D-1 Containing and Mixing Systems

Bladder Tanks systems are used for firefighting appliances to contain foam concentrate and mix it into the firefighting water with desired percentages to create a specific extinguishing agent called foam solution, with no external power needed other than the water pressure.

These systems are unique for their performance and for their low maintenance needs, since the functionality does not have rotating parts and the material does not consume during usage.

The system functions as follows: firefighting water under pressure enters the bladder tank mixer which is connected to the bladder tank vessel through piping. A part of the water travels into the bladder tank vessel’s waterside using the water piping between the equipment.

As the foam concentrate stays in the other size, which is separated by the membrane, water pressure enters to the volume of the bladder tank vessel, by squeezing it and pressurizes the foam concentrate. The foam concentrate piping transfers the foam concentrate under pressure to the flow inside of the mixer to create a mixture of the desired proportions.

A basic bladder tank system consists of:
A bladder tank vessel, where the foam concentrate is stored inside.
– A bladder tank mixer, where the foam concentrate is injected into the water stream.
– Piping and accessories which make the bladder tank vessel and the mixer perform several tasks.

Bladder tanks vessels are classified as simple pressure vessels, consisting of a metallic container manufactured by welding pseudo elliptical heads and cylindrical shell together. Pressure vessels are generally produced from P275NH-EN 10028:3, P355NH-EN 10028:3 or ASTM A 516 Gr 70 Fine grain Carbon Steels, and by request ASTM A 240 TP 304 or ASTM A 240 TP 316 stainless steel material options are also available.

Equipment is designed according to EN 13445 or ASME Boiler Pressure Vessel Code Division VIII standards. Standard design pressures are 12 bars or 16 bars. (Different design pressures are available at request) According to execution type, which can be Vertical up to 12000 liters nominal capacity or Horizontal up to 30000 liters, a separating membrane installed inside of the vessel from the thick flanges welded to the structure. Pressure vessels are self-standing units over bracket supports welded onto the skirt of the vessel for vertical models or standing over saddles for horizontal models.

Separating membranes (also known as diaphragm) are made out of a special fabric called Hypalon-Neoprene. The membrane for each capacity and type are designed and produced specifically to perfectly adhere to the internal shape of the metallic vessel.
The material used has a high resistance to tear and tensile strength to keep its form under the operating and standard storage conditions. Foam concentrate may be loaded inside or outside the membrane according to customer’s requirements.
The membrane is kept centered to vessel axes by using a perforated HDPE (high density polyethylene) pipe.
According to the execution type, the vessels will be equipped with manholes and inspection holes according to governing design standard.

As a minimum configuration, bladder tank vessel at the upper side are equipped with water inlet pipe, completed with vent valve and a safety valve calibrated according to ISO 4126 standard ensures integrity of the structure due to over pressure or external fire conditions. Foam concentrate leaves the vessel from its above-positioned piping which is equipped with a vent valve to purge the air that remains inside. At the bottom side of the vessel, a water drainage valve is provided and also the foam concentrate drainage valve piping, equipped with a level indicator (hydrometer type) for level measurement purposes.

Each and every bladder tank vessel is subjected to strict quality control processes at the end of production, with a non-destructive examinations of the welded seams, and a hydrostatic proof test according to design standard is always executed to complete with records of the activities that make part of the end of work book.

Internal and External coating cycles are applied internally according to customer’s requirements.

Bladder tanks can be used separately with their mixers as well as combined with multiple bladder tanks or multiple mixers.