By Gary Handwerk

In "The Ins and Outs of Fire Pumps: Intakes" (March 2016), we looked at the “ins” of fire pumps. This month, we will look at the “outs,” the discharge side of the pump system. This includes the pump body, the attached manifolds, piping, and valves.

Meeting the minimum National Fire Protection Association (NFPA) 1901, Standard for Automotive Fire Apparatus, or NFPA 1906, Standard for Wildland Fire Apparatus, performance does not guarantee optimum pump performance. Actually, it is somewhat easy to meet the NFPA performance requirements with almost any discharge combination. Not only is there performance to gain by optimizing your discharge manifold, piping, and valves, but there are noise and safety aspects that can be improved on. When pumping, there must be enough pressure supplied by the pump to overcome the discharge manifold, piping, and valve losses along with the discharge hose friction loss and any elevation changes to provide the correct pressure at the nozzle while supplying the required flow. Based on that, if we need to create more pressure to overcome the losses, that equals more core pump operating pressure, which leads to higher engine operating speed. More pressure needed generates more noise from the apparatus engine, which is not a good thing on the fireground-especially when the noisiest part of any apparatus is the engine. Additionally, operating the pump system at an overall lower pressure makes controlling everything easier and safer. In the past, we relied on using engine speed and power to create additional pressure to overcome manifold and piping losses.

Obtaining the maximum available performance is critical on high-flow applications such as industrial fires, where flowing through the pump is important. It is also important at the extreme opposite end of the market on slip-on wildland/grass apparatus, where the engine driving the pump is very small with limited power to overcome added discharge side pressure losses.

As a pump designer, I look at the velocity of the water traveling in the pipe, waterway, or hose as a reference point in any evaluation of this type. The water speed is commonly measured in feet per second. To calculate this, I use the following formula: Velocity in feet/second = (0.32 × gpm)/the area of the waterway in square inches.

Discharge Types

There are two basic types of discharges, one where the outlet is feeding a hoseline-this can be a preconnect for directly fighting fires or a feeder/supply line-and a hard-piped, directly connected device, such as monitor.

NFPA 1901 has stipulated that the safest optimum velocity, while keeping the hose losses workable, in a given discharge hose is 16.33 feet/second. So, the discharge piping and valve must accommodate this velocity at sufficient working pressure. While doing this, we still need to keep the losses to a minimum.

Part of NFPA 1901 requires two 2½-inch discharges and enough additional 2½-inch or larger hoseline connections, based on this 16.33 feet/second velocity, to equal the pump’s rated capacity. The requirement is for the first fixed hose connection only, and there are no standards for the manifold, piping, or valves feeding these hose connections. Hose-to-hose connection adapters are not counted. NFPA 1901 doesn’t require a 2½-inch outlet connection for every 250-gallon-per-minute (gpm) increment of the pump rating. A 1,500-gpm pump can be rated with two 2½-inch connections and one five-inch connection.

The second discharge type is not dictated by any specific standard, but anecdotal evidence does give some g

By Gary Handwerk

In "The Ins and Outs of Fire Pumps: Intakes" (March 2016), we looked at the “ins” of fire pumps. This month, we will look at the “outs,” the discharge side of the pump system. This includes the pump body, the attached manifolds, piping, and valves.

Meeting the minimum National Fire Protection Association (NFPA) 1901, Standard for Automotive Fire Apparatus, or NFPA 1906, Standard for Wildland Fire Apparatus, performance does not guarantee optimum pump performance. Actually, it is somewhat easy to meet the NFPA performance requirements with almost any discharge combination. Not only is there performance to gain by optimizing your discharge manifold, piping, and valves, but there are noise and safety aspects that can be improved on. When pumping, there must be enough pressure supplied by the pump to overcome the discharge manifold, piping, and valve losses along with the discharge hose friction loss and any elevation changes to provide the correct pressure at the nozzle while supplying the required flow. Based on that, if we need to create more pressure to overcome the losses, that equals more core pump operating pressure, which leads to higher engine operating speed. More pressure needed generates more noise from the apparatus engine, which is not a good thing on the fireground-especially when the noisiest part of any apparatus is the engine. Additionally, operating the pump system at an overall lower pressure makes controlling everything easier and safer. In the past, we relied on using engine speed and power to create additional pressure to overcome manifold and piping losses.

Obtaining the maximum available performance is critical on high-flow applications such as industrial fires, where flowing through the pump is important. It is also important at the extreme opposite end of the market on slip-on wildland/grass apparatus, where the engine driving the pump is very small with limited power to overcome added discharge side pressure losses.

