By Thomas V. Kraft, CFPS, acensium Inc.
Many large baseload power plants in the United States are beginning their fourth decade of operation and the wear and tear of power generation is starting to show. Fire protection systems, especially the water supply and distribution systems, are particularly affected by aging. Regardless of how well fire suppression and detection systems are maintained or how well the fire brigade and fire department are trained, none can function as intended without adequate water. In addition to system degradation over time, many plants do not have dedicated fire water systems; often firewater and service water systems are combined, resulting in the shortened service life of the fire pumps and an unreliable fire protection water supply.
Combined Fire/Wash Down System Issues
Because of the inherent risks associated with fuel sources, water supplies at power generation facilities are even more critical than water supplies at many other industrial facilities. Not only do power generation facilities have the typical risks associated with any industrial site, they have unique concerns such as combustible dust. Combustible dust leads to higher housekeeping and wash down demands. For facilities with a combined fire and service water system, the service water demand often exceeds the service water supply system’s capacity. This places extra demand on the fire system components. Fire pumps that run continually and fire water tanks that get depleted daily for service water use are a recipe for disaster.
Using fire water systems to support service water often causes unnecessary wear on fire protection components, keeping them from performing as designed. Additionally, in most cases, there is no interlock between the service water and fire protection systems to initiate service water shutdown in the event of a fire. This creates a scenario in which service water is being taken from the fire system during an incident, rendering the responsible fire suppression system or firefighters unable to control or combat the fire.
It is important to consider the following when assessing power plant water supply and distribution systems:
· Of 100 power plants queried in 1986, all but eight had some form of combined service water or wash down water and fire protection supply and distribution arrangement.
· While approximately 50 percent of these same plants could identify the intended water flow, pressure and reserve fire water volume established in the original fire protection systems’ design, they had no way of physically ensuring that their fire protection water reserve would not be encroached upon by increasing daily demands and “parasitic” service water flows.
· Not one plant could identify the design basis used to determine the maximum service water and/or wash down water demand.
· All plants agreed that service water and wash down water demands on the underground and above ground distribution system had steadily increased since the plant was constructed.
· Fewer than 15 percent of the plants could provide engineering documentation that compared the highest demand fire protection system (flow and pressure) with the system’s actual available water supply.
· Fewer than 40 percent of the plants conducted annual fire flow tests involving the entire distribution system and all subcomponents as required by the National Fire Protection Association’s (NFPA’s) Standard 25 (Standard for the Inspection, Testing and Maintenance of Water-based Fire Protection Systems).
· Only 6 percent of the plants had conducted flushing investigations of underground mains to determine aging factors and verify the absence of potentially obstructing materials.
· More than 60 percent of the plants had fire pumps or booster pumps that performed below their rated capacities or were not installed correctly per NFPA Standard 20 (Standard for the Installation of Stationary Fire Pumps for Fire Protection).
Of all the fire safety systems relied upon by a power plant, the water supply and distribution system is the most fundamental and critical. In a practical sense, all other fire protection systems rely on it to ensure they receive the right amount of water at the right pressure.
By establishing reliable fire protection systems, a power plant can control its fire risks. The first step in establishing reliable protection requires performing a full analysis of the water supply system to determine if it’s up to task. The analysis should include a full review of the original system design documentation to determine the demands (flow and pressure) of all fire protection suppression systems and hose stations, as well as the required water supply volume. It is also necessary to review the pump manufacturer’s original design documents and pump curves for all fire and booster pumps.
Next, plant personnel should test all fire protection water supply system distribution components (valves, hydrants, underground piping) and the water supply delivery system (fire pumps, booster pumps) to determine current operating parameters (flow and pressure). It is then necessary to develop a current hydraulic profile, including current hydraulic c-factors and available flows and pressures throughout the system.
A complete analysis of current test data and comparison with original design criteria is necessary to determine which systems, if any, are no longer being supplied with the correct flow and pressure from the fire water supply/distribution system. An analysis of the service water demand and effects, along with deficiency analysis is needed. Finally, solutions to any deficiencies identified should be developed.
By performing complete testing and analysis of the water supply system, a company can ensure that plant personnel and assets are protected. Although capital funds may be required to rectify major issues, many deficiencies can be addressed through increased testing, inspection and maintenance, or through administrative controls.