Tank Blanketing & Vapor Recovery

Inert gas protection and emission capture at the tank.

What It Is & How It Works

Tank blanketing valves and vapor recovery valves are pressure-regulating devices that manage gas composition inside a storage tank’s vapor space. Blanketing valves admit inert gas, typically nitrogen, when tank pressure drops below a set point, maintaining a positive blanket that prevents air from entering the tank. Vapor recovery valves route displaced vapors to a collection system during filling rather than venting them to atmosphere. Together, these devices address flammable vapor/air mixtures inside the tank and fugitive emissions to the environment.

A blanketing valve senses vapor space pressure through a diaphragm. When product withdrawal or temperature contraction reduces pressure below the blanket set point, the valve opens to admit nitrogen from a supply header. When pressure recovers, the valve closes to conserve blanket gas. A vapor recovery valve operates in the opposite direction: when filling or thermal expansion raises pressure above its set point, the valve routes vapors to a recovery header or thermal oxidizer instead of releasing them through the conservation vent.

Both devices mount on tank roof nozzles and connect to gas supply or collection piping. Sizing follows API 2000 breathing rate calculations. Blanketing valves are selected by blanket pressure and nitrogen supply capacity; vapor recovery valves by maximum vapor displacement rate.

Blanketing Valve vs. Vapor Recovery Valve

Blanketing valves let gas IN to the tank, maintaining a protective inert atmosphere when pressure drops. Vapor recovery valves let vapor OUT of the tank, capturing displaced vapors during filling instead of venting them. A tank may use both: a blanketing valve to preserve the nitrogen blanket during withdrawal, and a vapor recovery valve to capture vapors during filling. Blanketing protects the product; vapor recovery protects the environment.

When to Specify Tank Blanketing & Vapor Recovery

Blanketing and vapor recovery equipment is specified when a tank requires inert atmosphere protection, emission capture, or both:

Tanks Storing Oxidation-Sensitive or Moisture-Sensitive Products Chemical, pharmaceutical, and specialty product storage where exposure to atmospheric oxygen or moisture degrades product quality, requiring a continuous nitrogen blanket to exclude air from the vapor space during all operating conditions.
Flammable Liquid Storage Requiring Explosion Prevention Tanks storing products with flash points below ambient temperature where maintaining the vapor space below the lower explosive limit requires inert gas dilution per NFPA 69 (Standard on Explosion Prevention Systems), eliminating the oxygen concentration needed to support combustion.
Facilities Subject to EPA 40 CFR 60/63 Vapor Emission Limits Fixed-roof tanks where NSPS and NESHAP regulations require vapor capture during filling operations, routing displaced vapors to recovery or destruction rather than allowing them to vent through the conservation vent to atmosphere.
Terminals with Centralized Vapor Recovery Systems Multi-tank facilities with shared vapor collection headers where each tank requires an individual vapor recovery valve to connect to the common header, maintaining proper backpressure and preventing cross-contamination between tanks.
Chemical Plants Requiring Closed-Loop Vapor Management Process storage tanks where both inert blanketing and vapor recovery are mandated as part of a closed-loop system that prevents any uncontrolled vapor release during normal filling, withdrawal, and breathing operations.

Why Shand & Jurs Blanketing & Vapor Recovery Valves Excel

Tanks Where Blanket Gas Conservation Directly Affects Operating Costs

Precise set-point control and tight reseal minimize unnecessary nitrogen consumption by opening only when tank pressure genuinely drops below the blanket threshold, reducing the volume of purchased nitrogen consumed per year across multi-tank installations.

Facilities Where Vapor Emission Reductions Drive Regulatory Compliance

Vapor recovery valves capture displaced vapors at the source during filling, reducing the fugitive emissions that contribute to Title V inventories and eliminating the visible vapor plumes that trigger community complaints and regulatory attention.

Tanks Requiring Product Quality Protection Through Inert Atmosphere

The blanketing valve responds to pressure changes within seconds, maintaining the nitrogen blanket through rapid product withdrawal cycles without allowing atmospheric air to enter through the vacuum path, preserving product integrity batch after batch.

