Hydrocarbon Processing - January 2021 - 62

Valves, Pumps and Turbomachinery
The main function of reciprocating
compressor valves is to control flow in
and out of the compressor cylinders.
However, valves are critically important

components for reciprocating compressors; their functional integrity usually
governs the availability and efficiency of
these displacement compressors. FIG. 1

FIG. 3. A generic channel or reed valve,
legacy style.
FIG. 6. A generic poppet valve.

FIG. 4. A generic ring valve.

FIG. 5. A generic plate valve.

FIG. 7. A modular reed valve, one of many
possible drop-in replacement arrangements.

shows them at the top of failing components in reciprocating compressors.
Four or five styles of valve configurations are normally used in reciprocating
compressors. Except for suction valve unloaders, which use mechanisms to physically keep a valve open during partial or
entire stroke length (displacement) of a
piston, valves are actuated by differential
gas pressure. Valves open when the pressure on one side of the cylinder is greater
than the pressure on the opposing side.
Most living creatures breathe oxygen
based on the same principle.
The compressor designer's and
knowledgeable user's choice of valve
depends largely on the type of process
application. While valve type and size
should be specified by the compressor
manufacturer, the user-purchaser should
also be involved. Although new or novel
approaches are not entering the market
every year, these products nevertheless
exist and are well worth considering.
Reliability-focused users will be interested in understanding why certain,
radically new modular reed compressor
valves (FIG. 2) have been making inroads
since about 2014, when they were used
on offshore platforms. As of 2017, and
after initially concentrating on oil exploration and production facilities, these
modular-design straight flow-through
valves have made excellent progress in
oil refineries and other downstream facilities. Many modular reed valves are
presently installed in hydrogen compressors, with some individual machines approaching 20,000 bhp.
Being aware of a wide spectrum of
readers and their different levels of experience, we opted to begin this article with
a brief compressor valve refresher.
Types of valves. The most prevalent

FIG. 8. A stacked proprietary valvea (A) and staggered element/insert arrangement in the
stacked proprietary valvea (B).

62 JANUARY 2021 | HydrocarbonProcessing.com

" traditional " valve types are described
here. Note that these would often be
labeled legacy valves, and that some of
these have probably changed little, if any,
in the five decades from 1970 to 2020.
Channel and reed valves: Channel
and reed valves (FIG. 3) are now considered obsolete; they are used only in
small air compressors. While they can be
used at the highest practical speeds, they
will require higher-than-average maintenance. Moreover, they exhibit below-average efficiency, meaning above-average
power losses.

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Hydrocarbon Processing - January 2021

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