It’s a known fact that water extinguishes fires. But for water to offer sufficient fire protection, it must be available in adequate supply. Without adequate supply fire suppression systems will fail. But how much water is necessary for fire protection?
“Every plant depends on a fire protection system to control fires during an incident,” says Larry Edwards, regional manager of F.E. Moran Inc. Special Hazard Systems. “But without adequate water supply you are at risk for a catastrophic failure.”
He explains industrial facilities need ample water supply to maintain sufficient water pressure and volume in fire protection systems. Every part of a fire protection system has a minimum water supply design specification, and when the minimum supply is unavailable, the systems do not function as intended. As water supply diminishes, each demand item, whether a monitor, hose stream, or sprinkler system, becomes less effective.
“If you’re expecting to put out 50 gallons of water a minute from your most remote sprinkler but you don’t have that, the sprinkler won’t work properly, and you will not control the fire. It will get out of hand and become a real problem,” Edwards explains.
But often water supply issues escape notice until an incident occurs. Most testing, inspection and maintenance practices are aimed at the fire protection system itself. Often, these tests overlook testing water supply, leaving many facilities unaware of water supply issues.
NPFA 25 puts forth a baseline for inspection, testing, and maintenance of water-based fire protection systems. Complying with this mandate helps maximize system integrity to avoid failure and ensures fast, effective response in a fire emergency. The regulation looks at three key areas of fire protection systems:
- Water Supply Systems: The fire pump and its water supply represent the heart of a water-based fire protection system. An impairment or failure in water supply, such as a fire pump switched off or left in manual mode, can leave a site unprotected.
- Valves: Controlling valves are key components of water-based fire protection systems and should be properly inspected, exercised, and maintained. A partially closed valve can make a fire protection system ineffective, and a shut valve can leave a building unprotected.
- Sprinkler Systems: The most used and effective mechanism for controlling a fire is the sprinkler system. Periodic inspection, maintenance and testing routines will ensure proper system operation during the early stages of a fire.
“They should check fire pumps and suppression systems and flow the systems annually,” Edwards says. “But there are monthly and semi-annual tests too that can make sure everything is in working order.”
How Do Plants Lose Water Supply?
When engineers design a fire protection system, they perform hydraulic calculations to ensure adequate water flow. However, over time, companies change their sites and modify processing capabilities. As they do, they must make sure their fire protection systems comply with NFPA standards and insurance underwriter requirements.
But all too often, Edwards says facilities expand their fire protection systems as they change their processes but overlook hydraulic considerations, which puts them at risk.
“An impaired or poorly maintained fire protection system can have the same effect as not having a system at all, with an increased risk of a large, uncontrolled fire loss. A sound and robust Inspection, Testing and Maintenance (ITM) program will ensure that your fire protection equipment and systems will operate as designed when they are needed the most, during a fire emergency,” finds an article on Swiss Re Corporation Solutions, titled, “Inspection, Testing and Maintenance of Fire Protection Equipment and Systems.”
The most common problem occurs when plants depend on pumps or tanks or pumps for fire protection water supply. “Companies don’t maintain the pumps and over time the pumps won’t operate,” Edwards says. “Plants rarely maintain their fire pumps very well.”
He says the second most common issue is when plants rely on city water for fire water supply. “In these cases, they don’t test and operate their valves regularly,” he says. “The valves are turned off and they cannot provide water for fire protection systems.”
Further complicating matters, when plants change hands, they often lose original facility design data. Without this information, it’s difficult to project how much water systems need to function properly. When plants cannot verify their supply versus demand, they must conduct testing to establish whether the system requires modifications to increase water supply.
Calculating Water Supply
There are several methods plants can use to determine if fire protection systems are reserving enough water to operate effectively.
Gradient Flow Tests: These tests determine the volume of water available at any location. The tests are precise and collected from actual flow test results. Here, water flows through devices, such as a hydrant operating on city water, at increasing volumes to record residual pressure at each level. Plotting and analyzing data on a flow curve helps visualize flow volume in terms of gallons per minute (gpm) at a specific pressure.
“In this process, you can visually see if water supply is deteriorating,” Edwards says. “If you keep records of every flow test, you will see when the curve goes down. This means something is affecting water supply and you must determine what it is.”
Fire Pump Tests: These tests are like gradient flow tests in that they provide a visual record of water supply. However, the tests are less intensive than gradient flow tests. The first step is to determine the manufacturer’s pump ratings, such as gsm, pressure (psi) and pump speed (rpm), then NFPA 25 requires testing pumps on three points:
- Churn-no flow
- Rated Flow-Flowed at 100%
- Excess capacity-Flowed at 150%
“When you do annual fire pump tests and record the results, you can see the water supply and know when it’s going down, and you must take care of it,” he says.
Factor Testing: Factor testing rules out an obstruction within an underground piping system that impedes water flow. Factor tests observe two points in a straight run of pipe: a pressure measurement point and a flow point. The inspection records the distance between the two points, then flows water from the flow point. Later, the inspection compares collected data to flow characteristics of normal pipe interiors to determine if an obstruction impedes water flow.
Identify the Hazards
Changes in the hazard types can affect water supply needs, adds Edwards. It’s important to consider this information and plan accordingly.
A facility might rely on a manufacturing process using low combustible materials but later add a more efficient method of performing the work that uses highly combustible materials. The new process will increase water supply requirements, Edwards adds.
“A lot of times when plants make these changes, they don’t recognize the impacts,” he says. “They don’t consider that they are using a more combustible material and will need a larger water supply in a fire.”
Edwards advises regularly taking a detailed inventory of material hazards within the facility. Survey all handled and stored materials, the manufacturing processes, and occupancies to calculate hazard classifications throughout. This data will help companies assess water supply demands.
Facilities may not always give fire water supply the attention and priority it deserves, but insurance underwriters are working to elevate their attention. Often, insurance companies will not cover a facility without it.
Edwards says internal staff can calculate the supply and demand of a fire protection system but recommends hiring a qualified fire protection expert to perform the analyses and make recommendations.
“They need to bring in people at least once a year to make sure their operations are performing as they should,” Edwards says. “While internal staff can do these inspections, it’s better to have a third party perform them. A third party will provide an honest and accurate assessment; this testing is all they do.”
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