As I have mentioned before, this “temporary operations” mode confuses a lot of facilities. Almost all facilities will state, without hesitation, that they have no “temporary operations.” And almost always, as we proceed with our assessment/analysis, we find numerous “temporary operations.” As I write this posting, it is -10°F here in Cincinnati, OH, a temperature that is well outside our average lows. This winter, we have seen some really cold temperatures in this region of the country, and this leads me to another example of a “temporary operation.”…
The scenario involves an ammonia refrigeration process. In extremely cold weather, many of these processes will shut down their condenser water flows. On one hand, at cold enough outside temperatures, the water flow becomes less necessary, and the business can reduce costs by discontinuing water flows and using only the condenser fans to aid in the heat removal. But on freezing days, such as -10F, some processes that may need the water due to the load on the process will shut down the water flows for fear of having a mountain of ice on their rooftop condenser(s), leading to a potential NH3 release. Either reason would result in a planned and deliberate “temporary operation” (i.e., without water flow to the condensers).
Most facilities, especially the older ones, make this process change manually using an operator, pump(s) controls, and valve(s); however, some of the newer processes can actually have this water flow controlled by a PLC and several critical parameters being measured. Please keep in mind that if you are one of the lucky ones who have this process flow change managed by a computer, these “critical parameters” should become part of your Process Safety Information’s “Safe Upper and Lower Limits.” This should also be covered in your PHA as a “failure of engineering controls,” but I digress in my discussion.
Bottom line, when we KNOWINGLY run without water to our condensers during the winter months, this is INDEED a “TEMPORARY OPERATION” that is done with purpose. It is only temporary, by anyone’s definition, as we fully know that when warmer days return, so will the flow of water to the condensers. So if you agree with me on this point, we must ask ourselves… What controls do we have in place regarding this “temporary operation”?
1910.119(f)(1)(i)(C) requires that we cover these “temporary operations” in our operating procedures (e.g., SOPs). Items such as when does an operator shut off the water to the condensers should be covered in the Safe Operating Envelop. The consequences of deviation if he/she fails to act upon this process are needed. And by the way, a busted condenser tube can be the consequence of deviation if this “temporary operation” is not managed properly!! I will also add that how the operator carries out this task is CRITICAL. Forgetting to DRAIN the water lines can allow the lines to freeze internally, rupturing the lines. This will most likely not cause a release of NH3, but it sure will cause operational issues when those first warm days arrive in late winter, and you have no water flow capacity! But where the water line ruptures and how the system was shut down can still lead to a release of NH3! Case in point… shift rounds in the winter months were “unofficially” revised (without an MOC) and operators were no longer doing visual inspections on the rooftop condensers. In their minds, there was no need to since they were “out of service” with no fan operation or water flow; however, ammonia still flowed through the tubes. In this fictitious scenario, the water system was not shut down, purged, and isolated properly and thus a water line rupture occurred right at one of the condensers. Water sprayed onto the condenser coils from the ruptured water system, allowing ice to form and damage the coils, leading to a release of NH3.
To make this short, turning off your water flow to the condensers is without a doubt (in my mind) a “temporary operation.” Thus, we need an SOP to cover this “temporary operation.” This SOP needs to cover the safe upper and lower limits so as to instruct the operator when he/she is to stop flows and start flows; another procedure for how to “winterize” the condensers once it has been determined water flow is no longer needed; as well as including a “start-up” procedure when the water flows are re-established after the condenser(s) prolonged shutdown. Finally, look back at your PHA and review the scenario of “NO FLOW” for water to your condenser(s). This scenario is VERY MUCH seasonal, as in the summer months, water flow is CRITICAL to maintain system pressures. Condenser water, in my opinion, should be managed as a “critical utility” in an ammonia refrigeration process, as no flow of water can cause the process to deviate from its established safe upper limits, AND improper treatment of this water can cause corrosion issues on covered equipment which may lead to premature failure of the primary containment leading to a release of NH3.
So as we can see, simply turning off water flow to condensers for an extended period of time and running the process without this flow due to atmospheric conditions is indeed a “temporary operation”.
A comment, thoughts, challenges?????