Hard suction hose
Encyclopedia
Hard suction hose is a specific type of fire hose
used in drafting operations, when a fire engine uses a vacuum to draw water from a portable water tank
, pool, or other static water source. It is built to withstand vacuum, rather than pressure, abrasion, and heat. In the United States, it is standard equipment according to the National Fire Protection Association
standards for fire engines. It is used in both structural and wildland firefighting throughout the world, and is made in various diameters and connection types.
used in drafting operations. When using this technique, the fire engine draws water for fire fighting from an unpressurized supply, such as a portable water tank
, pool, or other static water source, instead of drawing water from a pressurized water supply, such as a fire hydrant
. Under complete vacuum conditions, a pump can lift water 33.9 feet (10.3 m), but "no pump on a fire apparatus is capable of producing a perfect vacuum". Due to this limitation and friction loss
, fire services do not recommend attempting to lift water more than 3 metres (9.8 ft).
Hard suction hose may also be used to connect a fire engine to a hydrant. This practice is common in Australia, but woven jacket fire hose is normally used for this purpose in the United States. Using hard suction hose in this manner requires that the fire engine be positioned carefully for the limited flexibility of the hose, and may require multiple firefighters due to the weight and bulk of the hose section. In certain circumstances, it may be possible to use hard suction hose to draft from a hydrant with adequate water supply but a low flow rate.
These hoses are built to withstand vacuum
, rather than water pressure, abrasion, and heat. They are, therefore, constructed differently to the standard fire hose and have different end fittings. In the United States, they are standard equipment according to the National Fire Protection Association
standards for fire engines. Since hard suction hose cannot be folded, it is typically mounted on the side of a fire engine, often opposite ground ladders. Such hose is used in both structural and wildland firefighting throughout the world.
Hard suction hose can also be used to extend the range of a water tender
's dumping capability, if the fittings of the hard suction hose match those of the tender dumping water. This could be used to fill a portable dump tank not immediately adjacent to the water tender, from which another fire engine can draft. Since water movement during dumping relies on gravity, rather than mechanical pressurization, hard suction hose is useful for this task.
in both its construction and usage:
Hard suction hose predates steam or gas powered fire engines and has been available since at least 1888, sometimes referred to as "spiral suction hose".
s. In the United States, NFPA 1901
requires engines to have hard suction hose that matches the engine's pump rating. For example, an engine with a 1000 gallons (3,785.4 l) per minute pump is required to carry 5 inches (12.7 cm) or larger hose, while a wildland fire engine will typically carry 2 to 2.5 in (5.1 to 6.4 cm) hard suction hose.
The United Kingdom, has a standardised range of metric hose diameters: 7, 9, 12.5 and 15 cm (2.8, 3.5, 4.9 and 5.9 in), with the two smallest diameters sometimes used twined to provide adequate flow rates. Within this range, the 7 centimetres (2.8 in) hoses are fitted with "Instantaneous Couplings"; the 12.5 and 15 cm (4.9 and 5.9 ) hoses have Storz
couplings; and the 9 centimetres (3.5 in) hose comes in two types, one with "Instantaneous Couplings" and one with Storz fittings. Fire Service Manuals provide tables of maximum volumetric flow rates for a given pump pressure, hose diameter and total hose length. The use of these tables, is to facilitate the selection of suitable hoses, taking into account the frictional losses
caused by transporting water through the strainer, hoses, pump and fire fighting nozzles, to draft water from source to the fireground.
When being used in a drafting
operation from a pool, portable water tank, or other uncovered water source, the length of hard suction hose farthest from the pump is usually attached to a strainer, to keep foreign objects in the water from being pulled into and damaging the pump. If used in a pond, stream, or other body of water, an appropriate flotation device must be used to keep the strainer below the surface and above the bottom, so that neither mud nor air are sucked into the fire engine's pump. When drafting from a solid-bottomed tank or pool, a strainer can safely rest on the bottom without suctioning mud into the fire engine's pump.
The United Kingdom official guidance is to:
Fire hose
A fire hose is a high-pressure hose used to carry water or other fire retardant to a fire to extinguish it. Outdoors, it is attached either to a fire engine or a fire hydrant. Indoors, it can be permanently attached to a building's standpipe or plumbing system...
used in drafting operations, when a fire engine uses a vacuum to draw water from a portable water tank
Portable water tank
A portable water tank is a collapsible temporary tank designed for the reserve storage of water in firefighting, emergency relief, and military applications. These tanks can be either supported or unsupported. The supported tanks have a steel or aluminum frame and range in size from 600 to 5000 US...
, pool, or other static water source. It is built to withstand vacuum, rather than pressure, abrasion, and heat. In the United States, it is standard equipment according to the National Fire Protection Association
National Fire Protection Association
The National Fire Protection Association is a United States trade association that creates and maintains private, copywrited, standards and codes for usage and adoption by local governments...
standards for fire engines. It is used in both structural and wildland firefighting throughout the world, and is made in various diameters and connection types.
