Positioners

In this case we are talking about a positioner that converts an electric signal (in our case we most commonly use 4 to 20mA) into a pneumatic position on the actuator. This will then in turn move the valve to that position that the actuator is in (the valve and actuator are joined so the valve position will mirror that of the actuator). If you think of a normal 90 degree turn valve when it operates it is usually either fully open or fully closed (the actuator will do a full cycle). By utilising a positioner it will allow the user to effectively choose any position between open or close for the valve.

This really depends upon the type of positioner (eg. digital or analogue) however they all aim to achieve the same objective and that is to move the pneumatic actuator to a desired position. For instance in the analogue positioner it will use a balancing diaphragm which acts as a medium between the air pressure supplied and exhausted from the cylinder. This will always slightly bleed air. This is compared to a digital positioner which will use a small poppet valve to supply and exhaust air either side of the pistons until the position is reached. It will then seal off completely. Both units (our units at least but not all positioners) will provide a 4 to 20mA output as well as input.

This depends upon the type of positioner. Some have a minimum air volume they need so they will not work correctly on very small pneumatic actuators. Most will give a minimum cubic volume needed. It is important to check this as well as they type of actuator they are designed to work with; for instance double acting or spring return.

Like any instrumentation this depends upon the environment and cycle rate that it operates under. As they are a precision instrument they do require instrument grade air (filtered and dried air) to function properly over a long period of time. 

The installation is quite straight forward however it is the setting and commissioning which is the more technical part. This is because the span will need to be set with the unit (fully open and fully closed need to be calibrated) to let the unit function properly.

Positioners are usually used on applications where flow needs to be regulated. This for instance is common on V port ball valves or even some butterfly valves (the degree of flow control will depend alot upon the type of valve so make sure you investigate this first). They can be mated on top of both double acting and spring return actuators (check with the type of positioner first).

This depends upon where you are based and the freight method chosen. If the express freight option is selected it is usually next day delivery to metropolitan areas in Australia for under 5kg. If free freight has been selected it will go by road freight which can be anywhere from 1 to 10 days depending upon your location. It usually averages 3 days.

All of our products come standard with a 12 month warranty. The good news is we have very strict quality controls and all positioners leave our warehouse tested (full material and testing certificates to API598 are available) and inspected so there are rarely any issues.