100mm bronze electric valve with standard actuator
50mm electric valve with low temperature atuator
250mm bronze valve with shock-resistant actuator

Electric Valves

The Walton electrically controlled system comprises a 3-way valve with electric actuator, an electronic controller and a platinum resistance thermometer (PRT).

The controller periodically samples the temperature of the coolant system via the PRT and compares this with the predetermined set temperature. If necessary it sends a signal to the valve’s actuator to adjust the position of the rotor within the valve. This varies the proportion of coolant passing through the system’s cooler to bring the system temperature in line with the set temperature.

The principle advantages of electric over self-acting valves are:

  • Increased power and speed of operation
  • The ability to sense the temperature remote from the valve which can provide more accurate temperature control
  • In sea water circuits the separation of the operating mechanism from the sea water minimises any corrosion risk to the mechanism

Description

The valve body has three ports leading into flanged branches. Fluid flow through the valve is controlled by a rotor, the end shutters of which travel over two of the ports to direct flow to either the cooler or bypass branches, or to proportion the flow between the two. The rotor is driven by an electric actuator mounted on the valve; this is activated by a signal from the Walton electronic controller.

 

The 3-way valve body is of the standard Walton type and interchangeable with the bodies used for the range of self-acting valves. This means that it is a simple matter to convert a valve from self-acting or pneumatic to electric operation, and this can usually be achieved without removing the valve body from the system or modifying the pipework.

The electric actuator is mounted on the valve and drives its shaft and thus rotates the rotor in response to control signals from the electronic controller.

 

Limit switches are set to prevent the actuator from attempting to close valve’s third (inlet or outlet) port. These are backed up by mechanical stops within the actuator, and also a stop cast on the valve's front cover which provides ultimate protection against the inlet port from being covered by the rotor.

 

In the event of failure of the electrical supply to the actuator, the position of the valve’s rotor may be controlled by a hand-wheel on the actuator which provides a manual over-ride. An optional fail-safe battery back-up is available.

 

An anti-condensation heater is incorporated into the actuator.

 

Actuator options include:

  • Potentiometer Unit (1k-10k)
  • Proportional control unit (In/Out: 0-10VDC, 4-20mA)
  • Current position transmitter (output 4-20mA)
  • Explosion proof enclosure ATEX II 2G Eexd IIB T4
  • Fire-proof housing (250°C/150min)
  • Fail-safe battery back-up

The actuator, complete with its mounting, may be removed from the valve without breaking into the pressure tightness of the system.  Alternatively, the actuator, its mounting and the valve's whole internal assembly can be removed without disturbing the valve's pipe connections.

 

The actuator requires a power supply of either 220/240V or 110/120V AC 50/60Hz 1 phase.

The function of the Walton electronic controller is to monitor the difference between the system's actual temperature and the desired operating temperature. When necessary, the controller sends instructions to the valve's actuator to adjust the flow of coolant so as to bring the two into line as quickly as possible.

 

The controller requires an input signal of the system's actual temperature. This is usually generated by a platinum resistance thermometer (PRT) which is installed in the system at the point where the temperature is to be sensed. The PRT converts the temperature into an electrical signal that the controller can recognise. Walton can supply PRTs suitable for most applications. Alternatively, a controller is available which responds to a 4-20mA signal; this can be generated by a wide range of devices.

 

The Walton electronic controller is available in the following configurations: 

  • Panel mounted This is installed in a control room's main console such that the controller's fascia is incorporated into a larger control system. The electronic parts of the controller are suspended beneath the control panel.
  • Totally enclosed In this design the controller is contained within an aluminium enclosure sealed to IP65. The fascia is accessed by removing the enclosure's cover. This arrangement is suitable for 'dirty' environments such as machinery spaces. Special enclosures are available for protection against sea water and other hostile environments.

The controller's fascia incorporates a facility to set the desired system operating temperature, as well as integral, proportional band and dead zone controls.

 

The controller requires a power supply of either 220/240V or 110/120V AC 50/60Hz 1 phase.

The controller requires an input signal of the system's actual temperature. This is usually generated by a platinum resistance thermometer (PRT) which is installed in the system at the point where control of the fluid temperature is required.

 

The PRT converts the temperature into an electrical signal that the controller can recognise. Walton can supply PRTs suitable for most applications. Alternatively, a controller is available which responds to a 4-20mA signal; this can be generated by a wide range of devices.

Electronic Controller

Sizes

Walton rotary self-acting valve bore sizes range from 25mm (1.00″) to 300mm (12.00″) diameter.

The maximum flow rates that can be accommodated in each valve size are shown here.

Maximum flow rates in m3/hour

Valve Bore Fresh Water Sea Water Lub. Oil

25mm

10

10

10

40mm

22

16

16

50mm

35

26

26

65mm

60

45

45

80mm

90

67

67

100mm

100

75

75

125mm

160

120

120

150mm

180

180

180

200mm

400

290

290

250mm

600

450

450

300mm

700

520

520

Voltages

The system can be supplied to operate at 220/240V or 110/120V AC 50/60Hz 1 phase, or alternatively 12-48V DC.

Available voltages

AC

110/117V

220/240V

DC

12V

24V

48V

Port configuration

Self acting rotary valves can be supplied in any of six possible port configurations (called handings) to suit your preferred pipework layout. This provides great flexibility – the valve can be supplied to suit the pipework, rather than the pipework having to be adapted to suit the valve.

The six handings are shown in the diagrams on the right. The arrow on each diagram shows the direction of rotation of the valve’s rotor to open the Cooler port when the system heats up.

LI Handing
LB Handing
LC Handing
RI Handing
RB Handing
RC Handing

System design

Mixing or diverting?

Walton valves may be installed to either mix fluids from two inlets and discharge through a single outlet (mixing), or to divide the flow from one inlet into two outlets (diverting).

 

When operating in mixing mode, the temperature control valve is fitted downstream of the cooler. The hot (bypass) and cold (cooler) fluid streams enter two valve ports in proportions determined by the position of the valve's rotor, thereby maintaining the temperature of the fluid leaving the third port within the operating range of the thermostatic element.

 

When operating as a diverter, the valve is fitted upstream of the cooler. The inlet from the heat source enters one port and is divided into two outlet streams to the cooler and bypass in proportions determined by the position of the valve's rotor. This maintains the temperature of the fluid returning to the heat source within the operating range of the thermostatic element.

 

In most applications it is recommended that the temperature control valve is fitted downstream of the cooler to operate as a mixing valve.

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

The operation of the system requires that the Walton controller periodically samples and compares the temperature in the coolant system with the predetermined set temperature and if necessary adjust the position of the rotor within the valve by means of an electrically driven actuator.

 

The time interval between samples is variable, but to achieve stable control within the system should be as long as possible. It should never be less than the system interval which is the time taken for ‘a given volume of fluid’ to complete the circuit of the system.

The resistance thermometer generating the operating signal is installed in the system at the point where control of the fluid temperature is required.

The system pipework should be as simple and compact as possible. The cooler by-pass pipe should be designed for minimal pressure loss. The pressure difference across the 3-way valve at full flow through either the cooler or cooler bypass should not exceed 0.8 bars.

 

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.

 

For marine applications, temperature variations, pipe expansion and movement of the ship's hull should be taken into account when designing the piping runs and supports.

Mixing valve
(LI / RI Handing example shown)
Diverting valve
(LI / RI Handing example shown)

We are always willing to create a customised solution for your application if none of our standard products are suitable

Our advanced computer aided design software and the flexible nature of the Walton valve design mean that this can often be a cost-effective approach.

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