Last month, Bulldozers, Dump Trucks, and Cranes delved into the subject of equipment sizing. It isn’t as easy as picking the biggest piece of equipment to meet the required load (driving a dump truck around every day just to move a load of dirt once a year). There is more to consider than simply staging multiple smaller pieces of equipment to meet the required loads. This month’s Brief discusses the importance of selecting the correct tool for the job.
Don’t Replace Like for Like
When it’s time to replace equipment, don’t automatically replace it with a new equivalent piece of the same capacity. This is a golden opportunity to evaluate current, near term, and long term needs to make sure the appropriate (type and size) piece of equipment is selected for the facility. Likely, the old equipment wasn’t sized correctly the first time, and system requirements aren’t the same as when the equipment was originally installed.
Consider the Application
Purchasing the wrong equipment for an application can be a waste of capital resources and may also cost more to operate. Consider a compressed air dryer. A desiccant style dryer wouldn’t be the best choice to install unless the low dew points they achieve are required. While it ultimately may get the same job done, it could cost twice as much to operate and costs more upfront too.
Efficiency Curves and Control Types Matter Too
The equipment’s performance characteristics, as well as the expected loading profile, need to be considered when selecting equipment. For example, when selecting the appropriate size for a chiller, one needs to consider if it is a rotary screw or a centrifugal chiller. Centrifugal chillers are typically at peak efficiency around 50% loaded whereas screw chillers are most efficient when fully loaded. The goal is to select the appropriate type and size the equipment so it is operating the majority of the time near its peak performance. Energy codes do not dictate these sorts of critical issues.
Design for Now – Plan for Later
Far too frequently, systems are grossly oversized and operate inefficiently because of expected future growth. The future is uncertain; plans for five years from now can easily be pushed back 10 years, or the plan may go in a completely different direction. Purchase equipment for current needs but keep future expansion in mind. This means designing the system to allow future expansion without compromising the system’s performance now.
Selecting and sizing equipment can be a complicated process. Each year, new features and technologies emerge and requirements change. Carefully consider these things when purchasing new equipment.