Description
Inline Foam Inductor is used to induct the foam liquid concentrate in water stream to supply proportioned solution of the liquid concentrate and water, to the foam producing equipment. The inductors are designed primarily for use in the fixed foam installation to
provide a simple and reliable method of proportioning in constant flow applications. Each Inductor is designed for a pre-determined water pressure to give the correct proportioning at that pressure and discharge rate. The increase or decrease of the inlet pressure will result in an increase or decrease in the flow rate, which in turn will change the proportioning.
SPECIFICATION
Inductors are available in two different materials of construction, a wide range of flow from 75 to 3500 litres per minute at inlet pressure between 6.4 to 12 bar as shown in the graph. Each Inductor is accurately calibrated at the factory to match the flow, pressure and the induction requirement of the system. This enables to ensure and achieve the correct performance. SYSTEM DESIGN DETAILS
The Inductor must be selected and installed in a hydraulically calculated system considering the limitation of permissible back pressure. The maximum back pressure allowed is expressed as 65% of pressure at the inlet of the Inductor. The optimum performance of Inline Inductor is with pressure above 8 Bar (115 psi). In the fixed foam system installation the inductor can be mounted above the concentrate storage tank. The maximum height of the Inductor suction pipe above the bottom of the storage tank to the inductor centre should not exceed 1.75 meters, with AFFF & 0.9 meter for AR-AFFF 3/3% foam concentrate. A minimum of 600mm of unobstructed straight pipe
line should be provided at the inlet and outlet of the inductor. The inductor must be installed in a system having minimum of 6.5 bar inlet pressure at inlet of inductor. The diameter of water supply pipe and water foam solution pipe should not be less than that of the
diameter of the inductor. A shut-off valve provided in the induction line must be full bore on-off valve. The non-return valve if fitted in the foam induction pipe line, then it must be supplied or recommended by HD, so that the induction rate is properly calibrated in factory before supply. For best performance the inlet pressure at the inline inductor should be 6.8 bar or higher.
APPLICATION
Inline Foam Inductors are quite suitable for application utilizing single fixed discharge device. The Inline Inductors are not suitable for variable flow or pressure applications. The Inline Inductors are not suitable for Sprinkler system or system utilizing multiple small orifice discharge devices, which may result in increased back pressure due to blockage of discharge device.
NOVEMBER, 2022 PAGE 2 OF 6 HD 187
INSTALLATION AND MAINTENANCE
Inductor must be supported firmly to prevent strain on the inductor itself. Qualified and trained person must commission the system. After few initial successful tests, an authorized person must be trained to perform inspection and testing of the system. It is recommended to carry out physical inspection of the system regularly. The system must be fully tested at least once in a year or in accordance with applicable NFPA codes or in accordance to the standard of the organization having local jurisdiction. Do not turn off the system or any valve to make repair or test the system, without placing a roving Fire Patrol in the area covered by the system. The Patrol
should continue until the system is back in service. Also inform the local security guard and control alarm station, so that a false alarm will not be signalled. SELECTION OF HD INLINE FOAM INDUCTOR SIZE Size of Inductor Inductor K-Factor range
65 NB 29.4 TO 170.00
80 NB 151.2 TO 340.00
100 NB 302.4 TO 680.00
150 NB 604.8 TO 1030.00
For selecting Inductor size, following formula to be used:
Q = K √P
Q = Total solution flow rate in litres per minute
K = Inductor constant
P = Inlet pressure in kg/sq.cm
Example: To find K-Factor
Q = 200 lpm
P = 8.0 kg/sq.cm
K = 200 ÷ √8
K = 70.71
This K=70.71 falls within the range of Inductor with 65 NB size. Hence 65 NB Inductor should be selected.
NOTES
1) It is recommended to select next higher size of inductor when the K-factor is very close to the higher range of model.
2) A pressuge gauge mounting socket at inlet and outlet of Inductor must be provided, which will help to analize the system during commissioning. The socket can be plugged in once the system has been commissioned successfully.
3) The maximum permissible back pressure is 65% of inlet pressure. The system designer should consider and design the system with 62%
or less than back pressure as safe design.
4) Inductor must be adequately supported so that no strain is imposed on the inductor b
