Sterling 882.00268.00 Functional Description, Models Covered in This Manual, General Description

Chapter 3: Functional Description

3-1 Models Covered in This Manual

This manual offers a general reference for the installation and operation of the Remote Proportioning Valve (RPV) with control configurations A, B, C, and D.

Material inlets and outlet sizes range from 1.5” to 2.5”.

3-2 General Description

The Remote Proportioning Valve is an efficient and economical means to proportion two different free-flowing granulated materials in a material conveying system. The most common application is mixing virgin and regrind materials in a plastic processing operation.

The design of the Remote Proportioning Valve lends itself to use in both central and machine-side conveying systems. The RPV also can turn a standard hopper loader or anyone’s vacuum hopper into a proportioning unit.

Mounting of a Remote Proportioning Valve can be at a convenient location away from the hopper or loader or on the material inlet tube of a vacuum hopper or hopper loader.

Two urethane plungers operated by compressed air are positioned in a central vacuum chamber to provide airflow control between two separate material conveying lines.

The operator controls the positioning of the plungers and dictates the percentage of the two materials to be delivered through a single hose to a material receiver.

Plunger operation can be governed by a variety of control alternatives, depending on the installation.

3-3 How it Works

The Remote Proportioning Valve proportions two free-flowing dry materials into a single vacuum conveyed stream. It can be mounted some distance from or directly on the vacuum receiver. Two material inlets lead into a central vacuum manifold. Compressed air operated plunger valves switch the vacuum supplied by a hopper loader or central system between two material pick-up devices.

Switching between the inlets at timed intervals creates a known mixture of virgin and regrind materials. The mixture can have a minimum accuracy of 5%, depending on how controlled the set-up of the Remote Proportioning Valve is.

The controls are set up on a timing cycle. The Material A plunger is opened to the vacuum stream for an adjustable period of time, and then closes. The Material B plunger opens immediately and conveys the second material for an adjustable period of time. By adjusting these intervals, the proportioning is controlled.

Under ideal conditions with identical total resistance in both material hoses and the Material A and B timers set at 10 and 5 seconds respectively, a 2-to-1 mixture is delivered to the vacuum receiver.

Under actual conditions, total resistances will not be identical. Two materials with different conveying characteristics, such as regrind and virgin, conveyed from differing pickup devices over differing distances, are not be conveyed at the same rate.

To ensure a mixture of known proportions, a weight test as described in Section 5-4 on page 24 should be performed for each application.

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