What are clean air and dirty air tests?
Ans:- clean air and dirty air flow tests are carried out for knowing coal mill performance.
When and where are they done?
Ans:- clean air test is conducted on standby coal mill or coal mill during shut-down and dirty air test is conducted on running coal mill.
What are the benefits of this activity?
  • To know the velocities in each coal pipe
  • To know the coal fineness of the coal mill
  • To adjust the flow from coal pipe by adjusting orifice.
  • To know the flow deviation
  • To know the air / coal ratio.
  • Combustion can be improved.
What are the conditions to carry out clean air and dirty air test?
Ans :--
  • Coal mill to be in cold condition for clean air test , and coal mill to be in running condition for dirty air test.
  • Test to be taken on full operating parameters of coal mill.
  • Boiler to be in boxed / running condition respectively.
What are the requirement from client for clean air and dirty air test?
Ans :--
  • Air supply to be available at port location.
  • Platforms to be made available at port locations.
  • ball valve to be available at port for isolation.
  • Ports are to be at 90 degree apart.
  • Ports are to be as nearer to burner as possible.
  • 40 mm port to be made available.
  • Coal mill parameters are to be kept constant during the time of dirty air test.
What is the procedure for clean air and dirty air test?
Ans :-- Procedure is attached herewith.
Can output be guaranteed from analysis of clean air and dirty air test?
Ans :-- Yes, Benefits are there , subject to operation at designed parameters and good maintenance practices.
What is justification of the budget of clean air and dirty air test?
Ans.:-- All the benefits are justification of the test cost.
Can it be done in any Boiler?
Ans :-- . it can be done only in P.F. boilers
What type of benefits are there by recommendations of this activity?
Ans :--
  • Coal mill performance will be improve.
  • Combustion will improve
What are the type of instruments used?
Ans :-- Instrument used for this testing is " Pitot tube , Manometer , iso-kinetic kit. etc. "
How much time is required for this test?
Ans :-- Four to five hours for clean air and eight to ten hours for dirty air test per mill..
How much time is required for implementations of recommendations (orifice correction)?
Ans :-- Five to six hours depending up on client man power..
How many persons are required for the test?
Ans :--Two to three for clean air and four to five for dirty air test.
What are the appliances are used during testing?
Ans :-- Mask , plain goggle, hand gloves , writing pads, required formats, control room data formats , pen , pitot tube , manometers ETC
What should be the frequency of this test?
Ans :-- It should be carried out in every overhaul of the unit / mill to know changes in flow and effect of any maintenance during running condition.