Block Replacement Policy

Block Replacement Policy (BRP)

A form of asset replacement policy that falls into the preventive replacement class (see figure).

If a system, such as electrical or mechanical, consists of a group of assets (the block), a unit is replaced upon failure and at times T, 2T, 3T...

The ages of the assets are not observed and only their failures are known, all units may be replaced periodically independently of their ages in use.

Each unit is individually replaced on failure during a specified time interval.

Beyond the failure replacement interval, failed units are left idle until a specified number of failures occur, then a block replacement is performed.

Attributes
Listed below are some of the key attributes of a block replacement policy:

The item undergoes a planned replacement at a sequence of equally spaced time points (fixed interval) independent of failure history.
BRP endeavours to provide a comprehensive project to leverage economies of scale.

Block replacement shares many characteristics with the following policies:

Candidates and Examples:
Generally, this approach applies to assets that have the following attributes:

Portable assets such as interior or exterior furniture and domestic appliances
Assets that have a low capitalization value (ie., they only have material value as a group), such as individual light fixtures.
Assets that are susceptible to capex-opex spillover.
An inventory of assets that have multiple baselines of placed in service dates.

Some examples of block replacement projects are as follows:

Group relamping and reballasting of a building.
Failed sealed glazing units replaced in batches rather than piecemeal.
Batch of fire extinguishers at each hydrostatic test cycle.
Batch replacement of fire alarm initiating devices, such as smoke alarms and heat detectors.

Evaluation
Some of the merits and limitations of this form of replacement policy are listed below.

Merits:

Simplicity - The main advantage of a BRP is its simplicity, because under this policy it is not necessary to keep detailed records about times of failures or ages of the assets.
Single Baseline - The owner is provided with a single baseline for tracking purposes
Administration - It is relatively easy to administer since the planned replacements occur at regular intervals and so can be readily scheduled.
Economies of scale can be leveraged by replacing assets in large batches.

Limitations

New Replacements - At planned replacement times the owners may be replacing some practically new items.
Lumpy Funding - Funding requirements will be lumpy due to the size of the block.

Fig. A summary network diagram of the different asset replacement strategies with Block Replacement Policy (BRP) forming one of the preventive replacement options.

Fig. Re-lamping and/or reballasting of all the strip fluorescent fixtures in a parkade as a single block replacement.

Fig. Fire extinguisher renewal in a block at the 6-year hydrostatic test cycle.

Other policies: