# US 11,441,682 B2 · Piston ring, reciprocating compressor, method for selecting piston ring and method for evaluating life of piston ring

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- Number: US 11,441,682 B2
- Document ID: US11441682B2
- Status: Granted
- Kind: B2
- Application number: 16/837,538
- Filed: 2020-04-01
- Published: 2020-10-29
- Granted: 2022-09-13
- Earliest claimed: 2019-04-26
- Assignees: Kobe Steel, Ltd.
- Applicants: Kobe Steel, Ltd.
- Inventors: Tomohiro Ootsuka; Naofumi Kanei
- Web page: https://patentgrep.com/patent/US11441682B2

## CPC

- F16J 9/26: characterised by the use of particular materials
- F04B 15/00: Pumps adapted to handle specific fluids, e.g. by selection of specific materials for pumps or pump parts
- F04B 27/0409: {Pistons}
- F04B 27/0878: {Pistons}
- F04B 39/0005: {adaptations of pistons}
- F04B 53/143: {Sealing provided on the piston}
- F04B 53/16: Casings; Cylinders; Cylinder liners or heads; Fluid connections
- F16J 9/28: of non-metals
- G01M 3/025: {Details with respect to the testing of engines or engine parts}
- G01M 3/3272: {for verifying the internal pressure of closed containers}
- G01M 15/08: by monitoring pressure in cylinders
- F04B 7/06: the pistons and cylinders being relatively reciprocated and rotated
- Y02E 60/32: Hydrogen storage
- F16J: PISTONS {(specially adapted for dampers F16F9/32)}; CYLINDERS; SEALINGS
- F04B: POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS (machines for liquids, or pumps, of rotary-piston or oscillating-piston type F04C; non-positive-displacement pumps F04D; pumping of fluid by direct contact of another fluid or by using inertia of fluid to be pumped F04F)
- G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

A piston ring is used for a reciprocating compressor. In the piston ring, polytetrafluoroethylene and polyetheretherketone or polyimide account for 50% or more by mass in total. The piston ring does not contain polyphenylene sulfide. The piston ring has a tensile strength within a range of more than 15 MPa and less than 100 MPa.

## Claims

### Claim 1

A piston ring used for a reciprocating compressor, wherein
polytetrafluoroethylene, and one selected from polyetheretherketone and polyimide account for 50% or more by mass in total,
the piston ring does not contain polyphenylene sulfide,
the piston ring has a tensile strength within a range of more than 15 MPa and less than 100 MPa.

### Claim 2 (depends on 1)

The piston ring according to claim 1, having a tensile strength of 55 MPa or less.

### Claim 3 (depends on 1)

A reciprocating compressor configured to pressurize hydrogen gas to a predetermined pressure in a hydrogen station, the reciprocating compressor comprising:
a cylinder provided with a compression chamber into which hydrogen gas is sucked;
a piston that is disposed in the cylinder and is reciprocated in the cylinder to change a volume of the compression chamber; and
the piston ring according to claim 1, being attached to an outer peripheral portion of the piston to seal a gap between the outer peripheral portion of the piston and an inner wall surface of the cylinder.

### Claim 4 (depends on 2)

A reciprocating compressor configured to pressurize hydrogen gas to a predetermined pressure in a hydrogen station, the reciprocating compressor comprising:
a cylinder provided with a compression chamber into which hydrogen gas is sucked;
a piston that is disposed in the cylinder and is reciprocated in the cylinder to change a volume of the compression chamber; and
the piston ring according to claim 2, being attached to an outer peripheral portion of the piston to seal a gap between the outer peripheral portion of the piston and an inner wall surface of the cylinder.

### Claim 5

A method for selecting a piston ring used for a reciprocating compressor, the method comprising the step of:
selecting a piston ring in which polytetrafluoroethylene, and one selected from polyetheretherketone and polyimide account for 50% or more by mass in total, polyphenylene sulfide is not contained and a tensile strength is within a range of more than 15 MPa and less than 100 MPa, as a piston ring to be attached to an outer peripheral portion of a piston.

### Claim 6

A method for evaluating life of a piston ring used in a reciprocating compressor, the method comprising the steps of:
investigating a correlation between an operating time of the reciprocating compressor and pressure in a space in which pressure can rise due to leakage of compressed hydrogen gas through a gap between the piston ring and a cylinder;
determining the operation time when the pressure in the space reaches a predetermined threshold based on the correlation; and
evaluating the determined operation time as the life of the piston ring.