Looking at hydrocarbons in SA

Looking at hydrocarbons in SA

We take a look at R290 and R600a to talk about safety, training and other requirements for dealing with flammable hydrocarbons. 

By Grant Laidlaw of ACRA.


Chris asks: Hi Grant, we are interested in looking at systems using hydrocarbons as a refrigerant. But where do we begin? I suppose we need to do some training? What about ignition sources, as we need to be aware of all hazards? Can present systems be retrofitted?


Chris, with respect to R290 and R600a, it is certainly early days for our industry in South Africa. The domestic market switched over to R600a several years ago and more recently the light commercial manufacturing companies in South Africa converted their facilities to R290. There is no doubt that flammable refrigerants will be used in many different system configurations, sizes and types of facilities, not only in refrigeration but also in the air-conditioning sector.

It follows that personnel responsible for the design, installation, commissioning, service, repair, and maintenance of these refrigeration or air-conditioning systems (referred to as technicians, engineers, mechanics or contractors) must be appropriately trained.

Training guidelines identifying the areas of study, together with the relevant knowledge, skills, and learning objectives for this training, eliminate confusion and may provide a road map for people struggling with the task of meeting the challenges we are going to face. South Africa has just registered a new education programme for the training for personnel in the Refrigeration and Air-conditioning sector. The curriculum is complete but much of the supporting structures are still under development.

In addition, the changes in the education system have forced changes to the South African Qualification and Certification Committee for Gas (SAQCC Gas) registration of authorised persons against the pressure vessel regulations. As this process has not been completed, I have looked at possible training outcomes that need to be attained.

We will need to identifyy the key competencies of each level of staff working with flammable refrigerants and define the training requirements to be a “competent person”. The current situation is to register competent persons against categories as laid down by SAQCC Gas.

We can define a competent person as someone who has acquired the knowledge and skills to carry out the task, through training, qualification or experience or, put another way, a competent person as a person who has had appropriate training or practical experience (or both) in the subject, sufficient to provide safe and satisfactory performance.

The minimum level that anyone who works on refrigeration and air conditioning systems containing flammable refrigerant should be trained on include but are not limited to:

  • Knowledge of legislation, regulation and standards relating to flammable refrigerants.
  • Safety aspects relating to flammable refrigerants.
  • Detailed knowledge of and skill in handling flammable refrigerants, personal protective equipment, refrigerant leakage prevention, handling of cylinders, charging, leak detection, recovery and disposal.
  • Knowledge of the properties and hazards of flammable refrigerant gases.

This represents the baseline, and there are of course, many other aspects to be considered, including flammability limits.

The current status quo for training and registration is as follows:

  • The user, operator level.
  • The learner, apprentice, semi-skilled personnel level.
  • Qualified trade tested technical personnel level.
  • Inspector level.
  • Designer level.

Changes will be made to the current registration system, but the changes are most likely to take the form of additional categories and will have to be in line with changes to legislation.

As the new qualifications scope has increased to include air conditioning, ammonia systems, carbon dioxide systems and flammable refrigerants, the scope of registration of competent persons will increase accordingly.

When focusing on hydrocarbons anyone designing, removing, altering, repairing, servicing, testing or certifying a hydrocarbon refrigerant based system or device (such as charging, discharging or breaking into a refrigeration system that uses hydrocarbon refrigerants) must hold a safe handling licence (hydrocarbon refrigerants) to do so.

A person responsible for the design of an HVAC&R system carries responsibility, and as such should be aware of the safety risks, standards and regulations involved with the design, installation, use and maintenance and operation of any refrigeration or air conditioning equipment intended to operate with a flammable refrigerant charge.

This situation extends to users, owners, site supervisors and managers, who will need knowledge of hydrocarbon refrigerant systems on their sites including emergency plan training. Non refrigeration workers who work in areas using flammable refrigerants will have to be trained as to the additional hazards and procedures. Where alarms are used, response training will be appropriate. Someone who oversees the day-to-day operations of a business carries some responsibility and, as such, should be aware of the safety risks involved with the operation of any refrigeration or air-conditioning equipment containing a flammable refrigerant installed on their premises.

