fans: operation and maintenance

MODULE 69
FANS: OPERATION
AND MAINTENANCE
This month’s Skills Workshop provides an overview of the maintenance
requirements for fans and associated systems. Last month, in part one,
we looked at the operation of fans.
MAINTENANCE
The maintenance imperative
PULLOUT
Most fan maintenance involves checking drives and belts for wear, performing
preventative or predictive maintenance activities on bearings, and ensuring
correct alignment and proper motor condition and function.
However, maintenance regimes also need to extend beyond the fan itself
and for many HVAC&R applications, “system maintenance” is crucial for
ensuring the energy-efficient operation of fans. For example, cleaning or
replacing the filters in an air conditioning system reduces system resistance
and reduces fan energy use.
PART TWO
Preventative routine maintenance extends the life of the fan and the
performance of the system. Maintenance routines comprise checking
and periodically replacing the wearing components.
Predictive maintenance
Predictive maintenance goes one step further and is generally applied to
critical systems where failure is costly or unacceptable. Predictive maintenance
includes continuously or periodically monitoring the fan key performance
indicators such as flow, temperature, pressure, current draw and vibration,
and using that data to predict future failure or reduction in performance.
Fan problems are detected and resolved early, prior to any critical failures.
WHS requirements place a duty of care on the building occupier or a person
conducting a business undertaking (PCBU) to maintain all equipment that
has an effect on the indoor environment quality (IEQ) of the building. The IEQ
impacts occupants and visitors, including maintenance staff and the public.
Refer to AIRAH DA19 for detailed information on HVAC&R system
maintenance. Further information is provided in the Guide to Best Practice
Maintenance & Operation of HVAC Systems for Energy Efficiency, which
can be found under the “Useful Documents” tab at www.airah.org.au
Mandatory maintenance
In some applications, maintenance of fans is a mandatory requirement;
including fans covered by NCC Volume One (BCA Class 2 to 9 Buildings)
Section J, and fans covered by AS/NZS 3666.2. Fans that operate as part
of the building’s essential fire safety measures under the requirements
of AS/NZS 1668.1, Section E2.2b of the BCA or Section G3.8 of the BCA
are required by state legislation and AS 1851 to be maintained and routinely
tested for satisfactory performance.
Access for maintenance
In order for a fan to be maintained, there must be adequate access
provided for service personnel and for parts and fan replacement. Where
adequate access for maintenance is not provided, then maintenance will
most likely not be carried out. The provision of access for maintenance
is a fundamental WHS requirement.
Preventative maintenance
Maintenance requirements vary with the type of fan, the type of installation
and the system application. Maintenance recommendations specified
by the manufacturer should take precedence.
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HVAC&R SKILLS WORKSHOP ▲ Module 69
Fan maintenance schedule
Action
Interval
(months)
Explanation
1. Adjust belt tension as necessary,
check for wear.
1
See Schedule A17 (DA19) for the steps to be taken.
2. Check drive and drive shaft guard firmly
in place.
1
All drives should be checked in accordance with Schedule A17 (DA19).
3. Check fan operates.
1
4. Check for vibration, bearing noise
or overheating.
1
5. Check mounts and holding down
bolts for security.
1
6. Lightly lubricate bearings to manufacturers’
recommendation where possible.
6
7. Spray or coat belts, where required, with
commercial compound to reduce pulley slip.
6
8. Check access panels for air leakage and seal.
12
9. Check drive alignment.
12
Vibration can be due to an out-of-balance fan rotor or failure of one of
the bearings. Heat or noise from the bearing will confirm that this is the
source of the problem, and appropriate steps can be taken to replace the
offending bearing. It is frequently necessary to replace both bearings as
vibration from one can cause damage to the second.
12
This is carried out by physical examination of keys, keyways and locking
bolts. Any movement in these components can lead to wear on the
shafts with resultant expensive replacement of the component becoming
necessary.
11. If accessible, check cleanliness of fan blades
and scroll or casing and record/report if
cleaning is required.
12
Where possible, inspect the internal surfaces of the fan casing and the
runner for any build-up of dirt, grime, grease, etc. Steam cleaning or
high-pressure water jets can be used to restore the surfaces to an as-new
condition. The surfaces should then be examined for corrosion and, if
necessary, they should be repainted.
12. Inspect for evidence of corrosion,
wear on flexible connections and other
deterioration, clean and repair minor
corrosion and report where repairs
are necessary
12
10. Check that impeller and drive are tight on shafts.
13. Replace flexible drive components.
36
Scheduled maintenance
Maintenance records
Mandatory and preventative maintenance routines are generally carried
out to a scheduled frequency. The frequency required for a particular fan
will vary by application, i.e. duty, location, corrosiveness of environment, etc.
Fan manufacturers have developed comprehensive maintenance procedures
that maintenance personnel should follow, in the interest of the owner and the
continued reliable operation of the equipment. As many fans run for extended
periods without being switched off, it is essential that the critical components
are checked in accordance with the manufacturer’s schedule
or the recommendations from AIRAH DA19.
