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Pipes are circular conduits that can carry liquid in pressure are of various sizes and different materials.
In the case of drinking water conveyance and distribution circular pipes are mostly used. Pipes are of different materials such as GI, DI, CI, WI, steel, cement concrete, HDPE, PPR, PVC, etc.
Selection of pipe materials depends upon fund availability, type of water to be conveyed and its life span and durability, corrosive properties, resistance to temperature stresses, ability to resist pressure, repair and maintenance cost, etc.
2. Requirement of Good Pipe Material
The requirement for good pipe materials is as follows:
1. It should have adequate structural strength so that able to resist pressure induce internally and externally, compressive and tensile temperature stress, load due to overlaying impact stresses, and shock.
2. It should be impervious, corrosion-resistant, durable and long, lasting.
3. It should be cost-effective and available in the market at a reasonable cost. 4. As far as possible Darcy’s frictional coefficient should be low and Hazen William’s constant high so that hydraulic efficiency maximizes.
5. Water may contain inorganic particles, especially in transmission mains like sand, silt, etc., which at high velocity of flow along the invert of the pipe and the erosion of material may take place due to abrasion, hence it should possess enough resistance to abrasion.
6. It should be light in weight so that easy to transport, handle and lay frig.
7. It should be easy to join, flexible in design, and easy to repair and maintain.
8. It should be environmentally friendly.
3. Types of Pipe Materials
The pipes are usually classified according to the pipe materials which are as follows;
a. Cast Iron Pipe (CI)
These pipes are widely used for the conveyance of water in the water supply scheme. These pipes are highly corrosion resistant and possess other desirable properties like durability, easy-to-make joint, long life, strong, and can resist maximum pressure likely to develop. Cast iron pipes are expensive and heavy hence difficult to transport.
CI pipes are available in 2.5 to 5.5 m lengths with various diameters. According to thickness CI pipes are classified as LA, A, and B class and can resist the pressure of 10, 12.5, and 16 kg/cm respectively.
Advantages of CI pipe
1. Cost of these pipes is moderate.
2. The pipes are easy to join.
3. The pipes are highly resistant to corrosion.
4. The pipes are strong and durable
5. Service connections can be easily made
6. Usual life is about 100 years
Disadvantage of CI pipes
1. CI pipes are heavier so that difficult in handling and transport.
2. The carrying capacity of these pipes decreases with the increase in life of pipes due to tuberculation.
3. These pipes generate a metallic taste in the water due to the iron leaching into the water from the rusting of the pipe.
4. These pipes are brittle. Since CI pipes are heavier use of larger size become uneconomical.
b. Galvanized iron pipe (GI pipe)
These are mild steel or wrought iron pipes, provided with a protective coating of zinc on both inner and outer surfaces.
These pipes are commonly used in house plumbing or after-service connection. For water pipe fittings 12mm to 25 mm diameter et corrode pipes are used and available in a length of 7 m. These are cheap, light, easy to join, and easy to transport and handle.
The life span of these pipes is around 20 years. GI pipes may be acidic or alkaline or otherwise activated waters also liable to insulation. In water, if chlorine is added as a disinfectant, an increase in the corrosion of iron materials can be expected.
Advantages of GI pipes
1. These pipes are cheap.
2. Light in weight and easy to handle.
3. The pipes are easy to join.
4. These pipes can be easily cut and threaded.
Disadvantages of GI pipes
1. The pipes are affected by acidic or alkaline waters.
2. The pipes are less durable.
3. Hydraulic efficiency decreases with time as decreases smoothness.
c. Steel pipe
These are fabricated by rolling the mild steel plates to the proper diameter and can be joined by riveting or welding. These pipes are strong, cheaper, and light in weight and can resist high pressure up to 400 m.
The welded steel pipes are made up to 2.4 m in diameter and up to 12 m in length. These pipes are costlier, liable to corrosion, and can’t resist pressure due to external load during vacuum inside.
Advantages of Steel pipes
1. Numbers of joints are less because these are available in long lengths.
2. The pipes are cheap at the first cost.
3. The pipes are durable and strong enough to resist high.
4. The pipes are flexible to some extent and laid on curves. and they can therefore 5. Transportation is easy because of its lightweight.
