Assessing the Internals
Assessing The Internals
Understanding NFPA 25 Chapter 14: Internal Assessments and Obstruction Investigations
Maintaining the integrity of internal piping in fire protection systems is crucial to ensuring reliable operation during an emergency. Over time, pipes can accumulate corrosion, scale, and other obstructions that may hinder water flow and impair system performance. To address these concerns, NFPA 25 The Standard for Inspection, Testing and Maintenance of Water-Based Fire Protection Systems, Chapter 14 outlines the requirements for assessing the internal condition of piping and conducting obstruction investigations. Though called obstruction prevention, the internal assessment has been required since the inception of NFPA 25 in 1992. These assessments help identify potential issues before they escalate into impairments of the systems.
Internal Assessment: A High-Level Overview
The purpose of an internal assessment is to provide reasonable assurance that corrosion and obstruction issues within fire protection systems are identified. However, this process is not meant to verify that every inch of piping is completely free from blockages. Instead, it is a systematic approach to determining whether further action is needed.
An internal assessment should be conducted every five years. For wet systems, an assessment is only required on every other system within a facility. If an issue is found in one, all systems must be assessed. This is only permitted for wet pipe sprinkler systems, all other systems such as dry systems, preaction systems, standpipes and fire pumps must all undergo internal assessments without exception.
Non-metallic piping, such as CPVC, is exempt from internal assessments, but copper, despite being non-ferrous, is still required to be assessed.
How is an Internal Assessment Conducted?
The assessment typically involves opening up the system at two points:
- A flushing connection at the end of one main
- Removing a fitting or branch line for visual inspection
Alternative methods, such as cameras and laboratory analysis, can indicate the presence of corrosion. However, ultrasonic testing is discouraged because it only measures pipe thickness and does not reveal internal conditions.
If a sufficient amount of foreign organic or inorganic material is found that could obstruct water flow, all systems within the facility must be assessed, and an obstruction investigation will be required.
Obstruction Investigations: When and Why?
Unlike internal assessments, obstruction investigations are not performed on a set schedule. Instead, they are triggered by specific conditions outlined in Section 14.3.1, which lists 16 triggers that necessitate further examination.
When an obstruction investigation is warranted, it must be conducted at the following five points:
- System valve or water control valve
- Most remote end of a cross main
- Branch line near the most remote cross main connection
- Branch line at the end of the most remote branch
- Branch line connected to the most remote low point drain
The goal of the investigation is to determine how far the system the obstruction extends. This will dictate whether flushing or pipe replacement is required.
Flushing and Removal of Obstructions
Once an obstruction investigation is completed, the debris can be removed using one of two flushing methods:
- Hydraulic Flushing: Uses high-pressure water to dislodge and remove debris.
- Hydropneumatic Flushing: Uses a combination of water and air to remove obstructions more effectively.
If the obstruction is severe enough to fully block the pipe, replacement may be necessary. Annex D.4.2 provides guidance on flushing connections, and D.5 details proper flushing procedures.
Ice Obstruction Investigations
Ice buildup is a unique obstruction hazard covered in Section 14.4, which requires annual investigations for piping that passes through freezers. This does not apply to dry barrel sprinklers but is essential for ensuring that frozen water does not impede fire suppression.
Final Thoughts
Understanding and applying NFPA 25 Chapter 14 is essential to maintaining the reliability of fire protection systems. Regular internal assessments help detect early signs of obstruction, while thorough investigations ensure that identified issues are properly addressed. By adhering to these guidelines, facility managers and fire protection professionals can ensure compliance, extend system longevity, and, most importantly, maintain readiness to protect lives and property.
Further Reading
