Description Lofilm® HD is a pressure responsive hydraulic seal specifically designed for use in arduous reciprocating gland applications, where fast pressure rises occur and side loads can be substantial. In heavy duty and horizontal applications, Lofilm® HD operates as a highly efficient seal and also provides substantial 'bearing' support for the ram.
The seal normally comprises one heavy-duty rubberised fabric intermediate ring, a gland ring/female adapter, and a moulded rubber asymmetrical header ring as the principal sealing element of the set.
An annular groove incorporated in the header increases its response to applied pressure. The ported 'odd-leg' header design allows gland loading to be transferred through the set to the neck bush - often not fixed - while allowing the system pressure to act on the annular groove. The rubber sealing lips also conform more easily to an uneven surface - such as a worn shaft - and thus improve sealing integrity.
In operation, the initial radial interference reduces the fluid film to a minimum over a wide range of conditions, particularly on down-stroking applications where excessive leakage can be hazardous. This is also important on equipment that uses auxiliary cylinders to provide rapid advance.
Special features
Robust, high integrity seal for heavy duty ram applications such as forging and extrusion presses.
Pressure responsive primary sealing ring gives instant seal response, even at low pressure.
Improved sealing integrity on worn shafts to extend ram operating life.
Can be supplied with Self-aligning Gland Ring.
Typical applications Arduous duties with rams on forging and extrusion presses, including heavy duty horizontal applications. Also, equipment with rapid advance mechanisms and pre-fill valves, where Lofilm® HD can prevent air being drawn into the system: this avoids uncontrollable movement of the main ram and possible severe damage to the seal and other components by cavitation.
Operating capabilities
Maximum operating pressure: 620bar.
Temperature range with standard materials: -20°C to +120°C.
Materials of construction Gland ring/female adapter (standard material):heavy duty cotton fabric proofed with medium nitrile NBR rubber. Gland ring/female adapter (special materials): heavy duty synthetic fabric proofed with hydrogenated nitrile HNBR, butyl IIR or fluorocarbon FKM. Intermediate ring (standard and special materials): as for gland ring. Header ring (standard material): nitrile NBR rubber. Header ring (special materials): hydrogenated nitrile HNBR, butyl IIR or fluorocarbon FKM.
Media capabilities Standard materials (medium nitrile NBR) are suitable for use with most mineral based hydraulic fluids, most fire-resistant fluids of the water/oil emulsion or water/glycol types at temperatures up to 120°C, and resist most lubricating oils, greases, air and water.
Alternative (special) materials are available that considerably extend the range of applications in terms of temperature, fluid compatibility and abrasion resistance.
How supplied Endless or split packing sets to suit standard housings of 540mm to 1935mm OD, or 20.5 inch to 76.125 inch OD. We also hold a substantial library of mould tools for non-standard sizes. Other sizes will incur tooling charges.
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