Paper 4: Volume 4 No.2 September 2005 Edition
Functional Availability
of Climate and Ventilation Systems
Sonny
Myrefelt
Department
of Building Services Engineering, KTH, 10044
Stockholm
,
Sweden
SKANSKA
Sydost,
Växjö
,
Sweden
Abstract
Functional availability is used to quantify the probability of a
system’s capability both to be in an operational state and, at the same
time, maintain the intended levels of the functions. The purpose of the
work described in this paper is to determine if functional availability
can be used for the evaluation of performance procurement contracts.
This study involved making
measurements in an office building over eight consecutive periods during
July and August. This monitoring showed that the HVAC-system did not
perform as well as it should and that, in each case, the system functional
availability was found to be below 0.7 (sometimes much less). This meant
that the performance criteria studied were attained for less than 70% of
the monitoring time. Although there was no contract regarding the level of
functional availability, it is evident that the situation was not
acceptable.
In this building, only the
operational staff handled the malfunctions and they were unable to secure
desirable conditions. Using the functional availability as an active tool,
during the whole building process, helps all of those involved to focus on
functions. This, in turn, should increase co-operation to reach these
aims.
This study showed that the
use of functional availability could form a basis for determining how well
functions are maintained. However, there is still much work needed before
it can be used for performance procurement contracts.
Key words: HVAC systems,
reliability, availability, maintenance management, indoor climate.
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