Refrigeration Insights Series. Season 2: The Enemy Within, installment 2.
The evaporator is the piece of equipment closest to the product, the personnel and the public. When it fails, the ammonia leak does not happen in the machine room: it happens in the cold room, in the freezing tunnel, over the processing line. That is why the mechanical integrity of evaporators deserves a chapter of its own, and why Joe Fazzari devoted a full technical paper to it at the IIAR 2023 conference.
The framework: periodic inspections or accumulated risk
The premise of the paper is direct: system owners and operators must periodically perform mechanical integrity inspections to ensure reliability and minimize the risk of an accidental release. The normative framework is IIAR 6, the inspection, testing and maintenance standard, with its tasks and frequencies per equipment type; we will cover it in depth in the next season of this series.
The value of Fazzari's work is that it turns that framework into a concrete list: the 12 most common problems to look for in a typical evaporator inspection.
The list of 12
1) Excessive frost or ice accumulation. 2) Corrosion on tubes, fins or connections. 3) Exceeding the maximum allowable working pressure (MAWP). 4) Hydraulic shock or trapped liquid. 5) Fan vibration and integrity. 6) Condition of the refrigerant distribution tubing. 7) Integrity of the cabinet and equipment supports. 8) Protection against traffic hazards. 9) Wiring and condition of electric motors. 10) Removed or damaged fan guards. 11) Maintenance of units with water defrost. 12) Proper operating conditions.
Three details of the list worth underlining:
Frost is not cosmetic. Accumulation on fins and drain pans reduces capacity, and the most common sources are mundane: dust and fibers from product packaging. The paper also documents a painful classic: the operator who tries to remove embedded ice by hitting it and ends up breaking the finned coil. Ice is managed with a properly calibrated defrost, not with a pry bar.
Corrosion gets photographed. The paper's practical recommendation: visually inspect all areas of the coil with a lamp and take photographs of any sign of corrosion for future comparison. Fin corrosion reduces cooling capacity; corrosion on tubes and connections ends in a leak. And a prevention tip: use only cleaning chemicals suitable for the equipment's materials of construction, with the manufacturer's recommendations at hand.
Hydraulic shock lives here too. Point 4 connects directly with the previous installment of this series: the evaporator and its lines are a typical place where trapped liquid and hydraulic shock do damage, especially around defrost sequences.
Why the list works
Twelve points fit on a laminated page hanging in the shop. That is the genius of the format: it requires no software, no consultants, no plant shutdown. It requires a lamp, a camera, a trained eye and record-keeping discipline (golden rule of the IIAR standards: without a record, the inspection did not happen).
The practical takeaway
Build your evaporator inspection round with the 12 points as columns and your units as rows. Once per defined period, one person in charge, one photo per finding, and comparison against the previous round. In three cycles you will have what most plants do not: the trend line of your evaporators' health.
Next week: purgers for non-condensable gases, or the air that sneaks into the system and shows up on the power bill.
Source: J. Fazzari, "Mechanical Integrity of Refrigeration Evaporators", Technical Paper #7, IIAR Natural Refrigeration Conference, 2023. Thermomac is an IIAR corporate member.
