Dwyer GFC User Manual

Page 17

5.6 Valve Test/Purge

At times, it may be necessary to purge the flow system with a neutralizing gas
such as pure dry nitrogen. The GFC transducer is capable of a full open condition
for the valve, regardless of setpoint conditions. Connecting the OPEN (PURGE)
pin (pin 4 on 15-pin "D" connector) to ground will fully open the valve.

The Motorized Valve: Connect pins 3 and 4 to OPEN the motorized control valve
A red light on top of the valve will indicated an OPEN valve condition, normal for
flow conditions.

Please Note: The valve stays OPEN even if power is no longer applied.
To CLOSE the Motorized Control Valve, connect pins 3 and 12.

6. MAINTENANCE

6.1 Introduction

It is important that the Mass Flow Controller/Controller is used with clean, filtered
gases only. Liquids may not be metered. Since the RTD sensor consists, in part,
of a small capillary stainless steel tube, it is prone to occlusion due to impedi-
ments or gas crystallization. Other flow passages are also easily obstructed.
Therefore, great care must be exercised to avoid the introduction of any potential
flow impediment. To protect the instrument a 50 micron (GFC17) or 60 micron
(GFC-113/114) filter is built into the inlet of the flow transducer. The filter screen
and the flow paths may require occasional cleaning as described below. There is
no other recommended maintenance required. It is good practice, however, to
keep the meter away from vibration, hot or corrosive environments and excessive
RF or magnetic interference.

If periodic calibrations are required they should be performed by qualified per-
sonnel and calibrating instruments, as described in section (7). It is recommend-
ed that units are returned to Dwyer for repair service and calibration.

CAUTION: TO PROTECT SERVICING PERSONNEL IT IS MANDATO-
RY THAT ANY INSTRUMENT BEING SERVICED IS COMPLETELY
PURGED AND NEUTRALIZED OF TOXIC, BACTERIOLOGICALLY
INFECTED, CORROSIVE OR RADIOACTIVE CONTENTS.

6.2 Flow Path Cleaning

Inspect visually the flow paths at the inlet and outlet ends of the meter for any
debris that may be clogging the flow through the meter. Remove debris carefully
using tweezers and blowing low pressure clean air or Nitrogen from the inlet side.
If the flow path is not unclogged, please return meter to Dwyer for servicing.

Do not attempt to disassemble the sensor. Disassembly will invalidate
calibration.