In-Line Balanced Pressure Proportioner Model KBP – ILBP


The in-line balanced pressure proportioner (ILPB) is a foam proportioning device which is used to balance the higher foam concentrate pressure to the lower system water pressure on pilot pressure regulating systems or foam pump proportioning systems. The ILBP is particularly useful in providing accurate proportioning at multiple riser locations that are situated remotely from the central foam concentrate storage tank. Different sizes of ILBP can be installed on the same foam concentrate supply system to ensure the most appropriate size and demand combination is used. The ILBP is tested and approved to work at different pressure and flow rates and will automatically adjust to give accurate proportioning across its working range.

This technical data is intended for trained experts.
Technical data can be found on the Fomtec website.

For further information, please contact Fomtec or refer to the technical documentation. The contents of this publication are subject to modifications without notice.


Listings and approvals

The ILBP is FM approved and UL listed as part of a fire extinguishing system combining designated foam concentrates, bladder tanks and discharge devices. It is also required for use with Viking low flow foam systems. FM approved and UL listed system components can be found at and

  • FM approved – Low Expansion Foam Systems (FM5130)
  • UL listed – Guide GHXV.EX26572 (UL162)
  • Other international approval certificates may be available upon request.
KBP-InLineBalancedProportioner - UL-Listed

Technical data – Construction features

  • Available in 3” (DN80), 4” (DN100), 6” (DN150), 8” (DN200)
  • Brass construction or nickel aluminium bronze construction for superior corrosion protection
  • Brass construction available on special order
  • Suitable for horizontal or vertical installation
  • Direction of flow indicator on body
  • For use with fresh or salt water
  • Identification tag plate

Please see Standard design specifications and Ordering information in the datasheet. 

Technical data - Standard materials

Body & nozzle Nickel aluminum bronze UNS C95800 - ASTM B148
Orifice UNS-C36000 or C46400 or C95800
Snap ring Stainless steel
Spool assembly See table 6.2.2 in the datasheet

Scope of supply

Ensure that all components are complete and in good condition.
The ILBP is supplied boxed, with a data plate and an integral sized orifice disc specific to its approved/listed concentrate.
The ILBP comes part assembled as detailed in Section 8 and Figure 8.1. The ILBP is supplied with these main components:

  • Balanced spool type balancing valve
  • Brass swing check valve
  • Duplex gauge which indicates both water pressure (black needle) and foam pressure (red needle)
  • Flexible braided sensing lines
  • Interconnecting brass nipples as indicated on the detailed drawings

System pipework grooved couplings are not included.


Please contact Fomtec for further information. The product is available directly from the manufacturer and official distributors only.

Product variants – Options

  • Suitable for Fomtec foam concentrate: AFFF 1% ULTRA LT C6 | AFFF 3%S C6 | ARC 3X3S C6
  • Brass UNS C84400 construction available on request
  • Pre-assembled with bladder tank and water/foam pipe work

See the tables/images of Dimensions and equivalent length and ILBP Assembly components, in the datasheet.


Refer to appropriate installation standards (i.e. NFPA, VdS, LPCB, etc.) and / or applicable FM Global Property Loss Prevention Data Sheets
such as 4-12, foam-water sprinkler systems. Do not alter the piping without consulting a system design representative. Before installing a ratio controller, check the system design drawing to ensure the controller location does not create excessive head pressure or frictional losses.
(Refer to Section 6.2 for identification of ILBP components.)

NOTE: On Viking low flow bladder tank system, the water supply flowing pressure at the inlet of the ratio controller and the discharge outlet of the Viking pressure regulating valve must be set at a minimum of 15 PSI (1.03 bar) lower than the system flowing pressure at the inlet to the Viking pressure regulating valve. (Refer to the website for instructions on how to adjust the outlet pressure on the Viking pilot operated pressure control valve, Model A-2 or B-1, under a flowing condition.)

For foam pump systems, the foam concentrate pressure must be a minimum of 15 PSI (1.03 bar) higher than the system water pressure at
the inlet of the ratio controller.

