Wet wood pulp fan tonal noise
“I have never seen such an amazing result from a consultant in my career.”
Remote fan noise control, UK to New Zealand, no site visits... New wet wood pulp fibre bulk solids conveyor fans at the Pan Pac facility in New Zealand had caused noise complaints. The company made the very proactive “good neighbour” decision to shut down the plant overnight despite a substantial cost that posed a threat to the business.
“Shutting down 30% of our operation overnight was a significant cost and particularly damaging after the site was flooded and out of operation for over a year and needing investment of over $150M in the site flood repairs.”
Within exactly 3 weeks of googling the options and contacting INVC, noise from all 3 fans had been diagnosed, the solutions designed and installed with zero additional downtime. This resolved the problem and the plant was returned to 24-hour operation.
“On behalf of Pan Pac (and probably our neighbours as per this text) I would like to thank Peter Wilson and the INVC team for the professional service you have given and for helping overcome, in a very short time, a major threat to our business.”
“I have never seen such an amazing result from a consultant in my career. We were going down the acoustic insulation route before I “Googled”. I will call it lucky I found your website. Please make sure you pass on my thanks to your team!” Roger Jones, General Manager.
What fan noise attenuation technology made this possible?
Conventional silencers would not have been practical due both to the low frequencies involved and the passage of wet pulp solids that would have clogged any attenuators very quickly.
Locations: Pan Pac, New Zealand. INVC, UK offices
The 3 week process
- Pan Pac googles “fan noise control”
- Email to INVC
- Smartphone video and fan details requested
- Videos sent, analysed, problem diagnosed, costed proposal provided
- POs received
- Detailed recommendations designed and issued
- 3 fans modified (using local engineers)
- Plant returns to 24-hour operation
- Neighbourhood happiness confirmed…
The diagnosis
The complaints were caused by fan blade pass hums at 89Hz, 95Hz and 280Hz from 3 different fans.
The solution
Designing bespoke aerodynamic inserts for each fan based on the fan geometries and flow paths. These were made locally in New Zealand (simple sheet metalwork) and welded into the fan volutes to reduce the turbulence causing the tonal noise at source.
This is a permanent, low-cost solution with no effect on performance that will last the lifetime of the fan without maintenance, despite the passage of wet pulp solids.
Conventional options?
Conventional silencers could never be practical for this application due both to the required length of around 10m and the fact that they would clog very rapidly. Acoustic lagging of the entire systems would have been very costly and caused problems with both maintenance and corrosion. Moreover, silencers would still have been required…
Pan Pac
For over 50 years, Pan Pac Forest Products has been growing, processing and delivering wood products.
The Pan Pac Pulpmill produces up to 850 tonnes/day of Bleached Chemi Thermo Mechanical (BCTMP) wood pulp.
Pan Pac BCTMP is used in in the production of paper products including packaging boards, paper towel and paper. The Pan Pac Pulp markets include New Zealand, Australia, China, Indonesia, South Korea, Japan, Malaysia, Taiwan, Vietnam, India, and Pakistan. https://www.panpac.co.nz/
