The most common tech support questions concern setting up for foam-eductor operations. For those who are having trouble making foam with the industry's default proportioning device, there is help available.

First, alcohol-resistant foam is supposed to be gel-like in appearance. The thicker it is, the more alcohol resistant it is. Eductors will work fine with AR-AFFFs. Most UL-listed AR foams use foam eductors.

Let's bust another myth: AFFF and AR-AFFF have no specific shelf life. Twenty-year-old foam is fine as long as the foam has been stored according to package instructions on its package. The secret is keeping containers airtight. Foam concentrate will evaporate if containers are left open or with lids ajar.

Placing an eductor somewhere in a hose-line is a pain in the neck. Try to keep the eductor attached to a pump discharge. The eductor is much better off at the pump, where the operator has light, communications, pressure gauges and a ready foam supply. A 1I-inch hose will handle 3% (97 parts water and 3 parts foam concentrate) or 6% 200 feet from the engine. Two-inch hose on a 95-gpm eductor will work 400 feet from the engine. (See “Foam-Eductor Distance in Feet at Level Ground” on page 80.)

If your eductor does not pull foam concentrate, try these steps:

1. Connect the subject eductor to a pump outlet; use a reducer if necessary.

2. Be sure all pick-up hose connections are tight and the hoses have no cracks.

3. If using AR-AFFF foam, take the strainer out of the pick-up tube end.

4. Connect 50 feet of hose with no nozzle attached.

5. Place the pick-up tube in a pail of water.

6. Set the proportioning meter at 6%.

7. Have someone hold the open hose butt so it doesn't flop around the ground.

8. Open the discharge all the way and throttle up to 200 psi. A 95-gpm eductor set at 6% will drain between 3 and 4 gallons of water from the bucket in 30 seconds. A 60-gpm eductor will drain almost 2 gallons in 30 seconds. If testing a 125-gpm eductor, it will drain slightly more than 3.5 gallons in 30 seconds.

9. Add a nozzle and repeat. If OK, add 50 feet of hose and try again. Keep adding hose until the eductor stops drinking water.

10. Substitute foam concentrate for the water in the bucket and repeat the test. After flowing foam for 30 seconds, put the pick-up tube back in the water bucket and flush for 60 seconds. If using a push-button-flush foam eductor, flush it by pressing the red button for one minute with pump pressure reduced to less than 50 psi. Throttle the discharge gate if necessary to get pressure low enough to press the button.

Another way of testing a foam eductor is to put an in-line pressure gauge on the outlet of the foam eductor to do this:

1. Attach the hose and nozzle system (95 gpm).

2. Open the discharge and slowly throttle up to 200 psi (eductor inlet pressure).

3. Open the nozzle.

4. If the gauge on the eductor's outlet reads higher than 130 psi, subtract hose or increase nozzle flow until the gauge falls below 130 psi.

5. If available, put a dual-pressure nozzle in the low-pressure setting before subtracting hose. Lowering nozzle pressure or subtracting hose will help control the back pressure problem.

Sixty-five percent of inlet pressure is available for hose loss and nozzle pressure. If the hose requirements are short and the low-pressure nozzle is a flow match for the eductor, operate at pressures less than 200 psi. (See table below.)

Remember, the nozzle flow rate must be the same or greater than the eductor's flow rate. A 60-gpm nozzle on a 95-gpm eductor will shut down the system because of excessive back pressure. Automatic nozzles are friendlier than most others because there are no flow settings to worry about. The nozzle is always in hydraulic balance with the eductor.

Eductors will operate just fine without a nozzle. To fill a water tank with foam solution, connect the male end of the hose to a tank fill or folding tank. Be sure to fill from the bottom up to minimize frothing.

If using 3% foam concentrate (or colored water), set the metering valve at 3%. At engine idle, put the pick-up tube in the foam pail before charging a dry line. With an onboard foam eductor system, open the eductor and foam tank valves before charging the hose. Immediately after opening the discharge at 50 psi, concentrate or colored water will move into the eductor. This happens at lower pressures because the eductor feels no back pressure. The eductor will continue to pull foam up the tube until the 3% solution has reached the closed nozzle. While the line is filling, throttle up to 200 psi. When the nozzle opens, the operator gets foam immediately, although that foam will be somewhat rich at first.

The time it takes foam solution to get from eductor outlet to nozzle inlet is called transit time. With 200 feet of 1I-inch hose at 95 gpm, it will take about nine to 10 seconds per 100 feet of hose. A 60-gpm eductor can take as much as 30 seconds for the solution to get to a nozzle that's 200 feet away. The larger the hose, the longer it will take. This also is true for all onboard foam systems. Whatever setting changes the user made at the eductor, it will take about or more seconds before the richer or leaner finished foam comes from the nozzle.

Making bubbles does not mean the foam will hold down gasoline vapors on a hot road spill. Industry standards allow proportioning as much as 1% rich, no leaner. Lean proportioning means fires might not be extinguished as quickly, or finished foam drains way too fast while trying to maintain vapor security at crash scenes. Because foam concentrate viscosities vary from type to type, it is wise to test all eductors for accuracy. NFPA now requires annual accuracy certification of all Class A and Class B onboard foam systems.

AR-AFFFs (ATCs) are the most viscous. Older foam eductors tend too be lean. Test proportioning accuracy using water.

