Groth 1720A User Manual

Installation, Operation and Maintenance Manual for

Pressure/Vacuum Relief Valves

Models 1720A, 1760A

IOM 1700A

January 2006

IOM 1700A

REV. A 12541

TABLE OF CONTENTS:

pumping rates and the temperature. Refer to
API Standard 2000 for the procedures to

DESCRIPTION PAGE
Introduction 2
Valve Design & Function 3
Safety Warnings 4
Inspection and Storage 4
Installation 4 & 5
Maintenance 6 & 7
Test Procedure & Weight Blocks 8 & 9

Bill of Materials & Submittal Drawings
Model 1720A 10
Model 1760A 11
Abbreviations 11
Model Identification 12
Product Limited Warranty 12

LIST OF FIGURES
Fig. 1- Typical Tank Installation 3
Fig. 2- Pressure Relief - Operation 3
Fig. 3- Vacuum Relief - Operation 3
Fig. 4- Pallet Assembly Detail/ Valve

7

Cross Section

LIST OF TABLES
Table 1 - Bolt Torque (Installation) 5
Table 2 - Valve Weights (Maximum) 5
Table 3 - Stem Length (Maintenance) 6
Table 4 - Spare Parts P/N 7
Table 5 - Pallet Assembly Weights 8
Table 6 - Maximum settings 8
Table 7 - Weight Block Dimensions 9

INTRODUCTION:

determine venting requirements.
A relief valve must be carefully maintained by

a qualified valve technician. It should only be
assembled under clean conditions, preferably
in a service shop environment. Carefully read
and understand this manual before installing
or attempting to repair a valve. Groth
Corporation or a factory authorized repair
center offers repair services for all products
manufactured by the Tank Protection
Division.

The table below shows the two different valve
Models covered in this manual and indicates
their Pressure (P) and/or Vacuum (V) relief
capabilities.

Model P V Description
1720A
1760A

 


Vent to Header

For a list of abbreviations used in this manual,
refer to page 11. For information not
contained in this manual, please contact:

Groth Corporation
13650 N. Promenade Blvd.
Stafford, Texas 77477, USA
[phone] (Office)
[phone] (Fax)

The nameplate below shows the basic
information that is listed for each relief valve:

Vent to Header

Pressure and/or vacuum relief valves are
used on liquid storage tanks and other
process vessels or systems to prevent
structural damage due to excess internal
pressure or vacuum.

Storage tanks are pressurized when liquid is
pumped in, compressing the existing vapor or
when rising temperatures cause increased
evaporation or expansion of existing vapor.
Conversely, a vacuum condition may be
created when pumping out or due to falling
temperature. To prevent tank damage, vapor
must be allowed into or out of the tank at
specified pressure/vacuum conditions. The
volume rate of venting depends upon the tank
size, volatility of the tank contents, the

2

GROTH

CORPORATION

STAFFORD

TEXAS

USA

SETTING

2 OSI

1 OSI

1760A-03-355-TOO

MD:
S/N:

117405-10-1

PSV-440

TAG:
FLANGE:

TYPE

PRESS.

VAC.

A CONTINENTAL DISC COMPANY

3" X 3" 150# RF

% OP

100

30

100

FLOW [SCMH]

26,600

15,694
14,500

VALVE DESIGN AND FUNCTION:

SEE NOTE 3

1720A
PRESSURE/VACUUM
RELIEF VALVE

BLANKET GAS REGULATOR

EMERGENCY RELIEF VALVE

SEE NOTE 2

Fig. 1 - Typical Tank Installation

Tank protection equipment typically includes
an operating valve which is designed to
provide pressure/vacuum relief under normal
pump in/out and thermal breathing conditions.
An emergency relief valve can also provide
both pressure and vacuum relief and normally
it is sized to provide pressure relief if there is
a fire in the immediate vicinity of the tank. It
may also be sized by the tank designer to
provide protection in the event of equipment
failure (such as the rupture of a process
steam line or an inert gas blanketing system
failing “wide open”) or operator error.

