Note: These anciliaries are not

delivered with VAD and should be

purchased separately

PN9400

series

actuator

VAD in

conjunction

with a PN9400

series actuator

VAD b :

70 mm travel for

applications that

require a higher

Kv of between:

Kv1.8toKv4.0

Water

VAD in

conjunction

with a PN9000

series actuator

VAD a :

30 mm travel Kv

0.1 to Kv 1.4 For

applications that

require a higher

Kv use a VAD b

6 m

Steam

flow

A typical installation illustrating a VAD variable area desuperheater in conjunction with a PN9000 series actuator

1st

Stop valve

VAD

VAD

Temperature sensor

Strainer

VAD

+

PN9000 series actuator

Position of nozzles

Check

valve

2nd

Stop valve

PN9000 series actuator

Control valves

Local regulations may restrict the use of this product to below the conditions quoted.

In the interests of development and improvement of the product, we reserve the right to change the specification without notice.

Desuperheaters

© Copyright 2016

VAD

Variable Area Desuperheaters

Desuperheater overview

Steam used in process plants can be superheated, that is, heated to a temperature above

saturation. The excess of temperature above its saturation is called 'superheat'.

Desuperheated steam is more efficient in the transfer of thermal energy, consequently

desuperheaters are used to bring the outlet steam temperature closer to that of saturation

for the steam pressure.

Desuperheaters reduce the temperature of superheated process steam by introducing

finely atomised cooling water droplets into the steam flow. As the droplets evaporate,

sensible heat from the superheated steam is converted into latent heat of vaporisation.

As standard the VAD is supplied with an actuator. The following optional extras can

be supplied if requested when placing an order: Positioner, Regulator and Limit switch.

A typical desuperheater installation is shown below:

1st stop valve

Strainer

Check valve

2nd stop valve

Required to isolate the system from inlet water.

Required with 100 mesh screen to maintain the water supply in a

condition that wont block the desuperheater nozzles.

Required to prevent steam from flowing back into the water inlet -

The prefered selection would be an LCV lift check valve as it will give

optimum performance in this application.

Required to isolate the system for maintenance.

4.8.24

TI-P451-01

CH Issue 3

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