Coolant monitoring in refrigeration circuits

The Jumo Instrument Co is now offering the new Jumo Aquis 500 series with the well-established ammonia electrode as an economical system for ammonia detection in cooling systems

The Jumo Instrument Co is now offering the new Jumo Aquis 500 series with the well-established ammonia electrode as an economical system for ammonia detection.

Because of its good thermodynamic properties, ammonia is used as a coolant not only in small refrigeration systems, but also in large industrial plant.

However, since ammonia is a corrosive and poisonous chemical, it represents a potential hazard that should not be underestimated and requires continuous monitoring.

This monitoring is even more important if the plant concerned is being supplied with water from rivers or open waters in the public domain.

Most systems consist of a primary circuit (with ammonia) and a secondary circuit.

The secondary circuit usually contains a mix of water and glycol or some other mixture.

There is a potential risk of leakage at the interface between the primary and secondary circuits.

One hazard is, for instance, corrosion of the refrigeration piping.

If this piping is made from copper, then the wall thickness of the pipe may become so reduced by the chemical reaction of the copper with the ammonia that a breakthrough occurs.

The ion-sensitive sensor operates over a range from 0.01 mg/l to 20g/l.

It consists of a pH glass electrode and a reference electrode.

Both electrodes are immersed in a special electrolyte.

A membrane that is permeable to ammonia separates the pH and reference electrodes from the medium being measured.

The presence of ammonia in the sample medium is strongly dependent on the pH value.

In the acidic range, there will be a predominance of ammonium ions (NH4+), which are not detected by the sensor.

In order to achieve optimum detection of the ammonia, Jumo offers a special flow-through fitting for the ammonia sensor.

This facilitates quick and easy connection of the sensor according to the process set-up.

The corresponding transmitter/controller for the Jumo Aquis 500 series is easy to use, the simple menu-led operation prevents incorrect programming.

Language problems and translation errors are frequent causes of programming errors.

This risk has been considerable reduced by the option of selecting between a number of integrated operating languages.

In the normal display setting, the Jumo Aquis 500 shows the principal measurement and the temperature, either as the usual numerical display or as a bar graph.

A trend indicator can also be activated, to provide information on the way in which the present measurement is changing.

The high level of enclosure protection (IP67) given by the plastic housing means that the instrument can be used either as a panel-mounted instrument or as an on-site measuring device.

Condensation in the electronics is prevented by a diffusion-open membrane.

All versions can be fitted with up to two electrically isolated analogue outputs, for 0(4) - 20mV or 0(2) - 10V, as process value or control outputs.

The type of output and the scaling are freely programmable.

Two additional outputs can be fitted with changeover relays.

These relays enable simple limit monitoring as well as a more demanding PID control loop function.

Three power supply versions permit operation with typical supply voltages: 12V DC, 20 - 53V AC/DC and 110 - 240V AC.

With the Jumo Aquis 500 the user has an economical monitoring device for ammonia detection, to prevent damage to the plant and the environment.

Quote datasheet number 20.1030.

For more information please see our website.

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