Cla-Val X133 User Manual

Flow Measuring System

100

100

90
80

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50
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30
20

20

10

0

0

Percent Wide Open Cv

Position (%)

Q = C

v DP / SG

To measure flow rate, the flow curve, once downloaded in
the RTU containing custom curve capabilities or directly
into the SCADA software, accepts valve position from the
position transmitter, which determines the valve Cv. The
flow rate is then calculated using the formula:

Where:
Q = flow (gpm)
DP = differential pressure (psi)
SG = specific gravity of fluid (water = 1.0)

The Cv is acquired from the valve curve provided on the
diskette. The Cv is given in tabular format from 1 to 100%
valve position in increments of 1% and in graphical format.
The following is a typical curve. In the example shown at
43% open the valve has a Cv, which is 37% of the maximum.

MODEL

X133

• Accurately Measures Flow Rate

• Reduces System Cost -

No External Meter Required

• Ideal for New Installations and

Retrofitting Existing Valves

• Completely Self-Contained -

Requiring Only Transmitter Loop Power

• Simple Information Integration into

RTU / PLC or SCADA software

The X-133 Flow Measuring System provides an econom­ical and precise method of getting flow rates from control
valves at field sites via an RTU to the SCADA control center.

It is a completely self contained system that, when factory
installed on new Cla-Val hydraulic control valves or field
installed as a kit on existing valves, accurately measures
flow rate. It can be used on globe pattern valves from
three through twenty-four inch size and is typically used
on pressure reducing, back pressure, flow limiting, pump
control and level control valves. *

The Flow Measuring System consists of a position transmitter,
differential or inlet & outlet pressure transducers and a
diskette containing the appropriate flow curve information
for a particular valve size and configuration.

The Flow Measuring System uses certified flow curves
that have been derived from pressure and flow tests for
this particular flow application. They have been generated
using pressure transducers located at the valve inlet and
outlet bosses and on the pipe adjacent to the valve. This
provides the versatility to be used in virtually all applications
and operating conditions.

(*For applications requiring flow measurement and
remote set point control, see 133-01 Metering Valve
brochure.)

C

Using Cla-Val Valve Meter software

High Pressure

Constant
Downstream
Pressure

3" 90-01

8" 90-01

To SCADA

3" Flow Rate
8" Flow Rate

3" 8"

There are 4 ways to calculate flow from the software provid­ed. These methods provide a wide variety of choices for
integration into your system.

Custom Curve Linearization in RTU

Many RTUs and PLCs have built-in custom curve capabili­ty. The Cv values at each valve position can be entered
into the field equipment for direct flow calculation at the
valve site for monitoring and/or control purposes. Best accu­racy is attained using values at each 1 or 2 % valve open­ing. A lower number of values may be used with variable
spacing of data points.

Q = Cv * sqrt(DP)

Where
Q = flow (gpm)
Cv = returned Cv at the current valve position
DP = difference between upstream and downstream
pressure (psi)
An example of using the function for a 6 inch 100-01
valve with

Upstream pressure = 100 psi
Downstream pressure = 50 psi
Valve position = 30 %

Manual Calculations in Microsoft Excel (v. 97 or later)

This method is for applications where valve position and
differential pressure or upstream and downstream pressure
is monitored by the SCADA system. The current values are
manually entered in Excel and the flow is calculated and
displayed. The calculated flow can be copied into other
programs for monitoring purposes.

Remote Excel calculations from SCADA software

Some SCADA software programs include Visual Basic pro­gramming capability for sending and receiving values to and
from Excel. The calculations in the above example are then
automated using this "remote automation" process.
Programming of the SCADA software is necessary to
accomplish this. Contact Cla-Val
for details.

Direct Flow Calculations in
SCADA Software

This method does not require
Excel if the SCADA software
includes Visual Basic program­ming capability to call dll functions.
In this case the SCADA software
calls the function for any valve
position. The returned Cv value is
then used in the flow calculation
formula.

Q = cv_6(30) * sqrt(100-50) = 82.6 * sqrt (50) = 584 gpm

cv_6() is the function name used in Visual Basic

Accuracy and Calibration Recommendations

All sensors must be calibrated for best accuracy. In addi­tion the differential pressure transmitter must be set to
the correct range. Typical accuracy is within 2 to 3% actu­al flow. Accuracy may be less than this if:

• Valve position is less than 5%

• Sensors are not calibrated or zeroed

• Incorrect range of differential pressure transmitter

• Valve is corroded

• Inlet conditions are not full pipe flow

• Valve pressure differential less than one-half psid

E-X133 (R-3/2011)

LA-VAL

PO Box 1325 Newport Beach CA 92659-0325

Phone: [phone] Fax: [phone]

CLA-VAL CANADA CLA-VAL EUROPE

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Beamsville, Ontario
Canada L0R 1B4
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©COPYRIGHT CLA-VAL 2011 Printed in USA

Specifications subject to change without notice.

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