Mixed double

Dual and angle sensor series monitor valve positions

Mixed double

Dual and angle sensors offer several benefits for position feedback with automated butterfly and ball valves. They do not require a separate housing and allow easy handling in compliance with Atex and SIL. Turck offers an extensive range of accessories to enable even specialised solutions to be implemented with standard sensors.

Position feedback signals, such as the open-closed signals from butterfly and ball valves or the valve position of three-way flaps, are extremely common in process engineering. The sensors required for this are generally installed in a plastic housing with a somewhat complex mechanical design. The huge diversity of the individual components puts up the price and usually means costly readjustment work in order to set the switch points. The Atex directive also stipulates that all the different components, such as the housing, sensors and microswitches including their associated wiring, must be tested separately. Testing in compliance with the SIL Directive IEC 61508 further increases the testing effort and the expense involved.

When combined with ingenious actuating elements, Turck’s dual sensors simplify considerably the detection of binary positions in the long term. These dual sensors come in a compact housing and offer an optimum range of connection options as well as being easy to install. The most important series in the dual sensor range is the DSC26 housing style for the food industry and the DSU35 series for the chemical, petrochemical and pharmaceutical industries.

Both ‘spring opening’ and ‘spring closing’ drives are used in installations, depending on the safety position. In this case, around ten percent of the drives are clockwise rotating with the ‘spring opening’ function. For these special cases, customers of other manufacturers either have to use different actuating elements (pucks) or assemble these elements manually. Both options have their disadvantages and often lead to unnecessary long downtimes when maintenance and servicing are due.

Turck has a solution for both requirements: the BTS-DSU35-EB1 actuating element can detect both rotation directions. It has two actuating pins, so that it can be used without any problem for both anticlockwise and clockwise rotating drives. It can also be read easily if it has to be mounted horizontally due to lack of space. The puck’s position indication is clearly visible from all sides and can be moved 90° without requiring any tools.

A second Turck actuating element provides a solution for another special case: applications sometimes necessitate NC monitoring. In such instances, it would also be possible to use sensors specifically designed with an NC output.

However, opting for Turck’s BTSDSU35-EU2 actuating element with an undampened end position is much easier. This inverts the detection of the end position and eliminates the need to change the sensor. This actuating element for undampened end positions can also be employed to change the LED function of Namur sensors. The LEDs on Namur devices are lit when the sensor is not actuated. In other words, the ‘Closed’ LED is lit when the valve is opened. The actuating element can hence be used to ensure the correct LED indication for the ‘Closed’ position. As described previously, this puck is equally suited for anticlockwise and clockwise rotating drives.

The extensive array of accessories for the Turck dual sensors adds considerably to their potential applications. The various actuating elements allow a wide range of application requirements to be met. Special stainless steel brackets enable the sensors to be fitted even to manual valves without difficulty.

Often the greatest challenge facing plant engineers is not the actual installation but the paperwork: getting the designs approved is regularly more complex than the designs themselves. Once again, the dual sensors are one step ahead of similar products: the SIL Directive IEC 61508 calls for an increasing number of position feedback signals. Modular housings mostly fail here due to their mechanical complexity. Customised solutions are frequently difficult to handle owing to their manufacturer-specific characteristics and any ‘second source’ suppliers available tend not to be approved or are restricted to a single type. By contrast, all standard Namur sensors from Turck are suitable and TÜV-certified for use in safety systems, including SIL2 in accordance with IEC 61508. One hundred percent compatibility with all standard Namur processor devices or (safety) PLC systems with Namur inputs is thus guaranteed.

Turck also offers robust, contactless solutions for capturing analogue flap positions on the entire range of angles: the Ri-DSU35 angle sensors and the well-established Ni4-DSU35 dual sensors are identical in design. While dual sensors only capture two positions, Ri-DSU35 sensors are able to monitor three-way flaps. For wiring into Ex zones 1 and 21, Turck offers loop-powered, intrinsically safe devices with a 4…20 mA output. An additional benefit of Ri-DSU35 sensors is the option of detecting the valve position during cleaning cycles. This is thanks to their 360° detection ability. The new sensors also contribute to better system availability because they detect seal wear. Wear results from a vast number of switching cycles causing the on-off positions to exceed the originally set angular range. Users simultaneously profit from the sensor’s enormous mounting flexibility. The device can be mounted to any standard rotary actuator in combination with the extensive range of accessories. Additional accessories could be needed for mounting to very large drives. Turck provides rugged spacer plates with matching accessories for this purpose. No matter how big the drive, the same sensor-actuator combination is always used.

Hall 9, Booth H55

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Sander Makkinga

Product Manager Position and Proximity Sensors,

Turck