Baseline Inspection Provides Head Start on Heater Reliability and Longevity
Special report by Quest Integrity, featured in Hydrocarbon Engineering.
Ultrasonic "smart pigging” inspection technology
can be utilised to detect a multitude of defects within fired heater
coils, aiding unit operators in identifying potential problems and
preventing unplanned shutdowns. Utilising In-Line Inspection (ILI)
technologies as a baseline allows for the earliest possible
identification of true tube wall conditions, which is vital when
planning future maintenance and tube life expectancy.
In March of 2017, Quest Integrity performed an inspection utilizing
its Furnace Tube Inspection System, FTIS™, on four platformer units in
Germany. The inspections included data gathering on 100% of each pipe
surface within the radiant section of the heater. At the time of
inspection, the units were still at the manufacturer site and had not
yet been shipped to the refinery. As such, the examination of the unit
was considered a baseline inspection.
The pipes within these units were designed as 3-in. tubes with a
nominal wall thickness of 4.0 mm (0.157 in.). However, the results of
the inspection showed numerous localised areas with remaining wall
thickness readings as low as 2.6 mm (0.102 in.), which was 35.0% thinner
than the design wall. Many pipes within all coils (passes) of these
heaters contained wall thickness readings between 0.2 mm (0.008 in.) and
1.4 mm (0.055 in.) thinner than the nominal design.
Figure 1. Baseline inspection reveals varying wall thicknesses within newly installed piping.
Wall thicknesses variations in new sections of piping is very
significant for an operator. Without the initial baseline inspection, it
would have been assumed that the thickness of the new piping was the
same as the nominal design wall before the unit went into operation.
the initial in-line inspection occurred sometime after the new section
had been placed in service, the operator may have concluded that wall
loss of up to 1.4 mm (0.055 in.) had occurred due to corrosion or
erosion. This would have resulted in a much lower remaining life for
many of the pipes, based on the assumption that damage was occurring at a
faster-than-normal rate. This is particularly important when
determining the true lifespan of the unit.
with ultrasonic in-line inspection technology should not be overlooked,
as baseline inspections can identify problems before unit start up, and
aid in future maintenance planning. The benefits of a baseline
inspection allow for the complete understanding of operating assets at
every life stage, providing confident decision-making, maximum
operability and a greater return on investment.