Even those cylinders designed and manufactured for repetitive use can pose safety hazards when refilling is done by inexperienced operators who lack adequate equipment and have insufficient knowledge of proper filling densities and other properties of the gases being handled. Liquid densities and, therefore, safe filling limits vary for each refrigerant. Cylinder rupture can result from inadvertent overfilling. To avoid hazards and prevent possible contamination of the refrigerant, all operations involving the transfer of refrigerant gases from one cylinder to another require adequate equipment and experienced personnel having a thorough understanding of equipment operation and maintenance.
Basic safety measures for handling and transporting compressed gases in cylinders are included in the regulations of the U.S. Department of Transportation. Among these regulations are:
- The specification for the required type of cylinder, valve protection and pressure-relief device based on the service pressure likely to be encountered for each particular refrigerant.
- Stipulation of a maximum filling limit by cylinder type for each refrigerant gas.
- The requirement for periodic reinspection or hydrostatic testing of cylinders.
- The frequent inspection, repair or replacement of pressure-relief devices and other components.
- 49 CFR Part 107.329(b) and 107.333 describe maximum civil and criminal penalties for violations of the regulations.
The risk of serious personal injury or property damage is sufficient basis for strongly discouraging the practice of transfilling refrigerant cylinders in the field. The possibility of degrading product quality to unacceptable levels reinforces this position.