Calibration is basically adjusting the foam concentrate proportioner to insure it understands what water is flowing and how much foam concentrate is being pumped.
An automatic electronic direct injection proportioner with a digital control head has its electronics stored inside the unit (either inside the pump mounted control head or in a control box mounted near the pump). A paddle wheel is mounted inside the fire pump’s plumbing just ahead of the foam manifold. Water flowing to the manifold spins the paddle wheel to tell the proportioner how much water is moving. The system electronics takes the paddle wheel input and determines how much concentrate to pump for the % solution requested by the operator. However, on occasion, the system doesn’t know exactly how much water is actually passing the paddle wheel or how much foam concentrate is actually being pumped. Calibration adjusts the system and refreshes the memory of the system to calculate an accurate water flow and accurate concentrate flow to meet the % solution needs.
Below is a general description – each system manufacturer has its own specific instructions. Always follow the manufacturer’s instructions. Several operations documents are listed in the CompressedAirFoam.com/Library for reference.
Water Flow calibration is flowing a known amount of water and comparing that amount to the gpm flow shown on the digital flow meter. If the amounts are the same, the unit is calibrated. If the amounts are different, the system must be adjusted until it matches the known flow. A simple way to flow a known amount is to attach a calibrated smooth bore tip to a foam discharge outlet and flow water at the specified pressure. The listed flow should match the flow on the digital display. If not, calibrate the control head flow as per the manufacturer’s instructions. For example, a known flow using a ½” tip at 50 psi will deliver 53 gpm. To ensure the best calibration, run the flows at various pressures and compare the gpm flowing on the display. If you do not have a labeled nozzle as shown below, refer to fire department hydraulics manuals to find known flows based on pressure and tip size, or go to the app store and download the Waterous Tech Tool – and check out the Smooth Nozzle Discharge Calculator.
Foam Concentrate Calibration – To calibrate the concentrate flow, use the bypass function of the concentrate pump (refer to the manufacturer’s instructions). Using a calibrated container (1, 2 or 5 gal container), place the pump in simulated mode, and flow the concentrate directly into the container. Once the concentrate fills the container to a calibrated amount, see if this amount is the same as that displayed on the digital control head. If not, adjust the control head amount to match that of the calibrated container (see manufacturer’s instructions). Repeat the flow more than 1 time to make sure the controller knows the amount flown. (see calibrated bucket photo)
Once the controller is calibrated to the concentrate flow, pour the concentrate from the calibrated bucket back intot he foam concentrate tank, and make sure to put the bypass valve back into inject mode to insure the concentrate flows to the foam manifold and hose lines and not out on the ground.
How often to calibrate? 1st, check with your manufacturer’s instructions. At CompressedAirFoam.com, we recommend a minimum of twice yearly – once in warm weather, once in cold weather. Temperature changes affect the flow of concentrates and the density of water. It is also recommended that the system be re-calibrated:
- Whenever the concentrate brand is changed (each brand can have varying viscosities).
- Whenever the system has been workd on or repaired.
- Whenever the system has been sitting for a length of time.
- Beginning of the season if the system is only used aprt of the year.
