Refinery Outgassing Bottleneck Resolved
Via Proper Control Valve Sizing & Selection
 Improved valve design avoids 15-month periodic repair & replacement.
 Improved reliability and increased throughput.
 Return-On-Investment: less than 24 hours.
Hot, low-pressure, flash drum level control in Gas-Oil Hydro
Treater (GOHT) producing light cycle gas oil (LCGO) in
combined duty shared with distillate hydrotreater (DHT).
Large refinery processor.
Customer was experiencing that, over time, its gas-oil
hydrotreater capacity had grown to the point where two
components of the high-pressure separator let-down service
would occasionally be flagged as unit constraints.
Refinery operations are such that the gas-oil hydrotreater
and distillate hydrotreater share the duty of Light Cycle Gas
Oil production (LCGO). During unit shutdown, the GOHT
was unable to handle LCGO production on it’s own, making
it a further constraint. The two units became the bottleneck
to achieving maximum LCGO production during a distillate
hydrotreater turnaround.
Further, corrective repair work to these two valves was
required every 15 months. This was due to valve and trim
washout and excessive vibration causing packing problems
and premature yoke failures. Improper valve sizing created
choked flow conditions which resulted in unit constraints
during normal and temporary feed slate conditions.
(Continued on back side.)
Custom-designed valve
trim prevents choked flow,
vibration & erosion due
to outgassing. Reduces
periodic maintenance
costs and turnaround
Fisher® Dirty Service
Trim for outgassing
applications (DST-G)
is a multi-stage
anti-cavitation trim.
It is used in services
where the fluid has
dissolved gases within
the fluid that come out
of solution due to a
reduction in pressure
and may also contain
entrained particulate.
DST-G is frequently
used in high-pressure
drop applications up to
2500 psi in the refining,
oil and gas industries.
Diagram of typical gas oil
hydrotreater process (at right);
cross section drawing (below
right) of the Fisher 3”x3” Type
HPAS with 2-Stage DST-G,
custom-designed for specific
customer refinery application.
(Continued from front side.)
Novaspect and Fisher® collaborated with customer process
engineers to understand the complete set of process conditions
that were creating the outgassing conditions in both normal and
temporary feed slate conditions. The Novaspect-Fisher experts
used a “bracket” sizing technique to understand the valve flow
coefficient (Cv) requirements that could result from different
outgassing phenomena.
The resulting solution was a customized Fisher 3”x3” Type HPAS
valve with 2-Stage DST-G outgassing trim designed specifically for
this application. Its valve body was designed to meet customer
piping and material specs with a contoured and expanded outlet
to prevent “choked flow” and other problems such as vibration
and erosion due to outgassing. The resulting trim was suitably
customized to meet the Cv requirements of the customer.
The project Return On Investment (ROI) was recorded at less than
24 hours, calculated during a temporary feed slate opportunity.
After installing the Novaspect solution, these valves have not failed
since (96 months) versus every 15 months before.
Emerson Process Management provided by Novaspect offers an
array of control system support services designed to help achieve
business objectives, reduce or contain operating and service
costs, and keep control systems running at peak performance. It
is a partnership that understands your business and can help you
operate your plant safely, reliably and more efficiently.
To learn more about how we can solve your challenging
process application, contact Novaspect today.
Novaspect Inc.
1124 Tower Road | Schaumburg, IL 60173
PH: 847.956.8020 | FX: 847.885.8200
Contact Us: www.novaspect.com
Rev. 04.14.15
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