Thursday, February 17, 2011

Types Of Pressure Vessels

When a container is pressurized then pressure is exerted against the walls of the vessels. Pressure is always normal to the surface regardless of the shape. Pressure vessel is a container that has pressure different from the atmospheric pressure. There are many types of pressure vessel they are; thin walled, thick walled, strong tanks, transportable containers, propane bottles and gas cylinders. Pressure vessel is a container that holds liquid, vapor or gas at different pressure other then atmospheric pressure at the same elevation. Generally, a pressure vessel is considered to be thin-walled if its radius is larger than 5 times its wall thickness. Under this condition, the stress in the wall may be considered uniform. Thin wall pressure vessels are in fairly common use. There are two specific types of pressure vessels they are; cylindrical pressure vessels and spherical pressure vessels. Under this condition, the stress in the wall may be considered uniform. The stress in thin walled vessel varies from a maximum value at the inside surface to a minimum value at the outside surface of the vessel. Storage tanks are a category of thin walled pressure vessel.

A thick walled pressure vessel is the one that its wall is 10 % thicker than inside diameter. Thick walled pressure elements working in high temperatures in power stations, chemical and petro chemical industries are subjected to damage as a result of high temperature, mechanical loading and corrosive environment. These factors cause thermal fatigue, creep-fatigue and other processes leading to degradation. When subject to internal and external pressure stress and strain exist in thick walled pressure vessel. They have high tensile strength and can withstand maximum stress.

Transportable containers are the most common pressure vessel and potentially the most ignored type. These are mass produced and require testing every 10 years for propane and gas. Steel pressure vessels are designed to perform the dual purposes air storage and partial separation of moisture. These are provided with all standards so as to operate safely. Pressure vessels have to be designed to perform efficiently at high pressure. Pressure vessel must be free of any cracks or leakages, thereby ensuring complete safety to the surrounding environment. Cracked and damaged vessel may result in leaks or rupture failure. Rupture failure may cause considerable damage to life and property. The safe design, installation, operation and maintenance of pressure vessel in accordance with appropriate codes and standards are necessary for workers safety and health.

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