# US 7,744,071 B2 · Safety relief valve having a low blow-down value and spring therefore

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- Number: US 7,744,071 B2
- Document ID: US7744071B2
- Status: Granted
- Kind: B2
- Application number: 10/601,304
- Filed: 2003-06-20
- Published: 2004-04-01
- Granted: 2010-06-29
- Earliest claimed: 2003-02-10
- Assignees: Mercer Valve Company, Inc.
- Inventors: Jeremy R. Choate; Michael J. Easton; Wesley L. Taylor
- Web page: https://patentgrep.com/patent/US7744071B2

## CPC

- F16K 17/0493: {with a spring other than a helicoidal spring}
- F16K 17/04: spring-loaded
- F16K 37/0083: {by measuring valve parameters}
- Y10T 29/49412: with assembly, disassembly or composite article making
- Y10T 137/0497: Fluid actuated or retarded
- Y10T 137/6086: Assembling or disassembling check valve
- Y10T 137/7738: Pop valves
- Y10T 137/7905: Plural biasing means
- Y10T 137/7929: Spring coaxial with valve
- F16K: VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING {(devices for emptying and evacuating the excess liquid in valves or conduits F16L55/07)}
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A safety relief valve is provided that comprises a body comprising a chamber therein and an inlet and an outlet, the inlet comprising an inlet valve seat; a disk member closable on the inlet valve seat; and a mechanism in the body biasing the disk member to rest on the inlet valve seat with a set force such that when the pressure in the inlet exceeds a set pressure resulting from the set force, the disk member is lifted from the inlet valve seat, the mechanism comprising a combination of a coil spring and one or more disk springs stacked in series with the coil spring. A method of preparing a coil spring for use in a pressure relief valve comprises measuring the spring rate of the coil spring and; modifying the spring so as to modify its spring rate to be within ±2% of a desired spring rate.

## Claims

### Claim 1

A method of preparing and using a coil spring in a pressure relief valve comprising:
a) measuring the spring rate of the coil spring;
b) modifying the spring after measuring its spring rate so as to modify its spring rate to be within ±2% of a target spring rate; and
c) building a pressure relief valve having an inlet comprising an inlet valve seat, a disk member closable on the inlet valve seat and a mechanism biasing the disk member on the inlet valve seat, a body, and an outlet, wherein the disk member and inlet valve seat are configured to provide a huddling chamber, with the modified coil spring being used in the biasing mechanism, and wherein the relief valve further comprises a secondary orifice between the inlet valve seat and the outlet, the inlet being configured so that gas flows from the inlet valve seat in a sonic flow when the valve opens due to a pressure in the inlet exceeding the set pressure, and the secondary orifice being sized so that gas flows through the secondary orifice in a sonic flow when the valve opens due to a pressure in the inlet exceeding the set pressure.

### Claim 2 (depends on 1)

The method of claim 1 wherein the spring rate is modified by having one or more disk springs stacked in series with the coil spring.

### Claim 3 (depends on 1)

The method of claim 1 wherein the spring rate is modified by shorting out a portion of the coils of the spring.

### Claim 4 (depends on 1)

The method of claim 1 wherein the spring rate is modified by having a portion of the surface of the spring removed.

### Claim 5 (depends on 4)

The method of claim 4 wherein the spring has material removed from its inside diameter.

### Claim 6 (depends on 4)

The method of claim 4 wherein the spring has material removed from its outside diameter.

### Claim 7 (depends on 1)

The method of claim 1 wherein the spring rate is modified by mechanically enlarging the internal diameter of the spring.

### Claim 8 (depends on 1)

The method of claim 1 wherein the outlet is located in the body radially of the huddling chamber.

### Claim 9 (depends on 1)

The method of claim 1 wherein the spring is built into a valve having a blow-down value of less than about 10%.

### Claim 10 (depends on 1)

The method of claim 1 wherein the spring is built into a valve having a blow-down value of less than about 5%.