OUR TECHNICAL ADVISOR, Mr. R.R. Nair Speaks Scroll below to know about Fire Hoses :
Fire hoses are used for two main purposes. The hoses used to discharge water from an attack engine on to the fire, are called “attack hoses” or “attack lines” or “discharge hoses”. The hoses used to deliver water to the attack engine, are called “supply hoses” or “supply lines” or “intake hoses”.
Fire hoses and appliances are the most basic fire fighting tools. In other words, fire hoses are regarded as the fire fighters lifeline. A fire hose should not fail at a critical movement. It should be durable, dependable in an emergency. It should also be assured that water pressure is not lost during an emergency as a result of kinking leakage or damage. Many appliances, adapters, reducers, and fittings allow hose to be configured and used in countless ways. This enables fire fighters endless combinations and possibilities for just about any situation that present itself.
Hoses have been in use since the first fire brigades were formed. First fire hose of modern era was developed in 1693 by Dutchemen, Jan Van Der Heiden, Superintendent of Fire Brigade, and his son Nicholaas. This hose was made of leather stitched into a length of about fifty feet’s. Later, Van Der Heiden developed the first suction hose by installing a wire through it, to keep it from collapsing. The present day of hoses came up after many changes and modifications made by various persons and organizations. Though technology has vastly improved their performance, but the basic principles of their use remain the same. Hose delivers water to fire pumps and from pumps to the fire. Hose comes in different sizes and types for a variety of uses.
2. Types of Hoses:
There are several types of hose designed specially for fire service. Those designed to operate under positive pressure are called discharge hoses. They include attack hose, supply hose, forestry hose and booster hose. Those designed to operate under negative pressure are called suction hoses. Fire hoses are used for two main purposes. The hoses used to discharge water from an attack engine on to the fire, are called “attack hoses” or “attack lines” or “discharge hoses”. The hoses used to deliver water to the attack engine, are called “supply hoses” or “supply lines” or “intake hoses”.
2.1. Attack Hoses
The term “attack hose” is referred by NFPA. The attack hose or discharge hose is a fabric – covered, flexible hose, used to pump water to a discharge point. Most attack hoses carry water directly from the attack engine to a nozzle that is used to direct water on to the fire. In some cases, an attack line is attached to a duck-gun, aerial device, or some other type of master stream appliance. Attack lines can also be used to deliver water to a fire department connection that supplies a standpipe or a sprinkler system inside a building. Attack hose ranges in size from one inch to 3 inches (25 to 76 mm) and is designed to operate at pressures up to about 400 psi (2070 kPa). The typical sizes used for attack hose include one inch, 1-3/4 inches, 2-1/2 inches and 3 inches inside diameter. The standard length of an attack hose is 50 feet (15.3m).
2.2. Supply Hoses
“Supply hoses” or “intake hoses”, often referred to as “supply lines”, is a fabric – covered, flexible hoses used to move water from a distant source to the pump. The water can come directly from a hydrant or it can come from another engine that is being used to provide a water supply for the attack engine. Depending on the water supply and the discharge flow requirements, several types of hose can be used. Supply hose sizes are 2-1/2 inches, 3 inches, 4 inches, 5 inches and 6 inches inside diameter. Supply hoses are designed to carry larger volumes of water at lower pressure. According to NFPA, that the supply hose not to be operated at pressure exceeding 185 psi. Supply hose can transfer water over longer distances with minimum loss of pressure due to friction because of the large diameter size of hose. Sift sleeve is typically a shorter section of the supply hose with female couplings on both ends used when the pump is close to a pressurized water supply such as hydrant. The standard length of a supply hose is 100 feet (30.6m).
2.3. Forestry Hoses
Forestry hose is a fabric – covered, flexible hose used to fight fires in grass, bush, and trees where a lightweight hose is needed in order to maneuver it over steep or high terrain. Forestry hose comes in 1 inch (25mm) and 1-1/2 inch (38mm) nominal inside diameters and is designed to operate at pressures up to about 450 psi. The standard length is 100 feet (30.6m).
2.4. Booster Hoses
Booster hose is a rubber – covered, thick walled, flexible hose used to fight small fires. It retains its round cross section when it not under pressure and is usually carried on a reel on the fire pumps, rather than being stored flat. Booster hose comes in ¾ inch (19mm) and 1 inch (25mm) normal inside diameters and is designed to operate at pressures up to 800 psi. The standard length is 100 feet (30.6 m).
