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In this part of the full fire fighting and fire protection series, we are going to learn about Pipes used in Fire Fighting.
Pipes used in Fire Fighting
The pipes used in firefighting are mainly classified into three types depending upon their materials of construction: -
1.) Solid metal pipes
2.) Hollow metal pipes
3.) Plastic pipes
The solid metal pipe consists of steel or iron having an outer diameter between 0.5 inch-13 inches (12mm-330mm) and an inner diameter between 1/8inch-16 inches (25mm-410mm). These pipes are manufactured as per the requirements of various industries including mining, power generation, etc.
Hollow metal pipes consist of two concentric tubes of metal. The inner tube provides a pathway for the flow of water while the outer tube is designed to withstand high temperatures. The outer shell of a hollow metal pipe is normally coated with rubber or plastic material to protect it against corrosion.
Plastic pipe is made of rigid polymers of the type ABS, PVC, PPE, PPF, or PE. The manufacturing processes involve mixing different chemicals and extruding them before they are molded into shape. The use of these kinds of pipes helps us to save time, money & effort without compromising on quality.
Other than these, there are many other methods of extinguishing fires. For instance, using water sprinklers that disperse the spray over a wide area, throwing sand or gravel onto the fire to smother it, applying a foam chemical mixture called CO2-AFCO2 (or similar name), using a gas that is heavier than air and hence rises to cool the hot gases, or even using a combination of several of these.
Black steel pipes
This material is commonly known as black steel pipe. It is widely used in fire sprinkler system due to its anti-corrosion property, high temperature strength, toughness, good chemical and thermal stability, etc. This kind of steel product is mainly composed of carbon (approximately 0.8-0.9%), manganese (approximately 0.25%) and chromium (approximately 0.08%).
Galvanized steel pipes
The galvanized pipes have been widely used in fire protection since the end of 1950's. Galvanized steel pipe is generally composed of copper-zinc alloy steel layer coated by zinc with a thickness of 1/16 inch to 4 inches.
It is not only the excellent anti-corrosion property, but it also has the following advantages:
1. The whole surface of the pipe is galvanized, therefore it is easily welded together without forming cracks; and the welding zone is less than 5 mm thick.
2. The pipe is flexible, and corrosion does not occur at the joint between two sections.
3. The galvanized steel pipe is much cheaper than ordinary non-galvanized steel pipe.
4. In general, the galvanized steel pipe has good heat conduction and high thermal conductivity.
5. The galvanized steel pipes are light, durable and convenient to install and maintain.
6. Compared with the ordinary stainless steel pipe, the galvanized steel pipes have lower cost and higher efficiency.
7. There is no need of sanding or painting after installation.
8. The galvanized steel piping can withstand direct flame.
9. The galvanized piping can bear pressure up to 75 psi (528 kPa).
10. It is easy to repair the damaged parts.
11. The galvanized steel is suitable for high temperature applications due to its good mechanical properties.
The galvanized pipes in fire protection play an important role in preventing or delaying the spread of fire. Galvanized pipes have high corrosion resistance and are widely used to prevent the spread of fire due to their high temperature resistance. Due to its excellent chemical stability, galvanized pipe material is suitable for use in the underground water system. Galvanized steel pipes are commonly used in many applications, including water supply systems, storm drainage, sewage collection and treatment systems, and industrial and commercial process piping.
Pipe materials are divided into four categories according to their uses. These are: general purpose, pressure-rated, burst resistant, and specialty. General purpose pipes are used in residential and commercial buildings. Pressure-rated pipes are used to transport fluids under pressure. Burst resistant pipes are used to protect people from injury caused by bursting pipes. Specialty pipes are used for special purposes, such as those containing hazardous gases or liquids, where the pipes must meet specific requirements.
General purpose pipes are used to provide potable water at low pressures. General purpose pipes are generally used in residential and commercial building projects.
These pipes can withstand temperatures up to 300°C (572°F) without loss of serviceability and safety. Galvanized piping is designed to resist deterioration caused by chemicals, heat, and moisture. However, regular maintenance is necessary to ensure that they are not corroded. Galvanization helps to protect piping systems from corrosion. The protective layer prevents rusting and ensures that it does not deteriorate over time. Galvanizing is done by immersing the piping into molten zinc. After dipping, the metal is rinsed with water to remove excess zinc. The resulting coating is then allowed to dry before being transported to the job site.
In addition to corrosion protection, galvanized piping is known for its durability. When galvanizing is applied properly, zinc will bond to the iron in the pipe, forming a strong outer layer of rust-resistant zinc around the pipe. Galvanized pipes are frequently used in municipal drinking water distribution networks. Galvanized pipes make good choices for these types of projects because they tend to be less expensive than copper pipes, which require extensive electrical work to install. They may also last longer than copper. If the pipes are buried deep enough, the steel frame will remain intact.