As a pump designer, I look at the velocity of the water traveling in the pipe, waterway, or hose as a reference point in any evaluation of this type. The water speed is commonly measured in feet per second. To calculate this, I use the following formula: Velocity in feet/second = (0.32 × gpm)/the area of the waterway in square inches.

Discharge Types

There are two basic types of discharges, one where the outlet is feeding a hoseline-this can be a preconnect for directly fighting fires or a feeder/supply line-and a hard-piped, directly connected device, such as monitor.

NFPA 1901 has stipulated that the safest optimum velocity, while keeping the hose losses workable, in a given discharge hose is 16.33 feet/second. So, the discharge piping and valve must accommodate this velocity at sufficient working pressure. While doing this, we still need to keep the losses to a minimum.

Part of NFPA 1901 requires two 2½-inch discharges and enough additional 2½-inch or larger hoseline connections, based on this 16.33 feet/second velocity, to equal the pump’s rated capacity. The requirement is for the first fixed hose connection only, and there are no standards for the manifold, piping, or valves feeding these hose connections. Hose-to-hose connection adapters are not counted. NFPA 1901 doesn’t require a 2½-inch outlet connection for every 250-gallon-per-minute (gpm) increment of the pump rating. A 1,500-gpm pump can be rated with two 2½-inch connections and one five-inch connection.

The second discharge type is not dictated by any specific standard, but anecdotal evidence does give some g

By Gary Handwerk

In "The Ins and Outs of Fire Pumps: Intakes" (March 2016), we looked at the “ins” of fire pumps. This month, we will look at the “outs,” the discharge side of the pump system. This includes the pump body, the attached manifolds, piping, and valves.

Meeting the minimum National Fire Protection Association (NFPA) 1901, Standard for Automotive Fire Apparatus, or NFPA 1906, Standard for Wildland Fire Apparatus, performance does not guarantee optimum pump performance. Actually, it is somewhat easy to meet the NFPA performance requirements with almost any discharge combination. Not only is there performance to gain by optimizing your discharge manifold, piping, and valves, but there are noise and safety aspects that can be improved on. When pumping, there must be enough pressure supplied by the pump to overcome the discharge manifold, piping, and valve losses along with the discharge hose friction loss and any elevation changes to provide the correct pressure at the nozzle while supplying the required flow. Based on that, if we need to create more pressure to overcome the losses, that equals more core pump operating pressure, which leads to higher engine operating speed. More pressure needed generates more noise from the apparatus engine, which is not a good thing on the fireground-especially when the noisiest part of any apparatus is the engine. Additionally, operating the pump system at an overall lower pressure makes controlling everything easier and safer. In the past, we relied on using engine speed and power to create additional pressure to overcome manifold and piping losses.

Obtaining the maximum available performance is critical on high-flow applications such as industrial fires, where flowing through the pump is important. It is also important at the extreme opposite end of the market on slip-on wildland/grass apparatus, where the engine driving the pump is very small with limited power to overcome added discharge side pressure losses.

As a pump designer, I look at the velocity of the water traveling in the pipe, waterway, or hose as a reference point in any evaluation of this type. The water speed is commonly measured in feet per second. To calculate this, I use the following formula: Velocity in feet/second = (0.32 × gpm)/the area of the waterway in square inches.

Discharge Types

There are two basic types of discharges, one where the outlet is feeding a hoseline-this can be a preconnect for directly fighting fires or a feeder/supply line-and a hard-piped, directly connected device, such as monitor.

NFPA 1901 has stipulated that the safest optimum velocity, while keeping the hose losses workable, in a given discharge hose is 16.33 feet/second. So, the discharge piping and valve must accommodate this velocity at sufficient working pressure. While doing this, we still need to keep the losses to a minimum.

Part of NFPA 1901 requires two 2½-inch discharges and enough additional 2½-inch or larger hoseline connections, based on this 16.33 feet/second velocity, to equal the pump’s rated capacity. The requirement is for the first fixed hose connection only, and there are no standards for the manifold, piping, or valves feeding these hose connections. Hose-to-hose connection adapters are not counted. NFPA 1901 doesn’t require a 2½-inch outlet connection for every 250-gallon-per-minute (gpm) increment of the pump rating. A 1,500-gpm pump can be rated with two 2½-inch connections and one five-inch connection.

The second discharge type is not dictated by any specific standard, but anecdotal evidence does give some g