Coker Valve Purging

The Need: The delayed coker process is crucial to a refinery’s profitability.  Coking is one of the most hostile environments in the refinery with process temperatures of 1000° F / 538° C and outputs a very abrasive and erosive coke by-product.  Valves are cycled more frequently than valves in other parts of the refinery and failure can lead to complete shut down of a unit leading to large process and financial costs.  A refinery in Fort McMurray, Canada realized these costs first hand with the plug valves locking up on a routine basis.  They had to shut down operation, take off the top of the valves and steam the plugs in order to free the debris and function properly.  Shutdowns were becoming routine, frequent and very costly.		It is essential to have a proper purge system installed on coker valves to work correctly.

The Function:

The delayed Coker process is a batch process, one of few in the refinery complex.  The process of switching from one drum to another requires a complex series of events take place in perfect sequence or equipment may be damaged.  Delayed coking is a semi-continuous thermal cracking process.  After being heated in a coke furnace, the coke feed (a liquid-vapor combination) is fed into and separated in a coke drum.  Delayed cokers are designed as pairs of drums so that one drum can be cleaned while the other remains in operation.  This application requires valves to cycle on a regular, reliable and constant basis.  Operating temperatures vary drastically and state change (coke formation) occurs while processing through the valves.  The main challenge for this refinery in Fort McMurray is when the media collects within the valve cavities, hardens and the valves begin to leak or lock-up.

The Solution:

The ValvTechnologies purge system is a preventative solution which removes the heavy hydrocarbon from the valves cavity before the hydrocarbon has the opportunity to change state.  This purging system is recommended for valves eight inches and larger.  ValvTechnologies was given the opportunity to install a test valve into this coker unit in Fort McMurray, Canada.  However, the client did not want a purging system installed with this valve due to concern of adding steam into the system.  Without the purging system, there were some initial issues getting the valve to function reliably over time.  It was realized quickly that this test valve was outperforming the plug valves that were currently in operation and as a result six more valves were ordered to replace these plug valves.  But this installation was without the purging system and reliability issues continued.  After convincing the client the necessity of the purge system the valves were pulled offline, fitted properly with a purge system and have been operating trouble free since 2004.  As a result of proper purging and the cost savings associated with this system, ValvTechnologies was contracted by this client as the sole-source supplier for their next delayed coking project.

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