PTFE Piston Ring Types

Traight Joint;Scarf Joint;Overlapped Joint;Gas-tight Joint

Traight Joint
Piston rings with straight joints are used for sealing pressure differences above 15 bar.

With this gap, the leakage is slightly higher than with piston rings that have a scarf joint. Because of the high compressor speeds (rpm) typically achieved today, the loss of gas from leakage has only a minor impact on compressor performance.

The amount of gas leakage is negligible.

Scarf Joint
Piston rings with scarf joints are used for sealing pressure differences above 15 bar. During the run-in period, the sealing effect of scarf joints is slightly better than that of piston rings with a straight joint.

Overlapped Joint
The overlapped joint achieves a favorable sealing effect.

For this reason, it is primarily used for sealing gases with a specific light weight. Because of bending stress and the resulting  risk of breakage in the overlapping areas, piston sealing rings with overlapped joints should only be used in compressors operating with pressure differences of max. 15  bar.

Gas-tight Joint
Our gas-tight piston rings achieve the best sealing effect.

The special design of the joint reduces leakage to a minimum. The differential pressure is limited to a maximum of 15 bar. During assembly, please note that the piston ring achieves a good sealing effect in one direction of pressure only.

Source:https://www.sukoptfe.com/ptfe-piston-ring-types

PTFE Piston Rings

Polytetrafluoroethylene (PTFE) seals and piston rings have started to replace their carbon counterpart as PTFE seals and rings offer greater durability, have a longer operating life, and can be operated at various pressures, velocities and temperatures.

PTFE seals and rings are becoming more common in a variety of applications and industries because of the unique advantages they offer.

PTFE Piston Rings and Guide Rings (Rider rings) for dry-running applications are currently a focal point of technical development. 

They significantly reduce a machine’s operating costs and, in today’s increasingly environmentally aware society, make it easier for operators to fulfill stricter environmental legislation.

Properties

Exceptionally low friction coefficient in combination with metals and plastics
Antiadhesive behavior without any stick-slip effect
High elongation properties enabling easy fitting 
of sealing and guide rings to one-piece pistons
Exceptionally large temperature range from –200°C to +260°C
Chemically resistant to almost all solid, liquid, and gaseous media
Ageing-resistant
Nonflammable
Physiologically neutral in the stated temperature range

Suitable for the Following Application Areas

Compressors operating under full- and low-lube conditions
Gas rotary pumps
Expansion machinery
Liquid gas and vacuum pumps
Rocking piston pumps
Rotary compressors for loading/unloading of silos
Generation of oil-free compressed air for the 
food processing industry, pharmaceutical industry, and dentistry
Compressed air for the craft and do-it-yourself market
Pneumatic hammer drills
Automotive technology, including ride leveling 
and air-conditioning systems

Source:https://www.sukoptfe.com/ptfe-piston-rings