Environmental Engineering Reference
In-Depth Information
6.4 SPARE PARTS INVENTORY
The operation and maintenance plan must anticipate equipment malfunctions and dam-
age. To minimize downtime, an adequate spare parts inventory should be maintained
and available for use during site visits. The inventory should include replacement up-
tower items such as sensors, booms, and associated mounting hardware. Additional
items may be needed. The following points should be considered when determining
inventory needs:
1. Size of the Monitoring Network. The size of the spare parts inventory depends in
part on the number of towers in the monitoring network. As a guide, a network
with six monitoring towers should have a parts inventory sufficient to outfit two
towers. For networks of this size and larger, it is also advisable to have a spare
data logger and remote communications device on hand.
2. Environmental Conditions. Towers in areas prone to extreme weather should
have additional spares. Recommended extras include spare anemometers, wind
vanes, and sensor mounting booms.
3. Equipment Availability. The inventory of spares should be increased for items
that require an extended lead time for delivery from the supplier. The turn-
around time for critical items, such as data loggers and sensors, is particularly
important.
4. Operations and Maintenance History. Inventories should be adjusted during the
program based on experience at each site. Sometimes sensors fail more often
than expected, so additional spares may be required.
5. Vandalism. Certain sites may be prone to vandalism. Cups on anemometers
are sometimes targeted for shooting practice, and equipment mounted near the
ground, such as solar panels and grounding system, may be stolen. If frequent
access is not needed for data retrieval, consider mounting the base equipment
(logger and peripherals) higher on the tower, out of easy reach. If vandalism is
a concern, consider installing a fence around the base of the tower.
6.5 QUESTIONS FOR DISCUSSION
1. The data recovery is defined as the percentage of all possible records in a given
period that are deemed valid. The data loss is 100% minus the data recovery. (i)
Explain how the data recovery can be affected by the frequency of data retrieval
from a wind monitoring station. (ii) Suppose the logger fails an average of once
a year. If the data are retrieved (either manually or remotely) and screened for
problems every 2 weeks, and any problems are immediately followed by a site
visit, what is the greatest data loss that might result from the failure? What is
the corresponding data recovery? (iii) How does the answer change if the data
are retrieved once a week? Once a month?
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