1. #1

    Join Date
    Mar 2009

    Default Hales TPM or total pressure master

    Need some feedback.

    for those that are familiar with this device what is your practice. I am now hearing that it is acceptable to set this device at what ever pressure is needed in order to prevent it from dumping water, then just gating back on the lines to get your correct pressures.

    My thoughts would be to set it correctly and dump the water. After all that what the thing was designed for.

    For those that are not familiar. The tpm is a two stage relief system. Stage one acts similar to the standard relief valve by dumping from the discharge back into the intake. Stage two kicks in when stage one no longer can handle the pressure and dumps water straight out onto the ground.

    My cons against setting this valve up to prevent from dumping water are.
    it was not designed for it. when the lines are shut down they will adjust to the high pressure no matter how much they are gated and you will have an initial "kick back" of the nozzle when reopened which can be dangerous if the pressure is really high. Too many variables to look at and the gating process will never stop as lines are shut and opened.

    Am I off base here.

  2. #2
    Forum Member
    caltom's Avatar
    Join Date
    Mar 2004
    Republic of Texas


    TPM is nothing but a fancy releif valve. It should be set like any other. If you run the pressure up and then start lowering the releif valve to stay open you are building unneccessary pump pressure and running the engine harder than it needs to. You'll spend your time chasing the releif valve as it runs pressure up and down while it opens and closes. The TPM is quick to open and slow to close, and from what I've seen discharge pressures will be varying about 50 psi. Handlines (or any discharge) will alternate between good flow and poor, making your crew wonder what the heck your doing out there.

    The proper way of setting the pump is:

    Use the throttle to build pump pressure for the discharge that requires the highest pressure. This discharge should be fully open and not gated. No higher pressure is required.

    Any other discharges needed that have lower pressures should be gated to the their proper pressure.

    Once established flows are at the correct pressure, set the releif valve by lowering the set point until the releif valve opens (the light comes on). I do this by lowering the set point 1/4 turn, wait a couple seconds, then repeat until the releif opens. TPM has an indicator that shows you roughly where the set point is so you know when your getting close, but it's not precise. Once the light comes on back it off until the light goes out then back off another 1/2 turn. The releif valve is now set to gaurd against high pressure such as nozzles closing on discharges moving high flows, apparatus shutting down flows on the same water line as yours, or a supply pumper giving you additional pressure.

    Handlines will always have that initial recoil when the nozzle is opened. Those who do it quickly will soon learn not to. No releif valve system or set point will stop it. It's just simple physics that the line is going from zero nozzle reaction to full nozzle reaction. How fast it does it depends on how fast the nozzle is opened.

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