Containing and mixing systems
Each separate volume (firefighting water and foam concentrate sides) has their air ventilation valves at the highest level and drainage valves at lowest level of the tanks.
Drainage ports for the foam concentrate at the bottom of the tanks are used to load foam concentrate into bladder tank and house a hydrometer type level indicator which shows the quantity of the foam concentrate remaining in the bladder tank. For correct reading of the level indicator, firefighting water should be drained from the vessel and air remaining in the water or foam side should be evacuated by opening the air vent valves at the top.
After construction of the bladder, non-destructive examinations of the welds as 10% X-Ray (Joint efficiency 0.85 for main weld seams) and Liquid Penetrant Tests are applied on each vessel. Each bladder tank, single or together with a pre-piped mixer hydrostatically tested prior to painting, as validation of construction and strength according to construction code rules.
Standard mixers are delivered with a water side connection which takes a small portion of the water passing through the mixer to transmit line pressure into the vessel's water part which compresses the bladder, and another connection which introduces the foam concentrate flow coming out of the vessel into the mixer. Water orifice creates a permanent pressure loss which enables the foam concentrate to be mixed with the flow, and foam orifice plate doses the amount of the foam concentrate to be mixed into flow. MIX model mixers ensure high accuracy at its nominal flow range with lowered pressure loses.
Orifice plates are engineered to create a maximum pressure drop up to 1 bar at maximum flow rates indicated at datasheets. Standard mixers are produced to have a single mixing percentage. On request, mixing ratio selector provided at the foam concentrate orifice which enables to choose suitable mixing ratio according to foam concentrate used. No moving part reduces maintenance needs.