A hydraulic safety valve limits the gas pressure in the fermenter with regard to overpressure and underpressure.

As the digestion towers required for the production of biogas must be gas-tight to prevent air contact and gas leaks, a safety device is required which blows off gas when the gas outlet is closed or blocked, thus preventing an impermissible overpressure from building up in the tank. This also avoids the risk of the tank imploding due to a vacuum caused by a liquid leak.

The hydraulic safety valve from EnvironTec offers safe and reliable protection against both overpressure and vacuum. It consists of a round tank which is divided into two sections by a separating wall. One section is connected to the gas area, the other to the open air. The pressures at which the safety valve is activated are determined by the hight of the liquid and the ground areas of the two parts. In the event of overpressure, the liquid on the gas side is pressed down until the gas can escape under the partition wall. Under vacuum, the liquid is pressed down on the air side so that air can flow into the fermenter.

The described system is available in various sizes and with different options.