Technical Safety BC conducted an ammonia release fault tree workshop to identify potential causes of ammonia releases from industrial refrigeration systems used in arenas and food storage facilities. The workshop is part of a Technical Safety BC project meant to detect and mitigate emerging and known technical safety risks in the province.
The project used the fault tree method which starts with choosing a final event such as an ammonia leak and working backward to identify all the causes that could have led to the event. Workshop participants identified two causal factors for ammonia releases:
- There was a lack of knowledge and engagement on the part of some facility owners and operators regarding the risks associated with the operation of an ammonia refrigeration facility. The level of understanding and support from these owners/operators to allow strong management systems to be developed and maintained was perceived to be lacking.
- The existence of multiple levels of certification (Refrigeration Operator, 4th Class Power Engineer, Ice Facility Operator, Refrigeration Safety Awareness certification, as well as trades used for maintenance) to allow operation of these facilities was observed to be a potential source of risk. The capabilities and limitations associated with each type of certification are different, and the work that should be delegated to each type of worker is potentially different.
At the conclusion of the ammonia release workshop, the working group reviewed the fault tree that had been created and tried to identify the common causal factors that appeared in the tree; either factors that were repeated in numerous locations, or factors that were deemed critical by those participating. The group then held a brainstorming session to develop actions and recommendations that could be carried forward by TechSafeBC to attempt to reduce the risks associated with ammonia refrigeration systems. These recommendations appear in full, below:
- Ammonia refrigeration systems in British Columbia are equipped with emergency discharge valves that allow the ammonia to be discharged directly to atmosphere. The
code requirement to add these valves to refrigeration systems has been in place for decades, but with modern safety systems and controls, the workshop participants were of the opinion that it no longer serves a useful purpose. Instead, it now constitutes a potential source of release due to inadvertent operation. TechSafeBC should consider deleting the requirement for emergency discharge valve from refrigeration system design; note that in the 2015 CSA B52 code, this valve is now optional. - TechSafeBC should consider issuing a safety directive or other regulatory notice requiring the removal of the emergency discharge valve from existing facilities when
system renovations are done, in order to eliminate one potential risk source. - Consider performing a gap analysis to identify inconsistencies between current Refrigeration Operator (RO) and 4th Class Power Operator training and allowed scope of
work, and undertaking regulatory and training changes to address identified gaps where ammonia refrigeration systems are involved. There is a concern on the part of workshop participants that operators may undertake work that they are not qualified to do, due to a lack of clear direction on what duties they are allowed to perform. - Consider developing additional guidance on seasonal shutdown of ammonia systems in ice arenas to determine whether a condition of non-supervision can be safely achieved on a seasonal outage.
- Consider reviewing contractor licensing requirements and quality control manual requirements to develop improved maintenance and operational performance through the licensing system.
- Consider developing improved guidance on methods of providing notification of relief through pressure safety valves, especially around nuisance alarming on current sensors – potentially through a working group to identify best practices. The working group noted that small releases through pressure relief devices are not uncommon, and that existing sensors make it difficult to differentiate between a small release and a significant discharge.
- Consider making refrigeration system design subject to professional engineering review, stamping, and registration in the province of British Columbia. Currently, there is no requirement for an engineering review of ammonia refrigeration system designs, despite the presence of a known hazardous chemical under pressure.
- Consider developing a regulatory requirement to maintain minimum records for each operating shift; the current code requires that a log book be kept, but does not specify what should be tracked. Actual minimum data to be recorded (i.e., operator name/certification, actions taken, maintenance done, baseline and actual operating
readings) should be specified to ensure that critical information is not overlooked due to a lack of awareness on the part of the operator. - Consider developing an owner education or awareness program addressing their responsibilities around CSA B52 as adopted in BC and pertaining to ammonia refrigeration systems, and the potential legal liabilities and implications of noncompliance. Topics that should be covered include change management, appropriate procedure development, capital replacement plans, maintenance plans, corrosion management, and insulation management.
- Consider increasing the level of regulatory oversight that is in place for this type of operation; a lack of oversight of work being performed was cited as a causal factor
multiple times during the fault tree development. Increasing oversight by the owner or operator of a facility is not directly within the purview of TechSafeBC, but an increase in regulatory oversight will drive increased oversight and compliance on the part of the operator. This could include an increased number of site visits or inspections, as well as a review of the current audit protocols and procedures to ensure that they are current, sufficiently detailed, and consistently applied. - Consider developing an education campaign focused on owners, operators, and contractors identifying key risks associated with operation of ammonia refrigeration
systems to create engagement on the part of these groups. - Consider developing best practice documentation around piping insulation requirements, the importance of proper maintenance, and the impact that insulation has on corrosion risks through the corrosion under insulation mechanism (CUI).
CLICK HERE for the full Ammonia Release Fault Tree Study
CLICK HERE for more details on the 12 recommendations above