Noisy Two Lobe Blower

Clearances and timing are critical. Is it mechanical noise?

Assuming no mechanical noise (Unredundant covers that) then it must be understood that Roots type blowers are inherently noisy things as they are fundamentally PD blowers with a pulsed flow, this can set up all kinds of resonances in the surrounding large pipework. Even with silencers you may battle to get much below about 85 to 90 dB. Acoustic insulation of the pipe (duct) work and a sound hood on the blower may help dampen the noise to acceptable levels.

Is the gearbox knackered worn out? If so, then the noise might be due to the two lobes coming into contact at each turn.

Consult the original equipment manufacturer for specialist advice, especially if the equipment is still under warranty.

Exactly, if the back-lash of the timing gears/synchronizing gears go more, the lobes are likely to contact. By design, lobe clearance is set more than the gear clearance. Had ther be a contact between the lobes, in bigger machines, can be inspected from the suction or discharge ports, by visual means or by inserting long feeler gauge which is meant for this purpose.

Thanks for your response. I want to add few more information. The machine is newly installed. Gear backlash and shaft vibration is within limits. Suction and discharge pipes are of 20" size. Simple adsorptive silencers of about 3000 mm length each are provided on both sides. Noise hood(acaustic enclosure) is provided for blower+motor. Filter house (installed upsream of suction silencer) also has acaustic enclosure. Still we are facing the problem of high noise level. With these additional information, I request members to give suggestions for reducing noise level.

That's a big Roots blower, estimated 400kW motor. So no surprise it's noisy, even if it's in good condition. To reduce noise, you might need to consider putting an acoustic enclosure round it.

Cheers..........Codey