It is often necessary to install a stand-by unit so that regular maintenance
can be carried out without losing use of the system.
The following recommendations for scheduled fan maintenance (see table
p.16) are reproduced from Schedule A22: Fans from AIRAH DA19, and cover
all types of fans. Only applicable action items should be used.
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Replace with new matched sets. This could refer to belts, in-belt drives,
buffers, indirect drives, or any other item that is provided for flexibility in
the drive. If replacement becomes necessary in less than 36 months due to
normal wear, then the maximum replacement period restarts from the time
of replacement.
A comprehensive and progressive record of all maintenance
activities should be kept for each fan, detailing maintenance interval,
components checked, preventative maintenance performed, and
any operational issues or future maintenance recommendations.
Maintenance records should be kept in a building log book and
made available for future review.
Under WHS requirements, there is a duty of care for PCBU to ensure
systems that control indoor air quality (IAQ) are maintained properly,
in accordance with the requirements of the O&M manuals. Therefore,
it is important that maintenance records are updated with information
on servicing and repairs carried out to HVAC&R equipment,
including fans.
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Maintenance procurement
The selection of a good maintenance service provider is the key to
satisfactory maintenance, which will result in reliable plant performance,
good plant life and reasonable expenditure. Lowest tender price is the least
appropriate way to select a service provider. Value for money should be the
determining factor. The ideal situation is where the customer and service
provider establish a partnering relationship, recognising that the service
provider needs to make a profit and the customer needs to contain the costs.
Thus a potential maintenance service provider should have the following
attributes:
• Competent, committed and well-trained technicians
• Appropriate licenses, insurances and accreditation
• Appropriate level of resources
• Efficient and accurate maintenance management system
• Informative reporting system
• Accurate and timely invoicing
• Economical and reliable after-hours service
• Quality, environmental and safety management systems.
PULLOUT
The assessment of maintenance contractors should include an evaluation
of their sustainability practices. It is important to incentivise maintenance
contractors to consider the energy-efficiency of the system during
maintenance inspections.
Recommissioning begins with a review of the system operating
requirements to determine what, if any, changes in requirements have
occurred. The system operating requirements need to be updated
or confirmed prior to any recommissioning activities commencing.
If changes have occurred, systems are reviewed to establish if corresponding
changes to equipment, controls or operation procedures are required. Systems
are then fully surveyed and a list of findings or issues compiled. System trend
logs or functional performance tests may be used to determine if the system
meets the performance defined in the reviewed operating requirements.
Extensive changes to operating requirements or installed plant may mean
that system retrocommissioning is required. Refer to AIRAH DA27 for full details
on recommissioning and retrocommissioning protocols.
Upgrades
Fan or plant replacement is carried out for a number of reasons, including
failure, degraded performance, and changed system goals or parameters.
Fan replacement could even be considered at initial commissioning if, due to
excessive margins, the selected fans are so oversized the system needs to be
excessively throttled.
When upgrading or replacing a fan, the system requirements should
be revisited and a fan selection process carried out. Do not simply replace
like for like.
A facility upgrade strategy might schedule the replacement of inefficient fans
and associated equipment with modern high-efficiency alternatives. However,
the load/system requirements should always be reviewed for changes. ▲
System tuning
In a typical HVAC&R system, chillers, pumps, valves, fans, and the like are all
required to operate together in coordination to achieve a space temperature
that is within specification. System tuning and the maintenance of controls
are crucial to achieving this. Prior to any tuning taking place, key performance
indicators for equipment and systems and condition responses need to be
established.
System management
There should also be some procedures or protocols put in place to manage
the system over time. Consideration should be given to how the following
issues are managed:
• System access – People who have access to the system plant or controls
should be limited to the nominated individuals so that changes cannot be
made to the system without being properly documented and approved.
• Documenting changes – Any changes made to the system should be
documented; the as-installed drawings and the operating and maintenance
manuals should be updated to reflect the changes made.
• Verifying improvements – any changes made to the system should be
verified against the stated goals or objectives of the change. Simply
assuming that the changes made have achieved the required objectives
is insufficient and confirmation should be encouraged to verify the
performance of any implemented improvements.
More information
THE AUSTRALIAN INSTITUTE OF REFRIGERATION, AIR CONDITIONING AND HEATING
DA13
FANS
APPLICATION MANUAL
Recommissioning
Systems change over time – components wear, set points are altered, control
calibrations drift – often resulting in deterioration of system performance.
Recommissioning is intended to bring a system back to its original
performance and operating efficiency, and is carried out periodically (every
three to five years) or in response to operating problems. Recommissioning
activities include tuning, calibrating, testing and verification and generally
follows the tests and methodology developed for the original commissioning
program.
Next month: Boiler efficiency
This month’s Skills Workshop was taken from AIRAH’s
application manual DA13: Fans, which was revised and
republished in 2013, and is available in AIRAH’s
online store at www.airah.org.au
www.hvacrnation.com.au | HVAC&R Nation | March 2014

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