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Hose clip for hydraulics
Multi-purpose polyurea grease Lithium prices, and consequently conventional lithium ep grease prices, have risen dramatically in recent years. Coupled with increasing pressure to extend machinery life, this has led to the development of a number of synthetic alternatives. Chevron have recently introduced a polyurea-acetate grease which is claimed to offer superior performance at a competitive price.
acetate grease and a conventional ep lithium 12 hydroxy-stearate based grease. The wear scar using polyureaacetate at a load of 27.2 kg (60 lb) is narrower than the scar using lithium grease at 20.4 kg (45 lbs). The polyurea complex grease gives Four Ball Weld Points and Load Wear Indices (ASTM D2596) about twice that of lithium greases.
ing lives, when the polyurea complex grease was used, were consistently longer over a range of operating temperatures.
Chevron Polyurea EP Grease, which is available in NLGI Nos 0, 1, and 2 grades, is designed for use in a wide range of applications: it could replace many specialised greases, decreasing stores inventories and reducing the chances of the wrong lubricant being applied. It is generally compatible with other greases, a useful property in situations where old grease cannot be removed.
The high temperature performance of Polyurea EP Grease'is also superior. The drop point is 258°C, for the NLGI No 2 grade, about 40°C higher than can be expected from conventional lithium ep greases. While this is not a quantative measure of performance, it does indicate that the grease can be used at higher temperatures for short periods. In an ASTM D3336 test bear-
Applications
Polyurea EP Grease contains oxidation and rust inhibitors, and retains the water resistance of polyurea greases. The product performed well in ASTM Rust and Water Wash-out tests.
Chevron daim that~he product can be used in every automotive application and in most industrial plant. The field experience quoted confirms the performance indicated by laboratory tests. Chevron Oil (UK) Ltd, Rothschild House, Whitgift Centre, Croydon CR9 3QQ, UK
Hose clip for hydraulics 'Nexus', described as the first serious challenge to the long established worm screw design of pipe and hose clips, is claimed to give increased sealing efficiency and a greater size span. It can be fitted like an open strap, often without separating the coupling.
Development
Polyurea greases have been in use for about a decade. They are reported to give good bearing lives at elevated temperatures, to have good pumpability, and to be highly water resistant. Calcium acetate is known to give good load carry capacity in greases. Calcium acetate-calcium soap complex greases currently available have good anti-wear and load carrying properties, but the high solids or thickener content can cause dispensing problems.
The clip comprises a notched stainless steel strip which is supplied flat, and a screw tensioning device. The strip is formed by hand to the approximate diameter required and then inserted into the tensioning device, giving both coarse adjustment and f'mal tightening. Six standard sizes cover diameters of 13-150 mm (½-6 in), a range usually covered by 19 worm screw clips. The reduction in stocked sizes made possible is said to offer substantial commercial benefits.
Chevron Polyurea EP grease is a combination of polyurea and calcium acetate. The complex formed gives improved thickening and good ep, antiwear, and high temperature performance. The pumpability is better than conventional lithium ep greases.
Properties Chemical ep agents often improve load carrying capacity at the expense of wear performance. Oxides, sulphides, phosphates or chlorides formed at the surface are worn preferentially, preventing seizure. There is evidence to suggest that 'physical' ep agents, such as calcium acetate, keep surfaces separated, improving load capacity without sacrificing wear performance. Fig 1 shows two blocks from Timken OK tests carried out using the polyurea-
Fig 1 Significantly different wear scars on the blocks used in comperative Timken OK tests on Chevron Polyurea EP grease (top) and a conventional l~thium based grease (bottom)
According to the manufacturers, the sealing efficiency of the Nexus clip is about twice that of a conventional clip, for a given applied torque. The clip is made of stainless steel and cadmiumplated components and could be specified for most industrial environments without risk of rapid corrosion. The company reports that interest has already been shown in the automotive, hydraulic, pneumatic, and many other industries. Newman Industrial Controls Ltd, Upper Mills Industrial Estate, Stonehouse, Gloucestershire, UK
TRIBOLOGY international December 1976
249
acetate grease and a conventional ep lithium 12 hydroxy-stearate based grease. The wear scar using polyureaacetate at a load of 27.2 kg (60 lb) is narrower than the scar using lithium grease at 20.4 kg (45 lbs). The polyurea complex grease gives Four Ball Weld Points and Load Wear Indices (ASTM D2596) about twice that of lithium greases.
