Hammer Unions have been used in the oil & gas industry for over fifty years. However, the hammer union has weaknesses and limitations for current critical applications. In response to this, TSI Flow Products has designed and manufactured the 3” DC15 Connection.
The 3” DC15 has many significant improvements over the 3” 1502 Hammer Union connection in both fatigue and bending loads to meet current oil & gas industry requirements.
3" 1502 Hammer Union
3" DC15 Connection
3" DC15 Design Features - Improvements - Benefits
DC15 Connection Design Features
- Improved contact geometry between components.
- Minimize stress concentration at external thread roots of the female connection.
- Minimized stress concentration at the male shoulder corner.
- Minimized stress concentration at the last full thread engagement nut.
- Improved DC15 union seal design offers longer lasting performance than 1502 hammer union seal.
- 3 piece load segments with special geometry to reduce stress concentration.
DC15 Connection Benefits
- Uniform bore between male, female and union seal.
- Reduce erosional damages at connection.
- Improved fatigue life of the equipment.
- Improvement in bending load.
3" 1502 Union Seal vs 3" DC15 Seal
| 3" 1502 Seal | 3" DC15 Seal | |
|---|---|---|
| Anti-Extrusion Ring Material | Brass | Stainless Steel |
| Metal Volume (Cubic Inches) | 0.094 | 0.0158 |
| Seal Volume | 2.418 | 1.185 |
| V-metal/V-total % | 3.74 | 11.76 |
| Seal Material | HNBR | Viton |
| Working Temperature Range | -20 to 350*F | -10 to 400*F |
| 3” DC15 Packing has 1.7 times more metal than the 3” 1502 union seal. | ||
| 3” 1502 union seal has 2.04 times more rubber than the 3” DC15 seal. | ||
3” DC15 Connection: Male-to-Female Contact
The DC15 Male and DC15 Female connections make flat face-to-face contact. Some of the external load is carried by the flat face contact. This improves the connection under bending loads.
Evaluation of 3” 1502 and 3” DC15 Connection with FEA
1502 vs DC15 Strength Analysis Results Summary
Load Cases
- Load with internal working pressure of 15,000 PSI.
- Load internal pressure to point of failure.
- Load with internal working pressure and tension applied to point of failure.
- Load with internal working pressure and bending applied to point of failure.
| Test | Condition | 3" 1502 | 3" DC15 |
|---|---|---|---|
| 1 | Stress Level at 15,000 PSIG Internal Pressure | Stress: 60,380 PSI | Stress 40,320 PSI |
| 2 | Stress Level at 30,000 PSIG Internal Pressure (Failure) | Stress: 97,870 PSI | Stress 78,210 PSI |
| 3 | Tension load to failure with 15,000 PSIG Internal Pressure | 60,000 lbf. | 212,500 lbf. |
| 4 | Bending moment to failure with 15,000 PSIG Internal Pressure | 16,300 ft*lbf | 42,500 ft*lbf |
Strength Analysis Results Summary 3” 1502 vs. 3” DC15 Resonant Fatigue Test
48 Times Stronger!
Significantly Reduce or Eliminate N.P.T. Due to Iron Failures.
Design Features Significantly Improve Tension, Bending and Fatigue.
3” 1502 vs 3” DC15 Fatigue Test Results
Based on the data and calculations, the mean DC15 connection performance is 48 times better than the 1502 connection performance. Both bending strains and number of cycles were monitored and recorded by SES’s fatigue data acquisition system. Gauges were located around the pipe circumference at orientations of 0°, 90°, 180°, and 270° on each side of the connection for a total of 8 gauges around the connection. One additional gauge was placed on each side of the connection to determine the bending moment distribution. All gauges were placed at a sufficient distance away from the test connection to be in nominal pipe and outside of any machined regions.
Three samples of both types of connections were tested. For each sample, the diameters and wall thicknesses at the gauge locations were measured and recorded. Testing progressed on each sample until failure occurred or until a run-out was declared. Failure was defined as a through-wall crack in the pipe or leak from the connection. The objective of the fatigue tests was to determine the fatigue performance of the DC15 connection compared to the existing 1502 connection.
3” 1502 vs 3” DC15 Fatigue Test Results Executive Summary
Stress Engineering Services, Inc. (SES) was requested by Tech-Seal International (TSI) to perform full scale fatigue tests on 3” Hammer Unions. TSI requested to test both existing 1502 connections and their DC15 connection. Three samples of both types of connections were tested. The objective of the fatigue tests was to determine the fatigue performance of the DC15 connection compared to the existing 1502 connection.
Fatigue testing was performed by SES per resonant fatigue proposal 1203695-TS-PQ-01_Rev2. All samples were tested at a stress range of 15,000 PSI. A static internal pressure of 7,500 PSI was applied throughout the entire duration of the fatigue test. The test results were compared to the 2014 BS7608 B and D mean fatigue curves, and the 2016 DNVGL B1 mean fatigue curve.
Testing was performed in June and July, 2017. Testing progressed on each sample until failure occurred or run-out was declared. Failure was defined as a through-wall crack in the pipe or leak from the connection. Based on the data and calculations, the mean DC15 connection performance is 48 times better than the 1502 connection performance.