2.5. Suction Hoses
Suction hose, sometimes called hard suction, is usually a rubber – covered, semi rigid hose with internal metal reinforcements. It is used to suck water out of un-pressurized sources, such as ponds or rivers, by means of vacuum. Suction hose ranges in nominal inside diameter from 2.5 inch (64 mm) to 6 inch (152 mm). The standard length is 10 feet (3.1 m).
3. Size of Hose
Fire hoses range in size from 1 inch to 6 inches in diameter. The normal hose size refer to the inside diameter of the hose when it is filled with water. The smaller diameter hoses (SDH) are used as attack lines and the larger diameter hoses (LDH) are almost always used as supply lines. Medium diameter hoses (MDH) can be used as either attack lines or supply lines. Smaller diameter hose (SDH) range in size from 1 inch to 2 inches in diameter. Many fire engines are equipped with a reel of ¾ inch or 1 inch hard rubber hose called a “booster hose” or “booster line”, which is used for small outdoor fires. A lightweight collapsible 1 inch hose known as “forestry hose” is often used to fight bush fires. The hoses that are most commonly used to attack interior fires are either 1-1/2 inches or 1-3/4 inches, in diameter. These hoses are usually connected directly to a hand-line nozzle. Some fire department also use 2 inches attack lines. Each section of attack hose is usually 50 feet long. Hoses of 2-1/2” inches or 3 inches in diameter are called medium diameter hose (MDH). Hoses in this range can be used as either supply lines or attack lines. Large hard-line nozzles are often used with 2-1/2 inches hose to attack larger fires. When used as an attack hose, the 3 inches size is more often used to deliver water to a master stream device or a fire department connection. These hoses also come in 50 feet long. Hose size of 3-1/2 inches or more in diameter are called large diameter hoses (LDH). The standard LDH sizes include 4 inches and 5 inches diameters, which are used as supply lines by many fire departments. The largest LDH size is 6 inches in diameter. The standard length of LDH is 50 feet or 100 feet.
4. Hose Construction
Most fire hose is constructed with an inner waterproof liner surrounded by either one or two outer layers. The outer layers provide the strength to withstand the high pressures that are exerted by water inside the hose. The strength is provided by a woven mesh made from high strength synthetic fiber such as nylon or polyester that are resistant to high temperatures, mildew, and many chemicals. These fibers can also withstand some mechanical abrasion. An attack hose must withstand higher pressure and is designed to be used in a fire environment where it can be subjected to high temperatures, sharp surfaces, abrasion and other potentially damaging conditions. Though large diameter hoses are connected to operate at lower pressure than attack hoses and in less severe operating conditions, it must still be durable and resistant to external damage. Usually two types of hoses viz. (1) double jacket hose and (2) rubber jacket hose are constructed.
4.1. Double Jacket Hose
“Double jacket hose” is constructed with two layers of woven fibers. The outer layer serves as a protective covering which the inner layer provides most of the strength. The tightly woven outer jacket can resist abrasion, cutting, hot embers, and other external damage. The woven fibers are treated to resist water and provide added protection from many common hazards that are likely to be encountered at the scene of fire.
4.2. Rubber Jacket Hose
Instead of a double jacket, some fire hose are made with durable rubber lime compound as the outer covering. This material is bonded to a single layer of strong woven fibers that provides the strength to keep the hose from rupturing under pressure. This type of construction is called “rubber covered hose” or “rubber jacket hose”.
5. Pressure Testing
The Standards set by the NFPA require that each length of new double jacket, rubber- lined attack hose must be pressure tested to 600 psi (4140 kPa), but most manufacturers test to 800 psi (5520 kPa). Subsequent to delivery, the hose is tested annually to 400 psi (2760 kPa) by the fire department. While the hose is under pressure, it is inspected for leaks and it is determined that the couplings are firmly attached. After testing, the hose must be drained, dried, rolled and transported to the customer.
Fire hose needs proper care and maintenance just as any other fire fighting equipment. A hose, if it is properly maintained can serve for decades. Double jacket hose and rubber jacket hose are designed to be stored flat and to fold easily when there is no water inside the hose. This allows a much greater length of hose to be stored in the hose box. The inner line of a hose is usually made of a synthetic rubber compound or a thin flexible membrane, a material that can be flexed and folded without developing leaks. There are many different ways to carry hose and transport it on fire apparatus. The method chosen is usually determined by the advantages of the method and the needs of the individual fire departments.