PINCH VALVESOperation, applications and selection

01 / INTRODUCTION

Valves for demanding media

A pinch valve shuts off or throttles flow by mechanically compressing a flexible rubber sleeve. The medium is in contact only with the working surface of the sleeve, while the valve body and pinching mechanism remain outside the flow channel.

When fully opened, a correctly selected sleeve returns to its full cross-section. There is no disc, wedge or other metal shut-off element in the pipeline bore. The straight flow path is beneficial for slurries, pulps, suspensions, heavily contaminated liquids and bulk solids.

This design is not a universal solution, however. Service life and correct operation depend on selection of the complete assembly: valve geometry, sleeve material and reinforcement, connections, actuator and control method.

Selection must be based on the actual process conditions, not on nominal diameter DN alone.

Scope

• operating principle and the difference between shut-off and flow control;
• applications, sleeve construction and available Metal-Gum executions;
• data required for selection and errors that lead to premature wear.

02 / OPERATING PRINCIPLE

From full bore to tight shut-off

In the open position, the flexible sleeve forms a full-bore flow channel. During closing, the mechanism compresses the sleeve from the outside. Opposing walls gradually move towards each other and, once they meet, close the flow path.

Because the shut-off element is not located in the flow stream, solid particles do not become trapped between metal sealing surfaces. Wear is concentrated on the replaceable sleeve, whose execution can be matched to the medium and process parameters.

Shut-off versus flow control

03 / APPLICATIONS

Media where a straight flow path matters

The full-bore design reduces locations where medium can accumulate inside the valve itself. It does not, however, eliminate the causes of sedimentation elsewhere in the installation, such as insufficient flow velocity or unfavourable pipeline geometry.

04 / CONSTRUCTION

The rubber sleeve is the working element

The sleeve both carries the medium and closes the valve. Its material, geometry and reinforcement must be selected for the operating loads.

Metal-Gum uses ready-made rubber compounds, selects them for the operating conditions and manufactures sleeves and other rubber components from them.

When is replacing the sleeve enough?

If the body, pinching mechanism and actuator are serviceable, a worn sleeve can be replaced. Before ordering, confirm the valve model, dimensions, mounting method, material and operating parameters.

The cause of wear should also be established. Premature damage may result from an unsuitable compound, exceeding the pressure or vacuum limits, excessive medium velocity, an installation error or intensive control service.

05 / CONNECTIONS AND TESTING

Standard execution and special requirements

• Typical flange drilling: PN10 or PN16, in accordance with the documentation for the specific execution.
• PN25 requires a different connection execution or an appropriately engineered installation arrangement. The solution must be agreed before ordering.
• The required scope of acceptance testing, including tests according to EN 12266-1, must be specified in the enquiry and confirmed in the offer for the specific valve.

The PN designation of the connection does not replace information about the actual operating pressure, maximum differential pressure, temperature and any vacuum conditions.

06 / METAL-GUM OFFER

Series and execution variants

These ranges are a starting point. Availability of a specific configuration is confirmed against the current product data sheet and the process parameters.

07 / ACTUATION

Actuator selected for the valve function

08 / SELECTION

Data that should be included in the enquiry

1. Medium — name and composition, concentration, density, viscosity and chemical aggressiveness.
2. Solids — type, size, hardness, shape and proportion in the medium.
3. Pressure — operating and maximum pressure, differential pressure, pulsation and vacuum.
4. Temperature — operating, minimum and maximum temperature, including during cleaning or start-up.
5. Flow — flow rate, velocity and whether the duty is shut-off or control.
6. Installation — DN, drilling pattern, face-to-face length, orientation and service space.
7. Actuator — type, supply, actuation time, signals and safe state.
8. Operation — number of cycles, time spent in intermediate positions, ambient conditions and required acceptance procedures.

A well-prepared enquiry shortens the selection process and reduces the risk of premature sleeve wear.

09 / PRACTICE

Common mistakes

• selecting only by DN, without pressure, temperature and a description of the medium;
• selecting an elastomer from the general name of the medium without composition and concentration;
• omitting particle size, hardness or solids concentration;
• omitting vacuum or maximum differential pressure;
• ordering a valve for control duty as a standard shut-off valve;
• ordering a sleeve without confirming the model, geometry and mounting method;
• treating the PN flange drilling designation as the permissible operating pressure of the complete assembly.

10 / FAQ

Quick answers

Metal-Gum selects the complete configuration: valve series, sleeve made from the appropriate compound, reinforcement, connections and actuator.