The Reefer Panel That Held Water Behind Its Liner

A refrigerated body is a sandwich. An outer skin, usually fibreglass reinforced plastic or sheet aluminium, an inner liner of the same family, and between them a core of polyurethane foam that was injected as a liquid and expanded in place against both faces. Extruded corner posts and bottom rails tie the panels together and carry the fastener loads.

That foamed in place construction is why these bodies insulate as well as they do, and it is also why they cannot be repaired the way a hollow wall can. The foam is bonded to both skins across its whole area. There is no cavity, no access and no path to run anything through. Whatever gets into the panel is in the panel until somebody cuts it open.

Rarely through the middle of a panel. Almost always at an interruption: a door post, a bottom rail joint, a hinge or latch fastener, a scuff line where a forklift has kissed the wall, or the seam where a panel meets a corner post. Those are the places where the skin is penetrated or joined, and a joint that has moved is a joint that lets water past.

Foam itself is closed cell and resists water reasonably well. What does not resist is the interface between the foam and the skin. Once water reaches that boundary it travels along it, following gravity and any slight debond, and it accumulates at the lowest point it can reach, which is the bottom rail. That is why a leak at the top of a door post produces a saturated zone at floor level several feet away.

• Door posts, latch and hinge fasteners, bottom rail joints
• Forklift scuff lines where the outer skin has been opened
• Panel to corner post seams that have worked loose
• Water travels the skin to foam boundary, then pools at the bottom rail

First, weight. Water is heavy and a saturated panel section carries hundreds of pounds of it. Every pound is payload the truck cannot carry and fuel the engine burns moving nothing. On this body the difference against its sister unit was around four hundred pounds on a scale.

Second, insulation value. Wet foam conducts heat far better than dry foam, so the refrigeration unit works longer to hold setpoint. Ninety extra minutes of run time a day is fuel, and it is also wear on a unit whose overhaul interval is measured in hours. Third, structure. Water at a bottom rail sits against fasteners and against whatever steel is in that assembly, and corrosion in a bottom rail eventually becomes a rail replacement.

Three tests, in increasing order of intrusion. Weigh the unit and compare against a known dry sister body or against its own recorded tare. A large unexplained gain is strong evidence on its own. Then run the box down to temperature and survey the exterior with a thermal camera. Wet insulation shows up as a clearly defined anomaly against the surrounding panel, and the boundary of that anomaly is the extent of the problem.

Third, tap it. A dry sandwich panel returns a bright report. A saturated section sounds dead and heavy. If the picture is still ambiguous, a small test hole low in the bottom rail area will tell you within seconds, and on this body it produced water. That hole is a legitimate diagnostic step and it gets properly sealed afterward as part of the repair rather than left as a drain.

People ask, reasonably, whether the panel can be dried. The answer is no in any practical sense. Water sits at the skin to foam boundary in a bonded assembly with no ventilation path. Heat applied from outside will drive some vapour toward the skins and can debond the foam further. Time does nothing, because there is nowhere for the moisture to go.

So the repair is removal. The affected skin section is cut out, the wet foam is removed back to dry material, new insulation is installed, and the skin is closed with either a laminated fibreglass repair or a bonded and riveted metal panel depending on the original construction. The interior liner gets the same treatment. It is real work and it is the only work that changes the outcome.

On this body the wet zone ran about five feet up from the bottom rail and roughly three feet forward of the door post. Skin off, foam out, new closed cell board bonded in with the joints sealed, skin closed with a laminated repair, liner replaced, and the bottom rail drainage path cleared where it had been packed with old sealant and debris. Six days in the bay including cure time between stages.

Prevention is unglamorous. Keep the interior scuff plates and door post kick plates in place and replace them when they are damaged, because they exist to take the forklift hit instead of the panel. Inspect door post seams at every service. And weigh bodies periodically, since a slow weight gain across a year is the earliest signal available and it needs no tools at all beyond a scale ticket.