Connection specifications
Stress / strain behavior
During end-preparation, the bell-end is cold-expanded by roughly 7-8% resulting in an increased nominal yield stress of the steel. Since the pin-end has a larger outside diameter than the bell's ID, a slight groove is added and its nose tapered to allow the connection process to start more easily in the field.
At the time of connection, the bell-end expands further into its elastic range and once completed that expansion recovers and applies significant compressive forces on the pin-end - these forces coupled with surface friction create the strength holding the Zap-Lok connection together.
Technical reports and documentation
The interference fit of the Zap-Lok connection has been carefully engineered to harness the full strength of the steel in order to ensure a significant margin of safety during operation.
For further documentation on the performance and capabilities of the Zap-Lok connection please consult the following resources.
Service and regulations
Standards compliance
- ANSI B31.3
- ANSI B31.4
- ANSI B31.8
- DOT 49 CFR Part 192
- DOT 49 CFR Part 195
- CFR 250 subpart J
Temperature of operation
Zapoxy 138 - is rated to withstand operating temperature of 250 degrees F, with intermittent peaks up to 300 degrees F.
Zapoxy 141 - is rated to withstand operating temperatures of 450 degrees F, with intermittent peaks up to 650 degrees F.
Hydrogen sulphide service
To comply with NACE MR-01-75/ISO 15156 (2001) the Zap-Lok bell-end is stress-relieved using portable induction heating since its OD deformation exceeds 5%.
Stress relieving lowers the final maximum hardness to below 22 HRC therefore increasing the permeability of the steel to better handle the presence of H2S.
High-pressure hydrostatic performance
Unlike most other mechanical connections Zap-Lok is not de-rated. The design of the pipeline remains a function of the pipe diameter, wall thickness and intended operating pressure.
Zap-Lok connections follow the industry standard testing specification of 90% SMYS (specified min. yield strength).
Ultimately to ensure confidence and safety, we have repeatedly tested the connection to hydrostatic failure and have observed that it maintains its integrity at pressures exceeding 140% SMYS.
High-pressure installations
| Project | Distance | Size | Pressure |
|---|---|---|---|
| Bakken shale WAG | 170 mi. | 2 3/8" - 8 5/8" | 2,700 - 2,900 psi |
| Barnett Shale - Gas gathering | 300 mi. | 12 3/4" | 1,440 psi |
| West Africa | 90 mi. | 12 3/4" | 3,400 psi |
Tensile & axial performance
The tensile and axial strength of the Zap-Lok connection allows for versatile construction techniques such as long pull-sections, bore-sections and complex field bending. Commonly, many contractors have utilized pull-sections of several thousand feet in steep terrain conditions seen in areas such as Colorado, Montana, New Mexico and throughout the Rocky Mountains.
Since 2004, Zap-Lok has been certified and installed in S-lay offshore construction projects in the Gulf of Mexico up to 220 ft. water depths.
OFFPIPE simulation
To simulate the axial and tensile forces present in an offshore installation, Zap-Lok connections have undergone extensive independent destructive testing.
OFFPIPE data was used to re-recreate the forces present for various pipe dimensions in underwater installations. An independent report concluded that the connection retains 100% integrity at 660 ft. water depths (test limit) and shows the potential to reach greater depths.
