One of a number of different types of
policies. which falls into the preventive
replacement class (see figure).
conscious decision by the Owner
Group to replace certain assets
at failure, or at a
whichever comes first.
A preventive replacement of
the asset is carried out once the age of the asset has reached a
specific/critical operational age. If the asset fails prior to that
year, a failure
replacement is performed and the next preventive
replacement is rescheduled.
Two types of age-based replacement
continuous time and loadings on the asset.
In failure studies, the time to failure is often measured in cycles to
failure and therefore discrete time failure distributions may be more
assets and examples
Listed below are
some common examples of assets that can be addressed under this type of
Let’s start our exploration with life safety assets, such
as fire alarm equipment. Here we have equipment that is highly
regulated and the owners are mandated to maintain on rigid schedules.
For example, we must test and recertify the extinguishers and smoke
detectors every year. Also, we must eventually replace these items on
pre-established age-based schedules that are written into local
statutes. For example, all fire extinguishers must be replaced after 12
years in service. Here we have assets where their life can never be “extended” but only “reached”
through maintenance. There is no value in trying optimize
maintenance to buy more life from these types of assets. While the
maintenance of life safety equipment is not “sexy” like washing of the
windows, the Return on Investment (ROI) and Time-to-Value (TTV) is crystal clear.
- Fire extinguishers
Listed below are some typical examples of age based renewals:
- Hydrostatic testing or replacement of ABC fire extinguishers
- Replacement of fire alarm initiating devices
- Replacement of batteries in emergency lighting packs
- Sample testing of dry sprinkler heads to NFPA standards with renewal as
- Replacement of gaskets on dry sprinkler valves.
- Replacement of oil and check valve in dry
of the merits or advantages of this approach to asset
replacement are summarized as follows:
- The approach is simple and is therefore
- It is well suited to some bounded assets where
fixed intervals time are mandated by local statutes.
of the limitations and cons of this approach are listed below:
- May result in wasteful replacement.
- Neglects cycles and discrete time.
- Assets may fail before the predicted
- Relies too heavily on absolute time.
Asset replacement policies must align to asset risk profiles in order
to achieve optimization and satisfy ISO 55001 requirements.
Fig. A balanced asset replacement mix helps the organization to achieve optimization in conformity with ISO 55001 principles.
A summary network diagram of
the different asset replacement strategies with Age-Based Replacement
(ARP) being one of the options under the preventive replacement
I. Care is attempting to slow down or reserve the sands of time so that
he can undo the deferred maintenance. A futile but valiant attempt.
Fig. Sample distribution of the percentage of assets under each of the five replacement strategies - ie., the replacement mix.
I. Care and his fellow owner/manager are debating whether the life of
assets are candidates for "extending life" or only "reaching