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Posted: Sep 1, 2018

Hose Friction Loss and Flow Testing Importance


Pump operators are responsible for delivering the required water flow [gallons per minute (gpm)] to the nozzle team with a nozzle reaction (NR) that can be safely handled by available firefighters. This can be done if operators can control pressure at the nozzle, since nozzle pressure (NP) largely determines volume flow and NR.

Friction Loss

The fire engine pump creates a mechanical energy force (pressure) measured in pounds per square inch (psi) to pump water. As water courses through the hose, it experiences friction created by rough hose linings, couplings, gravitational forces, and turbulent flow. Friction converts mechanical energy to heat energy, so by the time water reaches the nozzle it has lost a good part of its pressure. It is the operator’s responsibility to know the friction loss (FL) so he may control NP by adjusting pump discharge pressure (PDP). So, you can see the importance of friction loss measurement.

Another reason measurements are so important is that standard industry estimates for FL calculations are outdated and seriously overstated. Consider the equation: FL = c × (gpm/100)2 × L/100.

The “c” term is the so-called friction loss factor and measures the pressure loss per 100 feet. This is multiplied by the square of the volume flow (gpm) and hose length (L) to get total friction loss. The “c” factor is a handy way of comparing results from different tests and flow rates. By measuring friction loss and volume flow, we can determine the “c” factor. For example, 200 feet of 1¾-inch hose with a smooth bore 7⁄8-inch tip and 50-psi NP pumping at 161 gpm has a 49-psi friction loss. This translates to a “c” factor of 9.5 psi per 100 feet.

I have been gathering “c” factors from known fire department tests and research studies.1 Though the analysis is somewhat anecdotal, the results are instructive; “c” factors varied from c=8 to c=13, with a modal point of c= 9.5. The National Fire Protection Association (NFPA) uses an estimate of c=15.5 for 1¾-inch hose, as do many fire departments as well as hose manufacturers in their published FL tables. These “book” operations are not representative of line operations.

Figure 1: Measuring FL

What happens if you use c=15.5 and the actual is c=9.5? At c=15.5, the FL for 200 feet of 1¾-inch hose is calculated to be 80 psi, or 40 psi per 100 feet. To get an NP of 50 psi, discharge pressure would be set at 130 psi. But if the actual “c” was 9.5 or 49 psi, the NP would be 81 psi. You would be pumping 205 gpm with a NR of 97 pounds of force. Clearly, the pump operator needs accurate FL measures to properly do the job.

So, how do you directly measure FL? There are protocols established by the NFPA, but basically they appear as in Figure 1. The test is performed on level ground. Two pitot gauges (calibrated for accuracy) are installed in the hose—one near the discharge gate and one near the nozzle. During testing, the difference between the pitot gauges measures FL in psi.

Static Test

Before conducting the FL test, run the pump to fill the hose and close the nozzle. The readings on the two pitot gauges should be the same; otherwise, there is an elevation d

Read more
Posted: Sep 1, 2018

Hose Friction Loss and Flow Testing Importance


Pump operators are responsible for delivering the required water flow [gallons per minute (gpm)] to the nozzle team with a nozzle reaction (NR) that can be safely handled by available firefighters. This can be done if operators can control pressure at the nozzle, since nozzle pressure (NP) largely determines volume flow and NR.

Friction Loss

The fire engine pump creates a mechanical energy force (pressure) measured in pounds per square inch (psi) to pump water. As water courses through the hose, it experiences friction created by rough hose linings, couplings, gravitational forces, and turbulent flow. Friction converts mechanical energy to heat energy, so by the time water reaches the nozzle it has lost a good part of its pressure. It is the operator’s responsibility to know the friction loss (FL) so he may control NP by adjusting pump discharge pressure (PDP). So, you can see the importance of friction loss measurement.

Another reason measurements are so important is that standard industry estimates for FL calculations are outdated and seriously overstated. Consider the equation: FL = c × (gpm/100)2 × L/100.

The “c” term is the so-called friction loss factor and measures the pressure loss per 100 feet. This is multiplied by the square of the volume flow (gpm) and hose length (L) to get total friction loss. The “c” factor is a handy way of comparing results from different tests and flow rates. By measuring friction loss and volume flow, we can determine the “c” factor. For example, 200 feet of 1¾-inch hose with a smooth bore 7⁄8-inch tip and 50-psi NP pumping at 161 gpm has a 49-psi friction loss. This translates to a “c” factor of 9.5 psi per 100 feet.

I have been gathering “c” factors from known fire department tests and research studies.1 Though the analysis is somewhat anecdotal, the results are instructive; “c” factors varied from c=8 to c=13, with a modal point of c= 9.5. The National Fire Protection Association (NFPA) uses an estimate of c=15.5 for 1¾-inch hose, as do many fire departments as well as hose manufacturers in their published FL tables. These “book” operations are not representative of line operations.

Figure 1: Measuring FL

What happens if you use c=15.5 and the actual is c=9.5? At c=15.5, the FL for 200 feet of 1¾-inch hose is calculated to be 80 psi, or 40 psi per 100 feet. To get an NP of 50 psi, discharge pressure would be set at 130 psi. But if the actual “c” was 9.5 or 49 psi, the NP would be 81 psi. You would be pumping 205 gpm with a NR of 97 pounds of force. Clearly, the pump operator needs accurate FL measures to properly do the job.

So, how do you directly measure FL? There are protocols established by the NFPA, but basically they appear as in Figure 1. The test is performed on level ground. Two pitot gauges (calibrated for accuracy) are installed in the hose—one near the discharge gate and one near the nozzle. During testing, the difference between the pitot gauges measures FL in psi.

