Right conditions for cost saving

Condition-based maintenance of building services plant has obvious attractions, not least of which are the cost savings it can make. The gains are greatest if the collection, reporting and analysis of data are automated, the most logical and cost-effective way of achieving this being through the building management system.

Unlike planned maintenance, which is done at set time intervals or after a piece of equipment has run for a specified number of hours, condition-based servicing is only carried out when the plant actually needs attention. This can mean lower repair and energy bills and improved plant performance. By minimising the risk of services failing, it also reduces the possibility of costly disruption to the building user’s business.

To be truly effective, CBM requires a regular flow of monitored data. Building management systems are well placed to provide this. Sometimes they will already be measuring the appropriate variables for control purposes, particularly temperature data. When this is not the case, adding a few extra sensors will often be all that is called for.

The most common example of BMS use in condition based maintenance is for indicating when air handling unit filters need to be replaced, which the system determines from differential pressure readings. Condition monitoring of other types of plant may require it to measure a number of variables and then calculate operational efficiency. This is particularly worthwhile on items with high capital and operating costs, such as chillers and large boilers, for which it is especially important to maintain optimum performance.

An increasingly popular CBM technique, and one highly relevant to building services, is vibration monitoring of rotating machinery. Normally based on piezoelectric technology, it can warn of various potentially serious problems on equipment such as fan and pump motors. Importantly, vibration sensors are low cost, easy to install and are able to produce signals that can be output directly to a BMS. Depending on the amount of information available from a sensor, the BMS may be able to diagnose the cause of a problem, warning say that a bearing needs lubricating or a fan is out of balance.

Because it enables a more effective maintenance strategy, vibration monitoring should appeal to a wide range of users. It is of particular value where there is a high price to be paid if the services go down – eg, in data centres, clean rooms or operating theatres.

For a building management system to be an effective CBM tool it must be able to quickly send alarms to whoever needs to see them, on-site or off. A Trend BMS meets this requirement by offering a variety of alarm handling options. Through its Bureau, Trend also offers a remote condition monitoring service, which uses special software to automatically compare actual and expected profiles for particular variables (eg, boiler efficiency) and report any deviations. If it has sufficient data available it can even specify what remedial action is necessary.

The practice of only carrying out building services maintenance when plant actually fails is sadly far too common, presumably because it is thought to save money. Condition based maintenance is in fact the lower cost option.  What is more, it enables building users and owners to make the most of a very valuable asset – their building management system.

Andy Thorn
Commercial Sales Manager
Trend Control Systems Ltd