Introducing the GROTH 12-TH Thief Hatch

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Storage Tank- Gauge Hatches
The GROTH Model 12-TH Thief Hatch was designed to out perform the competition, with industry leading high flow rates and precision tolerances to provide a superior sealing performance.
Storage Tank- Gauge Hatches


The leakage is less than 1 SCFH of air @ 90% of the set pressure.

Why Thief Hatches are required?

Because we always make sure that:

Protect your tanks

Protects tank from overpressure/vacuum when sized properly.

Meet industry compliance

Minimizes evaporation emissions.

Features & Benefits

Superior Sealing Performance

  • Precision machining and manufacturing to accomplish superior sealing.
  • Ultra-tight sealing reduces product leakage and fugitive emissions.
  • Active envelope pressure gasket that expands around the base to increase seal
Storage Tank- Gauge Hatches
Storage Tank- Gauge Hatches

Industry Leading Flow Rates

  • Higher flow capacity to protect from excessive pressure build up.
  • Precision machining and manufacturing to accomplish high flow rates

Direct Replacement & Easy Maintenance

  • Direct replacement for any standard round API 12 thief hatch.
  • Designed for easy maintenance, thus reducing downtime and lowering operational cost.
  • Incorporates a mechanical lock system to be used with a pad lock or lock out bar
Storage Tank- Gauge Hatches

Technical Details

  • Size: 8” (200 mm)
  • Bolting: API 12
  • Available Pressure Settings: 4, 6, 8, 12, 16, 24 & 32 osig
  • Available Vacuum Settings: 0.4, 0.9 & 3.5 osig
  • Leak Rate: 1 SCFH air @ 90% of set pressure
  • Materials of Construction: Casting: Aluminum (Non-Sparking), Envelope Gasket: HNBR, FKM, or Fluorosilicone, Vacuum Diaphragm: HNBR, FKM, Fluorosilicone, or Fluoropolymer
  • Optional: Polyester/PTFE Coating
  • Accessories: Flange (base) Gasket, Mounting Kit


Flow Curves

Assentech supply, install and service full range of storage tank and fluid transfer equipment in the UK and Europe.

You can contact us by Phone 01726 844707, Email : or or using the enquiry form below.