Hydrocarbon Processing - February 2022 - 64

Plant Turnarounds
and Project
Management
P. DIXIT, Consultant, Baroda, India
Construction pitfalls in SRU-fabricated equipment
In the hydrocarbon processing industry,
sulfur recovery is a well-known
process. However, this process uses a variety
of equipment. Due to the number
of construction activities being carried
out onsite, this work requires special attention
and skill. This article covers lessons
learned by the author while working
on sulfur recovery units (SRUs). Many
of the pitfalls discussed could have been
avoided if supervision and site inspections
were more vigilant. The equipment
under consideration includes the reaction
furnace, the waste heat boiler (WHB),
sulfur condensers, Claus converters, sulfur
locks, incinerators and stack. Sharing
this information may be useful to engineers
working on similar equipment.
Choked pipe and leaking sulfur seal
locks. The Claus unit converts hydrogen
sulfide (H2
liquid sulfur from the condensers passes
through the sulfur locks (FIG. 1), which
provides a U-tube seal to stop the reverse
flow of H2
S. The equipment is tall
(7 m-8 m) and is placed in a casing underground,
making installation and removal
a rigorous job.
In one case, the seal locks choked,
FIG. 1. Leakage in the sulfur lock.
causing backflow into the condenser.
S) into liquid sulfur. The
This led to the seal lock casing filling
with sulfur, which overflowed, resulting
in a shutdown. The seal lock was then removed
and examined. It was discovered
that the bottom was full of debris. The
reason may have been that the upstream
equipment and piping were not thoroughly
cleaned prior to startup.
In addition, it was noticed that the
bottom flange of the seal lock had a leak.
The bottom flange was composed of a
plate flange with a raised face. The flange
face was likely damaged due to overtightening
during a hydrotest. The pair of
flanges were replaced by a weld neck, a
ring joint flange (which is much stronger
in design) and a ring gasket.
Cracked refractory in a waste boiler
tubesheet and broken ferrules.
WHBs and sulfur condensers recover
heat from flue gas and generate steam.
The steam is generated on the shell side.
The tubesheet that faces the reaction furnace
is subject to a considerable amount
of radiation and convection heat. This is
applied with refractory, which keeps the
tubesheet temperature low and protects
the tube-to-tubesheet joint. Ferrules (ceramic
inserts) are used at the end of the
tube to transfer heat flux away from the
tubesheet joint.
After curing of the refractory, cracks
were noticed in the refractory and part
of the ceramic ferrules were found broken
(FIG. 2). Investigation revealed that
there were a few unbroken ferrules in
FIG. 2. Cracks in ferrules and the refractory.
64 FEBRUARY 2022 | HydrocarbonProcessing.com
good condition. It was decided to break
these manually to determine the reason
of their survival.
As per design/drawings, each ferrule
was supposed to have ceramic paper
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