Safety and Monitoring Devices RAM-2000 and AM-2000 by Hermetic-Pumpen


The application range of canned motor pumps includes plants in which hazardous, toxic and/or explosive mixtures form or carcinogenic substances have to be moved in pipe systems. Such pumps have to be provided with the best possible safety and monitoring devices. The expenditure required to protect both humans and operating equipment is always justified.


The monitoring device RAM-2000 not only monitors the axial shaft position of the rotor but also indicates the direction of rotation.

At the motor end of the rotor a shaft is mounted which contains a multi-pole magnet ring. Over the shaft, a support pipe is flanged tightly to the motor end bearing cover, ensuring the hermetic sealing of the fluid to the atmosphere. The transducer RAM-2000 contains the sensor coils and electronic evaluation system. The measuring principle is similar to that of a speedometer, 2 axially mounted coils detect the axial position of the rotor (magnet) using a contactless method. The electronics forms an output signal of 8 - 16 mA. Four other coils register as well without contact the axial variation of the rotor and consequently the bearing play. This information is processed separately by the topped microprocessor electronic and prepared as separate linear norm signals. The direction of rotation of the pump rotor is derived from two speedometer coils, mounted radially at a 90° angle, and is displayed by 2 LEDs in the transducer cover plate.

The axial rotor position is measured, taken the mean over 15 minutes and stored in the microprocessor controlled peripheral unit RAM-2000 DA (Data Recording). However, only values measured during pump operation are considered.

The memory has a capacity of 370 days and is designed such that there is permanent access on the stored data over the last 370 days. The captured and stored values are retrievable from the RAM-2000 DA directly via the 2-line clear display menu, printed via the printer connection or transferred to a PC. The value and time range for the stored data can be preset.

Furthermore, the RAM-2000 DA always displays the current axial rotor position, thus ensuring a permanent control by the operator.

Apart from monitoring and documentation of the axial rotor position, the RAM-2000 DA is provided with a relay outlet for stopping the pump should the limit value be exceeded as well as with an additional relay outlet (signal) for triggering an external warning device (horn or similar).


The hydraulic compensation of the axially active forces is particularly important for canned motor pumps, since in these pumps there are no axial bearings. The stop collars at the slide bearings have only one fixing and control function and are therefore not in a position to pick up considerable axial thrusts.

If the axial thrust is disturbed e. g. through operation in the part- or overload sector, there might be considerable starting damages in the pump.

By means of the new developed AM-2000 by HERMETIC the axial play of the rotor can be measured hermetically and without contact.

The AM-2000 works with a speedometer and indicates the axial rotor position on an analogue instrument.

The measuring system does not need any extern voltage supply because of the tacho-principle.

At the motor side end of the pump rotor a plug gauge is mounted, which encloses a multi-pole ring magnet. There is a firm stay pipe over this plug gauge which is fixed over a flange at the motor side bearing cover. The stay pipe ensures the hermetic sealing of the delivery fluid to the atmosphere and serves as seat of the measuring transmitter AM-2000 with the reels and indicator instrument.

The measuring is based on the tacho-principle, two axially mounted coils register the axial position of the rotor. The middle position of the rotor within the pre-set axial play corresponds to the indication "zero" on the measuring instrument, independently of the synchronous speed. The excursion of the indicator from the zero position is linear to the mechanical excursion of the rotor from its middle, and is able to register measuring paths of + 4 mm.

With the AM-2000 therefore an effective and automatic early recognition at canned motor pumps during the operation is possible.

The max. temperature is 100°C, higher temperatures can be obtained with the insert of a thermal break. The nominal pressure is PN 64.

The lack of corresponding evaluation electronics and transmitter power supply unit ensures an excellent quality at a favourable price.

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