Visual level indicators keep track of refrigerant

An Able Instruments and Controls product story

Edited by the Engineeringtalk editorial team Apr 27, 2005

Able offers specially adapted Smart-Line 34000-A Series visual level indicators for monitoring liquid refrigerants such as Freon R134a.

Refrigeration plants are used in supermarkets, hotels, restaurants, hospitals, food processing industries, and in smaller food retail establishments.

A refrigeration plant uses a refrigerant such as Freon R134a stored in its liquid state in a reservoir tank forming part of the refrigeration cycle.

Visual indication of liquid refrigerant level and monitoring of low and high tank levels are necessary for efficient and safe plant operation.

In co-operation with OEMs and refrigeration plant supply firms, Able can offer a specially adapted Smart-Line 34000-A Series of visual level indicators for this application.

This reliable, accurate and economical refrigerant level instrument is regularly used in considerable numbers by the refrigeration industry.

Refrigerants are expensive, and leakage into the atmosphere has detrimental environmental consequences.

The entire refrigeration plant must be maintained in a leak-tight condition at all times.

Refrigerant leakage results not only in atmospheric pollution, but also in ineffective cooling functions.

The consequences of this can be severe: spoilage of the refrigerated foodstuffs, which must then be destroyed resulting in total loss.

If spoiled foodstuffs are accidentally passed on to consumers, the health consequences can be catastrophic, sometimes even fatal.

An effective way to detect refrigerant leakage is to monitor the level of liquid refrigerant in the reservoir tank, with automatic alarm generation for low-level conditions.

High liquid refrigerant level in the reservoir tank is an indication of possible problems in the refrigeration system, and therefore is an important plant diagnostic function.

To avoid calorific losses in piping, vessels, and also the visual level indicator, typically Armstrong type insulation is used.

In most cases, the refrigeration system supplier provides this as part of the plant.

Visual level indicators can be prefitted with this type of insulation on request.

An important part of the level instrument is the connection between the copper tubing of the refrigeration plant and the stainless steel level indicator.

For reliable leak-tightness, these connections are made with brazed joints.

Making these joints between stainless steel and copper requires special skills.

Visual level indicators for refrigeration plants are therefore available with pre-fitted copper tubing that can be handled in the usual way by refrigeration plant technicians.

For ease of maintenance, a Rotalock valve is used to block off the refrigerant.

The measuring of the visual level indicators can be selected arbitrarily.

In this application area it is generally in the 700 to 1700mm range.

The main components of the refrigeration cycle are the evaporator, compressor, condenser, and the refrigerant metering device (regulating valve).

The liquid refrigerant is fed into the evaporator through the injection line and a regulating valve that reduces the pressure of the refrigerant.

The reduction of pressure causes the refrigerant to boil and vaporise in the evaporator.

The phenomenon is similar to water boiled at 100C at atmospheric pressure.

The refrigerant has the property of evaporating at this reduced pressure.

Evaporation absorbs heat, and therefore the evaporator absorbs heat from the surrounding space, causing the refrigeration effect.

The refrigerant gets heated in the process, and is drawn off by the compressor, which increases its pressure.

The refrigerant is then fed into the condenser where it is returned to its liquid state.

Here, the heat of the refrigerant, generated by the evaporation process and the compression process, is transferred to the outside air through the heat transfer surfaces of the condenser that is usually air-cooled (eg at rear of a refrigerator).

The refrigerant that gets liquefied in the condenser is then fed to the reservoir tank, where the level is monitored by a Type 34000-A visual level indicator.