Below are the major components used with automatic direct injection proportioning systems.
Foam Concentrate Tank
The foam concentrate can be the original foam concentrate bucket, a stand alone tanks designed specifically for the foam concentrate, or an a foam concentrate cell integrated into the water tank.
A Foam tank is a very desirable add on for any engine incorporating a foam concentrate proportioning system. A properly designed, built, and maintained foam concentrate storage tank has several components as required by NFPA: 1) a lockdown, sealable lid with a vent valve; 2) an electronic floating trip switch to signal a concentrate proportioning system that concentrate is low; 3) a discharge line shut off valve (for maintenance and line breaks). The discharge line must be at the low end of the tank and can also act as a drain line. And 4) A clean-out trap (wye) to catch any debris that might enter the foam
concentrate tank (you would be surprised).
Even depending on the concentrate systems capability to pull a draft, the foam tank should be mounted higher than the concentrate pump. Concentrate tanks can be any size based on the fire department’s needs.
If a truck has a broken or no foam concentrate tank, a siphon or pick up tube can be used along with a 5 gallon concentrate bucket. However, items 1-4 above would not be available if needed. And, if the apparatus has pump and roll capabilities, the bucket will have to be secured. The foam level in the bucket would have to be constantly monitored as the bucket has no way to signal low concentrate leaving the system to continue running without concentrate (Not a good thing!!).
Wye Strainer
There should be two debris strainers on the foam system. The first is a screen inside the top of the foam tank that should catch large debris as the foamis being poured into the tank. The second strainer is usually a wye strainer (similart o that used on the hydraulic oil cooling systm). This second strainer shold catch smaller debris before it heads intot he concentrate pump. This strainer should be cleaned out periodically to insure that concentrate flows to the proportioner pump. (Note: be sure to turn off the concentrate tank to pump valve before opening the wye strainer. Failure to do so can result in the loss of a large amount of concentrate.
Tank Level Switch
An electronic floating trip switch to signal a concentrate proportioning system that concentrate is low.
Foam Proportioner
Many different types – see Concentrate Proportioners/Devices.
Foam Inject Check Valve
Foam concentrate is injected into the water plumbing just ahead of the Foam Manifold. The concentrate begins mixing with the water instantly (becoming Solution) and mixes more thoroughly in the Foam Manifold.
Foam Manifold
The foam manifold is a rectangular or round cylinder (vertical or horizontal) where the water and foam concentrate mix. The foam concentrate inject point occurs in the plumbing from the pump just prior to entering the foam manifold. From the manifold, plumping heads to each individual solution discharge.
Flow Meter (Paddle Wheel)