Disadvantages of Steel pipes
1 Maintenance cost is high.
2. The pipes are likely to be rusted by acidic or alkaline water.
3. The pipes require more time for repairs during breakdown and hence are not suitable for distribution pipes.
4. The pipes may deform in shape under the combined action of external forces.
d. Polyvinyl Chloride (PVC) Pipe
PVC pipes are made of a combination of plastic and vinyl. These plastic pipes are highly rigid, easy to join, strong in resisting pressure, and light in weight hence transportable can resist acids, alkalis, salts, and organic chemicals, cheaper so commonly used.
This pipe requires support closer due to flexibility so that can break or crack if miss-handled. PVC pipes can resist temperatures up to 60°C. Minimal skills and tools are required to install PVC pipes. As they do not rust, rot, or wear over time, these pipes are commonly used in water systems.
Advantages of PVC pipes
1. Pipes are cheap.
2. The pipes are durable.
3. The pipes are flexible.
4, The pipes are free from corrosion.
5. The pipes are good electrical insulators.
6. The pipes are light in weight and they can easy to mold any shape.
Disadvantages of PVC pipes
1. The co-efficient of expansion for plastic is high.
2. It is difficult to obtain plastic pipes of uniform composition.
3. The pipes are less resistant to heat.
4. Some pipes of plastic impart taste to the water.
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e. Polypropylene Random Copolymer (PPR) Pipe
Polypropylene random copolymers are thermoplastic resins produced through the polymerization of propylene, with ethylene links introduced in the polymer chain.
Homopolymer, random copolymer, and block copolymer are the types of polypropylene. These pipes can resist temperatures up to 70º C so they can be used for hot water supply.
Nowadays PPR pipes and fittings are popular in plumbing and water supply plants due to ease in the joint, perfect seal-tight system, no calcification problem, durable and long life expectancy, recyclable, good chemical resistance, etc.
Advantages of PPR Pipes
1. These pipes perform good hydraulic efficiency.
2. Light in weight and easy to handle.
3. The pipes possess high resistivity against heat.
4. It performs good resistivity to chemicals.
5. These pipes are eco-friendly and durable.
6. Calcification problem does not arise in these pipes.
7. Life expectancy of these pipes is of more than 50 years.
Disadvantages of PPR Pipes
1. Joining and repairing PPR pipes is possible by the use of a fusion-welding tool.
2. As PPR pipes are plastic products exposed to direct sunlight may dry out the oil content present in all plastics.
f. Ductile iron (DI) Pipe
These pipes are made of ductile iron commonly used for potable water transmission and distribution.
Typically, the pipe is manufactured using centrifugal casting in metal or resin-lined molds. Protective internal linings and external coatings are done to ductile iron pipes to overcome corrosion problems.
Hence these pipes are highly corrosion resistant and long life (100 yrs).
Advantages of DI pipes
1. Comparatively DI pipes possess greater ductility and impact resistance than CI pipes.
2. Lighter than CI pipes so that easy to handle and transport.
3. The pipes are easy to join and simple and also can accommodate some angular deflection.
4. These pipes are of more strength than CI pipes.
Disadvantages of DI pipes
1. The pipes require internal and external lining or protection.
2. Corrosion may take place as equal in CI pipes.
3. The polyethylene wrappings may cause damage.
|Read Also: Types of pipe fittings|
g. Concrete Pipe
Cement concrete pipe pipes may be either plain cement or reinforced cement concrete. PCC pipes can be used up to 15 m head whereas RCC pipes can be used up to the head of 60 in and for higher heads pre-stressed concrete can be used.
These pipes are also called on situ pipes so that they may be tasted in site also. Pipes of reinforced Pipe are also known as Hume pipes. These pipes are non-corrosive and have longer Life.
The maintenance cost of cement concrete pipe is less and joints are very simple. However, concrete pipes are inconvenient as they are heavy and less resistant to withstand impact and shock.
Advantages of concrete pipes
1. There are pipes that are most durable with usual life of about 75 years.
2. The pipes can be cast at site work and thus there is a reduction in transport charges.
3. Maintenance cost is less.
4. Inside surface of the pipe can be made smooth.
5. No danger of rusting.
Disadvantages of concrete pipes
1. Transportation is difficult.
2. Repair work is difficult.
3. Initial cost is high.
4. These pipes are affected by acids, alkalies, and salty waters.
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