Venting Gauge Hatches

• Premium deep-set gauge hatch with integral pressure & vacuum relief offers superior performance in normal and cold conditions.
• Reliable, bubble-tight sealing with standard FKM ( Viton) seal and stainless steel spring.
• Field adjustable pressure settings, from 2 oz si to 32 oz si.
• Manual relief, Inconel trim, alternative seals, and various coatings are optionally available.

• The Series 4000 Marsh Hawk TRV offers tank access combined with pressure and vacuum relief in a deep-set design.
• Situating valve seats below the tank roof permit latent heat from the product to keep the seals ice-free.

Reliable, Bubble-Tight Sealing

False-color cutaway of a Series 4000 Marsh Hawk TRV showing the deep-set seal (orange), pressure spacers(blue) and springs (red).

• The Series 4000 has class-leading seal performance as compared to any other premium or economy venting gauge hatch currently available.
• Improved sealing performance eliminates flutter and periodic small-scale venting which can cause frost closure in competitor top-mount hatches.

Variety of Pressure Settings

• The Series 4000 Marsh Hawk pressure relief is adjustable between 2 ozsi and 16 ozsi in 2 ozsi increments.
• The optional double-weight spring allows relief pressure between 18 and 32 ozsi, in 2 ozsi increments.
• 1 ozsi increments optionally available.
• Vacuum relief is fixed at 0.4 ozsi.

Suitable for Sour Service

• The Series 4000 is ready for Sour Service out of the box with FKM ( Viton) seals and stainless springs.
• For more adverse applications, alternative seal and spring materials are available, along with hard anodization or fusion-bond epoxy coatings.

Manual Relief
The manual relief option allows an operator to manually activate the vent. Pressing the hatch cover’s large red button actuates the vacuum pallet, relieving pressure in the tank to allow safe removal of the spider cage assembly for tank gauging or hatch maintenance. The button and actuating poppet are supported independently of the vacuum disc and do not interfere with normal relieving operation.

Hard Anodized (Type III)
All aluminum components are anodized to meet MIL-A-862F Type III Engineering Hardcoat. The anodization slightly darkens the cast components and imparts a slight bronze tinge to the machined components. Anodization improved performance in moderate brines, as well as acetic, boric and nitric acid. For prolonged exposure to concentrated brines, or strong mineral acids, consider the severe service coating.

Severe Service Coating
The body of the Marsh Hawk is coated with a red Fusion Bond Epoxy (FBE) for resistance to strong mineral acids,(including sulphuric and hydrochloric acids,) high-chloride ion solutions (including aluminum chloride, potassium chloride, and brine) as well as many other petrochemicals. The Marsh Hawk internals are coated in a proprietary black PFA (TEFLON) providing the same excellent fluoropolymer chemical resistance.