Petrotech Tubular Liquid Level gauges for tanks operating at low pressures. The instruments consist of a toughened continuous section of borosilicate glass tube which is connected at both the top and bottom to an isolation valve.  The connection between the valve and glass is sealed by means of a rubber gasket contained within a union on the valve.  The isolation valves used on this type of instrument are most commonly the ‘off set’ pattern type as this allows for the gauges to be cleaned.

The continuous glass section is protected by four stainless steel guard rods or C Channel Guards which run between the valves and the pressures within which the gauges can operate are limited by the maximum allowable pressure for the glass