A gas cylinder or tank is a pressure vessel used to store gases at high pressure. Gases stored this way are called bottled gases. Massive demand for nitrogen gas cylinders has to be met in india by the manufacturers, suppliers and vendors. This is primarily due to the manifold and versatile uses of nitrogen in different industries serving different purposes.Latest advancements in nitrogen cylinders are the nitrogen die cylinders there is disclosed a piston-cylinder assembly for use as a die spring wherein one end of the cylinder is connected to the source of nitrogen at high pressure to bias the piston outwardly through the opposite open end of the cylinder. The open end of the cylinder is provided with a high pressure seal and the opposite end of the piston is likewise provided with a high pressure seal. An annular chamber of relatively small cross sectional area is provided between the piston and the cylinder. A valve stem on the piston controls a passageway communicating with the annular chamber. Axial pressure is applied to the seal on the cylinder to produce firm sealing engagement with the piston by pressurizing the annular chamber or by arranging a compression spring between the seal and a shoulder on the cylinder. In press operations it is common practice to employ die springs in the form of fluid cylinders filled with or connected to a source of nitrogen under relatively high pressure. The nitrogen pressure frequently employed is 1000 psi or more so that a relatively small diameter cylinder is capable of exerting a substantially large force. Although the high nitrogen pressure is desirable from the standpoint of the compactness of the cylinders, it does give rise to problems relating to sealing of the piston within the cylinder. The sealing problem is also aggravated by the fact that the environment around a die in a press is frequently contaminated with oil, dirt, grinding dust, etc. Which, if permitted to leak into the cylinder, can cause serious problems in a relatively short period of time.
Seals have been developed for use on nitrogen die cylinders which operate quite effectively when they are subjected to relatively high axial pressure. However, such seals are frequently not entirely effective to prevent the ingress of contaminants into the cylinder when they are exposed to relatively low pressure. Sealing problems frequently arise because the gas pressure to which one or more of the seals are subjected may vary between relatively high and low values due to the rapid reciprocation of the piston. The reciprocating rate of the piston depends upon the speed of the press. On the upward stroke of a rapidly operating press the gas pressure at one side of a seal may be very low or even sub atmospheric because of the sudden expansion in volume of a chamber in the cylinder directly adjacent the seal. When this occurs there is a likelihood that contaminants may leak past the seal into the cylinder.
