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Installation, Operation and Maintenance Manual for
Models 5000 and 5100
Free Vents
©2009 Groth Corporation
IOM-5000
Rev. A 12072
Issue: 03/14/2012
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I. INTRODUCTION
Relief vents 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 pumping rates and the temperature. Refer to API Standard 2000, ISO 28300, or local
regulations for the procedures to determine venting requirements.
A relief vent must be carefully maintained by a qualified valve technician. It should only be
assembled under clean conditions, preferably in a service shop environme nt. Carefully read and
understand this manual before installing or attempting to repair a vent.
For information not contained in this manual, please contact:
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Groth Corporation
13650 N. Promenade Blvd.
Stafford, TX, 77477 USA
Phone: 281-295-6800
Fax: 281-295-6999
www.grothcorp.com
II. DESIGN AND FUNCTION
The Groth Model 5000 Series are high flow capacity free vents designed to be used on tanks
containing non-volatile liquids and on vent pipe extremities. These devices contain no moving
parts and allow storage vessels to freely in-breath or out-breath to the atmosphere.
III. 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 relief vent is to prevent excessive pressure or vacuum in a tank or process
system. The vent must be designed for the proper Maximum Allowable Working Pressure (MAWP)
and flow requirements of the system. Consult API Standard 2000, ISO 28300, or local regulations
for tank protection sizing procedures. An improperly specified or functioning relief vent may result
in structural damage to the tank or system, and can cause severe personal injury or death.
If the vent 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 or servicing
the vent. Take appropriate safety precautions regarding eye protection, respiration and skin
contact.
IV. INSPECTION AND STORAGE
The relief vent 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 vent should
be protected during handling and storage. Keep all the ports plugged to prevent intrusion of foreign
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materials. Before installation, inspect the unit for indications of physical damage or internal
contamination. If these are observed, the vent must be disassembled, cleaned and repaired before
installation.
V. INSTALLATION
WARNING: The vent should be installed in a vertical position. Other orientations are allowed, but
care must be taken to avoid orienting the vent such that condensate collects in the vent body.
To achieve nominal flow capacity, the tank nozzle bore must be at least the same nominal
dimension as the relief vent inlet body.
This series of vents all have 150# ANSI flange drilling, unless otherwise specified. Torque
guidelines are listed in Table 1. The vents are NOT rated for full flange pressure and do not require
high bolting torque. Consult factory for special applications.
The following guidelines should be observed at installation:
1. Remove all packing material from the valve before installation.
2. Inspect the gasket seating surface of the tank nozzle flange. It must be clean, free of
scratches, corrosion, tool marks, and flat.
3. Aluminum vents are furnished as a standard with flat face flanges; they should only be
installed on a mating flat face flange with a full faced gasket.
4. Inspect the gasket; make sure that the material is suitable for the application.
5. Lubricate all studs and nuts with an appropriate thread lubricant. If the vent will see high
temperature service or stainless steel fasteners are used, apply an anti-seize compound
such as moly-disulfide.
6. Center the gasket within the bolt circle.
7. Set the vent carefully on the nozzle. Install the studs and tighten nuts hand tight. For studs
selection for blind tapped holes see Table 1.
8. Torque all fasteners to half the value listed in Table 1, in a staggered, alternating pattern.
9. Make sure that the flanges are not distorted and that the gasket is evenly compressed.
Make up the final torque and check that no further nut rotation occurs at the torque value
specified on Table 1.
Table 1 – Bolt Torque & Stud Specifications – ANSI #150
Mounting
Flange
2” 30(41) 60(81) 4 5/8” – 11
3” 54(73) 108(146 4 5/8” – 11
4” 45(57) 78(106) 8 5/8” – 11
6” 90(122) 150(203) 8 3/4” – 10
8” 126(171) 228(309) 8 3/4” – 10
10” 138(187) 246(334) 12 7/8” – 9
12” 186(252) 348(472) 12 7/8” – 9
VI. MAINTENANCE INSTRUCTIONS
The vent should be inspected annually for corrosion and hardware tightness.
Raised Face Flat Face Thread
Flange Connections
Bolt Torque – lb-ft(N-m)
Number
of Bolts
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Studs
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