Pump Repair and Upgrade Standards

The pump industry is undergoing renewed interest in the technical aspects and quality of repairs. Pump users’ expectations of quality repairs must be matched by a well-defined set of specifications, to clearly state the extent and details of a repair job. The first specification has been initiated by a working group of the Pump Magazine Online, with the cooperation of Pumps & Systems magazine.

The reviewers are in process of working on the second draft. Users, manufacturers and repair shop facilities’ input is encouraged, to provide an inclusive and well-rounded basis for the final document to serve pump industry needs in quality repairs and overhauls of pumps.

The original draft was reviewed in September 2011 by the Pump Magazine Online Advisory Committee, and a working group is now being put together to get the Vertical Turbine Pump (VTP) Pump Repair Standard (VPRS) draft to the next step. For those interested, we can review your level of interest and background and include you in this group (see the list of group members at the end of this article). 

The initial draft documents are the result of ongoing development, some of which has been published and featured in my Pumps & Systems’ columns:

These articles can be found on www.pump-zone.com.

Table of Contents

The committee outlined several initial sections of the VPRS Standard, which are now being developed in detail. Additional sections will likely be added and/or modified. The initial table of contents is below:

Section 1: Vertical pump and driver condition monitoring prior to removal for service

1.1 Predictive versus proactive maintenance and monitoring

1.2 Catastrophic failures

1.3 Possible root causes of failures and RCA (root cause analysis)

1.4 Site inspection and system issues potentially affecting pump performance and reliability

Section 2: Pump and driver pre-removal planning

2.1 Site access and selection of lifting and transportation option

2.2 End user versus contractor responsibilities

2.3 Turnkey versus partial approach

2.4 The anticipated extent of the repair, overhaul and upgrade (with definitions)

2.5 Quotation process

2.5.1 Level 1 (basic repair)—with definitions

2.5.2 Level 2 (extended repair)—with definitions

2.5.3 Level 3 (complete overhaul)—with definitions

2.5.4 Upgrade options: materials, hydraulics, controls, monitoring

Section 3: Driver handling

Section 4: Open versus enclosed shaft design options

Section 5: Complete pump removal versus sectional removal

Section 6: Materials of construction

6.1 Cavitation protection

6.2 Abrasion resistant

6.3 Corrosion resistant

6.4 Combined

Section 7: Sump, piping and system effects

7.1 Anti-vortex methods

7.2 Air entrainment and minimum submergence required

Section 8: Repair shop inspection procedures

8.1 Disassembly and visual inspection

8.2 Shaft runout

8.3 Bushing clearances

8.4 Non-destructive examination if/when required 

8.4.1 Magnetic particle

8.4.2 Liquid penetration

8.4.3 Radiography

8.5 Witness inspection

Section 9: Re-installation in the field and start-up

Section 10: Documentation and record keeping

Recent Pump Users’ Comments

When a customer needs a pump repaired, we usually go through an evaluation process before providing a quotation so that we know exactly what it will cost for the repair/restoration. If I were in purchasing, I would definitely go with the Shop A (“Repair Standard for Vertical Pumps,”  February 2012) even though Level 1 is much more expensive than Shop C. Considering this is basically a “blind” quote. I would have to consider the possibility that an overhaul might be necessary and in that event, I would have to go with Shop A’s Level 3 quote as a measure to plan ahead and not take the risk of spending $300,000 for what could have cost $120,000.

Christi Prust, Magnatex Pumps, Engineering

I would get a quote for all three levels of rebuild from all three repair companies. I would choose the repair shop that has the cheapest quote for a Level 3 repair, even if they are the highest price on a Level 1 rebuild. The difference in prices at Level 1 is smaller than the difference in price at Level 3. I think the payment department will be happy with that.

Pumping Machinery Pump School class attendee 

Georgia Power, Maintenance

 

The VPRS Committee

Current VPRS Committee members are:

• Dick Lane, Maintech International, Inc., U.S., Southwest 
• Rick Mathis, Pumping Machinery Repair, LLC, U.S., Southeast
• Doug Davidson, PumpTech, Inc., U.S., Northwest
• David Tuck, Greenwood Municipality, U.S., 
South Carolina
• Lori Ditoro, Pumps & Systems, U.S., Alabama
• Michael Benjamin, Mekorot Waterworks, Middle 
East, Israel
• Lev Nelik, PML, Consultant

If you are interested or would like more information, please email me at drpump@pumpingmachinery.com.

Pumps & Systems, May 2012

Readers Respond

We are the part of the Hydro Group (Chicago) based in Australia. I was reading your article in the May 2012 issue on “Pump Repair and Upgrade Standards,” and one question that keeps coming to my mind is the allowable vibration at the motor top bearing in a vertical configuration.

