“There are utility systems that are relatively simple to shut down during cleaning or downtime and there are others where shutdowns carry a higher opportunity cost.
“During cleaning or downtime periods, the simplest utility systems to turn off are typically compressed air and vacuum systems. These systems do not have significant ‘collateral loss’ when shutting down. These systems can be deenergized by stopping the associated blowers or compressors and slowly relieving pressure. For industrial applications, these blowers and compressors are designed to be flexible for weekly shutdowns and best practices can help to mitigate cycling concerns (e.g. opening drain lines so condensation can freely drain).
“Conversely, there are utility systems where there is a relatively high collateral loss whenever there is a shutdown. These types of systems are typically steam, chilled water, clean-in-place (CIP) wash systems, and specialized water systems (e.g. WFI). These are systems that should only be shut down if direct maintenance is needed on the equipment or if the facility shutdown is going to be more than a few days.
“Specifically for steam systems, special steps are needed in order to protect the boiler(s) and steam distribution system during extended shutdowns. There is a myriad of layup procedures based on steam system size but they can include ambient air purge, nitrogen purge/blanketing of the distribution system, or putting (removable) desiccant into large vessels (e.g. deaerator).
“Anytime you deal with elevated pressures and temperatures, thermal cycling should be avoided in order to prevent premature failure of system components. The adverse effects of thermal cycling raises the collateral loss of shutting down steam systems.
“A subtle item that should be considered when shutting down utility systems during cleaning or downtime is interdependencies. Many facilities use compressed air for hose reel service drops, pneumatic actuating valves, and supply to processing/packaging equipment. Operators and facility engineers need to closely evaluate what other systems would be impacted by the utility system they are planning to shut down.
“Lastly, manufacturers should always keep safety in mind when coordinating short or long shutdowns. Anytime the decision is made to keep a system online during cleaning or shutdown in certain areas, it is critical to include that information in the daily shift meetings so that operators/cleaning staff know that the (e.g.) steam system is still on. Lock-out/tag-out (LOTO) procedures are not exclusive to electrical systems; they can be applied to utility systems as well.”