The scope of plumbing is enormous. Cities with massive office buildings and luxury hotels need intricate system of water supply and sanitation. Factories have intricate network of pipes. Every house needs pipe systems for city water supply, hot water supply, sanitation, and fittings.
So in the execution of all such plumbing work both skill and ingenuity are essential. Metals and other materials are worked in many different forms, their use is determined by the application and design. In addition to this craftsmanship is necessary in their manipulation.
Thus the plumber or technician responsible for such kind of job should have sufficient knowledge about the following things.
1. Type of metal used for piping and fitting work.
2. The manufacturing methods.
3. The properties of materials and their selection for a specific application.
4. Standard available sizes of pipes and fittings.
5. Joining techniques such as welding, brazing, soldering, wiping etc.
6. Methods of sealing, scaling materials and their selection.
7. Selection of right type of tools for each job.
8. Estimation of the size of pipe line and cost involved.
Types of pipes and piping materials
‘pipe’ is a term limited to tubular products which conforms to certain standard outside diameters and having uniform thickness for wall.
This distinguishes from ‘Tubing’ which is made of either outside or inside diameters with specific wall thickness. Tubes have smaller sizes than pipes.
The pipe can be specified in terms of ‘Nominal pipe sizes’ which is neither the outside not inside diameters. In the standard tables, all the properties of pipe are mentioned against its ‘nominal size’, for example its OD,ID, wall thickness, weight in N/meter length, surface areas and area of metal in square mm.
The pipes and tubes can be manufactured out of ferrous, non-ferrous, and non-metals as well.
In ‘ferrous category’ following materials are commonly used – cast irons, alloy cast irons, steels of different grades and alloy steels.
In ‘non-ferrous category’ we have copper and alloys of copper such as brasses and bronzes, aluminium and its alloys, lead etc.
In ‘non-metal category’ we have basically plastics – plain or reinforced, flexible hoses made out of rubbers, fibers – natural synthetic and so on.
Every metal has its own peculiar properties which make them suitable or unsuitable for specific purposes and conditions. The chief properties of metals are malleability, ductility, conductivity, strength, specific weight, fusibility, softness, hardness, elasticity and lustre.
1. Cast Iron Pipe
It has a very wide use in plumbing work and has superseded lead for many purposes, notably soil and waste pipes, rain water pipes, drain pipes and fittings, pipes for heating work, baths, sinks, etc. It is strong, durable and low cost material. Its tensile strength however, is low and its malleability is poor. It also rusts fast.
2. Galvanised Iron Pipe
It is black iron coated with zinc to resist corrosion and is used mainly for piping of domestic water supply. It gives longer service.
3. Steel pipe
Steel pipes are fabricated to conform to a number of specifications, such as working pressure, temperature, cost, type of fluid handled and so on. Welded or seamless steel pipes are used for plumbing and heating purposes for handling water, gas and air.
4. Alloy steel pipe
Alloy steel pipes are used where greater strength corrosion resistance and resistance to heat is required. They are used to handle milk and other food products, corrosive gases and liquids etc.
5. Brass and Copper Pipe
Brass and Copper Pipes are used for such services where their longer life expectancy compensates for the higher cost than that of ferrous pipe. They are used in paper and pulp industries, chemical industries, refrigeration and air-conditioning industries and so on.
6. Aluminium
Aluminium is widely used in the field of industrial piping. It has a low specific weight about 1/3 that of steel. Several alloys of aluminium are quite strong and are used in the form of pipe and fittings. They show high resistance to corrosion, but their strength is affected at elevated temperature.
7. Lead Pipe
Lead Pipe has long been used in the chemical industry for conveying of corrosive substance like strong acids.
8. Polyvinyl chloride (PVC) Pipe
It is plastic materials of construction, although comparatively new, have gone a long way towards filing a need for a light weight, corrosion resistance or non-contaminating materials for process industries. There are a number of materials available each with its own characteristics, costs and uses.
Polyvinyl chloride (PVC) – is one of the most widely used of the plastic pipe materials. It is marketed under various trade names. Due to short supply of stainless steel in World War II, PVC was used as substitute material to resist corrosion.
It is about one-sixth the weight of steel, does not support combustion and is highly resistant to wide range of acids, alkalies and alcohols. It is non-toxic and therefore may be used in the transportation of food products. It is non-magnetic and non-sparking.
There are commonly two grades of PVC in the market. The normal unplasticised material has the maximum resistance to chemicals over its entire working range. This material should not be used for solvents such as carbon tetra chloride or for concentrated acids.
The strength of PVC varies inversely with the temperature and therefore piping supports should be spaced from ½ to 1/3 the length of those for steel pipe. They are manufactured to iron pipe size outside diameters. Sizes upto 300mm diameter. PVC pipes are extruded seamless, while above that they may be fabricated by bending and welding flat sheets. The standard length of such pipe is 3,6 and 9 meters with plane ends. Ends may be threaded of grooved for connection or plain ends may be joined by solvent welding. Fittings such as 900 and 450 elbows or tees have similar centre to face dimensions in sizes corresponding to 12 mm to 50 mm malleable iron screwed fittings. Solvent welding method is generally preferred to jointing method.