Static Test

Before conducting the FL test, run the pump to fill the hose and close the nozzle. The readings on the two pitot gauges should be the same; otherwise, there is an elevation d

Read more
Posted: Sep 1, 2018

Hazmat Response

Richard Marinucci

If you look at how fire departments respond to incidents involving hazardous materials, you might wonder how the same people who rush into fires take such a different approach.

Richard Marinucci

Consider preparation (education and training), equipment, rules, regulations, standards, operations, rehab, physical examinations, and decontamination approaches. There are more, and there are good reasons for the approach taken. We can learn a lot from this that can make department operations more efficient and effective as well as less risky when the risk/benefit is not appropriate.

Personnel

Those who opt to specialize in hazardous materials (hazmat) response take it on themselves to become more educated. This could be combination of the type of people who respond and the regulations that require specific training based on the type of action to be taken. There are levels of training and certification—awareness, operations, technician, and specialist. Assignments are made based on the level of certification, and organizations are only supposed to provide service to the level at which they are prepared and staffed. Contrast this with a fire response where levels of training do not come into play when selecting strategy and tactics in many circumstances—nor does staffing! Take, for example, the two-in/two-out rule. There is an exception if life is in danger. The hazmat standards do not make exceptions.

It could be argued that most hazmat teams spend a great deal of time preparing for very low-frequency events. Fortunately, there are few major or significant incidents involving toxic chemicals that result from spills, leaks, ruptures, and the like. But, those involved with response teams take a sound approach to be ready should the rare event occur. They also know there may be a need for different approaches, depending on the circumstances. They monitor weather and other factors that influence the emergency. It is a very logical approach and offers lessons that can be learned for other emergencies.

Equipment

Now look at the equipment and protective clothing for hazmat responses. There are specific suits that are used for specific situations. If the suits are not available, then there is no entry. As part of any team, there are monitors to check to see if the atmosphere is safe and to determine the level of protection necessary. If there are no monitors, then there is no entry. The list can go on, but you should begin to see the picture. In a regulated response, rules are to be followed, or there are consequences. Contrast this with the approach taken by many fire departments and firefighters to a fire. How many firefighters (with the backing of their officers and fire departments) will take a shortcut to attempt to accomplish the mission during a fire response? Now, ask how many of those same people will do the same when the emergency involves an unknown chemical and no fire?

Rules, Regulations, and Standards

The discussion about this approach to response and operations continues with a look at rules, regulations, and standards. There are Occupational Safety and Health Administration rules, CFRs, and other mandatory standards. Responders are expected to know these and comply or face consequences such as fines. A well-trained and well-prepared response team wil

Read more
Posted: Sep 1, 2018

Hazmat Response

Richard Marinucci

If you look at how fire departments respond to incidents involving hazardous materials, you might wonder how the same people who rush into fires take such a different approach.

Richard Marinucci

Consider preparation (education and training), equipment, rules, regulations, standards, operations, rehab, physical examinations, and decontamination approaches. There are more, and there are good reasons for the approach taken. We can learn a lot from this that can make department operations more efficient and effective as well as less risky when the risk/benefit is not appropriate.

Personnel

Those who opt to specialize in hazardous materials (hazmat) response take it on themselves to become more educated. This could be combination of the type of people who respond and the regulations that require specific training based on the type of action to be taken. There are levels of training and certification—awareness, operations, technician, and specialist. Assignments are made based on the level of certification, and organizations are only supposed to provide service to the level at which they are prepared and staffed. Contrast this with a fire response where levels of training do not come into play when selecting strategy and tactics in many circumstances—nor does staffing! Take, for example, the two-in/two-out rule. There is an exception if life is in danger. The hazmat standards do not make exceptions.

It could be argued that most hazmat teams spend a great deal of time preparing for very low-frequency events. Fortunately, there are few major or significant incidents involving toxic chemicals that result from spills, leaks, ruptures, and the like. But, those involved with response teams take a sound approach to be ready should the rare event occur. They also know there may be a need for different approaches, depending on the circumstances. They monitor weather and other factors that influence the emergency. It is a very logical approach and offers lessons that can be learned for other emergencies.

Equipment

Now look at the equipment and protective clothing for hazmat responses. There are specific suits that are used for specific situations. If the suits are not available, then there is no entry. As part of any team, there are monitors to check to see if the atmosphere is safe and to determine the level of protection necessary. If there are no monitors, then there is no entry. The list can go on, but you should begin to see the picture. In a regulated response, rules are to be followed, or there are consequences. Contrast this with the approach taken by many fire departments and firefighters to a fire. How many firefighters (with the backing of their officers and fire departments) will take a shortcut to attempt to accomplish the mission during a fire response? Now, ask how many of those same people will do the same when the emergency involves an unknown chemical and no fire?

Rules, Regulations, and Standards

The discussion about this approach to response and operations continues with a look at rules, regulations, and standards. There are Occupational Safety and Health Administration rules, CFRs, and other mandatory standards. Responders are expected to know these and comply or face consequences such as fines. A well-trained and well-prepared response team wil

Read more
Posted: Aug 31, 2018

The Fire Station: Site Selection, Part 2

Ken Newell, of Stewart, Cooper, Newell Architects, discusses additional items that can impact your site selection when designing your next fire station.

These items include:

  1. Thorofare and roadway planning.
  2. Setbacks
  3. Utility Easements
  4. Weland and floodplains.

With these items in mind, Newell suggests you let your design professional evaluate properties you are interested in acquiring for construction before purchasing to ensure it is appropriate for your project.

Read more
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