FIR201 Assignment 6A (1) (1)

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Eastern Gateway Community College *

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201

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Feb 20, 2024

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1 Advanced Hydraulic Calculations Bobby Roseberry Fire Science Department, Eastern Gateway Community College FIR 201 Fire Service Hydraulics Professor Mansfield December 3, 2023

2 Advanced Hydraulic Calculations When firefighters are attacking a fire, the pump operator and Incident commander must use calculations to determine the correct pressures, gallons per minute, and numerous other calculations and formulas to fight each fire. Fighting a fire is not as easy as putting the water on the flames, there must be numerous items calculated to attack each fire successfully. The purpose of this paper is to discuss the challenges associated with siamese and wyed hose line operations, how these challenges can be overcomed, the calculation methods for the siamese and wyed hose operations, the maximum flow hydraulic calculation, and the impact on firefighter safety. Literature Review The two devices that are used in the fire service that will be discussed are, the siamese device and the wye device. These two devices may look the same but have different operations on how they are used. A siamese device is a device that is used to combine, at the minimum, two hose lines coming from a single pumper or multiple pumper into one operating line. A wye device is used for splitting one hose coming from a pumper into two, usually smaller lines. Siamese line operations can be accomplished by either using a siamese device or using a single pumper that is being supplied water from multiple pumpers. One of the biggest challenges that can occur with the use of siamese line operations being supplied from a single pumper that is receiving water from multiple pumpers is going to be making sure the pump discharge pressure is kept steady and within the correct operating pressure. When a pump is supplying water to an attack line with a set pressure and then when that pumper starts receiving water from additional pumpers it can cause a surge in the pressure to the discharge line. The best way to overcome this, is to have a pressure relief valve set at the pressure that needs to be supplied so that if there is a surge it will engage the relief valve to not over-pressure the line. The hydraulic calculation needed is going to be the same that is used on several operations. First you will need to know the gallons per minute each nozzle is flowing along with what pressure they are flowing at, and will

3 need the length of the hose along with the diameter of each hose. First the friction loss for each line/nozzle will need to be found by using FL100=CF*2Q squared. FL 100 = CF × 2 Q 2 . Once that equation has been solved, the answer will then be used for the next formula of, FL=FL100*L FL = FL 100 ×L , then the answer will be inserted in to the last formula of PDP = NP + FL 1 + FL 2 ± EP + AL PDP=NP+FL1+FL2+/-EP+AL(Crapo, 2017). When using wyed hose line operations on a fire scene the pump operator and any firefighter on the firefighter that may be using a line off a wye needs to have clear communication. When setting up wye line operations on a fire scene there may only be one line off of that wye device and the pressure and flow is set. However, as the fire scene goes on another firefighter may connect a fire hose to the vacant spot on the wye device and charge the line causing the required pressure and flow to not be effective on either line. For this to operate correctly there needs to be communication advising the pump operator that another line is being connected and charged from this device. Another issue that may arise with the use of wye hose line operation is when the pressure and flow is set for multiple lines from one device and one line stops flowing it can cause a major increase on the line or lines that are still flowing. When using calculations for wyed lines all the same formulas will be used. However when calculating the friction loss to the wye then total gallons per minute must be used, and if one of the lines requires a higher pressure, then the higher pressure will be the pump discharge pressure (Crapo, 2017). Maximum flow calculation is used to find what the maximum amount of water can be delivered under specific hose layouts and what the advantages are of using larger diameter supply lines (Crapo, 2017). There are five important pieces of information needed to carry out the maximum flow calculations. Will need to know the size of the supply line being used, the length of all the hose lays, the max pressure available at the source, whether there is a pumper that is placed at the source and if so what is the pumpers capacity, and if the water source is a

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4 hydrant, what is the capacity of said hydrant. To do the calculation you must first take the max available pressure and subtract 20 psi from it to get the pressure available for friction loss. That is the available pressure for friction loss and divide it by the length of hose in hundreds (1200 ft of hose would be expressed as 12). Then to find the capacity of gallons per minute use the following formula: Q=Square Root of FL100 divided by (CF*2) Q = √ ❑ (Crapo, 2017). Conclusion Firefighter safety on the fireground, at training, and in general is very important. All calculations that are used in the fire service can accomplish firefighter safety. If there is not enough pressure or water flow when attacking a fire it can cause injury due to the fire being able to grow and possibly entrap firefighters in a structure. If too much pressure is being pump to the nozzle it can cause damage to the nozzle, hose, and even the equipment that can lead to firefighters injury. When on a fire scene it can be crazy busy but as the pump operator one needs to either have pre- determined calculations done with a cheat sheet or take the time to get as close as possible with the calculation to provide not just firefighter safety but occupant and the general public safety. Reference Crapo, W. F. (2017). Fire protection hydraulics and water supply (3rd ed.). Jones & Bartlett.

FIR201 Assignment 6A (1) (1)

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