Orifice Plate Saves $12,000 Annually
Bypass & Original Lines
A 2” alumina ceramic valve in use at the a cogeneration plant in New York had to be replaced four times a year due to severe erosion. The control valve was installed on a pressure control loop to maintain lime slurry pressure feeding a wet scrubber. During peak electricity demand, the need for lime slurry increased and required the valve to operate at 80% open – which is proper sizing for a ceramic ball valve. However, during the night and throughout most of the day, electricity demand declined sharply, which meant less demand for lime slurry to the scrubber. The valve throttled back to between 25% to 30% open.
Quarterly Replacement: $3900
The low operating position of the valve, combined with a differential pressure of 80 psi and a percent solids content in the slurry approaching 35% yielded disastrous results for the valve. The valve’s ceramic body, ball, and seat, as well as the stem and packing had to be routinely replaced every three months at a cost of nearly $3,900.
18-Month Replacement Cycle
To solve the problem, a bypass line with a new ceramic valve was installed around the original valve, and Ceresist ceramic orifice plates were installed downstream of each of the valves to reduce differential pressure. During low demand only one of the valves was operational, but with a reduced differential pressure across the valve it allowed it to throttle at approximately 65%. During high demand, both valves open to approximately 70%. The bypass line combined with the ceramic orifice plates allowed both conditions to be met with dramatically reduced valve erosion. Each of the ceramic valves now operates in continuous service for approximately 18 to 24 months without maintenance.