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PIPE JOINTS 8

8.1 Introduction

Pipes are used for carrying fluids such as water, steam, gas, oil, etc., from one place to another.

As pipes are made in standard lengths, the desired length of a pipe may be obtained by joining

them. The type of joint used depends upon the material of the pipe and the purpose for which

it is used.

Generally, pipes are made of cast iron, wrought iron, steel, brass or copper. The material

selection is based on the nature of the fluid to be conveyed, viz., pressure, temperature, chemical

properties, etc. Now-a-days PVC pipes are extensively used with ease for various purposes.

In practice, a pipe size is designated by its bore diameter, called as nominal diameter.

Figure 8.1 shows the details of standard pipe thread and Fig. 8.2, the conventional representation

of pipe threads.

E0 E1 D

L3L3

T

L1 L2

L1 – Effective thread

L2 – Imperfect thread

L3 – Normal engagement by hand

P – Pitch

T – Taper 1 : 16 measured on dia.

E0 – Pitch diameter at end of pipe

E1 – Pitch diameter at large end

of internal thread

P

Taper shown Taper not shown

External thread

Side view Sectional view

Internal thread

Fig. 8.1 Standard pipe threads Fig. 8.2 Conventional representation

of pipe threads

8.2 Joints for Steam Pipes

These joints are used for the pipes carrying fluids under high temperature and pressure. Based

on the pipe materials, these are classified into cast iron pipes, copper pipes, steel pipes, etc.