Q. Must multiple pumps operated in series or parallel be identical in size? A. No, they do not have to be identical. However, pumps intended to operate in series must be close in size regarding...
Q.We have recently installed several double suction between bearing pumps and would like to verify that their vibration levels are within acceptable limits. How should this be done, and what is an...
Pumps & Systems, March 2007Q.What are the key requirements for good suction piping design for rotodynamic pumps?A.  Good suction piping design must eliminate air entrainment in the liquid,...
Hydraulic Institute Pump FAQs February 2007
Pumps and Systems, February 2007Q. We are operating a large axial split case pump which occasionally operates at about ten percent of its best efficiency rate of flow. At that rate of flow, the pump...
Q. What causes radial thrust on volute pump impellers? Should the pressure in the volute be uniform with proper design?A. Single and dual volute pumps are typically designed for uniform mean velocity...
Hydraulic Institute Pump FAQs January 2010
Q. I understand the significance for properly configured suction piping, but what are the piping requirements on the discharge side of a rotodynamic (centrifugal) pump?A. The maximum velocity at any...
Hydraulic Institute Pump FAQs February 2010
Q. We have an application for pumps handling hot oil at 700 deg F. What special care should we take in selecting and installing such pumps? A. Pumps for handling oils within the range of 150 deg...
Hydraulic Institute Pump FAQs March 2010
Q. Our pumps take their suction from an open tank. When the liquid level drops, surface vortices are formed that allow air to be drawn into the pumps. What changes can be made to the tank to correct...
Hydraulic Institute Pump FAQs August 2010
Q. What is the preferred method for starting reciprocating power pumps?A. Starting a reciprocating pump with a closed discharge valve is naturally difficult due to the high torque required to overcome...
Hydraulic Institute Pump FAQs September 2010
Centrifugal pumps: do they handle slurries, and what is their maximum allowable working pressure?Q. How do rotodynamic (centrifugal) pumps perform when handling slurries?A. The performance of a...
Hydraulic Institute Pump FAQs January 2011
Q. For centrifugal pump impellers, what is momentum change, and what is its significance?A. In single suction impellers the axial force related to the momentum of the incoming fluid should be...
Hydraulic Institute Pump FAQs January 2007
Q. I have been told that centrifugal pump impellers may still cavitate when operating with NPSH Available greater than NPSH Required. Is this true? If so, why do pump suppliers show NPSHR values when...
Q. If industry guidelines for intake design are followed, when is it advisable to conduct physical model tests of intake structures?A. Industry guidelines cannot always be followed. A properly...
Q. What symptoms are typical indicators of an inefficient pumping system?A. Many pumping system components are not dynamic. That is, these components allow fluid or heat transfer but, aside from...
Pumps & Systems, July 2008Q.Every pump manual clearly requires that a pump shaft must be carefully aligned with its driver shaft before operating the equipment. However, the precision of the...
Hydraulic Institute Pump FAQs December 2006
Q. I know that slurries require special attention when being pumped. What characteristics of slurries should be given consideration when specifying a rotodynamic pump?A.  First and foremost is...
Hydraulic Institute Pump FAQs October 2006
Q. Due to a recent thrust bearing failure in one of our deep well pumps, we would like to determine the down thrust on the bearing from the pump. Is there a simple way of calculating this?A....
Hydraulic Institute Pump FAQs October 2009
Q. What is the definition of specific speed, to what does it pertain and how is it used?A. Specific speed is an index of pump performance (developed total head) at the pump's best efficiency point...
Hydraulic Institute Pump FAQs June 2008
Q.When measuring vibration on vertical pumps, does the allowable vibration depend on the height of the motor or on the height above the baseplate where the readings are taken?A.The allowable vibration...
Q. What are the criteria for determining the maximum allowable forces and moments that can act on a centrifugal pump's nozzles without damaging the pump? What part of a pump is most likely to be...
Pumps and Systems, July 2009Q. Simplicity and low cost make rotary pumps a good choice for some applications. Is there a simple guide to the maximum flow rate and discharge pressure for which such...
Pumps & Systems, December 2008Q.Our office building has a pump room in the basement, which causes sufficient noise to be bothersome to the people in the office above it. What can be done to reduce...
Pumps & Systems, July 2007 Q. What is a jet pump? I do not see any reference to it in your standards and would like to learn more about it.A. A jet pump is actually a venturi nozzle or...
Hydraulic Institute Pump FAQs March 2009
Q. How can we tell if a pumping system is designed and operated properly? Some problems such as leaking seals are obvious, but should we watch for any other symptoms?A. A few symptoms in pumping...
Q. What is an acceptable amount of residual unbalance in an impeller after it has been balanced?A. High levels of residual unbalance in rotating parts can generate high unbalance forces, resulting in...
Pumps and Systems, May 2009Q. What can be done to avoid the high-pressure differential from rupturing the diaphragm in reciprocating diaphragm pumps?A.A hydraulically coupled disc diaphragm does not...
Pumps & Systems, August 2007Q. Is there a way of predicting the maximum operating speed for a reciprocating plunger pump when pumping a viscous liquid?A. Yes, but let's begin by setting the basic...
Q.  Most centrifugal pumps have a horsepower characteristic curve which rises as rate of flow increases to some level and then levels off or turns downward. However, other pumps have more level...
Hydraulic Institute Pump FAQs September 2007
Q. What are the most probable causes of insufficient discharge flow or pressure in centrifugal pumps?A. Before looking at the pump, check the measurement of total head and rate of flow. The proper...
Hydraulic Institute Pump FAQs 2008
Q. I have heard that the rate of flow through centrifugal pumps can be regulated by submergence control instead of by throttling the pump discharge. How does this work, and does it damage the pump?A....