ANDERSON GREENWOOD
TYPE 91 AND 94 PILOT OPERATED SAFETY RELIEF VALVES
INSTALLATION AND MAINTENANCE INSTRUCTIONS
© 2021 Emerson. All Rights Reserved.
Before installation these instructions must be fully read and understood
STORAGE AND HANDLING
Pressure relief valve performance may be
adversely affected if the valve is stored for an
extended period without proper protection.
Rough handling and dirt may damage, deform,
or cause misalignment of valve parts and may
alter the pressure setting and adversely affect
valve performance and seat tightness. It is
recommended that the valve be stored in the
original shipping container in a warehouse
or as a minimum on a dry surface with a
protective covering until installation. Inlet and
outlet protectors should remain in place until
the valve is ready to be installed in the system.
Emerson.com/FinalControl
The intent of these instructions is to acquaint
the user with the storage, installation and
operation of this product. Please read these
instructions carefully before installation.
WARNING
Removal of the seal wires in an attempt to adjust
and/or repair this product by unauthorized or
unqualified persons voids the product warranty
and may cause damage to equipment and serious
injury or death to persons.
The product is a safety related component intended
for use in critical applications. The improper
application, installation or maintenance of
the product or the use of parts or components not
manufactured by Anderson Greenwood may result
in a failure of the product.
Any installation, maintenance, adjustment, test, etc.
performed on the Product must be done in
accordance with the requirements of all applicable
Anderson Greenwood Procedures and Instructions
as well as applicable National and International
Codes and Standards.
SAFETY PRECAUTIONS
When the pressure relief valve is under pressure
never place any part of your body near the pilot
exhaust nor the outlet of the main valve.
The main valve outlet should be piped or vented to
a safe location.
Always wear proper safety gear to protect head,
eyes, ears, etc. anytime you are near pressurized
valves.
Never attempt to remove the pressure relief valve
from a system that is pressurized.
Never make adjustments to or perform
maintenance on the pressure relief valve while
in service unless the valve is isolated from
the system pressure. If not properly isolated from
the system pressure, the pressure relief valve
may inadvertently open resulting in serious injury.
1 GENERAL VALVE DESCRIPTION AND
START-UP
1.1 Operation
The Anderson Greenwood Pilot Operated Safety-
Relief Valves utilize the principle of backloading
the top, or large area, of a differential area
bellows with line pressure to hold the bellows
closed up to set pressure. At set pressure
the pilot valve relieves, partially evacuating
the dome (volume in the bellows) and the bellows
lifts permitting discharge from the main valve.
When the pilot reseats, line pressure is diverted
to the dome closing the main valve.
1.2 Installation
The valve should be installed in accordance
with accepted piping practices, in an upright
position as shown in Figure 1.
When remote pressure pick-up is used the pilot
supply tube is connected to a remote location
rather than to the inlet neck of the valve. If a
block valve is used in the remote pilot supply
line, be sure it is opened before pressurizing
the system or opening the isolating block valve
under the main valve, if one is used.
NOTE
Remote pressure pick-up piping must have
the equivalent flow area of ½” (15 mm) tubing for
lengths up to 20 feet (6.1 m). For lengths greater than
20 feet (6.1 m), larger tubing or pipe should be used.
VCIOM-06025-EN 21/06
Engineering Doc. #05.9040.080 Rev. K
TABLE OF CONTENTS
1. General valve description and start-up ....... 1
2. Main valve maintenance ............................... 2
3. Pilot maintenance ......................................... 4
4. Pilot set pressure adjustment ...................... 8
5. Accessory repair .......................................... 10
6. Leak testing assembly ................................ 11
7. Pilot set pressure field test procedure ...... 11
8. Repair kits .................................................... 12
Remove the pressure relief valve prior to
performing any pressure testing of the system.
The safety of lives and property often depends
on the proper operation of the pressure relief
valve. The valve must be maintained according to
appropriate instructions and must be periodically
tested and reconditioned to ensure correct function.
