For heavy washdown, chemical exposure, and unprotected outdoor weighing, hermetically sealed load cells (laser-welded stainless bodies with welded cable entries) are the more durable specification, and the higher unit cost is usually recovered through longer service life and fewer recalibrations [S1][S2][S8].
Epoxy-potted cells fill the internal cavity around the strain gauges and wiring with a potting compound (typically epoxy or silicone) to block moisture, but the body itself is not a welded pressure boundary, so seal performance is fundamentally lower under high-pressure spray, detergent chemistry, and thermal cycling [S7].
How the Two Seal Architectures Differ
A hermetically sealed load cell is an air- and water-tight weighing instrument: a welded seal (typically laser-welded stainless steel) encloses the gauge area, and the cable exit uses a welded header to preserve the seal across the connection, the most common leak path [S2].
A potted load cell, by contrast, has its internal cavity filled with an epoxy or silicone potting compound to seal the strain gauges and wiring against moisture, without a true welded boundary around the element [S7]. The construction data is not equivalent: welding is a metallurgical process, potting is a mechanical encapsulation around already-potted electronics.
The mechanical difference shows up under load. Practitioner reports on field-sealing load cells note that epoxy "may crack over time when the cell is under load," which is why liquid electrical tape or other flexible coatings are sometimes preferred for retrofit sealing [S4]. Hermetic welding does not have this failure mode because the strain gauge region is enclosed by metal, not a cured polymer.
Ingress Ratings and What They Demand
Washdown ratings such as IP67, IP69K, and NEMA 4 are referenced in field guidance as the minimum targets for wet-area weighing in food production, pharmaceutical manufacturing, and outdoor service [S4].
IP67 protects against temporary immersion to 1 m for 30 minutes; IP69K covers close-range, high-pressure, high-temperature spray; NEMA 4 (and 4X for corrosion) covers hosedown and rain on enclosures. A laser-welded hermetic cell with a welded cable entry is the construction that can credibly claim these ratings; a potted cell can usually clear splash ratings but typically not sustained immersion or 80°C, 80–100 bar washdown chemistry [S2][S4].
Rice Lake guidance on tough applications reaches the same conclusion: heavy washdown and chemical exposure call for a hermetically sealed cell rather than a basic environmental seal, and tool-steel cells (the lowest-cost body material) are explicitly flagged as unsuitable for wet service because moisture will rust the 4340 alloy body [S1][S3].
Materials, Capacities, and Body Construction
Hermetic cells for washdown are typically built from 17-4 PH heat-treated stainless steel, balancing accuracy, low deflection, and corrosion resistance. Transducer Techniques' HSW series, for example, uses 17-4 PH stainless, offers capacities from 1,000 to 50,000 lb, and adds a stainless molded connector system explicitly to resist washdown and most chemicals [S5].
For context on load cell material selection more broadly, the body alloy is the first decision: tool steel (commonly 4340) for dry, low-cost service; aluminum for low-capacity, weight-sensitive builds; stainless (typically 17-4 PH or 17-7 PH) for any environment where moisture or corrosive cleaning agents will reach the cell [S1].
Capacities in the hermetic-stainless segment span roughly 1,000 to 50,000 lb as a published commercial example, which covers most weigh-hopper, vessel, and platform-scale duties in food, chemical, and pharma plants [S5].
Decision Matrix: When Each Type Earns Its Slot
Use the following criteria to pick between hermetic, potted, and a third option (a basic environmentally sealed cell with a compression-gland cable entry) for a washdown application. Each row uses data grounded in the research above. [S2]
Ingress target. Heavy washdown with hot detergents at high pressure (IP69K, NEMA 4X): specify hermetic. Splash and humid air only: a potted cell is usually adequate. Sustained submersion beyond 1 m: only purpose-built submersible cells with full hermetic body and cable swaging, not retro-sealed cells [S2][S4].
Chemistry exposure. Caustic or acidic cleaning agents, chloride sanitizers, and chemical vapors degrade polymer potting over time. Laser-welded stainless with a welded header resists these; potting can absorb and slowly break down [S2][S8].
Mechanical strain on the body. Cells under high cyclic load, shock loading, or large dead-load-to-live-load ratios (common in weigh hoppers) put the encapsulation under repeated strain. Epoxy can crack under such duty, which is why field reports on retrofit sealing prefer flexible coatings over rigid epoxy [S4]. Hermetic welding removes the polymer from the load path.
