Provision for Refrigerant Removal
Most people who have worked around the ammonia refrigeration industry for any period of time recognize the importance that strainers play in the proper operation and maintenance of an ammonia refrigeration system. Typically located upstream of control valves, strainers perform the important function of filtering out debris that would otherwise damage control valves and prove detrimental to system operation. Strainers require periodic cleaning to remove debris that has been collected, but unfortunately, an all too common deficiency that I see at facilities is that no provision is made available to safely remove ammonia from the strainer as is necessary to safely facilitate maintenance. An often overlooked requirement of ANSI/IIAR 2-2008 Addendum B requires that “strainers shall be fitted with provision for refrigerant removal to facilitate maintenance“ (§10.3.3). Ignoring this simple requirement increases the risk associated with performing the routine tasks of cleaning a strainer and maintaining control valves.
Be aware that once these blow down valves are opened, they may not seal when closed, until the debris from the strainer is cleared from the seat. The blow down valve should be cleaned out before closing them and putting them back into service to prevent seat damage.