Vent; Operating Information; Pilots Without Optional Set Point Indication; Preliminary Adjustments - Fisher 4660 Instruction Manual

Vent

WARNING
If a flammable, toxic or reactive gas is to
be used as the supply pressure medium,
personal injury or property damage
could result from fire or explosion of ac-
cumulated gas or from contact with a
toxic, or reactive gas. The instrument
case and cover assembly does not form
a gas-tight seal, and when the assembly
is enclosed, a remote vent line, ade-
quate ventilation, and necessary safety
measures should be used. However, a
remote vent pipe alone cannot be relied
upon to remove all hazardous gas. Vent
line piping should comply with local
and regional codes and should be as
short as possible with adequate inside
diameter and few bends to reduce case
pressure buildup.
If a remote vent is required, use 3/4-inch (19mm)
(minimum inside diameter) pipe for runs up to 20 feet
(6.09 meters). For vent piping runs from 20 to 100 feet
(6.09 to 30.5 meters), use 1-inch (25.4 mm) (minimum
inside diameter) pipe. Remove the vent screen (key
20, figure 8) and install a remote vent pipe to exhaust
the vented gas to a safe, well-ventilated area.The
vent, as shown in figure 8, or the end of a remote vent
pipe must be protected against the entrance of all for-
eign matter that could block the vent. Check the vent
periodically to be certain it is not plugged.

Operating Information

For high-only and low-only constructions, perform the
procedures that are outlined in the adjustments portion
of this section. For high-only constructions, perform
only those procedures that pertain to setting and
checking the high set point. For low-only construc-
tions, perform only those procedures that pertain to
setting and checking the low set point. For high-low
constructions, perform procedures that pertain to both
the high and low set points.
WARNING
Avoid personal injury or property dam-
age from an uncontrolled process or
sudden release of process pressure. Be-
fore starting any adjustments:
Provide some temporary means of
process control before taking the pilot
out of service,
Shut off the process pressure line
and the supply pressure line, and bleed
all the supply pressure.
Bleed all process pressure from the
pilot so that no pressure is contained in
the Bourdon tube.
Use lock-out procedures to be sure
that the above measures stay in effect
while you are working on the equip-
ment.
Pilots Without Optional Set Point
Indication

Preliminary Adjustments

Make sure each of the following six steps have been
performed completely before setting either the high or
low set point pressures. Key numbers are shown in
figure 8.
1. Refer to the warning at the beginning of the Operat-
ing Information section. Make sure the Bourdon tube
contains no pressure.
2. Install either a pressure gauge or an optional output
indicator in the output pressure line.
3. Remove the cover screws and the cover (keys 6
and 4).
4. Unlock each locking disk (key 69) that holds each
set point knob in place. Turn the HIGH SET knob
clockwise until it has reached the end of its travel.
Turn the LOW SET knob (key 67) counterclockwise
until it has reached the end of its travel.
5. Turn on the supply pressure. To check that the sup-
ply pressure is turned on, push the SUPPLY TEST
button located in the cleanout assembly (key 54) on
the front plate (key 74) until a flow sound is heard.
WARNING
To avoid personal injury or property
damage caused by a sudden release of
pressure, do not exceed the process
pressure values in table 4.
6. Connect an external pressure source to the process
pressure connection. This external pressure source
should be a regulated air or gas supply that is adjust-
able to zero. The external pressure source must be
capable of supplying a process pressure that will be
equal to or greater than the desired high set point
pressure.
Type 4660
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