This discussion will review the most commonly used furnace isolation valves (i.e., transfer line and decoke valves) in the industry today with respect to the most common failures experienced with each design as well as recommended preventative maintenance (P/M) to maximize working life and intervals between repairs.

While considering valve type and P/M programs for Transfer Line and Decoke valves, which is better: the expensive, upfront cost of a specialized valve for the service in which relatively low maintenance is required over time or a cheaper design valve that can be replaced during scheduled maintenance outages? In either case, of paramount importance is the reliability of the valves between scheduled maintenance intervals. This, in large part, is influenced by the technology, feedstock, and throughput of individual furnaces.

The physical position of the valves in the lines can determine how much coke build-up is experienced in the valves or against closed, seated effluent valves. These, along with many other considerations, should have direct bearing on the type valves used as well as the degree of preventative maintenance performed.