Dwyer PDWS User Manual

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iNStallatiON

StRaiGht PiPe RecOMMeNDatiONS
(X = diameter)

10X

20X

30X

50X

Reduced Pipe

two elbows in Plane

two elbows, Out Of Plane

expanded Pipe

Swirling Flow

Propeller Meter

Partially Open

butterfly Valve

Spiral Flow

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PDWS

PVc Fittings.

A PVC fitting is usually installed by solvent

welding. PVC tees are supplied with some upstream straight

pipe, less than the recommended straight pipe require-

ments. It is not advisable to connect directly to the end of

these fittings with a flow disturbing device (valve, elbow), but

rather add straight pipe to the end of these fittings to meet

the straight pipe requirements for your application.

Meter installation.

After the meter fitting is installed in the

pipeline, the meter can be installed in the fitting. Press the

meter into the fitting as far as it will go. Retain the meter in

place by inserting the u-pin. The pin can be installed from

either side. It may be necessary to rotate the probe back

and forth slightly to start the pin into the slots on the probe.

Slide the pin in as far as it will go.

insertion Depth.

The PDWS Series are fixed-depth meters

that must be used with matched fittings appropriate to the

application and pipe size. This ensures that the flow sensor

is installed at the correct insertion depth to measure the av-

erage flow velocity of the stream.

Straight Pipe.

Straight pipe of at least 10 diameters up-

stream and five diameters downstream of the meter is

strongly recommended for proper accuracy. This is neces-

sary because the shape of the velocity profile changes as the

rate increases around an elbow; placing the meter too near

the elbow causes a distorted reading. Additional straight run

may be needed under specific adverse circumstances (see

next page).

If you can’t provide enough straight run to smooth out the

velocity profile, some decrease in accuracy may result. This

does not mean the meter’s reading is meaningless, however.

In some applications (e.g., control system, valve operation)

a repeatable reading may be more important than a highly

accurate one.

Fitting installation.

Stainless steel and brass fittings have

female pipe threads, requiring the appropriate male thread-

ed fittings. Saddle fittings require a hole to be cut in the

pipe (recommended hole size is 1-3/4”). Before cutting into

the pipe, observe the drawing below to choose your meter

orientation.

iNStallatiON

caution:

Never remove the u-clip retainer when

the pipe is under pressure. Always remove

pressure from the pipe before you attempt to

remove the meter. Removal under pressure

may result in damage or serious injury.

Diameter Minimum

(See Below)

DiStORteD FlOWS

Distorted

Flow Profile

Faster Flow
Causes Meter
To Read High

FLOW

10X

Diameter Minimum

(See Below)

BEST

Okay, if no air in pipe

Okay, if no sediment in pipe.

POSitiONiNG the MeteR