FRP Vents & Hatches

Corrosion-proof breathing and access for chemical storage.

What It Is & How It Works

FRP vents and hatches are fiberglass-reinforced polymer (FRP) tank fittings that provide pressure/vacuum breathing and personnel access on tanks storing highly corrosive liquids. They address the fundamental problem that metallic vents and hatches corrode and fail in concentrated acid, caustic, bleach, and brine service, creating both safety and emissions risks when sealing surfaces degrade.

FRP pressure/vacuum vents operate on the same pallet-and-seat principle as metallic conservation vents, opening at defined pressure and vacuum setpoints to relieve tank breathing while controlling emissions. The difference is material: FRP construction resists the chemical attack that destroys carbon steel and stainless steel in aggressive vapor environments. FRP gauge hatches and manway covers provide gas-tight inspection and personnel access using corrosion-resistant sealing surfaces that maintain integrity over years of chemical exposure.

FRP vents and hatches mount to standard FRP or lined-steel tank nozzles. Selection depends on the stored chemical, its vapor composition, the required breathing rate, and the tank design pressure. Where the stored product would corrode metallic alternatives within months, FRP devices provide service lives measured in years without seal degradation or setpoint drift.

FRP Vents vs. Metallic Vents

Metallic conservation vents (carbon steel, aluminum, stainless steel) serve the majority of petroleum and chemical storage applications where vapor corrosivity is manageable. FRP vents are specified when the vapor environment would corrode metallic alternatives, typically concentrated acids (sulfuric, hydrochloric, phosphoric), caustics (sodium hydroxide), bleach (sodium hypochlorite), and aggressive brine solutions. The choice is driven by chemical compatibility, not by pressure or breathing performance. Same function, different material.

When to Specify FRP Vents & Hatches

FRP vents and hatches are specified when the stored product’s vapor environment would corrode metallic tank fittings:

Concentrated Acid Storage Tanks storing sulfuric, hydrochloric, phosphoric, or nitric acid where acid vapor destroys metallic vent pallets and sealing surfaces within weeks or months of installation.
Caustic and Bleach Storage Sodium hydroxide and sodium hypochlorite tanks where alkaline or oxidizing vapors attack metallic components, causing seal failure and uncontrolled emissions.
Chemical Manufacturing and Processing Process tanks, day tanks, and intermediate storage in chemical plants where multiple corrosive products are handled and metallic vent replacement frequency is operationally unacceptable.
Water and Wastewater Chemical Feed Systems Chemical feed tanks at municipal and industrial water treatment plants storing treatment chemicals (ferric chloride, alum, polymer, hypochlorite) that corrode standard fittings.
FRP and Lined Tank Installations Fiberglass or rubber-lined steel tanks where the tank itself is corrosion-resistant and the vent or hatch must match that material capability to avoid being the weakest point in the system.

Why Shand & Jurs FRP Vents & Hatches Excel

Tanks Where Metallic Vents Fail Within Months

FRP construction resists the chemical attack that destroys carbon steel, aluminum, and stainless steel vent components in aggressive vapor service, providing service lives measured in years rather than months.

Facilities Where Frequent Vent Replacement Disrupts Operations

Replacing a corroded metallic vent requires taking the tank out of service, draining or purging the vapor space, and installing a new device. FRP vents eliminate this cycle by matching their service life to the tank itself.

Applications Requiring Consistent Setpoint Performance

Corroded metallic pallet and seat surfaces cause setpoint drift, allowing the vent to open early or leak continuously. FRP sealing surfaces maintain their dimensional accuracy and surface finish throughout the device’s service life.

Chemical Storage Subject to Emissions Regulations

Degraded metallic vent seals are a common source of fugitive emissions in chemical storage. FRP devices maintain seal integrity, supporting compliance with EPA 40 CFR 60/63 and state air quality regulations.

FRP and Lined Tanks Requiring Material Consistency

Installing a metallic vent on an FRP tank creates a corrosion-vulnerable point at the top of an otherwise corrosion-proof vessel. FRP vents and hatches match the tank’s material capability from nozzle to pallet.

FRP Vents vs. FRP Hatches — Selection Guide

Attribute	FRP Pressure/Vacuum Vents	FRP Gauge Hatches & Manway Covers
Primary Function	Pressure and vacuum breathing control with emissions containment	Gas-tight inspection and personnel access to the tank interior
Operating Mode	Opens automatically at defined pressure/vacuum setpoints	Opened manually by operator for gauging, sampling, or entry
Normal-condition State	Sealed; opens only when setpoint is reached	Sealed; remains closed until operator access is required
Sizing Basis	Breathing rate per API 2000 and tank filling/emptying operations	Standard gauging or personnel access dimensions
Regulatory Driver	EPA 40 CFR 60/63 emissions control, API 2000	API 653 inspection access, OSHA confined space entry
Sealing Technology	FRP pallet and seat with corrosion-resistant sealing surface	FRP cover with corrosion-resistant gasket or bolted closure
Recommendation	Specify for every corrosive-service tank requiring controlled breathing and emissions compliance	Specify when the tank requires routine interior access and the vapor environment would corrode metallic hatch components

What to Consider Alongside FRP Vents & Hatches

Non-corrosive or Mildly Corrosive Vapor Service The stored product’s vapor environment does not attack metallic components. Standard conservation vents in carbon steel, aluminum, or stainless steel provide equivalent breathing performance at lower cost. See Conservation Vents & Seals.
Emergency Overpressure Protection The tank requires fire-case relief capacity in addition to normal breathing. FRP emergency vents are not standard; metallic emergency vents sized per API 2000 are required. See Emergency Vents & Manway Covers.
Flame Protection at the Vent Opening The tank vapor space contains flammable vapors and requires certified flame interruption at the vent outlet. See Flame, Deflagration & Detonation Arresters.
Chemical Tank Inventory Monitoring Pair FRP vents with L&J Technologies radar or capacitance level gauges rated for corrosive service to provide inventory visibility on chemical tanks where both the vent and the gauge must resist chemical attack. See Clairvoyance.
Complete Corrosion-resistant Tank Top Assembly Combine FRP pressure/vacuum vents with FRP gauge hatches on the same tank to ensure every opening in the tank roof matches the corrosion resistance of the FRP or lined vessel below it. See Conservation Vents & Seals for metallic alternatives on mixed installations.