Gauge Hatches & Manway Covers

Vapor-tight access for gauging, sampling, and tank entry.

What It Is & How It Works

Gauge hatches and manway covers are tank-mounted access fittings that provide vapor-tight openings for manual gauging, product sampling, visual inspection, and personnel entry, while preventing fugitive emissions and protecting the vapor space from weather and contamination. They address the requirement that every tank opening seal when closed and provide controlled access when opened.

A gauge hatch is a hinged or bolted cover over a small roof opening, typically 8 to 20 inches, that an operator opens briefly for gauging tapes, thermometers, or sampling equipment, sealing against a gasket or machined seat when closed. A manway cover seals a larger opening, typically 20 to 24 inches, sized for personnel entry during inspection, cleaning, and maintenance. The Expanda-Seal™ design gives a gas-tight closure that operators open and close without special tools.

Both mount to standard tank roof or shell nozzles and come in carbon steel, stainless steel, aluminum, and FRP to match the product and vapor environment. Selection depends on nozzle size, the product’s vapor pressure and corrosivity, and whether the opening serves gauging, sampling, inspection, or full personnel entry.

Gauge Hatch vs. Manway Cover

Gauge hatches provide small-opening access for instruments and sampling. Manway covers provide large-opening access for personnel entry. Both seal the vapor space when closed, and a tank may need both: a gauge hatch for daily operations and a manway cover for periodic inspection per API 653.

When to Specify Gauge Hatches & Manway Covers

Gauge hatches and manway covers are specified when a tank requires vapor-tight access for measurement, sampling, inspection, or personnel entry:

Petroleum and Chemical Storage Tanks: Fixed-roof tanks storing crude, refined products, or chemicals where manual gauging and sampling must occur without releasing vapors, and EPA 40 CFR 60/63 requires vapor-tight closures on all openings.
Terminals Requiring API 653 Compliance: Multi-tank facilities where periodic internal inspection and cleaning need personnel access through manway covers, while daily inventory verification needs gauge hatch access for manual measurements.
Manual Gauging as Primary or Backup Measurement: Installations where manual tape gauging is the primary inventory method or an independent check against automatic tank gauging per API 2350 and custody-transfer verification.
Corrosive Product Storage: Tanks storing acids, caustics, bleach, or other corrosive liquids where FRP or stainless steel hatches and covers resist chemical attack at the access opening.
Tanks Requiring Controlled Vapor Release During Access: Vessels where the access procedure must limit vapor release, calling for self-closing or spring-assisted gauge hatches that minimize the time the opening is unsealed.

Why It Excels

Tanks Subject to Fugitive Emissions Regulations

Machined sealing surfaces and compression gaskets hold a vapor-tight closure that satisfies EPA 40 CFR 60/63 for sealed openings, cutting fugitive emissions at a common roof leak point.

Facilities Requiring Daily Manual Gauging or Sampling

Hinged and spring-assisted gauge hatches let operators open, gauge, and reseal quickly during daily rounds, minimizing both vapor exposure time and operator effort.

Tanks Requiring Personnel Entry for Inspection and Cleaning

The Expanda-Seal™ manway closure provides a gas-tight seal that opens and closes without special tools, simplifying confined-space entry preparation per OSHA requirements.

Corrosive Vapor Environments That Degrade Standard Closures

Carbon steel, stainless steel, aluminum, and FRP construction matches the product's corrosivity, preventing premature seal failure that would compromise emissions containment and access safety.

Gauge Hatches vs. Manway Covers — Selection Guide

Attribute	Gauge Hatches	Manway Covers
Primary Function	Small-opening access for manual gauging, sampling, and thermometer insertion	Large-opening access for personnel entry, internal inspection, and cleaning
Typical Opening Size	8 to 20 inches	20 to 24 inches
Access Frequency	Daily to weekly during routine operator rounds	Periodic: scheduled inspection, cleaning, and maintenance
Operating Mode	Hinged or spring-assisted; opened briefly then resealed	Bolted or Expanda-Seal™ closure; opened for extended entry
Regulatory Driver	EPA 40 CFR 60/63 vapor-tight closure, API 2350 manual verification	API 653 internal inspection access, OSHA confined-space entry
Material Options	Carbon steel, stainless steel, aluminum, FRP	Carbon steel, stainless steel, aluminum, FRP
Recommendation	Specify for every tank requiring manual gauging, sampling, or thermometer access with vapor containment	Specify for every tank requiring periodic personnel entry for internal inspection and maintenance per API 653

What to Consider Alongside Gauge Hatches & Manway Covers

Consider an alternative when:

You need a cover that also functions as a fire-case emergency vent, providing access and overpressure relief at one opening. See Emergency Vents.

The vapor environment requires fiberglass-reinforced construction throughout, across both vent and access devices. See FRP Vents & Hatches.

You need gas-tight access at an anaerobic digester cover rather than a petroleum or chemical storage tank. See Biogas Cover Equipment.

How Gauge Hatches and Manway Covers Fit Into a Larger System

Pair with conservation vents and flame arresters so every roof opening provides its intended function plus vapor containment. See Pressure & Vacuum Conservation Vents and Flame, Deflagration & Detonation Arresters.

Combine gauge hatch manual tape access with L&J Technologies automatic tank gauging feeding Clairvoyance for independent level verification supporting custody transfer and API 2350. See Float & Tape Level Gauges and FuelsManager®.