Discussion on the selection of fire foam pumps
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What type of pump is generally used for fire foam pumps? According to the design parameters of fire foam systems, both centrifugal pumps and gear pumps can be used. What are the main factors considered when choosing a gear pump as the foam pump?
For fire foam pumps, I have seen three models developed by major foreign design institutes, as well as two models developed by several domestic design institutes; all of them use centrifugal pumps. I’ve never seen a gear pump. It should be noted that the foam pump I mentioned above refers to a pump that provides a pressure of 8 to 12 kilograms to the foam generator. If you are referring to pumps that use turbines to extract foam concentrate, then in the two foam generation units produced by Americans that I have seen, gear pumps are indeed used (firewater drives the turbine, which in turn drives the gear foam pump). In my opinion, if the rotational speed remains constant and the pressure after the pump is relatively controllable, a centrifugal pump can be used. Because if the pressure after the pump is too low, the centrifugal pump motor can easily be damaged, whereas gear pumps do not face this risk. If the rotational speed changes significantly, the outlet pressure and flow rate of the centrifugal pump change even more noticeably. This is my personal opinion for reference only.
Thank you! By fire foam pump, I mean a gear pump that is used to mix fire water with fire foam in a ratio of 6% in order to deliver this foam mixture to the foam nozzles in the system. The fire water pump used to supply fire water to the foam generator is a centrifugal pump in our factory, while a gear pump is used for the fire foam pump. I would like to know why a centrifugal pump is chosen for transporting fire water, and why a gear pump is used for transporting the foam mixture. What are the main factors taken into consideration when making such choices?
Firstly, centrifugal pumps operate smoothly, have a simple structure, and are easy to maintain; therefore, other types of pumps are generally not used when a centrifugal pump is available. However, centrifugal pumps have disadvantages; for example, the particles in the fluid being pumped cannot be too numerous, its viscosity cannot be too high, and its gas content cannot be too high either. Gear pumps, on the other hand, are suitable for situations with high viscosity and many particles. By working backwards from these conditions, one can understand the physical properties of fire-fighting water and fire-fighting foam.
I’m also learning about *balance ratios, and I ran into this same issue.