Hydrocarbon Processing - January 2021 - 64

Valves, Pumps and Turbomachinery
High-flow modular petal straight-through valve
(136% better AR than Manufacturer " B " )

Stacked modular petal straight-through valve
(80% better AR than Manufacturer " B " )

28.2

Standard modular petal straight-through valve
(61% better AR than manufacturer " B " )

25.3

Valve from manufacturer " B "

15.7

Valve from manufacturer " A "
0

10
5
10
15
20
25
30
35
Area ratio (AR) = Effective area divided by valve port area

FIG. 12. Area ratio comparison for two widely used valves vs. three modular straight-through
flow valves.

might think. Downtime avoidance also
has value and should be part of the payback calculation. Again, clarification
obtained during the MQA should not
be viewed as burdensome; it will prove
valuable to both the owner-purchaser
and manufacturer-vendor.
Sharing knowledge. During scheduled pre-award meetings, a competent
valve vendor or manufacturer will explain design compromises, gas velocity
limitations, the meaning of valve lift (distance from seated to fully open, absence
of valve flutter), tolerance for liquids and
solid impurities carried in the gas, and
overall valve operation in clean vs. fouling services.
Recall that there are bone-dry gases
in some, and oil carryover in quasi-moist
services. Explore if and how compressor
valves tolerate these extremes. Find out
before a sequence of premature failures
tells you that experimentation with operating machinery is rarely acceptable
when important assets are involved.
Examining
modular
straightthrough flow valves. A new approach

to compressor valve technology was introduced to refineries and petrochemical plants in 2017. The old legacy valves,
FIGS. 3-6, can now be replaced by modular reed valves developed by a Houstonbased manufacturer.b Modular reed
valves can serve as drop-in replacements
for virtually any predecessor valve. The
novel technology is shown in FIG. 2 and
FIGS. 7-11; the modules (or modular elements) are an enhanced reed design
64 JANUARY 2021 | HydrocarbonProcessing.com

incorporating high-performance polymers under compressive stresses. The
inventor chose the generic term modular
straight-through flow valve.
The author found considerable evidence that the manufacturer's advertised
ease of service, improved compressor
flowrates and other claims were correct.
Servicing by lower-skilled workforce
members, operating performance over
an unusually wide speed range, and generally well-above-average availability/
reliability were factually proven. While
the first applications were in upstream
facilities (oil exploration and gathering), modular straight-through valves
have since made considerable inroads in
downstream facilities, such as oil refineries and petrochemical plants.
The success of these valves is largely
attributable to their straight-through
design. Other advantages are intuitively
evident; these include self-cleaning, an
estimated 80% reduction in inventory,
and validation through rigorous analyses. Test reports are among the various
items of backup documentation; they reaffirm that the inventor's understandable
enthusiasm was (and is) fully justified.
A high-flow version is shown in FIG. 7; a
stacked valve is depicted in FIG. 8.
Taken together, the seemingly small
advantages in this or that measurement
add up. Both standard and integral cage
modular flow-through valves are shown
in FIG. 9 and FIG. 10. Either style adds
value that cannot be ignored.
The flow area ratios of two widely
used valves are compared with three
modular straight-through flow valves

in FIG. 12; the percentage area improvements are significant. Elementary physics explains that, for a given volume of
gas, larger flow areas have less pressure
drop than smaller flow areas. Lower
maximum pressures in cylinders reduce
pressure ratios by a small amount. These
ratio reductions and larger areas of gas
passage save energy and increase compressor throughput.
We were able to verify that the success of modular reed technology in proprietary valvesa is linked to well-instrumented tests. It could be ascertained
that the reports did not refer to comparisons of new modular straight-through
flow valves with old and/or worn valves.
Instead, the comparisons were for unused, old-style valves vs. unused, newstyle valves.
The tests also showed sizeable improvements in energy efficiency, valve
flutter, vibration, noise, pressure drop
needed to activate valves, trouble-free
operating time and necessary maintenance outlays. The self-cleaning attributes of the proprietary valvesa (FIG. 11)
were convincingly demonstrated. FIG. 11A
shows one of the old, fouled valves removed from an oilfield compressor after
less than 6 wk of operation, while FIG. 11B
shows a modular reed valve removed
from the same compressor after 31 mos
of operation. FIG. 11C shows a traditional
valve from an oilfield compressor in
dirty natural gas service after 4 wk of operation-note that the valve is no longer
repairable. In contrast, a modular reed
valve from the same compressor taken
out after 4 wk-5 wk can be field-cleaned
in 10 min (FIG. 11D).
NOTES
a Zahroof 's StraightFlo valve
b Zahroof
HEINZ P. BLOCH resides in
Montgomery, Texas. His
professional career commenced
in 1962 and included long-term
assignments as Exxon Chemical's
Regional Machinery Specialist
for the U.S. He has authored
or coauthored more than 770 publications,
among them 23 comprehensive books on practical
machinery management, failure analysis, failure
avoidance, compressors, steam turbines, pumps,
oil mist lubrication and optimized lubrication
for industry. Mr. Bloch holds BS and MS degrees
(cum laude) in mechanical engineering from
the Newark College of Engineering (NCE) and
is one of 10 inaugural inductees into NCE's Hall of
Fame, which honors its most distinguished alumni.

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