V-Ring Packings

V-ring packings (also known as chevron packing or parachute packing) are multi-lip, dynamic seals that excel in heavy-duty, high-pressure reciprocating applications by utilizing a stack of V-shaped rings that self-adjust to pressure and wear. They are a robust solution for demanding environments where O-rings or other single-lip seals would fail.
Function and Design
A V-packing set is not a single seal but an assembly of components designed to work synergistically.
Multi-Lip Structure: A typical set consists of a number of intermediate V-shaped rings (also called pressure rings), a male adapter ring (bottom), and a female adapter ring (top).
Pressure-Activated Sealing: The unique V-shape allows the lips to expand radially (both inward against the rod and outward against the bore) when fluid pressure is applied. The higher the pressure, the tighter the seal, which provides reliable performance with fluctuating pressures and shock loads.
Adaptable: The multi-lip design distributes wear and tear across multiple surfaces, contributing to a significantly longer lifespan. This design is also tolerant of minor shaft misalignment and eccentric movement.
Field-Adjustable: One key advantage is that the compression on the V-rings can be adjusted (often via a gland nut) to compensate for wear, which is ideal for field maintenance and extending the seal's service life.
Materials
The materials are selected based on the operating conditions, including temperature, pressure, media, and surface speeds.
Nitrile Rubber (NBR): A common, general-purpose material, often with fabric reinforcement for enhanced mechanical properties and extrusion resistance in standard applications.
Polyurethane (PU): Known for excellent abrasion resistance and mechanical strength, making it ideal for heavy-duty construction and mining equipment applications.
PTFE (Polytetrafluoroethylene): Used for applications involving high temperatures, aggressive chemicals, or those requiring very low friction. PTFE V-rings often come in filled variants (e.g., glass, carbon, or bronze filled) to enhance strength and wear characteristics.
FKM (Fluoroelastomer/Viton): Provides excellent resistance to high temperatures and a broad range of aggressive chemicals, suitable for more demanding environments than NBR.
Common Applications
V-packing sets are designed for reciprocating motion and are widely used across various heavy-duty industries.
Hydraulic Cylinders: Used in large industrial presses, scrap shears, and other large cylinders where robustness and pressure resistance are paramount.
Earthmoving and Mining Equipment: Employed in excavators and bulldozers due to their durability in dirty and high-impact conditions.
Oil and Gas Industry: Used in various downhole equipment, pumps, and valves that experience extreme pressures and corrosive environments.
Reciprocating Pumps and Valves: The multi-lip design effectively manages the challenges of reciprocating motion in these applications.
Lifts and Jacks: Found in car lifts and elevators where a reliable seal for holding pressure is necessary.