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Direct operated valves

Direct operated valves

incorporate a temperature sensor inside the valve, and operate independently of external power supplies.

Electrically operated valves

Electrically operated valves

are powered by an external electric actuator, with control provided by a separate electronic control unit, and temperature sensing by resistance thermometer.

Pneumatically operated valves

Pneumatically operated valves

are powered by an external pneumatic actuator, with control provided by a pneumatic controller with external temperature sensing.

Gas operated valves

Gas operated valves

are designed to control refrigerant gas pressures – and hence the temperature of refrigerated or air-conditioned areas – in marine systems in which the condenser is cooled by sea water.

 

Valve Handings

Handing Li

Handing LI

HandingR i

Handing RI

Handing Lb

Handing LB

HandingRb

Handing RB

Handing Lc

Handing LC

Handing Rc

Handing RC

 

 

Gas Operated

The Walton gas operated control valve has been specifically designed for the control of refrigerant gas pressures - and hence the temperature of the air-conditioned areas - in marine air conditioning systems in which the condenser is cooled by sea water. The valve operates independently of any outside power source, and externally requires only a small bore pipe connection to the refrigerant sensor.

The valve can be supplied to any one of six possible handings to suit the piping arrangement. These are shown to the left, below.

Sizes range from 10mm bore to 250mm bore diameter. The flow rates that these valves can accommodate are shown here.Gas Operated Valve

Valve Description

The valve body is provided with 3 equi-spaced ports extending to flanged connections. A rotor operates over two of the ports to give flows varying from ‘full re-circulation/no overboard flow’ to ‘full overboard flow/no re-circulation’. The rotor is mounted upon a shaft extending through the front cover of the valve. This cover also carries the valve actuator on an integral bracket.

A lever secured to the shaft engages with a spherically ended drive pin. The drive pin is clamped into the control block and onto the control rod.

At one side of the bracket formed on the front cover is mounted a gas cylinder which contains a stainless steel edge welded bellows. The bellows with welded end fittings together with ‘O’ ring forms a 100% gas seal.

The whole internal assembly, actuator, etc. can be withdrawn by removing the front cover nuts and without disturbing the main pipe connections.

Valve Operation

In operation and before the refrigerant gas has reached its working temperature, the valve will re-circulate the full volume of sea water back to the pump suction. As the water temperature increases and the gas pressure rises into the control range, the gas load acting on the bellows will overcome the initial spring load and move the control rod which will turn the valve rotor through the ball and sleeve connection, opening the flow to overboard and reducing the amount of water being re-circulated. A further rise in gas pressure will increase the overboard flow and reduce the re-circulation until at some gas pressure within the overall control range, an equilibrium condition will be obtained with constant gas pressure and overboard discharge volume.

Any change of load on the machinery or sea water temperature will be compensated for by an adjustment in the volume discharged overboard, maintaining the gas pressure - and hence the air-conditioned areas - within the desired control range.

System design

General Arrangement

The valve is designed for installation in the sea water circuit of the refrigerant condenser downstream of the condenser, the piping arranged so that the valve can either discharge water overboard or re-circulate water to the pump suction or proportion the incoming flow of water to both the overboard and re-circulation branches in accordance with the gas pressure in the refrigerant condenser.

Attitude

To mitigate undue loading on the valve mechanism's main bearings, we would recommend that where possible the valve be installed with its actuator in the upright position.

Connections

The mounting of the valve should be such that it is not subject to excessive vibrations under running conditions. In positioning the valve, a clear space approximately equal to the valve body length is required to withdraw the rotor and in way of the actuator, spaces equal in length to the gas cylinder and the spring assembly are required for easy dismantling.

A degree of flexibility in at least one of the connecting pipes is desirable although, if care is taken on installation, not essential. Mounting of the valve should be such that it is not subjected to excessive loading or vibration under running conditions. Temperature variations, pipe expansion and movement of the ship's hull should be taken into account when designing the piping runs and supports.

Two tapped holes are provided in the end of the gas cylinder, one for connection to the refrigerant condenser and one spare for bleeding purposes and pressure gauge if required. The connection between the gas cylinder and the refrigerant condenser need be no greater than 1/8" (3mm) bore diameter

  

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