Usage
Hard suction hose, also known as a suction hose, is a specific type of rigid fire hoseFire hose
A fire hose is a high-pressure hose used to carry water or other fire retardant to a fire to extinguish it. Outdoors, it is attached either to a fire engine or a fire hydrant. Indoors, it can be permanently attached to a building's standpipe or plumbing system...
used in drafting operations. When using this technique, the fire engine draws water for fire fighting from an unpressurized supply, such as a portable water tank
Portable water tank
A portable water tank is a collapsible temporary tank designed for the reserve storage of water in firefighting, emergency relief, and military applications. These tanks can be either supported or unsupported. The supported tanks have a steel or aluminum frame and range in size from 600 to 5000 US...
, pool, or other static water source, instead of drawing water from a pressurized water supply, such as a fire hydrant
Fire hydrant
A fire hydrant , is an active fire protection measure, and a source of water provided in most urban, suburban and rural areas with municipal water service to enable firefighters to tap into the municipal water...
. Under complete vacuum conditions, a pump can lift water 33.9 feet (10.3 m), but "no pump on a fire apparatus is capable of producing a perfect vacuum". Due to this limitation and friction loss
Friction loss
Friction loss refers to that portion of pressure lost by fluids while moving through a pipe, hose, or other limited space. In mechanical systems such as internal combustion engines, it refers to the power lost overcoming the friction between two moving surfaces.- Causes :Friction loss has several...
, fire services do not recommend attempting to lift water more than 3 metres (9.8 ft).
Hard suction hose may also be used to connect a fire engine to a hydrant. This practice is common in Australia, but woven jacket fire hose is normally used for this purpose in the United States. Using hard suction hose in this manner requires that the fire engine be positioned carefully for the limited flexibility of the hose, and may require multiple firefighters due to the weight and bulk of the hose section. In certain circumstances, it may be possible to use hard suction hose to draft from a hydrant with adequate water supply but a low flow rate.
These hoses are built to withstand vacuum
Vacuum
In everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty". A perfect vacuum would be one with no particles in it at all, which is impossible to achieve in...
, rather than water pressure, abrasion, and heat. They are, therefore, constructed differently to the standard fire hose and have different end fittings. In the United States, they are standard equipment according to the National Fire Protection Association
National Fire Protection Association
The National Fire Protection Association is a United States trade association that creates and maintains private, copywrited, standards and codes for usage and adoption by local governments...
standards for fire engines. Since hard suction hose cannot be folded, it is typically mounted on the side of a fire engine, often opposite ground ladders. Such hose is used in both structural and wildland firefighting throughout the world.
Hard suction hose can also be used to extend the range of a water tender
Water tender
A water tender, also known as a tanker in some regions, is a specialized firefighting apparatus designed for transporting water from a water source to a fire scene...
's dumping capability, if the fittings of the hard suction hose match those of the tender dumping water. This could be used to fill a portable dump tank not immediately adjacent to the water tender, from which another fire engine can draft. Since water movement during dumping relies on gravity, rather than mechanical pressurization, hard suction hose is useful for this task.
Characteristics and construction
Hard suction hose differs from standard fire hoseFire hose
A fire hose is a high-pressure hose used to carry water or other fire retardant to a fire to extinguish it. Outdoors, it is attached either to a fire engine or a fire hydrant. Indoors, it can be permanently attached to a building's standpipe or plumbing system...
in both its construction and usage:
- It is rigid and generally scalloped. Often, such hose is manufactured using molded synthetic material (such as PVCPolyvinyl chloridePolyvinyl chloride, commonly abbreviated PVC, is a thermoplastic polymer. It is a vinyl polymer constructed of repeating vinyl groups having one hydrogen replaced by chloride. Polyvinyl chloride is the third most widely produced plastic, after polyethylene and polypropylene. PVC is widely used in...
) shaped into a series of rings. This shape allows the hose to be somewhat flexible, without allowing it to collapse in on itself under suctionSuctionSuction is the flow of a fluid into a partial vacuum, or region of low pressure. The pressure gradient between this region and the ambient pressure will propel matter toward the low pressure area. Suction is popularly thought of as an attractive effect, which is incorrect since vacuums do not...
, as a normal, woven-jacket fire hose would. - It uses suction gaskets. Gaskets in standard fire hose ("pressure gaskets") are designed to minimize the water leaking out between couplingsHose couplingA hose coupling is a connector on the end of a hose to connect it with another hose or with a tap or a hose appliance, such as an irrigation sprinkler...
. The gaskets connecting hard suction hose sections, pump, and strainer must instead prevent air from entering at the coupling, since that would spoil the vacuum and allow air into the pump intake. Large diameter (4 inches (10.2 cm) or greater) hard suction hose will typically use StorzStorzFor the beer, see Storz Brewing Company.Storz is a type of hose coupling invented by Carl August Guido Storz in 1882 that connects using interlocking hooks and flanges. It is sometimes referred to as a sexless coupling, because rather than having a male and a female end connected by screw threads,...
fittings, which are genderlessGender of connectors and fastenersIn electrical and mechanical trades and manufacturing, each half of a pair of mating connectors or fasteners is conventionally assigned the designation male or female...
