Tip Speed for Axial Fan Limits...

[Trublu97]

Anyone know the design limitations for specifying "blade tip speed" for an axial fan. I think the end use is blowing air to remove soot on the discharge of a boiler. Large volume, low pressure application.

Have an EPRI doc on fans but it doesn't really address the tip speed. No API standard for axial fans that I can find.

Thanks.

 

[speco]

Trublu,

There is an tip speed limit in the API standard for air-cooled exchangers. It's 12,000 ft/min except for small, directly-driven fans, which is (from memory) 14,500 ft/min.

Air-cooled exchangers typically have a static pressur on the order of .5" WG. If the fan static pressure is much higher in your application, you might need a higher tip speed.

One word of caution: Fans with tip speeds in this range will be very noisy. Lately most customers seem to be requiring tip speeds below 10,000 or even 9,000 ft/min.

Regards,

Speco

 

[Trublu97]

Thanks!
API 661
Heat exchangers standard, who would have thunk it.

7.2.3.5
BTS shall not exceed 12kft/min unless requested for the th buyer and in no case exceed 16Kft/min.