Bladder Tank systems are simple pressure vessels designed to contain and transfer gradually the stored foam concentrate into mixing units using the firefighting water enters to the vessel, with no external power needed other than the water pressure. Bladder tanks are designed to have double volume which is separated by a hypalon / neoprene based membrane which contains the foam concentrate, and another volume which is between the vessel wall and the membrane containing firefighting water. The membrane made out of hypalon/neoprene multiple layer material to have 6500 psi tensile strength measured according to ASTM D-412 to guarantee maximum resistance for normal operating conditions. During the operation of the system, firefighting water enters the pressure vessel to compress the membrane and to force the liquid foam concentrate stored to flow through the foam concentrate outlet pipe to create a proportional mixture at the mixing unit. Pressure vessels are designed according to EN 13445 or ASME Boiler Pressure Vessel Code Division VIII standards. Standard design pressures are 12 bars or 16 bars. According to specific requests, different design pressures are available in our production range. Pressure vessels are designed by using approved software to determine the thickness of the materials used according to design parameters. Additional corrosion allowance thicknesses are added onto raw material thickness and provided on request. Bladder tanks are comprised of pseudo elliptical heads and cylindrical shells. Elliptical heads are jointed to the shells by using approved welding procedures which combine root, intermediate and finishing seams according to design codes. Pressure vessels are generally produced from P275NH-EN 10028:3, P355NH-EN 10028:3 or ASTM A 516 Gr 70 Fine grain Carbon Steels, by request ASTM A 240 TP 304 or ASTM A 240 TP 316 stainless steel material options are also available.

Welders and welding specifications are qualified by third party organizations are kept up to date with internal planned re- certification procedures. The membrane is fixed to the pressure vessel structure, using its special incorporated elastic flanges at the inspection and manhole openings of the vessel. At the central part of the membrane, perforated HDPE (high density polyethylene) pole piping combinations according to design of the pressure vessel are used to ensure complete discharge of the foam concentrate stored therein. 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. Vessel supports are designed for low seismic activity, special requirements are validated and support designs are revised to meet customer's requirements accordingly to engineering calculations. According to specific requirements, bladder tanks and their mixer combinations can be furnished by C.S.I. S.r.l. with access ladders, sunshades (roofs), skids or spool piping and operational valve combinations. Bladder tanks are constructed as Vertical or Horizontal types. Vertical bladder tank capacities are limited to 12000 liters due to functional reasons, but horizontal bladder tanks can be constructed up to 30.000 liters on the request. Bladder tanks are equipped by direct acting pressure safety valves located on the upper part of the vessel where the firefighting water enters. Each pressure safety valve carries an identification serial number and comes with its calibration certificate released by its manufacturer according to EN ISO 4126 standard. Firefighting water enters the tank from the upper level and foam concentrate is discharged from the tank from another opening at the upper level of the tank.

This configuration allows foam concentrate to be kept stored in the tank all times in the tank not pressurized while some accidents or damages may occur on the piping between the pressure vessel and the mixer. Water and Foam concentrate inlet and outlet connections which located at the upper part of the tank enable the user to change mixer's flow direction, thanks to their symmetric design.
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.

Vertical Level gauges can be supplied by C.S.I. S.r.l. on request but the correct reading of the level of the foam concentrate remaining depends on draining and venting both volumes as described earlier. All bladder tanks constructed by C.S.I. S.r.l. are oversized to compensate thermal expansion of the stored liquids in the vessel. Pressure vessels are marked by CE according to the EN 13445 and PED within limits of the said normative documents.
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.

A hydrostatic test certificate always comes with documentation including the serial number of the vessel produced. Membranes are subjected to pneumatic pressure tests prior to their installation into the tank. Standard Painting procedure covers only the external painting of the bladder tanks which applied by C.S.I. S.r.l. staff at our workshop. On request different painting applications are provided by us, such as powder coating cycles, internal coating cycles or special coating cycles according to customer's specifications. Bladder tanks can be supplied with pre-piped mixers selected from the following pages as MIX, MSC, MAP ranges.

