Positioners offer cost-effective process control

Edited by the Engineeringtalk editorial team Sep 9, 2004

A new range of modular process valve positioner units provides a cost effective, space-saving and flexible method of achieving precise proportional control of liquids and gases.

A new range of modular positioner units for the E290 and E390 ranges of process valves provides users in a wide range of industries - process, food, pharmaceutical, automotive, water treatment and medical - with a cost effective, space-saving and flexible method of achieving precise proportional control of liquids and gases.

The introduction of the compact analogue 605 Series and the digital Posimatic 606 Series positioners extends the application range of the well proven E290 and E390 valves beyond sterilising, fluid mixing, dosing, diverting, separating and recycling tasks, providing greater functionality to perform precise proportional regulation where the flow of a liquid or gas needs to be controlled.

Typical applications that fall into these categories include: regulation of temperature systems (textile, laundry, sterilizers, exchangers etc); mixing product processes (food industry, chemical industry, pharmaceutical industry etc); and measuring systems (tank filling etc).

The most compact of the positioners - and probably the most compact of such positioners on the market - is the Series 605 analogue unit.

The Series 605 is a low cost positioner that mounts directly onto E290/390 valves.

It has been designed mainly for use with actuators that do not require significant airflow.

For greater levels of accuracy, the Series 605 operates in closed loop mode, comparing the stroke signal to a set point signal from a potentiometer.

This simple but effective method of setting enables changes to process variables to be made by accredited personnel easily and quickly, actually at the process.

Alternatively, the setpoint (0-10V, 0-20mA or 4-20mA) can be supplied remotely and automatically from the analogue output card of a suitable PLC.

The Posimatic Series 606 is the larger unit of the two positioners and offers users the enhanced benefits of digital functionality.

The unit provides a range of programmable flow control parameters that can be entered via an LCD screen and four data entry keys, all of which are environmentally protected.

The Series 606 operates in the same way as its smaller sister unit, (i.e in closed loop mode) but, with a flow rate 5 to 10 times higher, is designed for use in larger valve systems where both single and (third-party-supplied) double acting actuators are employed.

At the heart of the Series 606 is a linear variable displacement transducer, which provides accurate feedback to ensure that the valve always remains on setting - even after occurrences of power failure.

In these instances a memory function returns the valve to its prefailure setting as soon as power is restored.

In addition, a failsafe safety feature ensures that the valves always "fail open".

To provide the maximum degree of application flexibility, the Series 605 and Series 606 positioners are designed for use on a range of E290/390 bodies manufactured from 316L stainless steel, bronze and cast iron.

This enables users to employ the combination on the widest range of fluids, including water, air, neutral gas, oil, superheated water and steam, at temperatures up to 180C.