Originally introduced to address the risk of diesel fuel leakage, FM Approval Standard 7745, Hydrocarbon Leak Detectors, has been expanded and is now renamed Liquid Leak Detectors. This evolving standard—which now includes water detectors—was first enhanced in 2012 to include all types of liquid hydrocarbon detectors.
"The basic concept of liquid leak detection is the same for hydrocarbons or water," notes FM Approvals senior engineer Ed Laliberte. "Most detectors on the market measure conductivity. Hydrocarbons are in one range and water in another higher range. Of course, there are other differences between the detectors, but the basic idea is the same. The same control system can be used in a facility to monitor for hydrocarbon leaks and water leaks by using different sensors for each liquid. It made sense to make our standard more encompassing."
According to FM Global Property Loss Prevention Data Sheet 1-24, Protection Against Liquid Damage, water leakage can cause severe damage to facilities with finished interiors (Fig. 1) such as healthcare facilities, offices, hotels, condominiums, retail stores and schools. Escaped liquids can cause considerable harm to stored raw or finished goods within a facility or a building, as well as equipment malfunction and impairment.
In particular, healthcare and education facilities with high-value medical and laboratory equipment and devices are especially susceptible to liquid or water damage. And in all types of facilities with drywall, floor coverings, ceiling tiles, insulation, cabinetry, elevators and computer equipment, liquid damage can cause business interruption while affected areas are shut down for renovations and critical equipment is repaired or replaced.
Multiple-story buildings add a level of complexity as the escaped liquids often will flow to lower building levels below the point of origin. Basements are particularly susceptible. Water damage exposure has been identified as the leading cause of property losses by frequency in healthcare and education facilities.
High-risk sources for water damage to businesses include:
- Heating and cooling water supply systems
- Condensate drains
- Fire sprinkler systems
- Toilets, drains and other plumbing
- Basements
- Backflow preventers
- Roof and window leaks
Liquid leak detectors, including probes, sensing cables and other devices can provide quick and accurate detection and notification in event of a leak. These detectors are typically linked to a control panel that can provide various levels of automated alerts and other actions, including shutoff valves to limit damage.
Typical monitoring applications for liquid hydrocarbon detectors (Fig. 2) include: beneath day tanks, around pump pads, below valves or other flanged connections, near threaded indoor pipe couplings, and at flexible hose couplings to engine injector pumps. Water detectors can be deployed below raised floors in server rooms, telecommunications switching sites, control rooms, trading rooms, archival storage, museums, historic buildings, libraries, above medical diagnostic equipment, and in elevator pits.
Approval Standard 7745 requires all detectors to meet minimum detection levels, detect failures, be resettable, and demonstrate resistance to humidity, vibration, dust, and static discharge. Additional requirements apply, depending on the type of detector—hydrocarbon or water—including minimum detection level, stability, durability, and other factors.
The standard includes performance tests based on the manufacturer's specifications for minimum detection sensitivity for leaks on dry floors, film on water (hydrocarbons), and varying water depths. Leak detectors must respond within 30 seconds of exposure to the specified liquid.
Intelligent leak detection systems can even be tied into an overall building management system that monitors and 'learns' the patterns of water usage throughout a facility. When coupled with shutoff valves, these systems can not only prevent damage from leaks due to broken pipes and other devices, but also reduce wasted water from leaking toilets, HVAC systems and process equipment.
"We are working with a manufacturer of a water leak detection system right now and hope to have an Approved system soon," notes Laliberte. "We often hear about losses that occur when a pipe breaks over a weekend in an unstaffed facility and thousands of gallons of water flow down through ceilings. The damages can be extensive and take a long time to recover from; in some cases, water can cause irreversible damage when it involves artwork or archived documents. Properly installed leak detection systems can limit losses in those cases by sounding an alarm and even shutting off the flow automatically."