Hydrocarbon Processing - December 2021 - 37
Process Optimization
state operation is lower than the discharge pressure after the
steam trap. In these conditions, a secondary pressure drainer
pump/trap combination may be necessary.
When steam traps are appropriate, the best selection is a
float and thermostatic-style trap with instantaneous continuous
discharge, incorporating reinforced components to avoid
water hammer damage. Disc traps may sometimes be utilized
for tank coils, comfort heaters and small noncritical heat exchangers,
but they are not suitable for other process heating
applications. Inverted buckets may not be suitable because of
their cyclical operating characteristics or because of challenges
faced with non-condensable air in the system. Bimetal traps are
generally not recommended due to their operational reliance
on subcooling and their sensitivity to changes in back pressure,
which may result in condensate backup. This, in turn, may flood
equipment, reducing the heat transfer area.8
Bimetals may be
considered for small storage tank coils, where only approximate
temperature regulation is required, and also where it is not practical
to install a steam control valve and control system.
Flares. A steam-assisted flare requires a continuous low
volume of steam that is often supplied through an orifice plate
bypass around control valves to keep the flare tips hot while
the flare is not burning vapors. When flare gas is supplied to
the flare, the steam control valves open to supply steam for atomization
and flame stability. If wet steam is supplied, the flare
tips may become eroded. This can reduce the effectiveness of
the steam distribution at the tip and may cause unclean " sooty "
burning that could result in environmental issues. If the flare
steam lines upstream and downstream of the control valves are
not properly drained, then water slugs may be propelled to the
flare tip. This may severely damage the flare tip or extinguish
the pilot light before the flare gas is ignited. Both conditions
may result in environmental issues. Repair of the flare tips or
complete candelabra replacement may also be costly.
Due to the criticality and design of flare steam lines and
control stations, the best choice of steam trap, such as a float
and thermostatic style, will instantaneously and continuously
discharge condensate. Bimetal traps must not be used. Thermostatic
traps and inverted buckets are not a first choice. Disc
traps upstream of the control valve station may be acceptable
if the condensate collection pockets and the drain lines
are properly sized and designed. Special selections may be
required for drain locations after the control valve stations,
which may have extremely low operating pressures in standby
operation and may be close to grade.
Sulfur pit coils. Sulfur pit coils are below ground, and
steam traps usually must be installed above ground. Condensate
must be lifted from the coil to the trap. This can commonly
cause steam locking of the trap, which may prevent condensate
discharge and result in lowered temperatures, coil damage
and possible solidifications. Operators may then have to open
drainage location bypasses and blowdown valves to maintain
sulfur temperatures, which can cause energy loss and safety issues.
Steam locking of the sulfur pit coil may be mitigated by
the installation design and by selecting a trap with a small vent
hole to address steam locking.2
Structured approach to selection and documentation.
A structured approach is necessary to select the trap, and then
FIG. 2. Instrument enclosures require subcooling traps to avoid
burning instruments.
Hydrocarbon Processing | DECEMBER 2021 37
to document the selection and communicate it to maintenance
personnel, engineering contractors and capital project teams.
A trusted steam system specialist can help to guide steam trap
selection for any type of application and to provide established
procedures for documenting and communicating selection
standards. TABLE 1 shows an extract from a typical selection
document reviewing steam trap selections.
Install the steam trap correctly. Steam traps must be properly
installed so they can function correctly. Installation details
depend on the application, along with the existing factors in
the field and the type of steam trap selected. A steam trap is
typically installed as part of a condensate discharge location
(CDL), which includes other items such as an inlet isolation
valve, a strainer with blowdown, the steam trap, an outlet isolation
valve, a check valve, a disassembly component such as a
FIG. 1. A properly designed collecting leg/CDL has multiple
components that require correct installation.
