A large, industrial wastewater treatment facility with around-the-clock operations needed a solution to improve the on-stream reliability of two Regenerative Thermal Oxidizers (RTOs). Their systems were often shutting down multiple times a week - causing major operating and environmental compliance issues. Furthermore, since the plant runs 24/7, it could not afford to devote unplanned downtime for extensive system repairs.
A PolSys Senior Field Service Engineer was called in to visit the site and to meet with the Facilities Manager, perform an inspection, and speak with plant personnel to learn more detail about the shutdowns. After a comprehensive internal and external inspection of the RTOs and review of operating conditions, we determined that poppet valve failures were the root cause of the frequent system shutdowns.
In particular, three features were found to be problematic. First, the original manufacturer had specified a carbon steel shell with a Hastelloy liner, but a carbon steel shell with a lower-quality 304 Stainless Steel liner and expansion joints were provided. Secondly, warped shafts on the horizontal stroke poppet valves caused inconsistent proximity detection which resulted in faulty valve positioning reported to the PLC. Lastly, the original manufacturer employed single-directional pneumatic solenoid valves that rely on a single spring or tiny valve pin to operate. These pins are susceptible to sticking when exposed to moisture or debris, which was causing the pin to stick in this facility's high-humidity environment.
To solve these issues, we engineered and executed the following upgrades:
- We installed new high-quality poppet valve assemblies, interconnecting ductwork, and expansion joints below the RTO media beds
- Single-directional solenoids were replaced with high-quality, powered solenoids that rely on power to open and close vs. a spring
- Low-quality actuators prone to reliability issues were replaced with high-quality pneumatic actuators more immune to debris and moisture
- More suitable cylinders, proximity switches, wiring and gasketing were also installed
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