Answers
Blower and fan questions, answered
The questions our estimation desk is asked every week, with the arithmetic where it matters. If yours is not here, the form at the bottom goes to the same people.
Selection
Choosing the machine
What is the difference between static and total pressure?
Fan total pressure is the rise across the fan; fan static pressure is total pressure less the velocity pressure at the fan outlet. Catalogue curves quote one or the other, and the difference is not small on a free-discharge duty. We quote static pressure in mmWC on this site and we will restate any number in whichever basis your system design uses.
Is CMH the same as m3/hr?
Yes, cubic metres per hour. Our published data uses CMH and m3/hr interchangeably. We do not publish CFM, and we will convert if you need it.
Why does gas temperature change my fan?
Because density changes. Pressure and absorbed power at a fixed volume flow follow density, which falls as temperature rises. A fan selected cold will underperform hot, or overspeed to compensate. Use the worksheet on this site or send us the temperature with the duty.
Which wheel is most efficient?
Backward curved, up to about 85% static efficiency in our published range, then backward inclined, then radial blade last. Efficiency is bought with erosion resistance, so the most efficient wheel is often the wrong one on a dusty duty.
Axial or centrifugal?
Our own range documentation puts the boundary near 50 mmWC. Below that, an axial fan is smaller, cheaper and simpler. Above it, use a centrifugal machine.
Can a blower handle dust?
Yes, and it is the common case – but the wheel changes. Backward inclined for moderate load, radial blade or shrouded exhauster for heavy or abrasive load, with hard-facing and replaceable liners quoted as part of the machine.
Build
Materials, drives and construction
What materials do you build in?
Mild steel and structural grades including IS 2062 E250 and E350, SA516 Gr.70 plate, stainless SS 304/304L, SS 316/316L, SS 321, SS 310, SS 410, Duplex 2205, plus FRP and titanium for corrosive service, and hard-facing or wear plate on abrasion zones.
Which drive arrangement should I choose?
Direct drive (arrangement 1 or 3) is simpler, loses no belt power and needs no belt maintenance. Belt drive (4, 7, 8, 9) lets speed be trimmed at commissioning and keeps the motor away from hot or dirty gas. On retrofits belt drive usually wins because existing bases and motors can be reused.
What balance grade do you run?
ISO 1940-1 grade G6.3 as standard, tightened to G2.5 where the wheel is large or running fast. The G number is a permissible residual vibration velocity in mm/s, so the allowable specific unbalance falls as speed rises; balance quality for industrial fans is specified with ISO 14694.
Do you supply the motor?
We supply the fan with the driver specified on the order, commonly a standard IE-class induction motor to Indian supply at 415 V, three phase, 50 Hz. If your project specifies an efficiency class, a brand or a hazardous-area rating, tell us at enquiry – it changes lead time more than anything else on the drawing.
Testing
What gets tested and certified
Which test standard do you follow?
IS 4894, the Bureau of Indian Standards specification for centrifugal fans, is our normal requirements-and-test basis. Where a project demands a certified aerodynamic laboratory rating, ISO 5801 (performance testing using standardized airways) or ANSI/AMCA 210 (laboratory methods of testing fans for certified aerodynamic performance rating) is the right standard, and that is scoped and priced as a separate test programme.
Will you show me the fan tested?
Yes. Factory acceptance at the works is normal for capital orders: run test, vibration and temperature check, and on a test-programme order the performance run with the instrumentation witness list.
What documentation comes with the machine?
Approved general arrangement drawing, material test certificates, positive material identification where specified, balance certificate, test record and despatch documents. The set is agreed on the order so nobody discovers a missing certificate at handover.
Commercial
Lead time, warranty and logistics
What is the lead time?
Our published make-to-order lead times are 5 to 7 weeks for standard-scope builds and 8 to 12 weeks where material grade, impeller size or documentation load requires it. The number on your order confirmation is the one the works plans against.
What is the warranty?
One year from the invoice date, exclusive of bought-out items such as the motor, belts and drives, which carry their own manufacturer terms.
Do you export?
Yes, with packing, despatch marking and documentation to the destination requirement. Incoterms and destination port are settled at order stage; certification and test sequencing are what actually move the lead time.
Can you service or retrofit a fan you did not build?
Yes. Wheel rebuild, re-blading, hard-facing, balance correction, casing liner replacement, bearing and shaft upgrades are part of the services scope, on any manufacturer machine.
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