RECOMMENDATIONS FOR PULSATION CONTROL OF RECIPROCATING COMPRESSORS
Reciprocating Compressors Need a Suitable Evaluation of Pulsation
Control Devices in Order to Limit Pulsation, Vibration and Shaking Forces
By Amin Almasi
Editor’s Note — This presentation explains recommendations for evaluating pulsation suppression devices in terms of
reliability, availability, maintainability, vibration, shaking
forces, performance, safety, operation and commercial conditions. Useful recommendations for pulsation control, piping, pulsation vessel, shaking forces, low-pressure drop orifices and pulsation study report also are discussed.
Pressure pulsation comes from the discontinuous nature
of gas flow in reciprocating compressors (pulsating actions
of piston to compress gas). Pulsations can interact (for example, because of reflection) with plant facilities and piping upstream and downstream of a compressor. The level
of harmonic components can be considerably increased because of resonance with plant installations (resonance between harmonic frequency and natural frequency of piping
or facilities in plant). Reciprocating compressors need a
suitable evaluation of pulsation control devices in order to
limit the pulsation, vibration and shaking forces.
Figure 1 shows process reciprocating compressor
mechanism.
Figure 1. Mechanism of process reciprocating compressor (Picture
from Bloch, H. P. , Compressor and modern process application, 2006,
John Wiley and Sons, New Jersey, U.S.A.).
For process reciprocating compressors mechanism, a
schematic is shown in Figure 2.
Shaking forces caused by pulsation effects are sufficient
Amin Almasi is lead rotating equipment engineer in Technicas
Reunidas S.A., Madrid, Spain. He holds chartered engineer certificate from IMechE (CEng MIMechE) and chartered professional
engineer license from Engineers Australia (MIEAust CPEng –
Mechanical) and he also holds MS and BS in mechanical engineering. He specializes in rotating machines including reciprocating, centrifugal and screw compressors, gas and steam turbines, process pumps, condition monitoring and reliability.
Almasi is an active member of IMechE, Engineers Australia,
ASME, CMVI, Vibration Institute, SPE, IEEE, SMRP and IDGTE. He
has authored more than 30 papers and articles dealing with rotating machines, condition monitoring and reliability.
Figure 2. Mechanism of process reciprocating compressor.
to cause problems such as with valves, piping vibration,
fatigue failure, broken cylinder supports, broken bottle
supports, broken anchor bolts and grout deterioration, especially under crosshead guides. Pulsation also can alter
the timing of the valve motion and decrease efficiency
and reliability.
Significant proposed improvements include: 1. Optimum
pulsation control devices can reduce pressure drop and can
realize a significant financial reward through increase capacity
and reduce power consumption. 2. Avoid overly conservative
pulsation control design. Pulsation study is a necessary step
to ensure reliability and safety of reciprocating compressor.
Model and Formulation
A full one-dimensional time domain flow equations and solutions, applicable to any complex flow network (piping,
manifold, facilities, etc.) are shown below. The state of gas depends on two factors: 1. The kinematics of the reciprocating
compressor. 2. The fluid dynamic behavior (response) of the
piping, manifolds and facilities and passive outlet conditions.
Equations ( 1) and ( 2) define fluid motion and continuity.
( 1) + + + µ δδ δ δ ρ
=
( 2)
Pulsation in gas networks (compressor and related facilities) can be analyzed using the “Transfer Matrix Method.”
= ++
δ
δρ
δ
δ
δ
δ
( 3) [ ]{} { } =
( 4)
=
Parameters used in pulsation model and formulations
are as follows:
