Seamless pipe cap

Seamless pipe cap belongs to a kind of boiler part in pressure vessel. The medium frequency induction heating method is used to heat the pipes locally while mechanical transmission is used to bend the pipes. The power can reach 120KW, which can heat pipes of various sizes and specifications. The heating is fast, the power can be adjusted steplessly, the startup is powerful, the performance is stable, the floor area is small, and the operation and maintenance are easy. Elliptical head is a part of the container. According to different geometric shapes, it can be divided into spherical, elliptical, saucer shaped, spherical crown shaped, conical shell and flat cover, among which spherical, elliptical, saucer shaped and spherical crown shaped elliptical heads are collectively referred to as convex elliptical heads. It is applied to various vessel equipment, such as storage tank, heat exchanger, tower, reactor, boiler and separation equipment

The executive standards of seamless pipe caps include GB/T12459-2005, GB/T13401-2005, DL/T695-1999, D-GD87-0607, etc. Elliptical head is an excellent important part of pressure vessel equipment in petrochemical, atomic energy and food pharmaceutical industries. Elliptical head is the end cover on the pressure vessel and a main pressure bearing part of the pressure vessel. The quality of elliptical heads is directly related to the long-term good operation of pressure vessels

Seamless pipe cap is a head formed by the combination of rotating spherical surface and straight cylinder section. In elliptical heads, the head can be welded to the pipe and used as an end. In addition, elliptical heads can also be applied to pressure vessels, both at the upper and lower parts. Elliptical heads are very comprehensive and widely used in pressure vessels

Under the effect of thermal stress, the seamless pipe cap is pulled in the center because the initial temperature of the surface layer is lower than the center, and the shrinkage is also greater than the center. When the cooling is completed, the surface layer is pulled in the center because the cooling volume shrinkage cannot be carried out freely after the center. That is, under the action of thermal stress, the surface of the workpiece is finally compressed and the center is tensioned. This phenomenon is affected by cooling rate, material composition and heat treatment process. During the heat treatment of steel, due to the change of structure, that is, during the transformation from austenite to martensite, the increase of specific volume will be accompanied by the expansion of the workpiece volume, and each part of the workpiece will undergo phase transformation successively, resulting in inconsistent volume growth and generating organizational stress

In the heating and cooling process of seamless pipe cap, the cooling speed and time of the surface and the core are inconsistent, forming a temperature difference, which leads to uneven volume expansion and contraction, resulting in stress, namely thermal stress. The faster the cooling speed of elliptical head is, the higher the carbon content and alloy composition are, the greater the non-uniform plastic deformation under the action of thermal stress during cooling, and the greater the residual stress formed afterwards

Seamless pipe caps are made of carbon steel, alloy steel and stainless steel. Elliptical heads are widely used in food, aerospace, petroleum, electronics, machinery, chemical industry, textile and construction industries. Elliptical head has a long service life in use