Float valves are one valve type available to use within the InfoWater, H2ONET or H2OMAP Water software that may not be as widely used as more common valve types such as a Pressure Reducing Valves (PRVs) or a Flow Control Valves (FCVs). Because Float Valves are not used as much, users may not be aware of the full functionality of this type of valve or how this type of valve works. This blog post will explain the functionality of the valve and provide a few suggestions on how users can make use of this valve within their models .
First let’s start with a description of the Float Valve from the software help file as this gives a good explanation of what these valves represent:
Float Valves: – Many storage tanks and reservoirs are fitted with float valves (e.g., ball float valves) on the inlet pipe to control rate of flow and prevent overflow. These valves gradually close (increase the resistance of the inlet pipe) as the water level in the controlling tank rises. The headloss across the valve is modeled (via a curve) based on any user specified pairs of headloss vs. flow points. The valve is active if the water level in the controlling tank is below the lower control level or the water level is between the lower and upper levels after the valve opening. Likewise, the valve is closed if the water level in the controlling tank is at or above the upper control level or the water level is between the lower and upper after the valve closes.
Specify the Valve Type as Float Valve in the Type field of the Modeling Data section of the Model Explorer – Attribute Tab.
- Diameter – Diameter of valve, in. (mm)
- Curve – Select the curve ID that represents the Float Valve headloss vs. flow.
- PID – The tank whose levels dictate the behavior of the Float Valve.
- LCL – The low “turn-on” level of the tank.
- UCL – The high “turn-off” level of the tank.
Note: For float valve’s please do not enter any data to the elevation, setting and minor loss fields.
The following is also a description of the help file section for Headloss vs. Flow curves that are used by Float Valves.
Headloss vs. Flow (Control Valves – General Purpose, Float)
- Used for General Purpose Valves and Float Valves, the curve consists of a collection of points defining the headloss across the valve (Y-axis) and flow rate in flow units (X-axis). A sample table and curve are provided below:
Using a Float Valve as an Altitude Valve:
The most common use for a Float valve is to use it to represent an altitude valve within the model software. The advantage of using the built in Float valve is that it simplifies the use of a General Purpose Valve (GPV) as an altitude valve. GPVs used in the model can easily be closed by a control or initial status statement, but due to the nature of how valves require a “setting” to be made active and that GPV’s do not get assigned a setting, the modeler generally will put a open/close control on one of the pipes connected to the valve rather than on the valve itself to make it work properly. With a Float Valve, all of this is done internally and all the user has to do is assign the upper and lower tank limits and the Headloss vs. Flow curve for the valve. The software then will allow flow through the valve when the tank level is falls below the lower “on” setting until the tank reaches the upper or “off” setting of the tank. Flow through the valve is controlled via the specified Headloss vs. Flow curve used. This has the advantage that the modeler does not have to write any control statements for the valve or pipes to make the valve work.
This additional model valve type gives the modeler an additional way to model an altitude valve within the software besides using a Pressure Sustaining Valve or Flow Control Valve that may be a better match to actual operation if the Headloss vs. Flow characteristics of the valve can be identified. Many valve manufacturers publish Pressure drop vs. flow curves for their control valves which can be used to create the Headloss (in feet) vs. flow curves used in the model by simply converting the pressure drop into the appropriate units for Headloss for your model.
Developing a Headloss vs. Flow curve:
Example ClaVal Control valve technical Specification sheet for a model 100-20 valve (see http://www.mmcontrol.com/Claval/PDFs/124-01-TM.pdf ) published this curve for the typical ClaVal Hydrol Control Valve used by many utilities.
The highlighted curve for a 3 inch valve shows the headloss vs. flow would vary from about 1 psi (or 2.31 ft.) at 62 gpm up to 100 psi (or 231 ft.) at around 525 gpm of flow. This curve would be used as the basis for the Headloss vs. Flow curve used in the model.
Example Float Valve Results:
Here is a quick example of a float valve setup within InfoWater. The valve is used to feed Tank T5000 which supplies all the demand downstream of the tank exclusively. The valve is set to open at 10 ft and close at 22 ft and uses a curve based on a 3 inch ClaVal Float valve. The flow through the valve varies slightly both times when it operates as it is dependent on the available upstream head when it opens and it is slightly different each time it opens.
This image shows the layout of the valve and tank as well as the valve parameters and the output flow of the valve and the Tank Level. The tank begins to fill at 10 ft. and stops filling at 22 ft. as specified. The flow through the valve is determined by the head difference across the valve.
Summary of key model settings for a Float Valve:
To summarize, a float valve can be another way for users to model an altitude valves within the model. To use a float valve, the modeler needs to identify 5 key pieces of information for a Float Valve. Note: There is no valve setting or Minor Loss for a float valve). Here are the key information needed:
- Diameter for the valve
- Curve: You must specify the Headloss vs. Flow curve of the valve
- Control ID: The Tank ID of what tank the valve is filling
- Upper Level – The High water level in the Tank (The “off” level for the valve)
- Lower Level – The low water level in the Tank (The “on” level for the valve)