The emergency ventilation valve type Universal NEV is an overpressure valve with high flow capacity which is often applied as protection fitting in the low pressure area in storage tanks, silos and other procedural containers.
The emergency ventilation valve NEV is constructed as protection fitting specially for emergencies in order to protect containers during these emergencies against inadmissible high overpressure. An example for such an emergency is the breakdown of other protection systems. Fire is another example: If there is fire near a container, the gas volume in the container will rapidly expand and therefore a very high ventilation performance will be necessary. Among other things, the emergency ventilation valve is set out in Annex L of the European standard EN 14015 and the American standard API2000 for tanks used when the fire case is considered.
The valve pallet of the emergency ventilation valve type NEV is weight-loaded. An adjustable additional weight on a crank permits to set a higher opening pressure.
If the container pressure is below the opening pressure, the valve prevents an inadmissible product loss; the leakage rate is lower (better) than the limit leak rate given by API 2000 6th ed.
When reaching the opening pressure, the opening process of the emergency ventilation valve starts, after an increase in pressure of 20% above the opening pressure, the valve is completely opened and reaches the indicated volume flow.
The emergency ventilation valve type Universal NEV is available in the following versions:
Housing: Steel A 105 N ; and
Stainless steel (A 182 Gr.F304 / F304L)
A515 / A 516 Grade 60 ; A285 Gr. B (only flange acc. API)
Nominal sizes: starting from DN 4’’(DN 100) ending at DN 24’’(DN 600)
Set pressure: + 5 mbar up to +100 mbar
The emergency ventilation valve type Universal NEV is safety- related in accordance with the European standards EN 1127-1 and EN 13463-1, EN 13463-5 as a device according to the EC Directive 94/9 / EC with an EC type examination certificate.
December 2015