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Specifying Deck Gun Risers for Fire Trucks

By Bill Adams

Apparatus-mounted master stream appliances (deck guns) are also called deck pipes, monitors, deluge sets, and turrets. Regional descriptions refer to the appliance manufacturer such as Stang, Eastman, and McIntire. In his 2011 Fire Engineering article about master streams, Paul Shapiro states, “A master stream is a heavy-caliber stream delivered through an appliance when desired flows exceed 350 gpm.” (http://www.fireengineering.com/articles/2011/06/shapiro-smooth-bore.html) The appendix of National Fire Protection Association (NFPA) 1901, Standard for Automotive Fire Apparatus, appendix recommends carrying a minimum 1,000-gpm master stream appliance on pumpers. It doesn’t say it must be mounted and prepiped. How, where, and if you mount and supply it is a buyer and seller decision.

A Mack factory delivery photograph showing a 40-year-old installation of a deck gun. It shows the base of the deluge device with a female tapered pipe thread fitting (looks like a lock nut) attached to the riser pipe. Cut threads reduces a pipe’s wall thickness. (Photo courtesy of Harvey Eckart.)

A firefighter operating an apparatus-mounted deck gun more than 20 years ago was launched off the rig with the appliance when the riser pipe supplying it broke loose. A lawsuit followed. Caution: history has a way of repeating itself. Following are excerpts from recently published purchasing specifications describing riser pipes to deluge sets. Underlining is mine.

  1. A 3″ deluge riser shall be installed above the pump. Piping shall be rigidly braced.
  2. One (1) 3″ deck gun discharge outlet shall be provided above pump compartment. Piping shall be rigidly braced as necessary.
  3. The deck gun discharge shall be provided and located above the pump panel and shall terminate with NST threads and be capped for later use. The discharge shall be plumbed directly from the pump discharge manifold utilizing direct connect discharge valve flanges.
  4. A 3.00″ deluge riser shall be installed above the pump in such a manner that a monitor can be mounted and used effectively. Piping shall be installed securely so no movement develops when the line is charged. 

A flange mounted riser pipe on a 1987 quint. According to an industry expert’s testimony during litigation of a riser failure, a flange type arrangement increases the mounting surface area, thereby decreasing the pounds per square inch of reactionary forces. (Photo by author.)

When apparatus manufacturers supply the appliance, one could reasonably expect the manufacturer would support the riser per the appliance manufacturer’s instructions. If the purchaser provides an appliance after delivery (See #3 above – capped for later use), who’s responsible for adequately bracing the riser? If the next fire chief retrofits the pumper with a larger capacity appliance or later adds a telescoping riser pipe, who determines if the existing riser bracing is adequate? Do your homework if you decide later to use your deck gun for “high-pressure master stream operations using smooth bore tips.” Shapiro’s article shows nozzle reactions for high-pressure flows.

Purchasers should also be aware that some appliance manufacturers recommend the deck gun’s barrel with stream straightener and nozzle or stacked tips be supported when the rig is traveling–preventing stress on its internal parts and pieces. If you don’t spec it, you don’t get it. (Photo by author.)

Deck gun manufacturers have specific installation instructions. From an Elkhart manual found on the company’s Web site: “WARNING—The piping must be able to withstand a horizontal reaction force of at least 900 lbs. at the height of the discharge elbow and from any angle of rotation that the monitor is capable of turning. Additional support is required if the 8297 Stinger 2.0® is going to be used with an 8298EX 2.0. Serious injury to personnel and damage to equipment can result from improper installation.”

Task Force Tips’s Extend-a-Gun RC is a popular option for elevating a master stream. From its manual, also found on its Web site,: “The forces acting on the mounting brackets, when the Extend-A-Gun RC is in the extended position, are higher than the forces in a normal deck gun installation. The loads on the brackets created from nozzle reaction can exceed 3,000 lbs. when the Extend-A-Gun is fully extended. These loads are transferred directly to the mounting brackets and the structural members they are attached to. It is crucial that the structural members selected can withstand these forces. Qualified persons should calculate these forces and determine suitable mounting locations and structural members. Failure to properly secure the Extend-A-Gun RC, could result in damaged equipment and serious injury. WARNING—Reaction forces generated a master stream allows are very powerful and capable of causing injury and property damage. The Extend-A-Gun RC must be securely mounted to rigid truck support members. Qualified persons should determine suitable mounting locations. WARNING—Inferior welding or poor plate installation could result in serious injury or equipment damage. Qualified individuals should conduct mounting bracket installations.”

Purchasers should also be aware that some appliance manufacturers recommend the deck gun’s barrel with stream straightener and nozzle or stacked tips be supported when the rig is traveling–preventing stress on its internal parts and pieces. If you don’t spec it, you don’t get it. (Photo by author.)

Some apparatus manufacturers fabricate their own deck gun riser supports. Task Force Tips has its own. From its manual: “BRACKET SETS—For safe, dependable service, the Extend-A-Gun RC MUST be securely mounted. To make the Extend-A-Gun RC as versatile as possible, three mounting bracket kits are offered. Each kit has a different upper bracket. The lower bracket is the same in all three. WARNING—Task Force Tips strongly recommends that Extend-A-Gun RC be installed using the bracket sets sold by Task Force Tips that are designed for this purpose. For the Extend-A-Gun RC to operate safely and properly, it must be installed in such a way that the brackets can withstand the forces resulting from the nozzle reaction force. The Task Force Tips bracket sets are designed to fit the Extend-A-Gun RC outer tube very closely to prevent distortion of the outer tube and to give it adequate support.”

I do not endorse any manufacturer, type, or method of supporting risers. My intent is to show purchasers the importance of adequately describing how a deck gun will be used so manufacturers can adequately support it and its riser pipe. It’s also to show there’s more to retrofitting or increasing a deck gun’s performance than just screwing on a new component or raising the pump’s discharge pressure. The objective is to protect the firefighters when using the device.

Following is a summary of testimony from an expert in the lawsuit mentioned above. The testimony can be found at http://caselaw.findlaw.com/ca-court-of-appeal/1288485.html. When tank water supplied to the deck gun was exhausted, a hydrant connection was made allowing water to flow through the pump directly to the deck gun, causing a water hammer. A nozzle reaction occurred causing a reactionary force on the riser and its attachments to which the deck gun was attached with a three-inch threaded riser pipe. The threaded riser pipe did not fail or break at its connection with the deck gun, but the riser broke at the point it was mounted on the apparatus. The deck gun and its attachments separated from the fire truck mounting. The expert also made note of the absence of a flange mounting system commonly used today, the presence of corrosion on the riser pipe, an inadequate thread depth engagement on the riser pipe, and the fact that the riser was made out of material of insufficient strength.”

There can be many contributing factors to cause a deck gun riser to break loose, including choice of materials, methods of construction, human error, as well as inadequate training. Specification writers have the responsibility to inform apparatus manufacturers of the type of appliance, flows expected, and maximum pressures to be used. Apparatus manufacturers have an equal responsibility to properly “pipe” it. Fire departments have the important responsibility of adequately training their firefighters, and firefighters have the personal responsibility to use it correctly. Be safe.

BILL ADAMS is a member of the Fire Apparatus & Emergency Equipment editorial advisory board, a former fire apparatus salesman, and a past chief of the East Rochester (NY) Fire Department. He has 50 years of experience in the volunteer fire service.

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