Hydrocarbon Processing - April 2021 - 54

Engineering and Construction
Metallurgical improvements occur
regularly in the process industries. The
extent of implementation of superior
metallurgy in brownfield modifications
should be demarcated clearly along with
the greenfield project. The construction
material of piping, instrumentation and
equipment internals, etc., should be clearly marked on a material selection guide
(MSG) and material selection diagram
(MSD) to avoid the confusion of a superior metallurgy change in the old units.
Demolition and cleanup of any old
unit. Demolition of an old unit and site

clean-up to create space for a new unit is
normally part of any project. The scope

normally covers the removal and disposal
of old equipment, piping, foundations
and structure in a safe manner.
The area should be inspected for
hidden surprises, such as underground
cables, pipes, drains or any process lines
and old foundations. The area should be
thoroughly scanned by suitable tools (ultrasonic or other type) to avoid damage to
any live system.
Any adjoining building or structure
that is live and may get impacted during
excavation work should be identified and
an accordingly suitable reinforcement of
structure must be planned.
Excavation work near existing building/structure. Soil condition, depth

and angle coverage of excavation, and
distance from any existing structure or
pipe rack should be ascertained before
proceeding with excavation.
In one project, the soil condition was
found to be very unstable. Excavation
was required for the construction of a
concrete pit to stall an underground slop
tank. Excavating close to the existing pipe
rack could have damaged its stability.
The project personnel had to either
shift the location of the pit or use sheet
piling, as shown in FIG. 1, to protect the
foundation of the pipe rack. Shifting the
location was not possible without major
engineering changes, so the second option of sheet piling was used.
FIG. 2. A new culvert was designed to carry
pipes of two EPC contractors.

Mechanical functional area. Frontend engineering design (FEED) should
normally cover all relevant data, drawPipe by: EPC No. 2 contractor

Pipe rack
Tank dyke wall

Pipe by: EPC No. 1 contractor
Concrete sleeper

Tank area

HPP elevation
Pond
Space just enough for
crane movement

FIG. 3. To allow two contractors to carry out piping work between a tank dike wall and a pond,
with little space for vehicular/crane movement, a goal post-type frame was mounted on concrete
sleepers.

APRIL 2021 | HydrocarbonProcessing.com

ings and health check reports of existing
equipment (where modifications and alterations are planned).
Similarly, an equipment health check
on equipment, the foundations size and
depth, current condition and preferably
the old design calculations should also
be available.
Any change in old equipment loading
data due to change of internals will have
an impact on the foundation. Significant
changes can occur in equipment design
conditions, design codes, stress values,
wind and seismic conditions, etc.
Another project faced a height increase requirement of a distillation tower
to accommodate an extra packed bed
in the top section. Because an increase
in the column height in the top section
was needed, the column design required
a complete review based on the latest
codes, standards and new design conditions. However, the old foundation details and design calculations were unavailable, and it was challenging to carry out
a health assessment of the old foundation
and justify its adequacy.
Similarly, stress relieving and hydrotesting of an old column after modification
are other important issues, considering
the need to safely hold the tower during
heat treatment to check the suitability of
an old foundation for hydro test load.
Civil and structural area. When modifying or retrofitting any existing technology structure, pipe racks, road bridges,
and where process equipment, agitators,
etc., are added, an evaluation is required
for all static and dynamic loads, along
with their foundations as per the latest
rules, design codes and regulations.
Piping functional areas. Tie-in points
locations and accurate piping end connection details are vital. In a project, the
line/flange size of one tie-in could not
be ascertained, as it was at a high elevation and unapproachable. The information provided by the operators was relied
upon. However, during execution, the
pipe size was found to be different; this
resulted in a last-minute rush for design
changes, approvals and material procurement. Pipe metallurgy, size, flange facing
and rating, type of gasket and provisions
for piping isolation valves must be carefully checked for each tie-in.
Isolation valves are normally the

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Hydrocarbon Processing - April 2021

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