The Hydraulic Institute (HI) 1994 has a graph that defines the allowable vibration displacement as a function of height from the foundation against speed. Displacement could be converted to velocity with the assumption that the vibration is at running frequency. HI’s 2000 edition has changed the allowable figures in terms of velocity against power. This makes sense as it is a measure of energy.

We have lots of split case pumps mounted in vertical configurations in Australia. The motor is mounted on the top of the pump similar to a traditional vertical turbine pump. The configuration is inline, separate coupled, but it shows measurement locations at the pump. Logically, motor vibration would be equal or higher than allowed at the pump.

Customers/consultants accept the HI’s vibration level for the pump. However, applying ISO 10816.1 for motor vibration, which is much tighter, is not possible to achieve.
What is the experience in U.S. on allowable motor vibration in a vertical pump? Any guidelines, standards or practice available?

Chandra Verma, Manager, Engineering  
Hydro Australia Pty. Ltd.

Lev Nelik responds:

I am glad you found the information in “Pump Repair and Upgrade Standards” useful, and perhaps it will assist you and your customers (pump end users) in a practical way. You are absolutely right that the HI move to a modified (2000) version of the Vibration Guidelines (versus an earlier 1994) is in a right direction. However, even this version leaves room for clarification and refinement—or perhaps the term is simplification.

First, think about the difference between a recently installed pump and one that has been in operation for 10 years. Would you apply the same vibration standard to both? If you did, half the Australian pumps (and many U.S. pumps) would have to be shut down. We would be sitting in the dark, but happy that the pumps are HI compliant.

The original HI (1994) guidelines on vibration, showing units in mils, are too academic. True, large and critical pumps—such as high-energy boiler feed pumps for power plants—typically have proximity probes installed at the pump and motor bearings, usually at the 45-degree position. These measure rotor displacements (in mils). Having two probes (two channels) per location, allows operators to see the displacement value and to even construct the movement of the shaft, in orbits. In practice, however, plant operators are not as concerned about the orbits and simply have the person who selected the settings instrumentation show the Warning, or Alarm level, and/or shut down the unit.

Another group of people are those who conduct vibration analysis in the field. Of those, 95 percent do not require orbital analysis. In rare occasions when it does matter, these people are highly trained vibration specialists, arriving at the plant with a truckload of vibration sensors and other instrumentation and, they do a good job—for large and critical equipment—such as a 2,000-horsepower boiler feed pump or a 30,000-horsepower steam turbine with 15 bearings.

For the rest of the world (95 percent of cases), vibration is first sensed by the hand of the maintenance operator, who happened to come by the pump to check or change the oil. These operators do not have instrumentation but use simpler, but still reliable, vibration measurement instruments—such as accelerometers attached to their neck-held readout, reading overall (root mean square—RMS) vibration values and (if needed) spectral analysis capabilities—to get the fast Fourier transform (FFT) signature, to troubleshoot the unit if the unit appears to be at the overall level of vibrations that require troubleshooting. Therefore, the HI publication essentially reflects the value of a new installation, which design engineers, contractors and consulting firms usually use. If you take a closer look at the HI publications, note the scale values on the graphs—0.04, 0.08, 0.12, 0.16 … etc. Such plot scales would not be expected of a seasoned engineer. You attached ISO 10616-1, which also reveals the same type of authorship by well-qualified folks, but with “interesting” practical understanding of the world.

In practice and in the field, such academic methods are not used. To differentiate between a 0.17 inch per second at the pump and to allow 0.21 inch per second at the top of the motor is practically impossible. What they need to know is one number, which they can easily remember and which would be reasonably applicable to a wide range of pump types.
With this approach in mind, the typical field value for the warning is usually 0.30 inch per second and alarm at 0.50 inch per second, although most pumps, almost regardless of type, would run at about 0.1 inch per second to no higher than 0.2 inch per second. Spending most of my time these days in the field and seeing daily a different type of pump, this appears to be a mainstream of data.

Having set the field limit warning at 0.30 inch per second, one would be comfortable with a pump at 0.05 inch per second, its vertical motor at 0.12 inch per second. If the motor is tall, a comfortable number would be 0.16 inch per second, as an example. Therefore, the conservatism (practically speaking) of the selected value would dismiss the need of differentiating between a tall or short motor setting.

As you may know, the pump repair standard for vertical pumps is in the process of being drafted. If you are interested, please join our committee, representing Australia. We have representatives from the U.S., Middle East and Europe also on the committee. We are also working on a standard for horizontally split pumps. You may find related articles, available at the Pump Magazine (www.pump-magazine.com) or at www.pump-zone.com, where you originally saw the article.

Speaking specifically to your pump, I have seen double-suction split-case pumps mounted similar to what you have in Figure 1, in a vertical arrangement, and they usually have problems. What type bearing do you use? Do you have a sectional drawing you can email me? I hope these thoughts and ideas are helpful. Let me know if you want to join our committee.