SEE NOTE 1

FLOW

TUBING

Installation Notes: (See Fig. 1 above)

1. Minimum clearance between tank roof and
vacuum inlet port must be at least equal to
the valves’ nominal flange bore.

2. Tank nozzle bore must be > or = valve
inlet flange bore.

3. Inlet and outlet piping loads must be
supported by appropriate structural
supports, NOT by the valve body.

A typical tank installation is shown in Fig. 1
which includes the following Groth products:

 Model 1720A ‘P/V’ Weight Loaded Valve
 Model 3000 Gas Blanketing Regulator
 Model 2400 Emergency ‘P’ Relief Valve

Pressure Relief: As the pressure in the
storage tank increases, the vacuum pallet is
held shut. When the set pressure is reached,
the pressure pallet lifts and relieves to
atmosphere (or to a header if it is a pipe away
valve). See Fig. 2.

Vacuum Relief: As a vacuum is drawn in the
storage tank (for example, when fluid is being
pumped out), the pressure pallet is held shut
by atmospheric pressure. When the vacuum
setting is reached, the pallet lifts and air is
drawn in from the atmosphere. See Fig. 3.

Fig. 2- Pressure Relief

Fig. 3 - Vacuum Relief

3

SAFETY WARNINGS:

This section is an overview of safety
guidelines that should be followed during the
installation, operation and maintenance of
Groth Pressure/ Vacuum Relief Valves. To
understand the context of these instructions
and warnings, it is necessary to completely
read and understand the contents of this
manual.

The purpose of a weight loaded
pressure/vacuum relief valve is to prevent
excessive pressure or vacuum in a tank or
process system. The valve must be designed
for the proper MAWP and flow requirements
of the system. Consult API Standard 2000 for
tank protection sizing procedures. An
improperly specified or functioning relief valve
may result in structural damage to the tank or
system, and can cause severe personal injury
or death.

Valves are set at the factory according to
purchase specifications. Do NOT change
pressure ratings by adding additional weights
to the pallet assembly without consulting the
factory or your local Groth representative.
Adding weights to a valve may restrict pallet
lift and reduce the valves’ rated flow capacity.

INSPECTION AND STORAGE:

The pressure/vacuum relief valve is carefully
packaged to prevent damage or
contamination during shipping. Inspect all
equipment when it is received; report any
damage to the carrier immediately. The valve
should be protected during handling and
storage. Keep all the ports plugged to
prevent intrusion of foreign materials. Before
installation, inspect the unit for indications of
physical damage or internal contamination. If
these are observed, the valve must be
disassembled, cleaned and repaired before
installation.

INSTALLATION:

A typical valve installation on a tank or vessel
is illustrated in Fig.1 on Page 3 using a Model
1720A Pressure/Vacuum Relief Valve.

DO NOT mix pressure/vacuum pallet
assemblies. Failure to ensure that both pallet
assemblies are installed in the correct
location can change the pressure and
vacuum relief settings. This can cause a tank
failure.

DO NOT attempt to remove the valve from
the tank or process vessel without first
bleeding all pressure from the system.
ALTERNATIVE MEANS OF PRESSURE
RELIEF MUST BE PROVIDED WHEN THE
VALVE IS OUT OF SERVICE.

If the valve has been exposed to process
vapors while in service. Observe all plant
procedures and Material Safety Data Sheets
(MSDS) for the products in the system when
inspecting, adjusting or servicing the valve.
Take appropriate safety precautions
regarding eye protection, respiration and skin
contact.

The tank pressure required to discharge the
normal or emergency venting requirements of
the tank will be increased by the amount of
back pressure in the discharge header, on a
pipe away valve configuration. Maximum
possible discharge header pressure must be
considered when sizing the pressure relief
valve.

Groth's weight loaded Pressure/Vacuum
Relief Valves are designed to provide tank
protection for both pressure and/or vacuum to
+/-1 PSIG settings. The valves provide full
rated flow capacity at 100% over-pressure.
Consult factory for performance under other
conditions.

WARNING: The valve must be installed in a
vertical position as shown in Fig 1. To
achieve nominal flow capacity, the tank
nozzle bore must be at least the same
nominal dimension as the relief valve inlet
body.

This series of valves all have 150# ANSI
flange drilling compatibility. Torque
guidelines are listed in Table 1. The valves
are NOT rated for full flange pressure and do
not require high bolting torque. Consult
factory for special applications.

4