Control valves

Pressure reducing/surplussing valves

Pressure/temperature limits

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Pressure bar g

The product must not be used in this region.

The product should not be used in this region or beyond

its operating range as damage to the internals may occur.

Body design conditions

Inlet

PN10

Outlet see 'Pressure setting range' below

Sizing

The required Kv can be calculated from the following formulae:

where:

= Steam mass flow (kg/h)

= Liquid volume flow (m

3

/h)

= Gas flow at standard conditions: 0°C @ 1.013 bar a (m

3

/h)

Steam

saturation

curve

P

1

=

P

2

=

c =

S =

Upstream pressure (bar absolute)

Downstream pressure (bar absolute)

P

1

- P

2

(pressure drop factor)

P

1

Specific gravity

Absolute average gas temperature (Kelvin = °C + 273)

T =

Steam Critical pressure drop:

P

2

£ 0.58 P

1

Maximum design pressure

Maximum design temperature

Minimum design temperature

Maximum operating temperature

Maximum operating pressure (inlet)

Minimum operating temperature

Designed for a maximum cold hydraulic test pressure of 15.2 bar g

DN15 - DN50

Non-critical pressure drop: P

2

3 0.58 P

1

Liquid

9.5 bar @ 50°C

300°C @ 5.8 bar

-10°C

180°C

8 bar g

-10°C

Gas

Pressure setting range

Size

Inlet / outlet rating

Spring range

PN10 / PN2.5

PN10 / PN6

0.3 - 1.1 bar g

0.8 - 2.5 bar g

PN10 / PN10

1.0 - 5.0 bar g

Maximum permitted outlet pressure = 1.5 times set pressure

Kv values

Calculating the Kv and selecting a suitable valve

To maximise the control accuracy (especially for large load

variations) use the Kv values given at 20% offset. For safety valve

sizing use the maximum Kv values.

Using your maximum flowrate and smallest differential pressure

(P – P ), calculate the required Kv from one of the above formulae.

Valve size

Kv at 20% offset

Maximum Kv

For conversion:

DN15

2.0

2.6

DN20 DN25

3.0

3.5

3.9

4.6

DN32 DN40

DN50

Select a valve Kv that is 30% greater than the calculated Kv. The

optimum working range of the selected valve should ideally be

within the range of 10 to 70% of its Kv.

1

2

4.0

4.5

5.2

Recommended fluid velocities

Saturated

Superheated

Gas

up to 2 bar g

above 2 bar g

Liquids

For full details see the Installation and Maintenance Instructions

(IM-P186-09) supplied with the product.

The SRV66 should always be fitted with the inlet vertical and the

spring housing directly above the valve.

1 off Spirax Sarco DN25 SRV66 direct acting sanitary pressure

reducing valve having a pressure range of 1 – 5 bar g a

PN10 / PN6 rating, FPM diaphragm and ISO 2852 sanitary clamp

compatible connections.

The spare parts available are detailed below. No other parts are

supplied as spares.

Available spares

Diaphragm and 'O' ring

10, 11

Always order spares by using the description given in the column

headed 'Available spares' and state the size, model and pressure

range.

Example: 1 - Diaphragm and 'O' ring for a Spirax Sarco DN25

SRV66 direct acting pressure reducing valve having a pressure

range of 1 - 5 bar, a PN10/PN6 rating and an FPM diaphragm.

5.2

5.9

Cv (US) = Kv x 1.156

Steam

6.8

Cv (UK) = Kv x 0.93

10 to 40 m/s

15 to 60 m/s

2 to 10 m/s

5 to 40 m/s

1 to 5 m/s

Dimensions/weights (approximate) in mm and kg

B

C

A

A

A

B

90

138

120

138

120

138

120

200

120

200

120

200

Installation note:

Safety information, installation and maintenance

How to order example

Spare parts

Pressure range

Size

DN15 - DN25

DN32 - DN40

DN50

DN15 - DN25

DN32 - DN40

DN50

C Weight

200

2.0

200

2.5

200

3.0

200

3.0

200

3.5

200

4.0

1.0 to 5.0 bar

How to order spares

and

0.8 to 2.5 bar

0.3 to 1.1 bar

TI-P186-08 CH Issue 11

SRV66 Sanitary Pressure Reducing Valve

4.6.90

T

e

m

p

e

r

a

t

u

r

e

°

C