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SensoGate WA 131 M Retractable Fitting

The successful SensoGate WA 130/131 sensor lock-gates and their corresponding WA 130H/131H hygienic designs offer optimized solutions for all semi or fully automatic applications. However, a pneumatic fitting is not essential for many applications and is therefore too expensive. For this reason, Knick has now developed the SensoGate WA 131M, a state-of-the-art manual sensor lock-gate with a revolutionary rotary drive.

Revolutionary operation
The SensoGate WA 131M has a manual rotary drive, which enables the fitting to be operated up to a counter pressure of 10 bars. And this is all done with just two turns. Regardless of how unfavorable the angle or the operating height at which the fitting is installed, the low rotary forces can easily be applied using the wrist. This is not possible with the sliding motion of conventional fittings.

Very simple installation
The manual sensor lock-gate, sophisticated down to the smallest detail, offers a time saving of 80% for initial installation compared to conventional units and of up to 70% for replacing wearing parts. For example, the O-rings can be completely replaced in just 30 seconds; the seals are easily accessible and can be exchanged very quickly. Design innovations also ensure that the O-rings have an extremely long service life.

Superior functionality
With conventional units, the sensor was incorporated into the process through an O-ring lock-gate; the sensor windows in the immersion tube juddered through the O-rings into the process and back.

The resulting mechanical loads were frequently intensified by thermal and/or chemical stresses, which often led to problems such as swelling of the O-rings in the process. In addition, sticky layers frequently accumulated in the immersion tube or the sensor mount. Knick has now resolved these functional problems with a combination of the superior method of internal O-rings and the new lock-gate principle.

Cost savings for servicing and spare parts
Easy maintenance thanks to a user-friendly design was one of the primary demands when planning the development. The well thought-out design of the SensoGate WA 131MH guarantees that the technician can access all relevant parts as quickly as possible, on site, without having to take the sensor lock-gate into the workshop.
In case of a broken electrode, the front electrode sealing ring is often cut by the broken glass. With conventional retractable fittings, changing the seal and removing the fragments from the calibration chamber also require extensive dismantling of the unit. In contrast, the new manual SensoGate version uses the simple yet sophisticated construction of the WA 130/131 series.

Maximum process safety
In this area, the manual SensoGate WA 131M is also based on the successful design of the pneumatic versions. The configuration of the O-rings means that there is never any connection between the drain opening of the rinsing chamber and the process, even during the inward and outward movement. The process medium cannot escape into the drive unit or outwards. Not only would this be unhygienic, it would also impair functional reliability. At the same time, practically nothing can happen to the SensoGate WA 131M accidentally – the sensor can only be removed in the service position, while automatic extension protection reliably blocks the movement of the fitting and prevents extension into the process position with no sensor. Furthermore, the immersion tube is secured against twisting, which guarantees constant flow conditions for the sensor in the process.

Superior Immersion Depth
The lock-gate principle of SensoGate allows a greater sensor immersion depth compared to existing retractable fittings. Even on the short version, the sensor immersion depth is 65 mm (lower edge of fitting flange to tip of sensor). The total immersion depth (to end of immersion tube) is pleasingly short at just 88 mm. This allows a considerable sensor immersion depth even under constricted installation conditions (e.g. tubes with small diameters). This also guarantees that the sensor is reliably immersed in the process medium beyond the dead flow space of the flange. On previous retractable fittings, the immersion depth is often measured from the side of the fitting flange away from the process; this further reduces the effective sensor immersion depth by the thickness of the flange. To obtain even greater immersion depths – e.g. for use in coated and heat-insulated boilers – a version with a 143 mm immersion depth is available. Another key feature: all immersion depths are achieved with a short sensor length of just 225 mm. This eliminates the need for expensive 425-mm-long glass electrodes; handling is easier and the likelihood of electrode breakage is significantly reduced.

Cyclone rinsing for optimum cleaning
A further problem with previous retractable fittings lay in the inadequate rinsing and cleaning effect of the rinsing chamber due to the opposing inlet and outlet. This was always associated with the formation of shadows on the sensor. In contrast, the manual SensoGate 131M has the same effective sensor cleaning as the WA 130/131 and WA 130H/131H. The inflow holes are arranged like nozzles in a ring around the sensor head. This special arrangement provides a tangential flow of rinsing solution and creates a rotating flow (cyclone) around the sensor, which leaves the sensor through the outlet, also in a ring shape.

Modular Design
This exemplary modular design allows easy selection of various materials (1.4571, 1.4404, PVDF, PEEK, PP) for the process-wetted parts. Furthermore, the manual SensoGate can be combined with a wide range of process connections. The innovative sensor lock-gate is designed for use with gel-electrolyte as well as with refillable liquid-electrolyte sensors.

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