Application of pressurized barrier liquid external tank to feed clean liquid to the gland box; circulation is forced and maintained by internal pumping ring (or ”thermosiphon”). Barrier liquid pressure (in the tank) is higher than sealed process pressure in the gland box. Characteristics of the barrier liquid should be defined, to keep the operating conditions of sthe lide ring faces of the seal stable. Solution typical for double seals.

This system comprises a barrier liquid tank, a manual pump for barrier liquid refilling, necessary connectors and valves and control and measuring equipment. The sealed medium is fully hermetic, and only a slight amount of the barrier liquid goes into the product and out into the atmosphere. Pressure in the tank is maintained by connecting an external pressure source, e.g., compressed nitrogen from plant installation or cylinder. This installation is used with contaminated liquids which crystallize in contact with the air, which can be environmentally hazardous or toxic. The main functions of the barrier liquid involve, among other things, seal lubrication and cooling as well as preventing the sealed medium from getting inside the seal.