Page 22 - Energize July 2021

NEWS

INNOVATIVE PROCEDURE FOR BALANCING

OF LARGE ID FAN ROTORS APPROVED

proposal put forward by LH Marthinusen (LHM) to Eskom to introduce a new procedure for
balancing large induced draught (ID) axial fan rotors, as used on boilers after undergoing
A epairs, has been accepted by the utility. The new procedure offers substantial advantages
r
over the previous method applied for this purpose.
As a result, the new procedure is now used by LHM as part of the periodic inspections and
overhauls it performs on the ID axial fan rotors at the Majuba, Medupi and Kusile power stations.
The new procedure comprises a balancing test which is performed on each ID axial fan
rotor after its condition has been comprehensively assessed and all wear and damage has been
repaired and the rotors are returned to “as new” condition at LHM’s main repair facility in Denver,
Johannesburg.
“Previously the ID fan rotor balancing was done in situ after the repaired rotor was re-
installed in the plant. This involved having to test run it repeatedly with corrective adjustments
being made as imbalances were detected, resulting in delays on each occasion of up to 24 hours
before full operation could be resumed,” said Craig Johnston, General Manager of LHM’s Fan
Service division.
“Having balanced the ID fan rotors at our plant prior to delivery, they can go into full
operation immediately after being re-installed. This means significant time- and cost-saving
benefits for the power station, as it eliminates down-time on balancing before start-up, as well as
saving production time lost due to the prolonged balancing procedure applied previously.” A test technician conducts a test on a large ID
Johnston said putting the ID fan rotor testing system into effect was simply a matter of piggy- fan rotor from Majuba power station in the
backing on LHM’s Large Rotating Machines division’s existing large test bay at Denver. “All that’s Large Rotating Machines test bay at LHM’s
Denver facility.
required to temporarily convert the large machines balancing bay into a test bay suitable for our
purposes is the addition of a few items of ancillary equipment to the test bay,” he remarked.
To date the new balancing test procedure has been applied to a total of four large ID fan “For example, a rotor at Majuba weighs
rotors from the Majuba and Medupi power stations over the past year. 13,5 t and is driven by a 7,2 MW motor,
“The test is carried out once the comprehensive inspection-and-repair procedure we perform while a rotor from Kusile weighs 19,5 t and
on each ID fan rotor and its set of detachable axial fan blades, having operated continuously for a operates with a 10,2 MW motor,” Johnston
period of years, has been completed,” Johnston explained. pointed out.
The function of the ID fan is extraction of flue gas from the boiler in the power plant. The
design of the ID fan rotors and their axial fan blades for each of the three power stations differ Contact Craig Johnston, LH Marthinusen,
substantially from each other and also have a different mass and power rating in each case. Tel 011 615-6722, craigj@lhm.co.za

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