UPC variable example

A variable is used to combine values (from a range, table, logic operator, variable or constant value) to derive another value.

The following example shows a scenario for controlling a boosted flow into an area subject to low pressures within a gravity fed demand area. If the pressure at a sensor in the demand area falls below a given pressure, the booster pump will be switched ON to boost flow to the low pressure area . Under normal conditions, the booster pump will be switched OFF and the entire area will be gravity fed.

 

 

In this scenario, a variable is used to calculate a pressure offset at sensor Node A. The default status of the pump is OFF. If the pressure at Node A falls below 20m, the pump will be switched ON.

The scenario is defined by adding components to a pump regulator in the UPC window.

 

Component Parameters Effect

RANGE 1

Range type: Pressure

Location node: A

Minimum:
Maximum:

TRUE if pressure at Node A is between -/+ infinity

VARIABLE 1

Measurement: Pressure

Operator: Minus

Argument 1: RANGE 1

Argument 2: Constant (20)

Pressure at Node A - 20m

RANGE 2

Range Type: Variable

Location Definition: VARIABLE 1

Minimum:

Maximum: 0

TRUE if VARIABLE 1 is less than zero.

RULE 1

Condition: _default_

Type: OFF

Default status of pump is OFF

RULE 2

Condition: RANGE 2

Type: ON

Switch pump ON if RANGE 2 is TRUE

 

  1. Range 1: Defines Node A as the control point. ClosedShow image

  2. Variable 1: Calculates offset pressure at Node A. ClosedShow image

  3. Range 2: Defines the calculated offset pressure in Variable 1 as the control with a maximum value of 0. ClosedShow image

  4. Rule 1: Unless subsequent rules are TRUE, switch pump OFF. ClosedShow image

  5. Rule 2: If the pressure offset at Node A is less than 0 (pressure at Node A less than 20m) switch pump ON. ClosedShow image

 

This simple example could be modelled without the use of a variable, by using the actual pressure at Node A instead of an offset. For an example of how the use of variables can be extended, see UPC example (three point PRV).

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UPC example (three point PRV)

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