Прошу помощи еще с одним термином: non-closing device.

Контекст: Explosion Relief Valves

Explosion Relief Valve is a manual re-closing and reusable flameless venting device, which is made for the protection of personnel and equipment in case of dust explosions. During an explosion, the valve plate lifts up and relieves the overpressure through the integrated flame arrester. The valve plate remains open until the non closing device is released by hand manually. This type of valves can be used in combination with flap valves as explosion isolation barriers.

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