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 email@example.com.
Pumps & Systems, May 2012
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.