Roots booster rotors for JZJ liquid ring packages

What it does inside the pump

In a JZJ package a Roots booster sits ahead of the liquid ring pump and takes the system down to a pressure the liquid ring pump could not reach alone. The two figure-of-eight rotors never touch each other or the casing — they run on a few hundredths of a millimetre of clearance, held there by the timing gears, and that non-contact running is why they need no lubrication in the gas space.

How it fails, and what you see first

Rotors are damaged, not worn out. The damage comes from contact, and contact comes from timing gear backlash, bearing wear, thermal growth after running at too high an inlet pressure, or debris drawn in. The signature is scoring on the rotor flanks or the tips. A booster that has rubbed will be noisy and hot and will have lost its clearance permanently.

What to send us so the part is right

Package model and the booster model and serial (ZJ, ZJP or ZJQ). Rotor length and outside diameter, shaft diameter, and photographs of the flanks and the tips. Say what the measured backlash was at the timing gears, because replacing rotors without correcting the gears repeats the failure.

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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