. 3 inches (7.6 cm) or smaller hard suction hose will typically use threadedScrew threadA screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force. A screw thread is a ridge wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread and the latter called a tapered thread...
fittings. In each case, the hard suction hose connection will match the fittings of the pump intake and supply hose, so that hard suction hose can be used in place of supply hose as appropriate. - It is short. Typically, hard suction hose comes in 10 feet (3 m) lengths, while fire hose comes in 50 and 100 ft (15.2 and 30.5 m) lengths. Since a fire engine's pump only produces a partial vacuum, it is only recommended for lifting water 3 metres (9.8 ft) or less. For this reason, and because each junction is an opportunity for a crack or imperfect seal to spoil the vacuum, it is rare to see many sections of hard suction hose connected together.
- It is not designed for use in fire streams. The airtight nature of hard suction hose, necessary for drafting, renders the hose unsuitable for the high pressure water flow needed to spray a pressurized stream of water on a fire. Thus, hard suction hose is tested for the ability to "prevent collapse under vacuum conditions" rather than its ability to function as an attack hoseline.
Hard suction hose predates steam or gas powered fire engines and has been available since at least 1888, sometimes referred to as "spiral suction hose".
Diameter
Hard suction hose comes in multiple sizes, from 2 to 6 in (5.1 to 15.2 cm) in diameter. Large diameter hose are carried on full-size fire engines, but smaller diameters of hard suction hose can be carried on apparatus with smaller fire pump ratings, such as wildland fire engineWildland fire engine
Wildland fire engines use special equipment to spray water, foam, and chemicals. The engines are able to carry up to of water. Many wildland fire engines are also equipped with four wheel drive and special equipment for off-road use.*...
s. In the United States, NFPA 1901
NFPA 1901
NFPA 1901, the Standard for Automotive Fire Apparatus, is published by the National Fire Protection Association to outline the standard for firefighting apparatus...
requires engines to have hard suction hose that matches the engine's pump rating. For example, an engine with a 1000 gallons (3,785.4 l) per minute pump is required to carry 5 inches (12.7 cm) or larger hose, while a wildland fire engine will typically carry 2 to 2.5 in (5.1 to 6.4 cm) hard suction hose.
The United Kingdom, has a standardised range of metric hose diameters: 7, 9, 12.5 and 15 cm (2.8, 3.5, 4.9 and 5.9 in), with the two smallest diameters sometimes used twined to provide adequate flow rates. Within this range, the 7 centimetres (2.8 in) hoses are fitted with "Instantaneous Couplings"; the 12.5 and 15 cm (4.9 and 5.9 ) hoses have Storz
Storz
For the beer, see Storz Brewing Company.Storz is a type of hose coupling invented by Carl August Guido Storz in 1882 that connects using interlocking hooks and flanges. It is sometimes referred to as a sexless coupling, because rather than having a male and a female end connected by screw threads,...
couplings; and the 9 centimetres (3.5 in) hose comes in two types, one with "Instantaneous Couplings" and one with Storz fittings. Fire Service Manuals provide tables of maximum volumetric flow rates for a given pump pressure, hose diameter and total hose length. The use of these tables, is to facilitate the selection of suitable hoses, taking into account the frictional losses
Friction loss
Friction loss refers to that portion of pressure lost by fluids while moving through a pipe, hose, or other limited space. In mechanical systems such as internal combustion engines, it refers to the power lost overcoming the friction between two moving surfaces.- Causes :Friction loss has several...
caused by transporting water through the strainer, hoses, pump and fire fighting nozzles, to draft water from source to the fireground.
Strainers
Drafting
Drafting or draughting may refer to:* Campdrafting, an Australian equestrian sport* Drafting , slipstreaming* Technical drawing, the act and discipline of composing diagrams that communicates how something functions or is to be constructed. E.g.:** Architectural drawing** Electrical drawing**...
operation from a pool, portable water tank, or other uncovered water source, the length of hard suction hose farthest from the pump is usually attached to a strainer, to keep foreign objects in the water from being pulled into and damaging the pump. If used in a pond, stream, or other body of water, an appropriate flotation device must be used to keep the strainer below the surface and above the bottom, so that neither mud nor air are sucked into the fire engine's pump. When drafting from a solid-bottomed tank or pool, a strainer can safely rest on the bottom without suctioning mud into the fire engine's pump.
The United Kingdom official guidance is to:
- use ropes to take to the weight of the hose and the strainer, in order to avoid putting sideways loadings on the couplings;
- ensure that the strainer is a minimum of three strainer-diameters below the water surface to prevent air cavitationCavitationCavitation is the formation and then immediate implosion of cavities in a liquidi.e. small liquid-free zones that are the consequence of forces acting upon the liquid...
; - to support the hose with packing, where necessary, when it cross a wall or other obstruction to prevent an air pocket being formed.
External links
- Strainer pressure drop calculator Calculate pressure drop across a strainer.