Problem Of The Month
October 1997--How Much Life Is Lost From Specific Pump Practices

 

In the September '97 Problem Of The Month, pump practices and how they altered the inherent life of a pump were discussed.  Consider this situation: 1) You have more than adequate net positive suction head, 2)  You’re not operating your pump at the good practice of BEP, that’s best efficiency point, what are the impacts on pump life?—Figures 1 and 2 described some generalities about impact on life from pump practices.

Figure 1 shows the impact of loss of life for ANSI pumps.  Many people willing give up 47% of their pump life by operating too far away from BEP.

Figure 1:  Loss Of ANSI Pump Life From Variability Around BEP

Figure 2 shows the impact of loss of life for API pumps.  The rugged API pumps are more tolerant of off BEP operation and suffer only a 10% loss of life.

Figure 2:  Loss of API Pump Life From Variability Around BEP

If you want long life, control the pump for operation at BEP and this is a wonderful opportunity for variable speed drives and smart pumping controls to prevent loss of pump life and to save energy costs.  After all the most expensive thing about a pump is the energy it consumes during its life.  You can download a few PDF files concerning pump life and pump practices.

In this situation specific situations are mixed and matched to show how inherent pump life is decreased..

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Background
Respondents to a pump practices survey were asked to define good, better, and best practices--each practice is a higher grade of installation and use. Now the best practices are used to show the decrease in life by use of a single practice. These answers are obtained from the Life Cycle Cost Simulation spreadsheet which is a subset of MonteCarloSimulations. Version 2.beta5 are used for obtaining the answers.

When the financial results are calculated, the cost of each practices is obtained.

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The Problem
What deterioration of inherent life occurs for an API, ANSI Enhanced and ANSI pump based on use of best practices and a single exception of just a single lower grade installation/use practice?

The datum is a 100 horsepower pump with 8-inch discharge, 10-inch suction.

 Questions:
1) How much of the inherent life is lost for an API pump by use of best pump practices and individual lower grade practices?

2) How much of the inherent life is lost for an ANSI Enhanced pump by use of best pump practices and individual lower grade practices?

3) How much of the inherent life is lost for an ANSI pump by use of best pump practices and individual lower grade practices?

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Solutions:

Answer to Question 1): How much of the inherent life is lost for an API pump by use of best pump practices and individual lower grade practices?

2% of the inherent life is lost (582 hours) by using all of the best practices

10% of the inherent life is lost by using better practices for BEP--all other practices are the best
25% of the inherent life is lost by using good practices for BEP--all other practices are the best

8% of the inherent life is lost by using better practices for suction L/D--all other practices are the best
24% of the inherent life is lost by using good practices for suction L/D--all other practices are the best

8% of the inherent life is lost by using better practices for rotational alignment--all other practices are the best
35% of the inherent life is lost by using good practices for rotational alignment--all other practices are the best

8% of the inherent life is lost by using better practices for piping alignment--all other practices are the best
35% of the inherent life is lost by using good practices for piping alignment--all other practices are the best

7% of the inherent life is lost by using better practices for rotational balance--all other practices are the best
24% of the inherent life is lost by using good practices for rotational balance--all other practices are the best

9% of the inherent life is lost by using better practices for foundations--all other practices are the best
33% of the inherent life is lost by using good practices for foundations--all other practices are the best

9% of the inherent life is lost by using better practices for grouting --all other practices are the best
31% of the inherent life is lost by using good practices for grouting--all other practices are the best

Answer to Question 2): How much of the inherent life is lost for an ANSI Enhanced pump by use of best pump practices and individual lower grade practices?

3% of the inherent life is lost (470 hours) by using all of the best practices

12% of the inherent life is lost by using better practices for BEP--all other practices are the best
28% of the inherent life is lost by using good practices for BEP--all other practices are the best

8% of the inherent life is lost by using better practices for suction L/D--all other practices are the best
26% of the inherent life is lost by using good practices for suction L/D--all other practices are the best

10% of the inherent life is lost by using better practices for rotational alignment--all other practices are the best
38% of the inherent life is lost by using good practices for rotational alignment--all other practices are the best

9% of the inherent life is lost by using better practices for piping alignment--all other practices are the best
40% of the inherent life is lost by using good practices for piping alignment--all other practices are the best

8% of the inherent life is lost by using better practices for rotational balance--all other practices are the best
27% of the inherent life is lost by using good practices for rotational balance--all other practices are the best

10% of the inherent life is lost by using better practices for foundations--all other practices are the best
35% of the inherent life is lost by using good practices for foundations--all other practices are the best

10% of the inherent life is lost by using better practices for grouting --all other practices are the best
33% of the inherent life is lost by using good practices for grouting--all other practices are the best

Answer to Question 3): How much of the inherent life is lost for an ANSI pump by use of best pump practices and individual lower grade practices?

?% of the inherent life is lost (404 hours) by using all of the best practices

13% of the inherent life is lost by using better practices for BEP--all other practices are the best
31% of the inherent life is lost by using good practices for BEP--all other practices are the best

9% of the inherent life is lost by using better practices for suction L/D--all other practices are the best
29% of the inherent life is lost by using good practices for suction L/D--all other practices are the best

10% of the inherent life is lost by using better practices for rotational alignment--all other practices are the best
41% of the inherent life is lost by using good practices for rotational alignment--all other practices are the best

11% of the inherent life is lost by using better practices for piping alignment--all other practices are the best
455% of the inherent life is lost by using good practices for piping alignment--all other practices are the best

9% of the inherent life is lost by using better practices for rotational balance--all other practices are the best
29% of the inherent life is lost by using good practices for rotational balance--all other practices are the best

10% of the inherent life is lost by using better practices for foundations--all other practices are the best
38% of the inherent life is lost by using good practices for foundations--all other practices are the best

10% of the inherent life is lost by using better practices for grouting --all other practices are the best
36% of the inherent life is lost by using good practices for grouting--all other practices are the best

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Comments:

Certainly the loss of life is important--however, it's the costs that out trump all issues of life. The key is to find the right mix of costs and cost effective life enhancements that are affordable on a NPV basis. This is the reason for calculating the life based on Monte Carlo simulations of how things fail in service.

Refer to the caveats on the Problem Of The Month Page about the limitations of the following solution. Maybe you have a better idea on how to solve the problem. Maybe you find where I've screwed-up the solution and you can point out my errors as you check my calculations. E-mail your comments, criticism, and corrections to: Paul Barringer by     clicking here.

Technical tools are only interesting toys for engineers until results are converted into a business solution involving money and time. Complete your analysis with a bottom line which converts $'s and time so you have answers that will interest your management team!

Last revised 06/05/05
© Barringer & Associates, Inc. 1997

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