SRD FAQ #15

ADVANTAGES OF NEW STYLE:
One less moving part. (actuator)

Two less connections in DI loop

Adjustment of DI recirculation flow is not needed.

Disadvantages: None

This is the old style DI valve assembly with an extra WR-20 actuator. The WR-20 actuator is open when the rinse actuator is closed and closed when the rinse actuator is open. The DI flow through the recirculation loop is generally set with an adjustable restrictor.

The new style DI valve assembly is now used by Semitool on all new SRDs .

The new style DI valve assembly eliminates the extra WR-20 actuator reducing the number of moving parts. The DI flow through the recirculation loop is set with a fixed restrictor.

The new style DI valve assembly connects to the SRD the same as the old style. When upgraded as part of a restoration all of the facility hook-ups are the same. (Minor internal plumbing adjustments from the actuator to the facility bulkhead are needed when the upgrade is performed in the field).
There is no noticeable differences to the operation of the SRD.