POOR PUMP DESIGN CONSIDERATIONS
CAN LIMIT OPERATIONS
In this case study, a reciprocating diaphragm metering pump installation
was held to 25% of rated capacity
By Jordan Grose, Beta Machinery Analysis
Relatively small reciprocating pumps,
smaller than 47 hp ( 35 k W), are usually
considered noncritical but they can create operational and production headaches at onshore and offshore facilities.
This article will discuss a case where
a reciprocating diaphragm metering
pump installation was limited to 25%
of rated flow capacity.
Operators of two diaphragm amine
pumps were very concerned about high
vibrations around the pumps once the
flow rate went above 25% of rated flow.
These pumps had three fluid ends, and
were flow controlled with a variable
speed electric motor drive (see Photo 1).
Above 25% flow, much of the proc-ess piping — especially the auxiliary
small-bore piping — would shake violently. The operator had to run both
pumps to make up the process flow
shortfall, thus eliminating their 100%
redundant operation scheme.
This example illustrates how high
operating risk is completely avoidable
with adequate considerations at the
A troubleshooting team investigating
this problem observed much auxiliary
Photo 1. Reciprocating diaphragm pump
Jordan Grose is manager of Pump
Services for Beta Machinery Analysis, Calgary, Alberta, Canada. Grose is a rotating
machinery engineer specializing in vibration and reliability issues for reciprocating and centrifugal pumping systems
including pulsation and mechanical
analysis, water hammer and transient
studies, small-bore piping analysis and
other related design work. Beta Machinery
Analysis is a market leader in providing engineering services for rotating and
small-bore piping around the pumps
to accomplish the triple redundant
control system strategy for this facility
(see Photo 2).
The auxiliary systems were most often
piped high in the air and were poorly
supported with flimsy pipe racks. This
made for highly flexible small-bore piping arrangements with very low mechanical natural frequencies (MNFs).
The system had bladder-type pul-
sation dampeners installed on both
the suction and discharge systems.
Pressure pulsation measurements
showed that the pulsation dampen-
ers were not adequately controlling
the pulsations in the suction and dis-
charge piping at all speeds (flows) of
the pumps, even though they were
being properly maintained.