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Thread: floating valve

  1. #1
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    floating valve

    I have a tank and I want to include a floating valve

    Without any valve the connecting pipe has a flow about 1000 cmd and a headloss about 2 m

    The minimum tank level is 1m, and the maximum tank level is 6m

    I set up the floating valve by:
    Ciontrol ID= the ID of the tank
    Upper level = 6m
    Lower level = 1m
    Curve:
    200 cmd = 0.2 m
    300 cmd = 0.3 m
    400 cmd = 0.5 m (Actually I tried different curves)

    When I include the floating valve I get 0 flow.

    What can be the problem?

  2. #2
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    Innovyze Employee



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    Vladimir,

    Make sure when using a float valve that the upper level is less than the tank Max level and that the lower level is above the tank min level. If you have the valve initially off since the float valve controls are off when level > Upper level and turn on when tank level is < lower level, the valve will not work properly if you use the max and min tank levels as it can never get below or above those levels.

    If you adjust your lower level to 1.2 M and make sure the Upper level is < the max level it should work as expected.

    Patrick Moore

  3. #3
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    Thank you very much
    One more question.
    Are there any guidances for the float valve flow vs headloss curve? or each brand provides its own curves?

  4. #4
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    Vladimir,

    You really need to know the specifics for what specific valve is there as there is no "one curve" that is likely to fit. However as it is relevant to the discussion please see the paragraph below on suggestions on how to determine the best way to model an altitude valve in your model.

    The Float valve is essentially a General Purpose Valve with controls placed on one of the pipes to open or close on the upper and lower level. It does a lot of the programming for you though which can make it useful. However, it is not the only way to model an altitude valve. Determining which method to use usually depends on how the "real world" valve works. Most Altitude valves are either controlling flow (i.e. can be modeled as a FCV) or using some combination of a pressure sustaining feature to make sure the "filling" of the tank does not cause low pressures in the system. One of the best ways to determine what your valve does is to 1) talk to the operations and utility staff to get as much information on how the valve works and 2) get SCADA data to see how the tank fills. If the fill rate is fairly constant using a FCV in the model is usually close enough, but the important thing is to know how it works. If the tank being filled is a "ground storage" type tank there will be a lot of head to burn in the valve in order to slow down the fill, but if the tank is "floating" on the system HGL then usually there is very little headloss needed by the valve. Knowing how much headloss is occurring when the valve is operating is helpful no matter what type of method you use, but is essential when using a float valve as the headloss vs flow curve will control the rate of fill to the tank. If you set it too low, the valve will fill too quickly, and if you set it too high the tank will fill too slowly.

    But if you have SCADA you can at least verify if your modeling method (Float Valve, FCV with Controls, PSV with controls, or other method) is matching the real world operation close enough that your model satisfies your calibration criteria. The good news for you is that even if you can't find a true manufacturers curve you can estimate one and adjust it as needed if you have real world data to compare it to. This is always the ideal way to check things in a model if you can get it. But I would start with the valve manufacturer web page. Most have some type of headloss vs flow curve or pressure drop vs flow curve you can use to develop the model "headloss vs. flow" curve needed by a float valve.

    Do what works best for you and that you feel as the engineer is most reasonable. For what it's worth, I mostly used FCV's over the years and found these generally fit the data reasonably well, but check it and use what makes the most sense to you. You have lot's of potential options that all can work well if set up properly.

    Good luck!

    Patrick Moore

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