Hopefully, following these instructions will help reduce your foam eductor headaches and lead to easier setup.

---

Jim Cottrell is the president of Cottrell Associates Inc., Combat Support Products division.

Foam-Eductor Distance in Feet at Level Ground

Foam-eductor gpm at 200 psi	Fire control size AFFF and AR-AFFF	Concentrate flow gpm	Nozzle or hose outlet psi	1½-inch hose	1¾-inch hose	2-inch hose	2½-inch hose	3-inch hose	4-inch hose	5-inch hose
60 gpm	Hydrocarbon 600 sq. ft. AFFF and AR-AFFF polar Solvent 300 sq. ft.	1%=0.6	100	300 ft.	700 ft.	850 ft.	3,300 ft.
		3%=1.8	75	600 ft.	1,250	1,550 ft.	6,100 ft.
		6%=3.6	50	850 ft.	1,850 ft.	2,200 ft.	8,800 ft.
			10	1,300 ft.ft.	2,800 ft.	3,400 ft.	13,300 ft.
95 gpm	Hydrocarbon 950 sq. ft. AFFF and AR-AFFF polar solvent 425 sq. ft.	1%=1.0	100	100 ft.	200 ft.	350 ft.	1,200 ft.	3,300 ft.
		3%=3.0	75	250 ft.	350 ft.	650 ft.	2,200 ft.	6,100 ft.
		6%=6.0	50	350 ft.	500 ft.	1,000 ft.	3,200 ft.	8,850 ft.
			10	550 ft.	800 ft.	1,500 ft.	4,800 ft.	13,300 ft.
125 gpm	Hydrocarbon 1,250 sq. ft. AFFF and AR-AFFF polar solvent 625 sq. ft.	1%=1.25	100	50 ft.	100 ft.	250 ft.	750 ft.	1,900 ft.
		3%=3.75	75	175 ft.	200 ft.	450 ft.	1,400 ft.	3,500 ft.
		6%=7.2	50	250 ft.	300 ft.	650 ft.	2,200 ft.	5,100 ft.
			10	400 ft.	500 ft.	1,000 ft.	3,000 ft.	8,000 ft.
250 gpm	Hydrocarbon 2,500 sq. ft. AFFF and AR-AFFF polar solvent 1,250 sq. ft.	1%=2.5	100				200 ft.	480 ft.	3,000 ft.
		3%=7.5	75				350 ft.	880 ft.	5,500 ft.
		6%=15	50				500 ft.	1,280 ft.	8,000 ft.
			10				800 ft.	1,920 ft.	12,000 ft.
350 gpm	Hydrocarbon 3,500 sq. ft. AFFF and AR-AFFF polar solvent 1,750 sq. ft.	1%=3.5	100				150 ft.	250 ft.	1,250 ft.	4,800 ft.
		3%=10.5	75				250 ft.	450 ft.	2,300 ft.	8,800 ft.
		6%=21	50				400 ft.	650 ft.	3,300 ft.	12,800 ft.
			10				600 ft.	1,000 ft.	5,000 ft.	20,800 ft.
500 gpm	Hydrocarbon 5,000 sq. ft. AFFF and AR-AFFF polar solvent 2,500 sq. ft.	1%=5	100				50 ft.	100 ft.	600 ft.	2,000 ft.
		3%=15	75				100 ft.	200 ft.	1,100 ft.	3,600 ft.
		6%=30	50				100 ft.	300 ft.	1,600 ft.	5,300 ft.
			10				200 ft.	450 ft.	2,400 ft.	8,000 ft.
NFPA 11 requires a 15-minute foam concentrate supply for spill fires (one inch or less). NFPA 11 requires a 65-minute foam concentrate supply for fire in depth (tank-type fires). Eductor back pressure cannot exceed 65% of inlet pressure. Back pressure is sum of hose friction loss, elevation and nozzle pressure. Put a pressure gauge on eductor inlet and outlet. At 200 psi inlet pressure, do not exceed 130 psi on the outlet gauge (65% of inlet psi). Distance to hose outlet is based on NFPA friction loss tables and/or actual field experience. Be sure to add or subtract elevation head. Source: Cottrell Associates Inc.

Inlet pressure	Outlet BP (hose + nozzle and elevation back pressure)
225 psi	145 psi max. Proportions are a little lean.
200 psi	130 max. Just right.
175 psi	114 max. A little rich.
150 psi	98 max. A little richer.

Simple Class B Foam System

For the once-in-a-blue-moon Class B fire, use a TFT, self-flushing, 95-gpm eductor screwed to a pumper outlet. Connect the pick-up tube to your pump panel's foam tank connection. A 95-gpm eductor will handle a 95-square-foot fuel oil spill fire, or 425-foot polar solvent job using National's Universal Gold 1% to 3% AR-AFFF.

Leave the electric Class A foam system to do what it does best. Rarely will electric A and B systems proportion AR-AFFF (B) foams accurately. They tend to run quite lean, which is not good for crash scene security blankets or fighting blended gasoline fires.

1. Pull open foam tank valve.

2. At idle, open discharge, filling dry hose with foam solution.

3. Open nozzle. Throttle up to 200 psi. Fight fire.

4. 1¾-inch hose will get you 200 feet with a 100 psi nozzle, 300 feet with a 75 psi nozzle and 500 feet with a 50 psi nozzle.