Refrigeration systems place demanding requirements on the piping system. Not only is the primary piping system critical to the efficient, reliable operation of the refrigeration plant, but the secondary refrigerant fluid system also plays a critical role in optimizing running costs, energy efficiency and keeping maintenance to an absolute minimum. Choosing the correct material for both piping systems is important for optimizing plant costs and performance.
Often the same piping material is used for the secondary system as for the primary system. In breweries, wineries, cold storage facilities and other below-freezing applications, this means that copper or steel typically is used for the whole system. Using the same material for high-pressure gases and a 45 to 60 psi glycol or brine fluid system is not necessarily cost-effective in terms of the initial costs or the total costs of ownership.
However, the only alternatives for secondary piping have been copper, steel or stainless steel, all of which have potential drawbacks. Some plants have even used polyvinyl chloride (PVC), which has a low-temperature limit of 32°F (0°C) - highly unsuitable for glycol, which has a temperature of 17 to 28°F (-8 to -2°C).
Anyone who works with steel, copper or PVC piping is familiar with the problems experienced at below-freezing temperatures. The insulation used on these pipes often absorbs water from the atmosphere, which negatively affects the insulation and reduces the system efficiency by increasing operating costs. Water absorption also can cause ice buildup, which will crack PVC pipes and cause corrosion on metal pipes. These problems lead to excessive maintenance and downtime.
The roughness of the pipe also can affect the cooling system’s efficiency. Steel’s roughness factor of 0.02 creates a pressure loss that reduces flow in the pipe. Copper and PVC offer a smoother pipe option, but any efficiency gains are likely to be offset by cracking or corrosion problems.
The ABS OptionWithin the last 15 years, acrylonitrile butadiene styrene (ABS) piping materials have been developed that provide a durable, long-lasting alternative in these applications. Retrofitting cold applications to ABS piping can provide a savings in maintenance and operations costs.
ABS is a thermoplastic material that performs well in temperatures from -40 to 140°F (-40 to 60°C) with less condensation and ice buildup compared to other piping materials. Piping made from ABS does not corrode and is crack resistant, thus reducing maintenance to a minimum. ABS piping typically lasts 25 years or more with virtually no maintenance requirements. The piping also has a roughness factor of 0.007, which is six times smoother than steel. The smoothness of the plastic pipes prohibits a buildup of deposits from the fluid, thereby preventing the reduction of flow in the pipe. Unrestricted flow also optimizes the efficiency of the system in terms of reduced pressure loss, a performance characteristic that remains constant over the life of the pipe.
Retrofit Considerations. Cost is an important factor when considering any upgrade or retrofit. Material costs, the labor required to install the pipe and the amount of downtime required to complete the retrofit all are part of the upfront costs associated with the project. However, these costs can be recouped relatively quickly with ABS piping due to the reduced downtime, replacement and repair requirements.
In breweries, wineries, cold storage facilities and other applications using glycol or brine cooling systems, secondary piping can be a key factor in determining an operation’s efficiency and profitability. Retrofitting a steel, copper or PVC system to ABS piping can reduce maintenance costs and downtime while also increasing the overall efficiency of the cooling system.