Ignition sources

Chris, moving on to more technical matters, you asked about ignition sources.

When flammable refrigerants are used in a system, there must be no potential sources of ignition associated with or in the vicinity of the equipment that could ignite any refrigerant that leaks from the system.

Let us begin by saying that flammable materials should not be stored near or around a refrigeration system containing flammable refrigerants, as this will obviously increase the level of the hazard.

Potential sources of ignition can include:

  • A hot surface
  • A spark from an electrical source
  • An open or naked flame
  • Static electricity
  • Lightning
  • Mechanical equipment

Hot surfaces: All parts of equipment should be checked to ensure that the temperature of any surface that may be exposed to leaked refrigerant cannot exceed the auto-ignition temperature of the flammable refrigerant, reduced by 100K for safety reasons. This temperature equates to about 350°C for many hydrocarbon refrigerants.

Condensate tray heaters and defrost heaters are prime candidates for hot surfaces within refrigeration and air conditioning equipment. Unless a maximum surface temperature is stated by the manufacturer, the temperature should be checked.

An additional factor is that some lubricants decompose when heated and emit toxic compounds. This means that a toxic hazard can develop (even if ignition does not occur) as a result of refrigerant release due to a leak or servicing procedure. Thermal decomposition usually occurs at temperatures near to the auto-ignition temperature.

When dealing with fluorinated refrigerants, be particularly aware of the potential for hydrogen fluoride and carbonyl halide generation.

Electrical sources of ignition: Refrigeration and air conditioning equipment using flammable refrigerant must be designed and constructed so that any leaked refrigerant will not flow or stagnate where electrical components, which could be a source of ignition, are fitted.

Typical electrical components, which form part of the refrigeration system, and could be a source of ignition include but are not limited to:

  • • On / off, isolator switches or contactors
  • • Start relays and potential relays
  • • Switches - pressure, defrost, flow, oil differential, liquid level, fan delay or time
  • • Thermal overloads
  • • Fan motors
  • • Thermostats
  • • Condensate pumps
  • • Miniature circuit breakers
  • • Condensate tray heaters
  • • Fan speed controllers
  • • Programmable controllers

Electrical equipment such as fans, heaters, electrical sockets, power outlets, motors and any other electrical equipment installed or likely to be used near systems containing flammable refrigerant should also be considered, particularly equipment mounted below the refrigeration system and at or near floor level (R290 and R600a are heavier than air).

Options for dealing with sources of ignition within a potentially flammable zone / hazardous area classification include the following:

  • Move the source of ignition outside the hazardous area (potentially flammable zone); or
  • Replace the source of ignition with a suitable device as noted above; or
  • Increase the uncontaminated air flow and / or maintain a permanent airflow to reduce the potentially flammable zones to below the lower flammability limit of the flammable refrigerant. (Uncontaminated air is typically drawn in from high level and discharged at low level.)
  • Alarms and warning devices, extraction ventilation systems installed as necessary.

Naked flame ignition sources: Refrigeration and air-conditioning equipment charged with flammable refrigerant should not be installed or located in areas that have naked flames present. This can include areas with gas stove tops and ovens, gas water heaters and gas or wood-fired room or space heaters.

Static electricity and lightning: To avoid static electricity or lightning introducing a potential ignition source, metal structures around a system should be electrically earthed.

Mechanical equipment (static and frictional sparks): Mechanical equipment may introduce other sources of ignition (sparks) that should be considered in the design of the system.

Examples include:

  • Static electricity from belts, etc.
  • Frictional sparking risks from different metals, including any rotating parts.

Chris, hopefully this gives you an idea as to how to use flammable refrigerants and some of what is entailed. Retrofitting current systems is possible, and I will look into this in future issues.

References:

  • ACRA
  • SARACCA

 

 


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