New Safety Device for Flame Transmission Proof Ventilation of Biogas Digesters
Under the brand PROTEGO® the company Braunschweiger Flammenfilter GmbH developed and successfully type-tested a deflagration- and endurance burning-proof pressure and vacuum diaphragm valve for application on biogas digesters.
The pressure and vacuum diaphragm valve PROTEGO® UB/SF-IIA1 is approved according to ATEX for explosion group IIA1 and hence for methane applications for the nominal diameters of DN 80, 100 and 150. The diaphragm valve protects digesters of biogas and sewage gas plants against incorrect pressure and vacuum and at the same time it protects against atmospheric deflagration and endurance burning.
The diaphragm valve PROTEGO® UB/SF-IIA1 guarantees pressure maintenance in the digester that is close to the set pressure with a tightness that is far superior to the conventional standard due to our highly developed manufacturing technology. Product losses and environmental pollution are therefore reduced to a minimum. The biogas resistant internal coating of the valve allow for a trouble-free application in this area.
At the opening of the pressure and vacuum relief valves of digesters methane is vented to the atmosphere and consequently a flammable methane-air mixture is arising. In order to avoid a flashback into the digester and hence serious damages the application of a deflagration and endurance proof flame arrester is of decisive importance.
The deflagration and endurance burning proof characteristics of the PROTEGO® UB/SF-IIA1 valve is based on a dynamic flame arresting feature. If the adjusted set pressure of the valve is exceeded, the methane-air mixture will be blown into the atmosphere. A flashback into the digester will be prevented, if the mixture ignites. During continuous mixture flow the dynamic flame arresting feature prevents flashback ignition into the digester even in the case of endurance burning.
The safe operation of the Pressure and Vacuum Diaphragm Valve PROTEGO® UB/SF-IIA1 is also assured at low temperatures. Therefor the set pressure is adjusted with a freeze resistant water glycol mixture. Different to the often applied pressure and vacuum safeguards with water trap the liquid remains within the valve chambers also when relieving pressure. Therefore a daily repeatedly refilling of the loading liquid is not required. The liquid column height can be monitored by level indicators from outside. This considerably facilitates the maintenance of the valve. The requirements according EN 12255-10:2000 paragraph 5.4.1 in terms of frost-proof safety devices against exceeding of the acceptable operating pressure and against unacceptable vacuum for digesters and low pressure gas tanks are achieved.
Besides the level indicators the compact, modular design and the hinged vent cap of the valve allow for very easy maintenance. For monitoring, cleaning and maintenance the valve top can be opened easily. In case of frequent foaming the valve can optional be fitted with a special cleaning nozzle for internal cleaning.