Emergency Relief Vents & Access Manways

Foaming Relief Vents

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Pressure-Only and Pressure/Vacuum Emergency Relief Vents


Elmac's range of non-sparking, emergency relief vents permit access to low pressure storage tanks whilst providing emergency venting capacity in the event of fire. These vents are used extensively on bulk storage tanks, including floating roof tanks.
Sizes range from 10" (250mm) to 24" (600mm). Typical applications include: bulk storage tanks, low pressure gas pipeline systems, digesters, and gas holders.

Principle of Operation

Emergency relief vents are fitted to storage tanks to allow emergency flow due to the excessive venting requirement from a fire burning around a storage tank. Their use eliminates a costly tank rupture by providing emergency venting from abnormal internal pressure beyond the capability of the pressure relief vent. In the event of a fire the pallet lifts at a pre-determined pressure, thus supplying a large venting area.

These models employ a PTFE insert, affording a tight seal below set pressure, between the pallet and the corrosion resistant seat. The pressure/vacuum model is fitted with an additional spring-loaded vacuum valve that will open under negative pressure to protect the tank from any vacuum condition damage that may occur.

Unit Options

Size Range10", 12", 18", 20", 24"
Process ConnectionsAPI 650 (20" & 24"), ANSI 150#, Special
MaterialsAluminium, Cast Iron, Carbon Steel, Stainless Steel, Special
Diaphragm & InsertPTFE
WeightsLead Plate (Standard), Stainless Plate (Special)

Unit Pressure & Vacuum Settings

DescriptionPressure Relief OnlyPressure & Vacuum Relief
Pressure Settings3"wg (7.5mbar) - 36.2"wg (90mbar)3"wg (7.5mbar) - 8"wg (20mbar)
Vacuum Settings-3.46"wg (9mbar) - 10"wg (25mbar)

Access Manways for Bulk Storage Tanks

Elmac’s range of non-sparking, low pressure manhole covers provide easy access to low pressure storage tanks for maintenance and cleaning purposes.

The manhole is secured by a transverse beam which is attached to the centre of the cover. This ensures even distribution of the retaining force to form a gas tight fitting.

Unit Options

Size Range18", 20", 24"
Process ConnectionsAPI 650 (20" & 24"), ANSI 150#, Special
MaterialsAluminium, Carbon Steel, Stainless Steel
InsertsNitrile Rubber, PTFE
Pressure Settings≤2.5 psig

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