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STORIES IN THE MAKING

Not All Drywells Are Created Equal: True Protection

Evan Burley Lightnin Mixers & Agitators
Philadelphia Mixing Solutions Raven Drywell Cutaway

In mixing applications where contamination and safety aren’t optional—they’re essential—selecting the right drive system isn’t just smart, it’s mission-critical. And at the center of that decision is one component that’s often misunderstood, misrepresented, or entirely missing: the drywell.

What is a True Drywell—And Why It Matters

At its core, a true drywell is a non-contacting, stationary barrier that separates the gearbox’s lubricating oil from the output shaft and the process zone. Its function is straightforward: to prevent oil migration that can compromise product purity, create safety hazards, and increase maintenance.

Lesser designs, like lip seals, double lip seals, or oil slingers, rely on contact-based sealing methods that wear over time. True drywells, on the other hand, are built into the gearbox casting and require no maintenance or replacement to remain effective.

Lightnin 70 Series with Stand

Why the True Drywell Is the Only Right Choice

A true drywell does more than prevent lubricant contamination. It:

  • Protects the Process – Ensures zero oil intrusion into your product
  • Protects People – Avoids oil leaks on production floors that cause slips, trips, and injuries
  • Protects the Gearbox – Prevents bearing failure due to oil washout
  • Protects the Business – Reduces downtime, regulatory risk, and warranty issues
  • Reduces Maintenance – Frees up time to focus on more critical needs

Industries That Can’t Afford to Compromise

  • Pharmaceuticals – Where cleanliness and sterility are mandated
  • Food & Beverage – Where consumer safety is non-negotiable
  • Chemicals & Coatings – Where contamination can destroy entire batches
  • Water Treatment – Where leaks cause compliance and environmental issues
Lightnin 981 Series Cutaway

SPX FLOW Mixer Drives with Built-In True Drywells

SPX FLOW Mixing Solutions integrates true drywells into select gearboxes across our Lightnin and Philadelphia product lines, including:

These AGMA-rated, mixer-specific drives are purpose-built to handle high bending moments, overhung loads, and long shafts, while maintaining absolute isolation between lubricant and process.

The misrepresentation of lesser technologies to circumvent a true drywell is becoming more commonplace, causing undesirable outcomes for the user.

That’s why we emphasize clarity in both specification and communication. The wrong gearbox might work, for a while. But in critical mixing applications, "good enough" simply isn’t.

When Purity, Safety, and Reliability Matter Most, Specify a True Drywell

Let’s not leave this to chance. If you’re unsure whether your drive includes a true drywell, or want help with specification language, our team is here to guide you.

Talk to our experts at SPX FLOW Mixing Solutions to specify the right gearbox for your application, engineered with true drywell protection, from the start.

Frequently Asked Questions

 

While that may sound convincing, double lip seals are still contact-based and subject to wear. In demanding applications, they can fail unexpectedly. A true drywell offers permanent, non-contacting protection by design.

Use precise language: “Mixer gearbox must include a non-contacting, stationary barrier drywell that prevents oil migration into the output shaft assembly.” Always verify that it's not a seal pack solution.

Oil leaks from failed seals are a leading cause of floor contamination and workplace injuries in industrial mixing areas. A true drywell eliminates this risk entirely.

Lip seals are consumable parts that rely on contact to function and degrade over time. A true drywell offers continuous, maintenance-free protection throughout the lifespan of the drive system.

Over time, lip seals or double lip seals will wear and require replacement. Servicing these seals often demands significant downtime and labor, since accessing them may require removing the gearbox from its mounting structure. Because a true drywell is integral to the gearbox casting and does not rely on contact to function, there is no concern of wear or the need for scheduled replacement.

No. Unlike lip seal arrangements, which depend on contact and can wear rapidly under shaft deflection, a true drywell is non-contacting and therefore unaffected by even excessive deflection. This makes it ideal for heavy-duty top-entry mixing applications.

Most general-purpose gearboxes are designed for flexibility across multiple applications and orientations, many of which do not require a drywell. Incorporating a true drywell adds complexity and cost to the design, which is why it's rarely found in standard reducers. Mixer-specific gearboxes, like those from SPX FLOW, include drywells because they are engineered specifically for vertical, top-entry applications where contamination risk and shaft loads are significantly higher.