This isn't cheap, but you forgot one fan:
o NMB 4110KL-04W-B10
Ticking in the tier-1 fans:
1) Foremost design criteria is life over extended temperatures
---- cheapy fans die at high or low temps
---- PSUs run hot, usually dual-ball-bearing specified
---- traffic control circuits run cold, same again
---- comes down to oil re quality & viscosity range
---- Papst will do 80-120,000hrs at 25oC
---- NMB will do similarly 100-140,000hrs at 25oC
---- Panaflo field data shows 114,000hrs at 70oC & 0 failures in 20M
---- all have ppm failure of below 50, and they scrap like kids over it
2) Material selection is thus based around rugged longevity
---- main (radial) fan bearings can have their own noise
-------- Papst > NMB > Panaflo - altho the latter two swap re some sizes
---- supplementary (axial) fan bearings also have some noise
-------- Papst & Panaflo use a thrust bearing
-------- NMB don't usually by the way their bearings are made
NMB use a pre-loaded, opposed fitted, ultra-precise ball-bearing.
o Ball-bearing fans have an inner & outer bearing
o NMB pre-load their ball-bearings in opposition
---- so reducing axial thrust noises
---- and extreme precision gives low radial noise too
o Papst bearings vary, the 80mm aren't the best
---- but the 50mm (Hungary) & some 120mm (Hungary) are very good
You may well want to repeat your test with a 4312L (120x32mm).
o 4312L is of the 4312MV series (variofan) which is 21dB(A) at 25oC
o 4312 lineage is the one that sets the life record for Papst also
The Panaflo thrust bearing is totally separate from the fan bearing,
shares nothing re lubricant - it just sits co-axial on the same shaft.
o The Hydrowave bearing is a large heavy ultra-precise sealed capsule
---- the top of the 3 fluid bearings (the simpler pivot is below)
---- cam rotates in a housing, with incredibly tiny grooves on the wall
---- it's playing with boundary layers & fluid dynamics re effect
---- the grooves & cam together never touch, but act to create pressure
---- thus it wears the least, and is the most rugged bearing
o Outside of the capsule casing is a hardened steel thrust shim
o Beyond that thrust shim is a brass/bronze thrust bearing/bushing
If you slap a Panaflo you'll hear a very distinct metallic clack.
If you push the intake side of a Panaflo in & release you get the clack.
o As you push the rotor in, the pre-loading thrust spring resists you
o Pushing the rotor in increases the thrust gap re capsule/shim/thrust-bearing
o Release the capsule/shim/thrust-bearing collide (capsule is heavy steel)
The shim isn't round, it's specially shaped, and has a hole in it which is
also not round but also specially shaped. The shim is free floating and can
spin occasionally, continually or as it feels like it. Thus you can get a
swish sound if you hold a Panaflo against your ear (literally) and disconnect
the power, it's hard to pick up but you can just about hear it. It can also
be a factor in ticking, or as a very external sounding metallic scraping.
I've wondered if the future is its replacement and another set of grooves
with a different cam shape (on ends) creating higher thrust resistance there.
However, I think the rugged requirements are as much re static (off) levels,
since the fan is heavily specified in arduous industrial not just medical.
Panaflo & NMB merged on Apr04 - about time.
The Joint Development Programme was good, but you still have two S.G.& A
structures in the two companies to support - like a gas & electric utility.
Merging the company rids the new organisation of that baggage, and brings
the capacity of NMB to bear on Panaflo - capacity restricted despite the
new plant in China & those in Japan (eg, Osaka). The unofficial name of
the new company is M3, but I guess that could change - immaterial really.
So there is a lot of change underway.
There will be some new fans - FBZ 60mm, perhaps more sizes.
However, there will never be a 120x25mm Hydrowave:
o The aspect ratio of the required size is not possible
o You can't do a co-axial shorter bearing either - idea didn't fly
Some benefits have already been noticed, the blade profile has changed a
little, the tolerances of rotor-to-hub co-axial location is tighter etc.
The cables are also moving to NMBs high temperature very tough material.
Well worth testing the NMB 120mm:
o Probably the most balanced of the fans
o Ball bearings which are a world apart from most others you've had
---- eg, NMB keyboards even used still command nearly 3 figures
The real future is the junking of the dB(A) standard, it's crap
o Fan testing is mainly rpm, current draw and such like
---- rest is engineered in re process & input quality
o So variation from say NMB & Panaflo is very slight
---- even for Papst, despite the broadband noise etc, is very slight
o Basically it is not a factor in longevity
---- running fans on/off at 7-sec gap in a 92oC overtemp HALT confirms
---- actual field data from the makers & acceptance testing is better tho
However, dB(A), Bels, Sones etc really don't work well for quiet fans.
They don't capture the narrowband/broadband difference or motor-ics,
or the human perception nuances & qualitative preferences. Doing a
sound sample, then fast fourier transform (FFT) & such can show the
differences eg, Papst above NMB above Panaflo (altho the latter swap).
However, a better standard is required - as well as a testing standard.
The standards are lagging the market need right now, not just in fans
but broadly from the testing of thermal materials to CFD/FEA data on
components, packaging, and so on.
So might be worth adding the NMB 120x25mm B10 noise spec to your tests.
Note, you will not get tacho on that NMB model - and it can be hard to
track down, since some country distributors list it as non-production,
and some other country distributors list it as a production model.
Papst are improving things - an E spec which has 85oC max temp limit,
up from 70oC which is quite a good jump (altho more for industrial use).
New blade research published, which may result in a new variation of
the Panaflo FBL to make it a bit more attractive - the data is good,
but as to whether it is better than an FBA is enclosure specific.
Waiting on the FBZ 60mm anyway.
Unfortunately the NMB is around £22 ex vat in the UK from the main
distributor (RS Components, www.rswww.com
) but as the merger into
M3 continues that means better availability = competition = prices
NMB are also very good at creating very big thin fans - eg, 174x25mm.
Not difficult to create an OEM line of very low rpm, low noise versions as
they use the same size bearing as the 120mm. Conversely the Panaflo
120mm hydrowave bearing is the size & weight of a small SUV.