Groth 8860 - Manual (Page 4)

IOM -8860
Page 4 of 13
13650 N. Promenade Blvd. * Stafford, TX 77477
Office: (281) – 295-6800 * (800) – 354-7684 * Fax: (281) – 295-6999 * www.grothcorp.com
II. DESIGN AND FUNCTION
The Groth Model 8860 Back Pressure regulator is a high capacity, low pressure in-line pressure relief
valve. It controls upstream pressure by discharging excess vapor downstream.
When the diaphragm force, due to upstream pressure, equals the spring compression, the regulator
begins to open. Opening is controlled to accommodate the required vapor flow. Full capacity is
achieved at 15-25% over-pressure [above set pressure]. When system pressure returns to set
pressure or below, the regulator closes.
Upstream vapor pressure, acting on a large diaphragm, forces the regulator open at the specified set
pressure. For best performance, set pressure should be sensed at a remote location at least ten pipe
diameters upstream from the regulator. The upstream pressure acts on the lower surface of the
diaphragm. The upper side of the diaphragm must be vented to atmosphere.
Set pressure is determined by the compression of the spring; the greater the compression of the
spring, the higher line pressure required to overcome the spring force. The scale located on the
regulator is a close approximation of the set pressure. A manometer is recommended for a high
accuracy reading of the set pressure. The manometer should be plumbed upstream of the Back
Pressure Regulator, at lease ten pipe diameters.
The seat and disc are lapped flat surfaces with metal to metal contact.
III. SAFETY WARNINGS
This section is intended as an overview of safety guidelines that should be followed during the
installation, operation and maintenance of the Groth Model 8860 Back Pressure Regulator. To
understand the context of these warnings and instructions, read and understand this complete manual.
In the event of an actuator diaphragm failure, the regulator will fail in the CLOSED position.
Vapor flow will be shut off. WITHOUT PROPER PIPELINE PRESSURE SENSING, EXCESSIVE
PRESSURE CAN BE REACHED.
Regulator flow capacity is based on a fully open regulator flowing air or a vapor with SG=0.7.
Consult factory for capacity under other conditions.
DO NOT attempt to re-adjust the set pressure beyond the limits specified in Table 3.
The regulator is to be connected to the upstream line with a minimum .31" ID tubing sense line.
This line must be kept open and unobstructed to ensure that the regulator senses the actual
line pressure. Long sense lines may require a larger diameter and care must be taken DURING
INSTALLATION to assure that the line is self-draining.
DO NOT attempt to remove the regulator from the line or perform field repairs in line without
first isolating the regulator from both upstream and downstream systems.
The regulator body and actuator housing are exposed to process vapors. Observe all safety
precautions as specified on the Material Safety Data Sheet(s) for the product(s) that are in the
system.
The vent on the upper actuator housing must be clean and open to the atmosphere and SHALL
be inspected periodically.
The recommended set pressure range of the regulator spring is stamped on the nameplate.
Never adjust a spring for a set pressure beyond its design range as specified in Table 3.