Hydraulic Dog
The most common fluids used in hydraulic systems are based on mineral oil. In recent years there has been a lot of attention to fluids Hydraulic environmentally acceptable, but its use so far is limited, mainly due to their relatively high cost in connection with mineral oil. In many cases, Standard Piston seals can be used in these fluids. Fire resistant fluids such as water based fluids discharged, have applications in specific areas such as long wall mining and led to the development of specialized labels, but the vast majority of applications use mineral hydraulic oil. Two main factors affecting the mineral oil-based systems are cost and leakage.
This article discusses two key issues: --
• The effect of finishing tube seal performance - lower cost tube, can not give the desired performance
• The influence of the wiper on the leakage of the gland
THE EFFECT OF TUBE FINISH SEAL PERFORMANCE
A seal of the piston of a hydraulic cylinder is only part of the system sealed. Their lives depend on a number of factors, one important is the nature of the surface against which it is running. Steel pipes of hydraulic cylinders in general, have a surface finish, which occurs in one of three ways: --
• Honing
• Roller-burnished
• the formulation of more a mandrel (DOM)
Stamps Hallite have conducted significant studies on the performance of double acting seals, used as both a unique quality and dual-purpose of examining the effect of tube manufacturing methods and, therefore, the surface texture of the tube, on the seal performance of a typical double-acting piston.
Manufacture of cylinder tubes
Hydraulic Cylinder Tubes are usually of steel to be drawn on a mandrel (DOM). This process work hardens the material and give desirable mechanical properties. The final tube surface is obtained in one of three ways. In the process of honing the tube is machined to obtain the required roundness and tolerance of the hole and to remove surface imperfections, and then finished for internal grinding or honing. In the pipe beveling and polishing roll back the hose is inside machining (beveled) and crushed by the rollers in the machining head. More recently, drawing techniques have been developed so that the tube is considered ready for use in the state as drawn. This is known as special diameter smooth interior (SSID) or 'smooth-bore "tube.
In terms of cost classification finished tube from the cheapest DOM is SSID, the roller grinding and perfected. DOM tube SSID can be 30% cheaper than the roller burnished, so that places of interest to the developer cylinder are evident. However, the quality of these tubes can be a problem that could lead to premature seal failure.
The limitations of As-Drawn (SSID) of tube
SSID tube has shown its limitations in its application, particularly when the board of double acting piston is being driven in pressure. This may occur, for example, when reducing the load is being controlled by the release of fluid from the cavity completely. The manufacturing process of the results of tube axial traction as the marker of the tube, tube rollers polished and perfected, these defects are eliminated by the finish of the tube in a circumferential direction. These ratings may provide sites for axial fluid jet on the seal face of eroding contact, especially when the seal is being driven in pressure. Another difficulty is that these defects are not detected by the usual methods of measuring surface finish.
THE INFLUENCE OF THE ESCAPE WIPER in the gland
The gland sealing system of a hydraulic cylinder is a series of elements, including housing seal, stamp rod, bar cleaner, bar bearing, hydraulic fluid and the rod itself. The rods are usually hard chrome finish relatively constant. The wiper bar has the primary role in the prevention of external contamination reaching the rod seal and bearings of the gland, and for this reason fits the vast majority of hydraulic cylinders. However, this component was often overlooked in laboratory tests of piston seals.
The numerous studies have been conducted on factors affecting performance alternative including stamp counter surface finish of the face and the effects of pollution.
Stamps Hallite carried out a series of tests that evaluate the performance of five cleaners drain different working with a common seal polyurethane bar. It is demonstrated that clean is an important factor in controlling leakage of the hydraulic cylinder gland. Single wiper lip can give a much greater loss than the seal on their own, without a windshield wiper. This is the result of the lips clean oil collection on Rod, which provides boundary lubrication to the seal. The use of double lip cleaning reduces the spread in the level of its own stamp, but there is a danger of trapping pressure between seal and wiper. A double-lip wiper profile has been developed, which minimizes the oil ring on the dipstick collected by the lip erased, and also has ventilation function to release the oil in the case of an accumulation of pressure between the seal and wiper.
About the Author:
Hallite Seals International are an ISO 9001 accredited manufacturer and provider of Hydraulic Seals and sealing solutions to the global fluid power industry. We operate in all five continents of the world, and work with a number of major international brands - renowned for their commitment to engineering excellence.
For over 100 years Hallite Seals International has been at the cutting edge of fluid power technology, manufacturing a wide range of rod / gland, piston, and static seals, as well as support and bearing components, for technically challenging applications, from a wide range of materials which include Polytetrafluoroethylene (PTFE), Polyurethane (AU), nitrile rubbers (NBR) and Fluoro-elastomers (FKM).
Article Source: ArticlesBase.com - Reciprocating Seals for Hydraulic Cylinders
