Alternative methods for internal pipe assessments
BY MATT KLAUS
AUTOMATIC SPRINKLER SYSTEMS have a phenomenal record for saving lives and reducing property damage—when they’re active. In order to confirm that the piping network associated with sprinkler systems has not become compromised due to corrosion (commonly microbiologically influenced corrosion, or MIC), NFPA 25, Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems, requires that the internal condition of sprinkler system piping be assessed every five years.
This assessment, not to be confused with an obstruction investigation, historically has been conducted by draining the system, disconnecting pipes and fittings, and physically looking inside the system. This is still the most common method for conducting the five-year internal assessment, but it also requires the system (or at least a portion of it) to be out of service for a period time. For larger facilities or high-rise buildings with multiple systems, this can mean several days (and in some cases weeks) of downtime for their sprinkler systems. In many cases, shutting down the sprinkler systems means that day-to-day business operations must be halted or modified due to system shutdown. This can be costly from both a financial and a productivity perspective and is untenable to many owners and facility managers.
As identified in A.14.2.1 of NFPA 25, though, draining the system and opening a flushing connection is not the only means for conducting the internal assessment. This section specifically states that nondestructive or noninvasive methods for conducting the assessment are permitted.
One such nondestructive approach involves the use of ultrasound, or ultrasonic technology. This technology allows an assessment to be performed without shutting down the system as the testing is being conducted. By applying ultrasonic transducers to the pipe’s exterior surface, internal conditions can be identified quickly and accurately. Pulse echo and guided wave technology are two types of ultrasound that have been used in the sprinkler industry for years with great success.
Pulse echo ultrasonic technology works by measuring the amount of time it takes for an ultrasonic straight beam signal to travel through the wall of the pipe and reflect off the back wall, resulting in a “remaining wall thickness” measured down to 1/1000th of an inch. Guided wrap wave, or lamb wave, ultrasonic technology travels around the circumference of the pipe, exposing the internal surface conditions. Both technologies allow technicians to obtain an instantaneous understanding of the internal condition of a segment of pipe. This allows for dozens of pipe segments to be analyzed in the time it would normally take to look at only a handful of segments. It also allows facility managers to reduce operational downtime and maintain the facility’s normal operating schedule.
While commonly associated with obstruction investigations, portable x-ray technology has also been employed as a means for conducting the periodic internal assessment. This noninvasive approach to conducting the assessment is also consistent with the intent of Chapter 14 of NFPA 25 and typically does not require draining the system.
While draining the system and looking inside the pipe has remained an industry staple for conducting internal assessments, it is not the only recognized approach. For facilities that are sensitive to downtime or the potential for water damage, such as hospitals, data centers, and production facilities, alternative assessment methods may be a better fit and tell a more complete picture for the facility manager.