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| Hot air rework station pumps - food for thought ? |
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| ebastler:
--- Quote from: Fraser on April 20, 2021, 05:11:42 pm ---The diaphragm, motor driven piston and Regenerative compressors can produce decent air pressure at low air flow rates. The simple turbine and centrifugal ‘blowers’ are not normally capable of producing much air pressure at low air flow rates. Why does this matter ? Well in the case of a hot air rework station you do not want very high air flow that blows components off of the PCB yet you do want air pressure that is maintained even with highly restrictive small cross section air output nozzles. --- End quote --- Seems to me that, as long as the restriction (i.e. the nozzle diameter) does not vary dynamically, the "pressure vs. flow rate" property of the air source is not too critical. Choose a nozzle diameter, then set the fan speed such that you get the desired air flow -- done. This should work with any old fan, and works well enough in practice, as witnessed by my cheap Chinese hot air station. |
| Fraser:
Pneuvay Engineering comment on Centrigual vs Regenerative blowers..... http://www.pneuvay.com.au/pneumatic-conveying/news/Centrifugal-blowers-vs-regenerative-blowers---The-BIG-difference/ CENTRIFUGAL BLOWERS VS REGENERATIVE BLOWERS - THE BIG DIFFERENCE Centrifugal and regenerative blowers are widely used in industrial processes. Both can look very similar but there are many distinct differences you should know about these two blowers such as the following: CONFIGURATION OF CENTRIFUGAL BLOWERS AND REGENERATIVE BLOWERS Distinct differences are clearly seen in the configuration of these two blowers as explained below: Centrifugal blowers are configured such as its inlet and outlet are perpendicular. The inlet feeds air into the centre of the impeller while the outlet stays in tangential to the rotation of the impeller as shown in the image below. centrifugal blowers vs regenerative blowers On the other hand, regenerative blowers have parallel inlets and outlets that are positioned perpendicular to the rotation of the impeller as illustrated above. IMPELLERS AND IMPELLER CASING OF CENTRIFUGAL BLOWERS AND REGENERATIVE BLOWERS Centrifugal blowers allow air to enter at the centre of its rotating impeller where a number of fixed vanes acts as paddles that pushes volumes of air to the outlet. Through a centrifugal action, air is forced to the impeller and housing where it is discharged as steady steam through the outlet. This creates negative pressure at the centre hub that sucks in more air. Centrifugal blower working principle Unlike centrifugal blowers, regenerative blowers are fashioned in a different manner. It consists of an impeller that spins within a housing compartment, which contains both an inboard channel and an outboard channel; thus an alternate name given to it as side channel blowers. The moment the impeller spins past the intake import, air is drawn in and is trapped between its impeller blades. As it continues to spin, air is pushed both inward and outward through both of the channels. This continues until the impeller stops rotating. As a result, regenerative blowers can act either as a pressure blower or a vacuum blower. Regenerative blower operating principle MAINTENANCE OF CENTRIFUGAL BLOWERS AND REGENERATIVE BLOWERS In comparison, centrifugal blowers require more frequent maintenance compared to regenerative blowers because of certain parts that requires lubrication, particularly its bearings. Regenerative blowers are considered contact free machines thus it is virtually maintenance free and can operate up to 40,000 hours without the need of being serviced. NOISE LEVELS OF CENTRIFUGAL AND REGENERATIVE BLOWERS Regenerative blowers showcase extremely low noise which make it a favourite for noise-sensitive applications. Talk to us to know more about our centrifugal blowers with low noise level for your specific requirement. APPLICATION TO INDUSTRIES OF CENTRIFUGAL BLOWERS AND REGENERATIVE BLOWERS As a general rule centrifugal blowers are considered low pressure, high flow blowers while regenerative blowers are high pressure, low flow blowers. This makes it ideal for the following industry applications: APPLICATIONS OF CENTRIFUGAL BLOWERS Centrifugal blowers work for applications such as heating a furnace with hot air where a large air volume is required to fill the space. This includes: Climate control Cooling machinery Dryers Dust collectors Exhausting gases and vapours Filter installations Food industries Furnaces Grain elevators Printing machines Hot air blowers Household machines Incinerators Machinery for the food and beverage industries Plastic extruders, laminators, film processing machines Pneumatic transport Pollution control equipment Uniform temperature equipment Textile machines Woodworking machines APPLICATIONS OF REGENERATIVE BLOWERS Regenerative blowers are mostly used in flammable gas, hazardous duty, industrial air movement, water treatment, and heavy duty transportation applications such as: Aquaculture/pond aeration Chip removal for engraving equipment Dust and smoke removal Industrial vacuum systems Packaging applications Pneumatic conveying Printing presses Spas and dryers Sewage aeration Soil vapour extraction Vacuum lifting Vacuum packaging Vacuum sintering and casting Pneuvay Engineering distributes Spencer centrifugal blowers and regenerative blowers. Talk to us at 1300721458 to know how we can deliver these to your business. |
| Fraser:
The Weller hot air station also uses a centrifugal blower. https://www.eevblog.com/forum/reviews/weller-wha-900-hot-air-station-teardown/ So it would appear that centrifugal blowers can be made to work in a hot air station application. Interesting that they do not use the more appropriate regenerative pump/blower though. Could it be cost related or maybe marketing based on the high "litres per minute" of air that they can produce....... a daft characteristic to use where SMT reflow is involved though. High flow for shrinking heat shrink maybe, but when working on tiny SMT components it is just asking for trouble. As Alex on the NorthridgeFIX Youtube channel would say.... they would get blown into the 9th dimension ! ;D |
| wraper:
--- Quote from: Fraser on April 20, 2021, 08:50:34 pm ---Could it be cost related or maybe marketing based on the high "litres per minute" of air that they can produce....... a daft characteristic to use where SMT reflow is involved though. High flow for shrinking heat shrink maybe, but when working on tiny SMT components it is just asking for trouble. --- End quote --- Quick works just fine within full 1-120 l/min range. Not to say with lower airflow there is a way less pressure to supply. |
| Fraser:
Wraper, 120l/min is not that bad, as you say. My pace units maximum airflow is around 25 l/m and the JBC is 34 l/m. The AMETEK centrifugal fans I was looking at had figures of 700 l/m ! My little 3" AMETEK blowers are rated at 18cfm which is 500 l/m ! It would appear that the Quick blower, despite its relatively large size is not running at anything like its full output flow capability. That is why I was wondering whether manufacturers are using an 'oversize' centrifugal blower and just not running it hard in order to better cope with the variable output port dimensions. As I previously said, this is not a topic that I have studied so I am just curious. I attach pictures of my diminutive 3" AMETEK centrifugal blower. They are usually scary expensive at around $500 each but I bought them new for £25 each. Very nicely made 6Vdc to 14Vdc units. The BLDC motors have a built in controller that uses supply voltage to set shaft RPM. Even if I do not use them for the hot air station upgrades, I feel sure they will come in useful. Sadly mini regenerative blowers are anything but common and those I found were also around $500 ! |
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