Program 4 - Pepperl+Fuchs 7500 User Manual

7500 S M  P
erieS anual
4.4.4

Program 4

Program 4 is used in hazardous gas atmospheres.
Sequence of Events for Program 4
P > P1
enclosure
Pre-Purge
The purge valve (SV) is immediately energized regardless of enclosure pressure.
z
If enclosure pressure goes above P4 during purging, the SV shuts off but will energize when
z
below P4. Oscillation of SV may be noticed.
Setting the pressurization valve on the manifold has to be done after purging, or power to SV will
z
have to be interrupted to set this pressure. The solenoid valve on the manifold is immediately
energized before this pressure can be set.
The purge timer begins counting down when enclosure pressure is greater than P3, and it has to
z
remain greater than P3 to purge successfully. If the pressure drops below P3 at any time, or for
any length of time during purging, the purge timer is reset and will not begin counting down until
pressure is greater than P3.
WArNINg!
If enclosure pressure is below P1 when K1 is used to provide power to the
enclosure during operation, K1 will remain energized. An alarm is required and
must be located such that an operator will be notified of the alarm.
Operation Mode
After the purge timer counts down, the SV shuts off and K1 is energized.
z
If enclosure pressure drops below P3, the SV is energized and will stay energized for the value
z
of HYST (%, leakage compensation). If HYST is set to 0, leakage compensation is turned off.
However, Program 4 is usually used when a continuous purging through the enclosure is required
during operation mode.
If enclosure pressure drops below P1, K1 remains on and an alarm will sound. K2 can be set to
z
P- or Alarm to indicate below safe or operating pressure.
If enclosure pressure goes above P4, K1 remains. If K2 is set up as Alarm, K2 will energize.
z
50
rograMMing
P < P3
Clean
Purge valve
ON
K1 ON
P > P1
Bypass
ON
In menu
K1 ON
P < P1
K2 ON