Can a single-passage rotary union be converted to dual-passage?

No — pick the passage count up-front. Maier supplies single through 8+ passages.

How long does a mechanical seal last?

On clean water, 5+ years. On steam or hot oil, 1–3 years depending on duty.

Resources

A correctly specified rotary union runs for years. A wrongly specified one leaks within days. These are the six parameters that matter.

Water, hot water, steam, hydraulic oil, thermal oil, coolant, compressed air. Each drives material and seal compound.

The combination matters — saturated steam at 10 bar is far more aggressive than cold water at 10 bar.

Surface speed at the seal interface drives wear. High-speed rotary unions need balanced mechanical seals.

Single, dual or multi-passage. Multi-passage adds size and cost but eliminates the need for slip rings on instrumented spindles.

Packed seals — simple, maintenance-light. Mechanical seals — leak-tight, long-life, the default for steam and hot oil.

Self-supported or fixed-bearing — depends on shaft runout and operating speed.

Can a single-passage rotary union be converted to dual-passage?: No — pick the passage count up-front. Maier supplies single through 8+ passages.
How long does a mechanical seal last?: On clean water, 5+ years. On steam or hot oil, 1–3 years depending on duty.

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