Application
Elmac Technologies' range of non-sparking emergency relief manhole covers permit access to low pressure storage tanks and provides emergency venting capacity in the event of fire. These valves 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 Application

		Emergency relief manways 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.

Benefits
The emergency relief manways have the following features and benefits:

• Wide size range
• Materials to suit a range of applications
• Hinged pallet can be manually lifted to provide access to tanks for cleaning/inspection without need for gasket replacement/unbolting
• PTFE insert ensures a tight seal, below set pressure, between pallet and corrosion-resistant seat
• Wide range of pressure settings for maximum tank protection with minimum gas loss
• Low-cost maintenance
• Valve sizing service for optimum value performance/cost specification
• ATEX approved to directive 94/9/EC