MIX model standard range mixers use orifice combinations to ensure a correct mixing ratio up to 1:6 flow range between minimum and maximum nominal flow rates declared. MIX model mixers house two calibrated orifice plates at firefighting water and foam concentrate lines which are engineered by using highlights of ASME PTC 19.5 standard. Foam concentrate side orifice plates house an embedded check valve to allow back flow into the tank from the mixer.
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.

MIX-ST is an economic version of MIX where water delivery connection to the bladder tank is absent, to be made by installer/designer on site. The equipment works with the same principle of operation as described at MIX section. The most important point is to respect the pipe lengths limitations indicated at product datasheet.

MSC model medium range mixers are produced to use with bladder tank systems to create a larger range of mix with high precision. Construction consists of a single body with a pre-calibrated metering hole and a connection part with an interchangeable foam concentrate orifice plate which doses liquid concentrate flow into the water stream. MSC model mixers offer up to 1:10 flow range with high accuracy.

MAP model variable geometry wide range mixers are produced to use in conjunction with bladder tank systems. Flow ranges of these types of mixers are the best solution for foam sprinkler systems where, system actuation may be only a single discharge head or multiple discharge heads when fed by a single premixing system. MAP model mixers ensure correct mixing ratio of the foam concentrate into the water stream thanks to their unique design with tandem working clapets which regulate foam concentrate flow according to water flow passing through the mixer.

SMV-mini model small capacity bladder tanks are generally produced for foam stations where an accurate foam mixing ratio is needed with lower residual available firewater pressure. SMV-mini model bladder tanks come with incorporated MIX model mixers. Functioning is identical to the SMV models whilst the dimensions are respectfully smaller. Standard capacities available are 25 and 50 liter, different capacities available on request.

SMP model hose cabinets are a combination of standard hose reels with SMV-mini model bladder tank systems and come as a complete foam concentrate mixing and manual intervention station. Outlets available on the mixer enables user to connect a remote actuated valve to feed a fixed system in case needed.

MDL model inline mixers are produced by C.S.I. S.r.l. using the Venturi principle to suck foam concentrate and mix into the water stream. Inline mixers are economically low cost applications where the flow rate, the pressure and the mixing ratio needed by the fixed or portable systems are always the same. The major disadvantage of this equipment is, precision and flow rate is sensitive to pressure variations since the internal geometry of the equipment is always the same and does not compensate parameter fluctuations. MDL model inline mixers are produced in different sizes to satisfy market needs up to 7000 l/min flow rates with lowered pressure loses and high precision. Each inline mixer produced by C.S.I. S.r.l. is subject to a real time functional performance test to meet client's requirements and a test report is released for each inline mixer according to EN 13565 norm.

SS model atmospheric tanks are produced by our company to contain the foam concentrate ready to be used by foam pump systems, or inline mixer applications. Standard models are shown on individual data sheet of the equipment but on request different materials and different capacities can be produced by our company. Combinations of the atmospheric tanks with inline mixers are available from our product range.

FDT model Foam drum trailers are designed to carry standard 200 liter foam drums and have relevant supports on the structure to house equipment to be used in case of an extinguishing intervention. FDT model small trailers are completely plug and play equipment where the pressurized firefighting water is available (for example a hydrant) using hoses, system creates the mixture by MDL inline mixers and can be discharged onto the fire as low expansion using LP series portable branch pipes and also as medium expansion using GSM series medium expansion generators.

PMCS and PECS model pumps with manual or electric operated foam pumps are used to load foam concentrate into vessels in a gentle way to avoid foam expansion during transfer. Explosion proof models are available on request for both manual and electric driven models. For manual models a fixing support can be provided on request on bladder tank mixer bodies with relevant suction and discharge piping.

FDT model Foam drum trailers are designed to carry standard 200 liter foam drums and have relevant supports on the structure to house equipment to be used in case of an extinguishing intervention. FDT model small trailers are completely plug and play equipment where the pressurized firefighting water is available (for example a hydrant) using hoses, system creates the mixture by MDL inline mixers and can be discharged onto the fire as low expansion using LP series portable branch pipes and also as medium expansion using GSM series medium expansion generators.