Refrigeration in Industry

Ammonia has become a popular refrigerant gas in industry since the demise of CFC gases.  Halons are still used for refrigeration applications but they are not easily measured using our products and there are alternatives available using semiconductor technology that we find very difficult to compete with.  For this reason I will only deal with ammonia here.

Ammonia as a refrigerant

Relevant standard - BS4434:1995 safety aspects in the design, construction and installation of refrigerating appliances and systems.

Ammonia is a group 2 refrigerant, thus systems that use it should be protected against explosion. As the refrigeration systems are not explosion proof, the protection against explosion for ammonia systems is provided by gas detection. 

The requirement of BS4434 is that gas detectors in the machinery rooms should activate alarms if concentrations exceed 1vol% of group 2 refrigerants.

           as  15vol% NH3 = 100%LEL

                     1vol% NH3 = 6.67%LEL @  7%LEL

A pre-alarm is also usually incorporated at ~0.5vol% NH3, i.e. 3.5%LEL.

Activation of alarms should usually switch on ventilation system and in unmanned areas, isolate all electrical circuits (except lighting and ventilation).

A low range is required as alarms are lower than normal thus a 0-25%LEL NH3 range should be offered - this is perfectly acceptable using the VQ41 pellistors.

The responsibility for this will normally rest with the safety manager on the site of an end user. He may well also be interested in the SGT-P for personal protection against the toxic risk of ammonia.

The other application is with refrigeration equipment suppliers. They will typically supply a SI-100IM type system with every refrigeration plant they supply. They will be interested only in the flammable risks outlined above. The best contacts here are electrical engineers and purchasing. The current standard supplier for this industry is Sieger.