Hydrocarbon Processing - December 2021
Table of Contents for the Digital Edition of Hydrocarbon Processing - December 2021
Contents
Hydrocarbon Processing - December 2021 - Cover1
Hydrocarbon Processing - December 2021 - Cover2
Hydrocarbon Processing - December 2021 - Contents
Hydrocarbon Processing - December 2021 - 4
Hydrocarbon Processing - December 2021 - 5
Hydrocarbon Processing - December 2021 - 6
Hydrocarbon Processing - December 2021 - 7
Hydrocarbon Processing - December 2021 - 8
Hydrocarbon Processing - December 2021 - 9
Hydrocarbon Processing - December 2021 - 10
Hydrocarbon Processing - December 2021 - 11
Hydrocarbon Processing - December 2021 - 12
Hydrocarbon Processing - December 2021 - 13
Hydrocarbon Processing - December 2021 - 14
Hydrocarbon Processing - December 2021 - 15
Hydrocarbon Processing - December 2021 - 16
Hydrocarbon Processing - December 2021 - 17
Hydrocarbon Processing - December 2021 - 18
Hydrocarbon Processing - December 2021 - 19
Hydrocarbon Processing - December 2021 - 20
Hydrocarbon Processing - December 2021 - 21
Hydrocarbon Processing - December 2021 - 22
Hydrocarbon Processing - December 2021 - 23
Hydrocarbon Processing - December 2021 - 24
Hydrocarbon Processing - December 2021 - 25
Hydrocarbon Processing - December 2021 - 26
Hydrocarbon Processing - December 2021 - 27
Hydrocarbon Processing - December 2021 - 28
Hydrocarbon Processing - December 2021 - 29
Hydrocarbon Processing - December 2021 - 30
Hydrocarbon Processing - December 2021 - 31
Hydrocarbon Processing - December 2021 - 32
Hydrocarbon Processing - December 2021 - 33
Hydrocarbon Processing - December 2021 - 34
Hydrocarbon Processing - December 2021 - 35
Hydrocarbon Processing - December 2021 - 36
Hydrocarbon Processing - December 2021 - 37
Hydrocarbon Processing - December 2021 - 38
Hydrocarbon Processing - December 2021 - 39
Hydrocarbon Processing - December 2021 - 40
Hydrocarbon Processing - December 2021 - 41
Hydrocarbon Processing - December 2021 - 42
Hydrocarbon Processing - December 2021 - 43
Hydrocarbon Processing - December 2021 - 44
Hydrocarbon Processing - December 2021 - 45
Hydrocarbon Processing - December 2021 - 46
Hydrocarbon Processing - December 2021 - 47
Hydrocarbon Processing - December 2021 - 48
Hydrocarbon Processing - December 2021 - 49
Hydrocarbon Processing - December 2021 - 50
Hydrocarbon Processing - December 2021 - 51
Hydrocarbon Processing - December 2021 - 52
Hydrocarbon Processing - December 2021 - 53
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Hydrocarbon Processing - December 2021 - 55
Hydrocarbon Processing - December 2021 - 56
Hydrocarbon Processing - December 2021 - 57
Hydrocarbon Processing - December 2021 - 58
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Hydrocarbon Processing - December 2021 - 60
Hydrocarbon Processing - December 2021 - 61
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Hydrocarbon Processing - December 2021 - 63
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Hydrocarbon Processing - December 2021 - 65
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Hydrocarbon Processing - December 2021 - 67
Hydrocarbon Processing - December 2021 - 68
Hydrocarbon Processing - December 2021 - 69
Hydrocarbon Processing - December 2021 - 70
Hydrocarbon Processing - December 2021 - 71
Hydrocarbon Processing - December 2021 - 72
Hydrocarbon Processing - December 2021 - 73
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Hydrocarbon Processing - December 2021 - 75
Hydrocarbon Processing - December 2021 - 76
Hydrocarbon Processing - December 2021 - 77
Hydrocarbon Processing - December 2021 - 78
Hydrocarbon Processing - December 2021 - 79
Hydrocarbon Processing - December 2021 - 80
Hydrocarbon Processing - December 2021 - 81
Hydrocarbon Processing - December 2021 - 82
Hydrocarbon Processing - December 2021 - Cover3
Hydrocarbon Processing - December 2021 - Cover4
Hydrocarbon Processing - December 2021 - GP-1
Hydrocarbon Processing - December 2021 - GP-2
Hydrocarbon Processing - December 2021 - GP-3
Hydrocarbon Processing - December 2021 - GP-4
Hydrocarbon Processing - December 2021 - GP-5
Hydrocarbon Processing - December 2021 - GP-6
Hydrocarbon Processing - December 2021 - GP-7
Hydrocarbon Processing - December 2021 - GP-8
Hydrocarbon Processing - December 2021 - GP-9
Hydrocarbon Processing - December 2021 - GP-10
Hydrocarbon Processing - December 2021 - GP-11
Hydrocarbon Processing - December 2021 - GP-12
Hydrocarbon Processing - December 2021 - GP-13
Hydrocarbon Processing - December 2021 - GP-14
Hydrocarbon Processing - December 2021 - GP-15
Hydrocarbon Processing - December 2021 - GP-16
Hydrocarbon Processing - December 2021 - GP-17
Hydrocarbon Processing - December 2021 - GP-18
Hydrocarbon Processing - December 2021 - GP-19
Hydrocarbon Processing - December 2021 - GP-20
Hydrocarbon Processing - December 2021 - GP-21
Hydrocarbon Processing - December 2021 - GP-22
Hydrocarbon Processing - December 2021 - GP-23
Hydrocarbon Processing - December 2021 - GP-24
Hydrocarbon Processing - December 2021 - GP-25
Hydrocarbon Processing - December 2021 - GP-26
Hydrocarbon Processing - December 2021 - GP-27
Hydrocarbon Processing - December 2021 - GP-28
Hydrocarbon Processing - December 2021 - GP-29
Hydrocarbon Processing - December 2021 - GP-30
Hydrocarbon Processing - December 2021 - GP-31
Hydrocarbon Processing - December 2021 - GP-32
Hydrocarbon Processing - December 2021 - GP-33
Hydrocarbon Processing - December 2021 - GP-34
Hydrocarbon Processing - December 2021 - GP-35
Hydrocarbon Processing - December 2021 - GP-36
Hydrocarbon Processing - December 2021 - GP-37
Hydrocarbon Processing - December 2021 - GP-38
Hydrocarbon Processing - December 2021 - GP-39
Hydrocarbon Processing - December 2021 - GP-40
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