August
2011
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© Copyright 2011
BDP Inc.
All Rights Reserved.
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Project News:
Layered
safety protection improves safety
integrity at gas processing
facility
The BDP Inc. team
traditionally provides process
control systems for gas
processing plants and compressor
stations to perform overall
facility control while
integrating various OEM packages.
As plant sites are
assembled using processing
equipment from various OEM
suppliers, it is important to
compare inlet pipeline pressure
to maximum allowable operating
pressure (MAOP) for downstream
packages. In certain
situations, it may be possible to
overpressure systems which are
designed for low pressure service
by inadvertently allowing gas
blow-by due to a loss of liquid
level in the upstream process
equipment. Such high
pressure events are typically
safety interlocked and/or
protected by relief valve
systems. However,
coordination of these design
conditions between independently
purchased OEM packages may be
challenging to detect and control
until the entire facility is
assembled for operation.
One means of
enhanced safety protection to
address potential gas blow-by is
to add a stand-alone HIPPS (high
integrity pressure protection
system) to supplement the
existing safety interlocks and
relief valve system. The
additional HIPPS equipment
typically includes new
safety-rated instruments only,
using new pressure transmitters,
new electronic alarm/interlock
devices, and new solenoid valves
added to the existing ESD valve
to isolate the inlet pipeline
from downstream low pressure
vessels.
The HIPPS design is
typically based on 2-out-of-3
voting (2oo3) between independent
pressure transmitters which are
wired to the safety-rated
alarm/interlock devices.
When pressure conditions exceed
pre-set pressure limits on at
least two pressure transmitters,
the alarm/interlock devices
de-energize two new safety-rated
solenoid valves that are tubed in
series with the existing
safety-interlocked ESD valve
actuator. The HIPPS action
is independent of the existing
safety interlocks, and provides
high integrity pressure
protection using three safety
inputs to trigger two safety
outputs, ensuring that a single
device failure will not adversely
affect the HIPPS performance,
while using 2oo3 voting logic to
avoid unnecessary shutdowns. In
addition, to achieve high Safety
Integrity Level (SIL) ratings,
the ESD valve(s) must be placed
on rigorous testing schedules
utilizing parallel valves,
partial stroke testing, or other
means to assure the required risk
reduction.
Should a process
hazard analysis (PHA) identify a
potential for gas blow-by or
another high pressure event, then
a stand-alone HIPPS can be added
to the inlet ESD valve as an
additional layer of protection
without modification to the
existing safety interlocks or
relief valve system. These
BDP engineering services
compliment the skills and
resources available at the
processing plant, and enable our
clients to maximize the benefit
of their installed control
systems. Contact BDP Inc. for more
information on similar control
system services and process
control improvements to enhance
your plant operations today.
Partial
List of Current Projects at BDP:
<> Process
control consulting and APC
commissioning for NGL
fractionation strategies at a
Texas gas plant.
<>
Engineering, configuration, and
commissioning support for PLC/
HMI applications at two
compressor stations in North
Dakota.
<> Electrical
and instrument design services
for new compressor stations in
the Marcellus Shale region.
<>
Engineering, configuration, E/I
design and equipment selection
for a skid-mounted cryogenic gas
plant to be exported to Nigeria.
Partial
List of Systems included in
recent BDP projects:
<> Emerson Delta V control
system.
<> Honeywell Experion PKS
system.
<> PAC8000 process
control system from GE
Intelligent Platforms.
<> Wonderware
InTouch HMI with
Allen-Bradley ControlLogix PLC. |
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