipated condition with a greater differential effect) remains substantially constant during any one cycle of
operation. This difference in strains produces a corresponding
stress differential, the displacement stress range, which is used as
the criterion in the design of piping for flexibility.” A previous
article in this newsletter (Expansion Case for Temperatures Below
Ambient, May 1993, p32) discusses this requirement, using an
example situation where the system has two temperatures, one
above ambient and one below ambient. To summarize, in this
situation, CAESAR II would recommend the following load cases:

 

[odion]

THANKS GUYS YOUR CONTRUBUTION REALLY HELP