SVI-II Instruc Man.book - Fagerberg

Masoneilan Dresser
SVI II AP Instruction Manual
Pneumatic Module
Current-to-Pressure Converter, I/P
Single Acting Pneumatic Relay
The pneumatic module consists of an I/P and Relay assembly.
The I/P converts a current signal to a pressure signal in the following manner.
A fixed coil creates a magnetic field proportional to the applied current. The
field magnetically pulls a flexure towards a nozzle to increase pressure on the
flexure. The pressure on the flexure increases in response to an increase in
the coil current. Encapsulation of the coil provides protection from the
environment.
The single acting pneumatic relay amplifies the pressure from the I/P and
increases airflow as required for stable, responsive, actuator performance.
The single acting relay operates on any supply pressure that is at least 5 psi
(.345 bar, 34.5 kPa) above the required actuator pressure, up to 100 psi
(6.9 bar, 690 kPa).
I/P Current to Pneumatic Converter
Relay
(Pneumatic Amplifier)
Vent
Figure 41 Pneumatic Module with Single Acting Relay
92