Installations Where Maintenance Simplicity Affects Total Cost of Ownership

Diaphragm-actuated blanketing valves and weight-loaded vapor recovery valves use mechanical designs with minimal moving parts, providing reliable operation between maintenance intervals without the complexity of electronic controllers or pneumatic positioners.

Multi-Tank Terminals Requiring Consistent Performance Across the Facility

Standardized valve platforms across dozens of tanks allow uniform set-point management, common spare parts inventory, and consistent maintenance procedures, reducing the operational complexity of managing blanketing and vapor recovery across a large terminal.

Blanketing Valve vs. Vapor Recovery Valve — Selection Guide

Attribute	Blanketing Valve	Vapor Recovery Valve
Primary Function	Admits inert gas (nitrogen) into the tank vapor space when pressure drops below the blanket set point	Routes displaced vapors from the tank to a collection or destruction system when pressure rises above the recovery set point
Gas Flow Direction	Into the tank: from nitrogen supply header to tank vapor space	Out of the tank: from tank vapor space to vapor recovery header, scrubber, or thermal oxidizer
Trigger Condition	Tank pressure drops below blanket set point during product withdrawal, thermal contraction, or breathing	Tank pressure rises above recovery set point during product filling, thermal expansion, or blanketing overshoot
Actuation Method	Diaphragm or piston senses vapor space pressure and opens the nitrogen supply port against a spring or weight	Weight-loaded pallet or diaphragm senses vapor space pressure and opens the vapor outlet path to the recovery header
Regulatory Driver	NFPA 69 (explosion prevention through inerting), product quality specifications requiring inert atmosphere	EPA 40 CFR 60/63 (NSPS/NESHAP vapor emission limits), state VOC emission regulations, Title V permits
Common Pairing	Pressure-only conservation vent for overpressure relief at the same tank; the blanketing valve handles vacuum makeup	Conservation vent remains as backup atmospheric relief; vapor recovery valve captures the majority of displaced vapor
Recommendation	Specify on every tank requiring inert atmosphere protection for product quality, explosion prevention, or moisture exclusion	Specify on every tank where displaced vapors must be captured to meet emission regulations or where vapor has economic recovery value

What to Consider Alongside Blanketing & Vapor Recovery

The Tank Does Not Require Inert Atmosphere Protection When the stored product is not oxidation-sensitive, not moisture-sensitive, and the vapor space does not present an explosion risk, a standard P/V conservation vent provides adequate breathing protection at lower cost and without nitrogen supply infrastructure. See Conservation Vents & Seals.
Emission Control is Needed but Vapor Recovery Infrastructure Does Not Exist When the facility lacks a vapor collection header, scrubber, or thermal oxidizer, a pilot-operated relief valve with tight seal provides emission reduction at the vent without requiring downstream vapor processing equipment. See Pilot-Operated Relief Valves.
The Application Involves Biogas Rather Than Petroleum or Chemical Vapors Biogas systems require specialized equipment designed for the corrosive, moisture-laden gas streams found in anaerobic digestion. See Biogas Stream Equipment.
Complete Blanketed Tank Protection Assembly Pair the blanketing valve with a pressure-only conservation vent for overpressure relief, a flame arrester at the vent outlet for ignition prevention, an emergency vent for fire-case protection, and a vapor recovery valve for emission capture during filling to create a fully managed, closed-loop tank breathing system. See Pressure Conservation Vents, Flame & Detonation Arresters, and Emergency Vents & Manway Covers.
Blanket Pressure Monitoring and Optimization Combine blanketing valves with L&J Technologies level and pressure instrumentation feeding Clairvoyance to monitor blanket pressure trends, correlate nitrogen consumption with product movement cycles, and identify valves that are cycling excessively due to set-point drift or seat wear.

Featured Products

94270 — Tank Blanketing Valve

Diaphragm-actuated nitrogen blanketing valve that maintains a precise inert gas blanket in the tank vapor space, conserving blanket gas by opening only when pressure drops below the set point.

94261 — Vapor Recovery Valve

Weight-loaded vapor recovery valve that routes displaced vapors to a collection header during filling operations, reducing fugitive emissions while maintaining proper backpressure on the recovery system.

94130 — Pressure Conservation Vent

Weight-loaded pressure relief for atmospheric storage tanks on blanketed or sealed systems, providing vapor-tight overpressure protection sized per API 2000.