Pressure-rated pipes carry fluid at high pressures. A typical example of a pipe rated for higher pressures is a gas transmission pipeline. Pressure-rated pipes should be able to withstand internal pressures ranging from 10 psig to 50 psig. An example of a product that makes use of pressure-rated pipes is a well pump. Galvanized steel pipe is often used to build pipelines in marine environments, since it provides superior corrosion resistance.
Burst-resistant pipes are used to protect workers from injuries that could result if the pipe bursts. They are specially designed to minimize the risk of injury from a broken piece of piping. These pipes are rated based on the amount of force that would cause them to break or leak. A standard practice is to rate the pipes at a range of forces. The lower the rating number, the greater the degree of protection provided. Pipe ratings are expressed in pounds per square inch, psi, or kilograms per meter, as appropriate. Standard pipe sizes are specified in terms of diameter. Pipelines with diameters between 4 inches (10 cm) and 16 inches (40 cm) are called “diameter-limited”; larger pipelines are called “pressure-limited.” Diameter-limited pipelines are typically used only to move liquid in small volumes.
Specialty pipes are used for specialized purposes, such as pipelines carrying flammables or corrosives. In some cases, specialty pipes are custom fabricated. In others, they are already manufactured and sold as finished goods. Common examples of specialty products include:
• Chemical transportation pipelines
• Process communication and control pipelines
• High-temperature industrial pipelines
• Liquefied petroleum gas pipelines
• Hazardous gas pipelines
• Corrosion-resistant welded steel
HDPE (High Density Polyethylene) pipes
1. HDPE pipes have been widely applied in fire protection due to its non-toxic property, low cost, good thermal conductivity and high melting point. However, HDPE pipes have some drawbacks including that their mechanical performance at high temperature cannot satisfy many applications, they have poor corrosion resistance and are easily damaged under certain conditions. The failure may cause serious accidents and even lead to fires.
2. HDPE piping systems are mainly composed of two parts: inner pipe and outer shell. When the inner pipe reaches the service temperature of the application, the internal pressure of the pipe system increases rapidly. Under this condition, the pipe wall expands severely and cracks occur due to the mismatch between the expansion coefficient of the pipe material and the surrounding material. This results in pipeline rupture. To avoid this problem, HDPE pipes should be installed with adequate space between the inner pipe and the surrounding environment. In addition, the outside surface of the HDPE pipes should be protected with proper coating materials or paint. Otherwise, the pipe will not only fail to protect the whole pipeline system, but also endanger people’s safety.
3. For the purpose of resisting damage caused by high temperatures, the exterior wall of the pipe should be thickened and reinforced appropriately. High-temperature resistant coatings containing polyurethane resin (PU), modified epoxy resin (ME) and other types of resin should be coated on the surface of the HDPE pipe. The thickness of these coatings should be controlled to achieve the purpose of protecting the pipe. If the coating does not meet the requirement, then another type of coating should be used.
4. There are two ways to reduce the risk of pipeline rupture. One way is to strengthen the design of the structure. Another way is to improve the quality of pipe products. The former method includes increasing the thickness of the pipe wall and strengthening the connection between different layers. The latter method includes selecting high-quality raw materials, optimizing processing parameters, and conducting strict QC testing before production.
5. The following are the defects of HDPE pipes:
(a) Inadequate thickness of the pipe wall
(b) Improper welding, clamping, and fastening methods
(c) Unreasonable layout and installation
(d) Pipe joints are not connected well
(e) Insufficient welding preparation
(f) Use of improper welding wire
UPVC (Poly Vinyl Chloride) pipes
How does UPVC (Polyvinyl Chloride) work?
The material is made up mainly of plasticised PVC. If it comes into contact with fire, then it melts and evaporates leaving a residue that burns out almost instantly. It forms a protective layer over the surface of the pipe. The outer layer of the pipe contains additives that prevent UV rays reaching the inner core.
What are the advantages of using UPVC pipes?
PVC pipes have been proven to be highly resistant to damage caused by flames and high temperatures. They provide excellent insulation and sound dampening. Since they are non-combustible, they do not emit toxic gases, nor leave any harmful fumes behind. Due to their flexibility, they allow for quick installation and removal. They are also strong enough to withstand extreme weather conditions.
What are the disadvantages of UPVC piping?
Since PVC pipes are not considered environmentally friendly, it can cause harm to the environment if left untreated after use. In addition, since they cannot be recycled, they become useless once destroyed. There are many parts in the world where these materials are not permitted due to environmental concerns.
The use of UPVC pipes in fire fighting is not entirely new. Upvc pipes have been used in fire fighting since the early 1980's. They have some advantages over metal pipes. The first being that they are lighter than steel pipes and therefore easier to handle. There are many companies making upvc fire hydrants. These can vary greatly in quality, size, weight, and price. A good company will give you a number of options to choose from. The second advantage is that UPVC pipe can stop leaks faster than steel pipes. Metal pipes tend to leak at high pressures. The third advantage of using UPVC pipes is that they do not rust. So if your system does get damaged and the pipe starts leaking you don’t need to worry about damaging your water supply.
Access all the previous parts of this full fire fighting series by clicking the links provided below:
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