Bypass valves for Roots booster packages

What it does inside the pump

The bypass valve protects the Roots booster at high inlet pressure. A Roots booster generates heat in proportion to the pressure difference across it, and at start-up, when the system is still at or near atmosphere, that difference is at its worst. The bypass opens and recirculates gas around the booster until the pressure has been pulled down, then closes and lets the booster do its job.

How it fails, and what you see first

Bypass valves fail stuck, and the direction matters. Stuck shut means the booster runs at full differential from the first second of every start and overheats — this is the failure that ends with rubbed rotors. Stuck open means the package never reaches its rated ultimate pressure, and the usual misdiagnosis is that the liquid ring pump has lost performance. Springs also relax, so a valve can open at the wrong pressure while still moving freely.

What to send us so the part is right

Package model and serial, valve size and the set pressure it should open at. Say whether it is spring-loaded, weight-loaded or actuated. If the package has been overheating at start-up, tell us the discharge temperature you measured — it tells us whether the valve or the timing gears are the problem.

Which models take this part (21)

Grouped by pump family. Model numbers in blue have their own page with the full specification table; the rest are supplied from the same frame — send the model and we confirm against the drawing.

Other parts for the same machine

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