The little valve with the big difference 


Most pipeline systems require some form of check valve device to maintain flow in one direction to prevent either contamination of liquids already in the system or damage to the pipework and its ancillary components. Quite a simple function you might think! -bitter experience however tells us a different story .

What are the features that the piping engineer is looking for?

  • Tight shut off under minimum back pressure
  • Quick response to no-flow or reverse flow conditions.
  • Low resistance to forward flow
  • Lightweight construction.
  • Ease of installation with unskilled operators
  • No maintenance.

The NORVAL - Non Return Valve has all these features plus one or two less obvious benefits.

  • It is extremely simple.
  • It operates in any direction, vertically up or down, or horizontal.
  • High material specification.
  • Less noise due to slamming shut under reverse flow.
  • Can be incorporated in a variety of body configurations or simply built into original equipment as a cone and diaphragm assembly.

Method of Operation

Flow takes place in the direction of the arrows under forward and reverse flow.

A -Valve Open
C -Diaphragm
B -Valve Closed D -Cone

With flow in the forward direction the diaphragm deflects inwards (A) allowing .easy passage of the liquid with little pressure loss. When a no flow, or back pressure, condition occurs the diaphragm returns to its relaxed position (8) sealing off all flow in the reverse direction.

This action is unaffected by the orientation of the valve.

  Valve Specifications 

Type CD

This valve comprises an integral increased flange cone in stainless steel 316 type and is available in the size range 40 mm (1 1/2 in) to 200 mm (8 in) diameter for mounting between adjacent pipe flanges to BS 4504 NP 16 or equivalent. Cone and diaphragm assemblies are also available in nominal 25 mm (1 in) and 32 mm (1 1/4 in) diameters but are not normally suitable for bolting between standard flanges. Diaphragms to suit application.

Type CD/S

A screwed pattern valve incorporating the basic cone and diaphragm assembly with a specially reduced diameter flange in a two piece bronze body to SS 1400- LG2C (ASTM equivalent B 145-836). End connections screwed 15 mm (1/2 in) to 50mm(2in) BSP.

Type CD/F

A flanged check valve incorporating the basic cone and diaphragm assembly housed in a flanged cast iron body BS 1452 grade 17 (ASTM equivalent 48
Gr.35). Available in the size range 40 mm (1 Y2 in) to 200 mm (8in) diameter with flanges to BS 4504 NP
16 or equivalent. Fabricated steel bodies are available as an option. Diaphragms to suit application.

Frequency of Operation

When selecting NORVAL particular attention should be given to the period that the valve will remain in the open position without a flow reversal taking place. The elastic memory of the diaphragm is time dependant and if left
open for long periods may result in slow closure of the
valve under reverse flow with subsequent leakage.

The degree of diaphragm deformation is a function of the service, temperature and material. Unlike conventional valves, the more arduous and frequent the operating cycle the better NORVAL works.

Velocity Limitations

Liquids -
NORVAL valves are designed for maximum continuous liquid velocities of 3m/sec with intermittent peak velocities up to 3.6m/sec. Where velocity conditions exceed these maximums you are recommended to fit a larger valve.

Gas and Compressed Air -

Since NORVAL is essentially a liquid services valve you should consult our technical dept. before considering for gas and air app1ications.