Case Study Steps
Issue
As part of the planned maintenance at the Saudi Aramco Riyadh Refinery, the crude oil pre-heater was taken out of commission in order to clean the internals of the pipe work to remove any deposits which would reduce the efficiency of the heat transfer process. Pipe cleaning pigs of different diameters were put into the pipe and driven through the pipe using high pressure water on one side of the pig. Part way through the cleaning process the pig stopped moving and despite increasing the water pressure it could not be retrieved. Any delay in completing the planned maintenance activities would delay the return of the refinery to production, with massive cost penalties due to lost production.
Approach
Despite applying water pressure alternately to the up and downstream faces of the cleaning pig, the maintenance team were unable to retrieve it from the heat exchanger pipe work.
It was decided that in order to resolve the problem action would have to be focused at the location of the pig. One idea was to apply localized heat on the outside of the pipe in the vicinity of the pig with the aim of slightly increasing the bore of the pipe and, with the aid of water pressure, moving the pig along the pipe. However, the precise location was not known. A quick solution to confirm the location of the pig was required before the agreed approach could be implemented.
It was decided that in order to resolve the problem action would have to be focused at the location of the pig. One idea was to apply localized heat on the outside of the pipe in the vicinity of the pig with the aim of slightly increasing the bore of the pipe and, with the aid of water pressure, moving the pig along the pipe. However, the precise location was not known. A quick solution to confirm the location of the pig was required before the agreed approach could be implemented.
Solution
ACC recognized that ultrasound technology could be used to precisely locate the pig. Upstream of the pig the pipe was filled with water, downstream
of the pig the pipe was opened to drain and therefore empty (or full of air).
Using a clamp-on ultrasonic flow meter designed for liquid applications the diagnostic parameters would give a clear indication whether there was water or air at the measurement point. Because the transducers are located on the outside of the pipe and since we weren’t looking for accurate flow measurement it was possible to hold the transducers in position. This meant it only took a few seconds to check each point before moving to the next position along the pipe. It only took a few minutes to accurately locate the pig, compared with the many hours it had taken to scaffold the pre-heater in order to give access to the pipes.
of the pig the pipe was opened to drain and therefore empty (or full of air).
Using a clamp-on ultrasonic flow meter designed for liquid applications the diagnostic parameters would give a clear indication whether there was water or air at the measurement point. Because the transducers are located on the outside of the pipe and since we weren’t looking for accurate flow measurement it was possible to hold the transducers in position. This meant it only took a few seconds to check each point before moving to the next position along the pipe. It only took a few minutes to accurately locate the pig, compared with the many hours it had taken to scaffold the pre-heater in order to give access to the pipes.
Benefits
Knowing the precise location of the pig the customer was able to focus their efforts at that specific point and not across the many tens of meters of pipework within the preheater. Once localized heat was applied the pig was quickly retrieved by applying water pressure on one side of the pig.
