Hydrocarbon Processing - August 2021 - 30

Valves, Pumps and Turbomachinery
* Ask the vendor to use a bellows
design featuring a hightemperature,
corrosion-resistant
metal, and to review the bellows
material. Ensure that the seal faces
remain parallel to each other, even
over a wide variety of temperatures,
as this helps to reduce thermal
distortion.
* Calculate the cost of using Plan 32
in an FB configuration. If an FB
configuration must be used, select
an effective seal flush liquid with
a lower cost, if possible.
* Ask the vendor to provide a seal
simulation calculation to check
the effect of API Plan 32 on
seal cooling. Compare the seal
temperature condition with and
without using Plan 32.
* Always check the accuracy of
the flowmeter, pressure and
temperature gauges used in Plan
32. Use separate flowmeters and
gauges for each cartridge.
* Make sure there is always a stable
supply of seal flush. Check the
risk of back pressure and
fluctuation in the seal flush.
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www.borsig.de
BORSIG GmbH
Phone: +49 (0)30 4301-01
Fax: +49 (0)30 4301-2236
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Germany
30 AUGUST 2021 | HydrocarbonProcessing.com
* Use stainless-steel piping material
for Plan 32 as much as possible.
* Ensure that there is no
misalignment between the
pump casing and the seal gland
and cartridge.
* Measure and confirm the thermal
grout of the nozzle, piping and
pump casing/pedestal.
* Consider the effects of coke
formation in the mechanical
seal during balance ratio sizing.
Vendors design seal faces with a
balance ratio to minimize heat
generation between seal faces.
This seal ratio also impacts seal
faces' opening and closing forces.
* Remember that, per API 682,
the most desirable viscosity for
hydrocarbon barrier/buffer fluids
is between 2 mm2
/sec (2 cSt)
and 10 mm2/sec (10 cSt) at
operating temperature.
* Consider the auto-ignition
temperature of the barrier liquid
to prevent risks of fire in case of
an outer seal failure.
* Consider that using diamond
against silicon carbide instead
of SiC-SiC rings could result in
a reduction of friction by more
than eight times. This reduction
would mean significantly less heat
generated at the seal faces and
would help prevent coking. This
would lower the heat load of the
seal and would help Plan 53B, 53C
or 54 perform better.
* Consider that a diamond coating
will provide less heat generation
and better abrasive resistance.
However, it will also substantially
increase barrier fluid consumption
and reduce the refill period for
Plan 53B, 53C and 54 systems,
and two diamond coated rings
will wear extremely slowly vs.
SiCar-SiCar or SiCar-carbon.
This means that barrier fluid
consumption will remain high,
and the seal will not wear in.
* Ask the vendor to design the
cartridges to switch to other
configurations in the future,
with minimum cost.
Takeaway. Mechanical seal selection
and sizing for hot pumping services must
be done with experienced personnel.
Many factors should be considered. The
purchaser should ensure that the vendor's
proposed seal is a proven design.
This article explained the lessons learned
in using Arrangement 3 for hot pumping
services.
NOTE
The recommendations outlined in this article are
based on personal experience and are not related to
any company.
LITERATURE CITED
1
API, API Standard 682, " Pumps-Shaft Sealing
Systems for Centrifugal and Rotary Pumps, " 4th edition,
May 2014.
SHAHAB ZARDYNEZHAD is a
registered Senior Mechanical
Engineer in Alberta with more
than 29 yr of experience working
on many of the world's largest oil,
gas and petrochemical projects.
He has experience in engineering,
procurement services, manufacturing, shop/field
inspection, installation, commissioning, startup,
reliability, and the maintenance and operation of
pumps, compressors and turbines. Mr. Zardynezhad
holds a BS degree in mechanical engineering from
the University of Petroleum of Iran, an MS degree
in industrial engineering from I.U.S.T-Iran, an MS
degree in project management and an MS degree
in mechanical engineering from the University
of Calgary. He is a certified API inspector for
rotating equipment.
http://www.borsig.de http://www.HydrocarbonProcessing.com
Hydrocarbon Processing - August 2021

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