Abstract

High ingress protection ratings and stainless-steel construction are widely regarded as sufficient safeguards for food-processing and cold-storage environments. Field data, however, reveals a recurring failure mode — internal condensation — that lies outside the scope of IP certification. This report documents the thermodynamic mechanism responsible, identifies the operating conditions that elevate risk, and describes the engineering countermeasures implemented in Fidelity Measurement's current stainless-steel indicator line.

Keywords: condensation, IP rating, stainless-steel indicator, cold storage, food processing, breathable vent, long-term reliability

§ 1 Background and Observed Failure Pattern

Over the years, Fidelity Measurement has received periodic field reports describing membrane keyboard failures on stainless-steel weighing indicators operating in food-processing and cold-storage environments. On the surface, these failures appear difficult to explain: the affected units carry IP66, IP67, or IP68 ratings and are housed in corrosion-resistant SUS304 enclosures — specifications that should, in theory, provide adequate protection against moisture ingress.

Closer investigation pointed to a failure pathway that standard protection ratings are not designed to address: condensation forming inside the sealed housing itself.

Figure 1 — Fidelity Measurement Stainless-Steel Weighing Indicators Under Washdown Conditions

Both models are housed in SUS304 stainless steel and rated IP66. Water droplets visible on the housing surface illustrate the washdown and moisture-exposure conditions discussed in this report.

§ 2 The Thermodynamic Mechanism

Most weighing systems are assembled, calibrated, and tested under normal room-temperature conditions. The air sealed inside the housing at the time of manufacture reflects that ambient environment. When the unit is subsequently installed in a cold-storage or refrigerated production setting, the enclosed air mass contracts as temperature falls.

The critical insight is that this mechanism is intrinsic to the physics of sealed enclosures operating across temperature gradients. An indicator does not need to be immersed in water, exposed to a washdown jet, or suffer a seal failure for condensation to occur. The process is driven entirely by repeated thermal cycling.

§ 3 High-Risk Operating Environments

The following facility types represent the conditions most associated with condensation-related failures in field data. The common factor is not extreme cold in isolation, but the frequency of transition between warm, humid areas and cold production or storage zones.

§ 4 The Sealing Paradox

This is the counterintuitive nature of the problem. Higher-rated seals reduce the rate at which internal pressure differences can equalize with the external environment. While this prevents liquid ingress during washdown or immersion, it also prevents the slow equilibration that would otherwise dissipate accumulated humidity. The result is that IP67- and IP68-rated enclosures may, under repeated thermal cycling, trap more internal moisture over time than lower-rated designs that allow some degree of passive pressure relief.

§ 5 Engineering Countermeasures

After investigating field reports and working closely with customers to characterize the failure mode, Fidelity Measurement conducted a structured review of the housing design, sealing architecture, pressure behavior, and long-term reliability requirements of its stainless-steel indicator product line.

As part of a continuous product improvement program, several design measures were implemented with the aim of reducing condensation risk in temperature-cycling applications. The primary measure is the incorporation of a waterproof breathable vent into the housing design. This component allows controlled pressure equalization in response to thermal cycling, while maintaining protection against liquid ingress and particulate contamination.

Field experience following the design change has shown a meaningful reduction in condensation-related failures compared with conventional fully sealed designs. No single engineering measure can completely eliminate condensation under all operating conditions; however, addressing the pressure differential that drives moisture accumulation represents a material improvement in long-term reliability.

§ 6 Consequences of Unaddressed Internal Condensation

When moisture accumulates inside a sealed enclosure over multiple thermal cycles, the resulting effects are progressive and cumulative. Field data identified the following outcomes, presented in approximate order of manifestation:

§ 7 Product Design Summary

The following summarizes the key design characteristics of the current Fidelity Measurement stainless-steel indicator line as relevant to the reliability considerations discussed in this report.