What is Duct test ?
Ans :- It is gas flow distribution test in the duct
Where it is done ?
Ans :- It can be done in any duct . mainly the testing is done in duct from air heater out let to ESP inlet duct and ESP out let to ID fan inlet duct.
What are the benefits of this activity ?
Ans :-
  • It can predict the pressure drop in the duct
  • Leakages can be predicted
  • Re circulation zone can be identified
  • Actual Gas flow can be observed
  • Loading of the fan can be reduced by attending the observations.
  • Gas flow will be equalized in all the passes.
What are the condition to carry out Duct test ?
Ans :--
  • Unit should be on full load
  • Preferably testing to be in day light for safety point of view.
  • Boiler parameters are to be kept constant during testing
  • Testing to be carried out in one go only
What are the requirement from client for Duct test?
Ans :-
  • Test ports of 100mm ID are to be ready at inlet and out let of the ducts with flanges.
  • Preferably test ports are to be on top of the duct
  • Set to on full load , ie. gas flow should be 90 to 100% of the MCR .
  • Boiler parameters are to be kept constant at the time of testing
  • Clear and safe approach near test port.
What is the procedure for Duct test ?
Ans :- Procedure is enclosed herewith.
Can output be guaranteed of Duct test
Ans :- Yes.
  • Gas flow balance in all the duct within variation of 10% can be achieved subject to no air leakage in the duct.
  • Reduction of ID fan current approximately 5 % subject to same boiler parameters and condition.
What is justification of the budget of Duct test?
Ans :--
  • Cost of Power saving / auxiliary consumption.
  • ESP loading will be equal by laminar flow.
Can it be done in any Boiler duct ?
Ans :-- Yes , the test can be done in any boiler duct as per requirement of the client. What all the tables in report indicates. Ans :--
  • Static pressure
  • Dynamic pressure
  • Velocity of that zone
What is static pressure ?
Ans :--
  • Resistance to flow
  • The pressure exerted by liquid or gas when the bodies on which the pressure is exerted are not in motion.
What is Dynamic pressure ?
Ans :--
  • The dynamic pressure is equal to the difference between the stagnation ( static) pressure and the static pressure
  • Dynamic pressure is the kinetic energy per unit volume of a fluid
What is velocity ?
Ans :- Velocity is defined as the rate of change of position with respect to time
What is the type of instruments used ?
Ans :-- It is done by use of pitot tube and MANOMETER.
How much time is required for this test ?
Ans :-- Normally six to eight hours , by one team , team having three to four person depend upon number of ports and capacity of unit.
How much time is required for implementations of recommendations ( Diverter plats ) ?
Ans :-- Approximately fifteen to twenty days , depending upon the number of diverter plates are to be erected.
What appliances are the used during testing ?
Ans :-- 'S' Type Pitot tube , extension if required, manometer ,connecting tubing , helmets, safety shoes , writing pad , pen etc.
How erosion occurs in Duct ?
Ans :--
  • Ash particle hits the duct surface .
  • angle of impingement
  • Duct lay out i.e. flow divert.
Where Duct leakage are expected more ?
Ans :--
  • From joint of gates and dampers.
  • From expansion joints.
  • From corner of ducts
  • From side and top wall of the ducts.
What should be the frequency of this test ?
Ans :-- It should be carried out in every overhaul of the unit to know changes in flow and effect of any maintenance during the span of one year.