ing lives, when the polyurea complex grease was used, were consistently longer over a range of operating temperatures.
Chevron Polyurea EP Grease, which is available in NLGI Nos 0, 1, and 2 grades, is designed for use in a wide range of applications: it could replace many specialised greases, decreasing stores inventories and reducing the chances of the wrong lubricant being applied. It is generally compatible with other greases, a useful property in situations where old grease cannot be removed.
The high temperature performance of Polyurea EP Grease'is also superior. The drop point is 258°C, for the NLGI No 2 grade, about 40°C higher than can be expected from conventional lithium ep greases. While this is not a quantative measure of performance, it does indicate that the grease can be used at higher temperatures for short periods. In an ASTM D3336 test bear-
Applications
Polyurea EP Grease contains oxidation and rust inhibitors, and retains the water resistance of polyurea greases. The product performed well in ASTM Rust and Water Wash-out tests.
Chevron daim that~he product can be used in every automotive application and in most industrial plant. The field experience quoted confirms the performance indicated by laboratory tests. Chevron Oil (UK) Ltd, Rothschild House, Whitgift Centre, Croydon CR9 3QQ, UK
Hose clip for hydraulics 'Nexus', described as the first serious challenge to the long established worm screw design of pipe and hose clips, is claimed to give increased sealing efficiency and a greater size span. It can be fitted like an open strap, often without separating the coupling.
Development
Polyurea greases have been in use for about a decade. They are reported to give good bearing lives at elevated temperatures, to have good pumpability, and to be highly water resistant. Calcium acetate is known to give good load carry capacity in greases. Calcium acetate-calcium soap complex greases currently available have good anti-wear and load carrying properties, but the high solids or thickener content can cause dispensing problems.
The clip comprises a notched stainless steel strip which is supplied flat, and a screw tensioning device. The strip is formed by hand to the approximate diameter required and then inserted into the tensioning device, giving both coarse adjustment and f'mal tightening. Six standard sizes cover diameters of 13-150 mm (½-6 in), a range usually covered by 19 worm screw clips. The reduction in stocked sizes made possible is said to offer substantial commercial benefits.
Chevron Polyurea EP grease is a combination of polyurea and calcium acetate. The complex formed gives improved thickening and good ep, antiwear, and high temperature performance. The pumpability is better than conventional lithium ep greases.
Properties Chemical ep agents often improve load carrying capacity at the expense of wear performance. Oxides, sulphides, phosphates or chlorides formed at the surface are worn preferentially, preventing seizure. There is evidence to suggest that 'physical' ep agents, such as calcium acetate, keep surfaces separated, improving load capacity without sacrificing wear performance. Fig 1 shows two blocks from Timken OK tests carried out using the polyurea-
Fig 1 Significantly different wear scars on the blocks used in comperative Timken OK tests on Chevron Polyurea EP grease (top) and a conventional l~thium based grease (bottom)
According to the manufacturers, the sealing efficiency of the Nexus clip is about twice that of a conventional clip, for a given applied torque. The clip is made of stainless steel and cadmiumplated components and could be specified for most industrial environments without risk of rapid corrosion. The company reports that interest has already been shown in the automotive, hydraulic, pneumatic, and many other industries. Newman Industrial Controls Ltd, Upper Mills Industrial Estate, Stonehouse, Gloucestershire, UK
TRIBOLOGY international December 1976
249