Total cost of ownership. A hermetic cell costs more at purchase but avoids the "repeated maintenance and replacement" of non-sealed cells and reduces the risk of "sudden failure" that causes process downtime; for harsh chemical, washdown, and outdoor service, the higher first cost is typically the lower lifecycle cost [S8].
For a practical fit, the criteria line up as: pick hermetic when any two of (IP69K target, chemistry exposure, cyclic/shock loading) apply; pick potted when the duty is light splash, no chemistry, and the cell sees steady low-cyclic loading; pick a basic sealed cell for benign indoor weighing where moisture is incidental.
Failure Modes and Field Pitfalls
On a hermetic cell, the cable-to-body interface is the most frequent leak path, because the strain-gauge cavity may be perfectly welded while the cable gland is the weak link. Cable damage (a nick in the jacket) can wick water past the gland and into the body, so cable routing, strain relief, and cordgrip or swaged terminations are part of the specification, not an afterthought [S2][S4].
On a potted cell, the failure modes are different: encapsulation cracking under load, chemical attack on the polymer, and air-pocket voids during the original potting that let moisture condense on the gauges. Even successful potting does not make a potted cell equivalent to a hermetic one for high-pressure spray or immersion duty [S4][S7].
There is a related pitfall specific to immersed force measurement: a load cell is a force sensor, but if the application treats it as a scale (mass) sensor, buoyancy of the hardware and the load in the working fluid must be subtracted. This is independent of seal type but shows up in any "load cell underwater" project, including the practitioner thread on submersible weighing [S4].
Standards, Sourcing, and Selection Checklist
Two reference points from the research drive a clean specification. First, Rice Lake's tough-application guidance: define the wet/dry/chemical/vibration/shock/immersion profile of the site before choosing the cell, and select body material (tool steel vs aluminum vs stainless) to match [S1]. Second, Rice Lake's seal-type overview: hermetic seals are "best suited for heavy washdown or corrosive environments" because they are air- and watertight [S6].
Use this pre-purchase checklist so the spec lines up with the application:
(1) Document the washdown regime: pressure, temperature, chemistry, frequency, and whether the cell will ever be immersed. Map that to an ingress target (IP67, IP69K, NEMA 4 or 4X) [S4].
(2) Specify body material as 17-4 PH (or 17-7 PH) stainless for any wet or corrosive duty, and reject tool steel for those environments [S1][S5].
(3) Require a welded (not glued, not gasketed) cable entry on any hermetic cell, with cordgrip or swaged strain relief, and plan cable routing to prevent jacket damage that could wick water inward [S2][S4].
(4) Match capacity to the vessel with headroom for shock and dead load; commercial hermetic lines such as the HSW series cover 1,000 to 50,000 lb as a reference range [S5].
(5) If selecting a load cell module or weigh module assembly (for example a vessel-weighing system), confirm the module's hardware is also rated for the washdown regime; a hermetic cell inside a non-sealed module loses much of its advantage [S8].
Verdict for the Spec Writer
For any washdown service that involves hot detergents, high-pressure spray, chemical sanitizers, or outdoor exposure, write the spec for a hermetically sealed, laser-welded stainless load cell with a welded cable entry, and accept the higher unit cost as a lifecycle trade [S1][S2][S8].
For light splash and benign indoor duty, an epoxy-potted cell remains a cost-effective choice, but the spec should still call out the ingress target, the potting compound (epoxy vs silicone), and the cable-termination method, so the cell does not get oversold into a duty it cannot handle [S7].
Trackable signals to watch on the next sourcing cycle: vendor disclosures of IP69K test data (not just IP67), NEMA 4X certification on the whole weigh module (not only the cell), and published mean-time-between-failure data for hermetic cells in food, pharma, and chemical washdown, which would let a buyer convert the "longer life" claim into a quantified service interval [S2][S4][S8]. For related mechanical-equipment decisions in the same plant context, a spec-driven comparison of sealless magnetic drive vs mechanical seal centrifugal pumps follows the same selection logic of matching seal architecture to the chemistry and exposure profile.
The underlying component specifications are covered under electronic load.