Pipes are available in standard sizes and lengths. Standard wrought iron or steel pipes always measure slightly over their nominal size. Plumber has to lay pipes according to the layout of pipe line. It is therefore, essential to use suitable elements at the end of the pipe lines called as ‘pipe fittings’. Pipe fittings are made of malleable iron or cast iron. Cast iron fittings are more heavily constructed and their use is largely confined to steam and hot water heating systems. Malleable fittings may be secured either black or galvanized.
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Pipe Fittings
All fittings are tapped for right-hand-threads unless otherwise stated. The size of the fittings is stated in terms of the size of pipe on which it is to be screwed.
Reducing fittings such as reducing elbows, reducing couplings and bushings are specified by stating larger size first – e.g., 18 x 12 x 9 mm Tee. In case of Tee fittings, if all the sizes of Tee connections are same then it can be stated as 15 mm Tee. If the opening are for pipes of different sizes the centre is specified last.
How to find the end to end length of pipe for joining purpose in a pipe assembly. When measuring pipe, allowance must be made for the amount that enters the fitting. The allowance varies with different sizes of pipe.
A general arrangement for making a pipe frame. Pipe frames and railing can be made to serve many purpose in the manufacturing shops and in the house. The use of union in the frame is to avoid left hand threaded piece of pipe at one end to close the frame.
Pipe cements for making tight joints :
Various pipe cements are now-a-days available commercially to prevent leakages in pipe joints. They are available in the powder or paste form.
Fine hemp strands wound on the pipe in the same direction in which the fitting is to be turned is often used on water pipe joints.
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Pipe Fittings Use
Asbestos fibres and strands are used to prevent leakages in steam and hot water carrying pipe lines and fittings as they act as insulating medium as well.
Red lead and boiled linseed oil, mixed to a thin paste, is used for water, gas and air pipe lines.
Litharge and glycerine is used for oil and gasoline pipe lines.
Old paints can also serve the purpose on some odd jobs e.g., pipe fittings on water tanks, domestic water supply lines etc.