The ILBP is a partially pre-assembled proportioning device, complete with a duplex water and foam pressure gauge, spool valve, concentrate controller, check valve, sensing lines and associated brass piping. It is an integral part of the Viking low flow foam system, and must be installed in accordance with the following instructions.

The ILBP unit is shipped with the foam pressure sensing line already installed at the end of the spool valve. The water sensing line
must be field installed following the schematics above. The foam concentrate supply line from the Viking Halar® coated concentrate
valve is then connected to the inlet of the swing check valve. Refer to the appropriate Viking technical data pages for instructions as
to completing the system installation and testing of the low flow foam system or foam pump system.

  • The ILBP (ratio controller) must be installed with the arrow pointing in the direction of the water flow
  • The ILBP (ratio controller) can be installed in the vertical or horizontal position
  • The balancing spool valve must always lie horizontally (as shown below)
  • The foam concentrate supply line diameter may need to be increased above the foam inlet size (“F” Fig 6.2.1) due to friction loss in piping from the riser back to the foam source
  • In deluge and preaction systems a removable section of pipe should be installed between the concentrate control valve and ILBP foam inlet to allow the flushing of foam concentrate after system activation or testing
  • A foam concentrate supply pressure gauge is recommended adjacent to foam inlet of the CCV
  • If installed in a horizontal header, the check valve (“22” Fig 6.2.1) must be oriented so that the clapper is perpendicular to the floor and access hole is facing up (as shown below)
  • Straight piping equal to a minimum of five (5) pipe diameters should be installed before and after the ILBP (ratio controller)to help ensure proportioning accuracy


The system water pressure, under a water flow condition, must be at least 15 PSI (1.03 bar) lower than the foam concentrate pressure at the ratio controller (1).

  • The reduction in system water pressure for a Viking low flow bladder tank system is accomplished by the use of the Viking pilot pressure regulating valve, which is also a component of the Viking low flow foam system
  • For foam pump systems, the foam pressure at the ILBP must be at least 15 PSI (1.03 bar) higher than the water pressure

Upon system actuation, water begins to flow through the piping network, including the ILBP.

The ILBP water sensing line (connected upstream of the ratio controller by installer) and foam sensing line are connected to upper and lower side of internal hydraulic piston. The piston is integrally attached to the balanced spool of the pressure balancing valve.

As the foam concentrate discharge pressure from the spool valve increases above the inlet water pressure, the spool closes over the discharge ports of the balancing valve until the foam pressure equals water pressure. This allows the correct balanced pressure foam concentrate to flow through the metering orifice of the ratio controller.

As the discharge foam concentrate pressure is lowered below the water supply pressure due to increase in flow and metering pressure drop caused by the venturi of the ratio controller, the piston and spool open to allow more flow as required. When the foam concentrate inlet pressure is equal to the water inlet pressure of the ratio controller, the proper mixture of foam solution is developed at the mini-mum and maximum flow rates shown for each size ILBP and foam concentrate being applied.

Due to the foam concentrate pressure being supplied at a higher pressure than the water supply, a positive injection of foam concen-trate occurs where only a few sprinklers have opened. This will cause rich foam solution below the minimum flow rates shown or at the initial fire condition where a small discharge flow rate occurs. As additional sprinklers operate and flow increases, the metering pressure drop across the ratio controller’s venturi matches the sized foam concentrate metering orifice thus producing the desired solution of water and foam mixture as indicated in table 3.4.1, inte datasheet.


For details of warranty, contact Fomtec directly.

Inspections, tests and maintenance

Refer to respective requirements, according to the relevant standards for inspection, testing and maintenance.If applicable, refer to FM Global Property Loss Prevention Datasheet 4-12 for specific test and commissioning criteria. In addition, the “Authority Having Jurisdiction” (AHJ) may have additional maintenance, testing and inspection requirements that must be followed.

Warning: Any system maintenance or testing that involves placing a control valve or detection system out of service may eliminate the fire protection of that system. Prior to proceeding, notify all Authorities Having Jurisdiction.
Consideration should be given to employment of a fire patrol in the affected area.


At end of use the product described here should be disposed of via the national recycling system.

Accessories and spares

Refer to table 6.2.2

Declaration of conformity

If required, contact Fomtec or further assistance.