There have been legislation changes since the January 1, 2020, with virgin HFC refrigerants being banned from use. Although recycled refrigerants can continue to be used, which are ozone depleting, their price is expected to increase. There will also be stringent reporting requirements for leakages (as in section 608). With the possibility of heavy fines for infringement, which in 2020 were as much as $300,000 for one indictment, it remains questionable whether the benefits of reusing historic fluids outweigh the initial higher outlay of using environmentally friendly refrigerants and the range of process improvements utilizing such liquids can bring.

Natural refrigerants such as carbon dioxide, ammonia, and hydrocarbons including isobutane, propane and propene are offered as alternatives providing a range of benefits and process improvements.  These benefits include contributing less to global warming, conducting heat or cooling more efficiently and thus reducing the amount of work compressors are required to undertake, leading to a reduction in the running, repair, and replacement costs.

Click chart to enlarge. (Courtesy of EPA)

Natural refrigerants are set to lead the way in not only reducing total cost of ownership for cold room storage and HVAC projects, but also as a way for organizations to work towards meeting their carbon neutral goals and increase social responsibility.

With the use of natural refrigerants, and the range of pressures and temperatures used, the effects on pumps and process equipment can be quite severe if not researched prior to install.

Whether additional equipment will require retrofitting or upgrading is a decision each contractor will have to consider on a project basis, but what might a change in refrigerant mean for pumps used to offload, or circulate refrigerant in cooling applications?

Common Issues of Pumping New Refrigerants

With the change of liquids used, there have been various issues experienced by contractors upon upgrading currently installed equipment. A breakdown by fluid type of the issues experienced are as follows:

Carbon Dioxide: This has a poor lubricity meaning increased pump wear is experienced. It requires very low temperatures and high pressures to remain in liquid form. It can create slippage within designs of pumps whereby its viscosity is so low it recirculates within the pump head, rather than being discharged from the system. If the incorrect pump design is selected it can lead to the liquid boiling (gassing off) or premature destruction of the pump due to cavitation.

Ammonia: Ammonia is similarly known for its low inlet pressure also known as Net Positive Suction Head (NPSH) requirement, again leaving a pump at risk of cavitation. Slippage is common and poor lubrication of pump parts leads to accelerated pump wear and increased maintenance intervals.

Propane, isobutane, propene, and propylene – Similarly, these have a low NPSH requirement, with risk of cavitation but with the increased risk of being flammable, meaning newly installed equipment should be ATEX, and their use can be prohibited in particular areas.  

It is not only pumps which need to checked but also variable speed drives (VSD’s), which may need adjusting according to newly designed equipment and fluids density, specific gravity, and other properties to ensure pumps operate as desired maximizing life expectancy.

Pump Features to Consider

Various design enhancements are available for pumps to reduce total cost of ownership, improve speed of maintenance, and reduce risk to process and personnel. Pump features to consider for your process when upgrading pumps include:

1. Magnetic drive coupling designs eliminate the need for seal replacement as the pump head is connected to the driving element via a magnetic coupling. As there are no seals to wear there is zero chance of leakage, fewer maintenance intervals, and less downtime for users to experience. Furthermore, as units are seal-less they do not rely on auxiliary devices such as having flushing connections or a tank for lubrication, and as such they generally require less maintenance. If a seal is required, cartridge seals can speed up maintenance as all the necessary setting up of clearances has already been undertaken.
2. Low NPSH designs of pump such as side channel can accommodate an inlet pressure as low as 0.3M, making it an ideal pump type to enable stripping of tankers completely during offloading but also ensuring less chance of pumping issues such as cavitation caused by low inlet pressures. Side channel pumps have a similar performance criteria to multistage pumps being low flow at high pressures, meaning they can accommodate high inlet pressures, extreme temperature ranges whilst also being able to handle liquid, and air mixtures in addition to being self-priming.
3. Variable speed enabled units facilitate efficient pumping across a range of pressures and lower power consumption. Speed can be altered according to the flow demanded providing energy savings up to 60%.

When changing the refrigerant used within your pumping application, it is always worth discussing the application with a process specialist to evaluate whether the existing pump setup also requires replacement.