tailieunhanh - Text Book of Machine Design P8

Pipes and Pipe Joints | CONTENTS c H A P T E R 8 Pipes and Pipe Joints 1. Introduction. 2. Stresses in Pipes. 3. Design of Pipes. 4. Pipe Joints. 5. Standard Pipe Flanges for Steam. 6. Hydraulic Pipe Joint for High Pressures. 7. Design of Circular Flanged Pipe Joint. 8. Design of Oval Flanged Pipe Joint. 9. Design of Square Flanged Pipe Joint. Introduction The pipes are used for transporting various fluids like water steam different types of gases oil and other chemicals with or without pressure from one place to another. Cast iron wrought iron steel and brass are the materials generally used for pipes in engineering practice. The use of cast iron pipes is limited to pressures of about N mm2 because of its low resistance to shocks which may be created due to the action of water hammer. These pipes are best suited for water and sewage systems. The wrought iron and steel pipes are used chiefly for conveying steam air and oil. Brass pipes in small sizes finds use in pressure lubrication systems on prime movers. These are made up and threaded to the same standards as wrought iron and steel pipes. Brass pipe is not liable to corrosion. The pipes used in petroleum industry are generally seamless pipes made of heat-resistant chromemolybdenum alloy steel. Such type of pipes can resist pressures more than 4 N mm2 and temperatures greater than 440 C. 261 CONTENTS 262 A Textbook of Machine Design Stresses in Pipes The stresses in pipes due to the internal fluid pressure are determined by Lame s equation as discussed in the previous chapter Art. . According to Lame s equation tangential stress at any radius x p r 2 1 L 1 ro 2 - r 2 L xx _ and radial stress at any radius x _ P r- 2 R _ ro 2 x2 x2 2 ro - r L x j where p Internal fluid pressure in the pipe rt Inner radius of the pipe and ro Outer radius of the pipe. . . ii The tangential stress is maximum at the inner surface when x r of the pipe and minimum at the outer surface when x ro of the pipe. Substituting the values of x rt and