In-line balanced pressure proportioning systems function by maintaining equal pressure to the foam concentrate and water inlets of a proportioner. However, many such systems have proven unable to maintain that equal pressure at low-flow rates, according to ANSUL territory manager Skip Westbrook.
“A typical proportioner uses a standard ILBP (in-line balanced pressure proportioning) module that may begin proportioning too rich at low flow rates,” Westbrook said. “It may add more foam concentrate than the ratio required.”
By contrast, the Ansul Flowmax PPW variable range proportioner utilizes a variable orifice to meter an accurate flow of liquid foam concentrate over a wider range of flows and pressures than standard balanced pressure pump proportioners, stated Westbrook.
“Our product is pretty unique in that it can actually balance the pressures even for closed head sprinkler systems using a pump skid.” ANSUL FLOWMAX PPW variable range proportioners are part of an in-line balanced proportioning system using an atmospheric foam concentrate tank connected to a positive displacement foam concentrate pump. The system responds quickly and accurately to changes in the water inlet pressures and flow rates, utilizing a positive displacement foam pump to pressurize foam concentrate within the supply manifold.
“A pressure sustaining valve, located in the return line to the foam concentrate storage tank, is set to maintain a regulated pressure in the supply manifold at a nominal 15 psi (1 bar) higher than the maximum pressure in the water supply line,” Westbrook explained. Foam concentrate not required by the proportioner returns to the atmospheric storage tank through a sustaining control valve. The integral balancing valve in the ANSUL FLOWMAX PPW proportioner senses the foam concentrate pressure and water pressure. This balancing valve automatically adjusts the foam concentrate to the water pressure. “As foam concentrate enters the proportioner, a variable orifice regulates the flow of pressurized concentrate entering the water stream,” said Westbrook.
The units are available in two standard sizes, 6-inch and 8-inch, with flow rates from 55 to 4,875 gpm (208 to 18,453 lpm). Each unit consists of a foam proportioner with integral pressure balancing valve, and pressure sensing tubing. The proportioner construction includes a bronze body, stainless steel deflector, stainless steel spring, stainless steel foam metering cone and orifice, and a bronze balancing valve with stainless steel fasteners.
The proportioner is typically installed between 6-inch or 8-inch pipe flanges (flat or raised race) corresponding to the respective proportioner size. To assist with proper installation, the unit is marked with arrows to indicate direction of flow for water and foam concentrate. A minimum five nominal diameters of straight pipe is required in the water line upstream of the proportioner and a minimum 2.5 nominal diameters of straight pipe downstream for proper installation.
ANSULITE AFCB 3% AFFF and ANSULITE A334-LV 3X3 AR-AFFF are the only concentrates UL-listed and FM-approved for use with the ANSUL FLOWMAX PPW proportioners. Typical applications include:
Flammable liquid storage where protection requires multiple devices with a wide range of flow rates. For example, tank farm protection systems per NFPA 11 using foam chambers, or other means of foam delivery where varied flow rates are encountered or where low flows may be required for supplementary foam handline(s).
Aircraft hangar protection per NFPA 409 involving closed head foam-water sprinkler systems utilizing ANSULITE 3% AFFF foam concentrates. The proportioners are often located long distances from the foam concentrate supply.
Closed head foam-water sprinkler systems for warehouse storage, chemical processing, loading racks, as well as flammable liquids processing, storage and transportation areas.
The ANSUL portfolio of firefighting foam concentrates, hardware and engineered systems provides an extensive range of high-quality, field-proven fixed and semi-fixed solutions for special hazard protection. With expert technical service, dedicated customer support, innovative R&D, and customized systems, ANSUL products protect oil and gas, petrochemical, industrial, aviation, marine, transport, and warehouse installations around the world.