Dry Ash Transmitter Maintenance Problem

We are using dense phase conveying system for dry ash collection. There are four ash transmitters/ ash vessels for collecting ash from ESP hoppers and subsequently transporting it to the silo for further use. The ash transmitters consist of damper valves at the inlet to allow introduction of ash into the ash transmitters and further isolation of the ash transmitter for pressurising the inside of ash transmitters to facilitate transportation of ash to silo.

The damper valve consists of rubber seal of material "Viton-A" which fails in every 15 days. Recently we have tried with "Viton- E 60 C". The performance is better.

Can we use pneumatically operated knife edge gate valve instead of pneumatically operated damper valve at the inlet to reduce the maintenance cost? If yes, which company offers such knife edge gate valves suitable for this application? The valve is required to withstand a temperature of 160 Deg C and a pressure of 6kg/cm2.