Frequently asked questions
Almost since the industry began from its embryonic stages in the 1860s, steel pipelines have been used to transport oil and gas from the wellheads, through gathering systems and then on into the downstream markets. Welding has been at the forefront of pipeline construction in parallel to the development of the industry. However, the science of mechanical interference fit technology has certainly been around for more than 50 years. In validating, proving and approving the Stealth-Lock MIF technology, our technical experts are almost always asked the following FAQs:
Yes. During independent third-party validation tests carried out at Stress Engineering in Houston, Texas, the destructive test results were outstanding. During pressure to failure tests, the maximum peaks where the joint yielded were recorded as high as 186% of SMYS (Specified Minimum Yield Strength).
The lowest recorded yield during testing was at 142% of SMYS. Pressure performance of the Stealth-Lock joint is therefore well above the industry testing baseline standard of 90% SMYS. To put that into perspective, a typical 6-inch nominal diameter carbon steel pipe with 5.6 mm wall thickness yielded at 594 bar that’s a little over 8600 psi.
No. The strength integrity derives purely from the friction fit forces opposing between the OD of the Pin and the ID of the Bell. In fact to prove our point, we have often joined test samples without the application of epoxy and then subjected those samples to destructive testing. The strength and integrity results are almost as good as the joints that have had our epoxy applied.
For clarity, the epoxy performs three functions: Firstly, it is a very good lubricant when joining the mating parts of the pipe. Secondly, the epoxy forms a “secondary seal” around the OD of the pipe on the butt end and on the ID of the pipe on the pin end. Thirdly, when used in conjunction with FBE applied coatings, our epoxy closes the coated surfaces and forms a 100% holiday free connection.
This can vary depending on diameter, environment, topography, weather conditions and of course, oilfield congestion. However, it’s fair to say that an eight-man crew can construct an average of 2 km per working day. We have experience in working in emergency and project recovery situations where Stealth-Lock has been called in to construct pipelines as quickly and as safely as possible.
One of our best examples of this situation is a 25 km, 12-inch diameter, carbon steel pipeline with 47 expansion loops and 12 major road crossings. When we arrived, a little less than 1 km had been constructed. With the permission and supervision of the client Health, Safety & Environmental department, we laid on double dayshifts, swapping crews in and out for night and day. This gave us 20 hours of construction each and every day. We completed the Stealth-Lock straight lines in 8 days with a further 8 days to construct and tie-in the expansion loops and the road crossings.
Extremely well. The Stealth-Lock system is designed to interlock with ID and OD coatings such as Fusion Bonded Epoxy and phenolic primers to resist H2S, CO2 and CH4. In fact, the system has been proven to increase pipeline lifetime well beyond 20 years when applied in critical sour service conditions.
There is also a speed and commercial benefit to combining Stealth-Lock with FBE internally coated pipe. This is because our system negates the need of a circumferential protective sleeve that is required when welding the FBE coated joints together. Such sleeves on the market can add more than $20,000 per kilometer in material costs alone to any project. With Stealth-Lock, not only does the client save this cost but also, the asset integrity team can be sure that they get a holiday free connection on every joint.
For more information regarding the high-confidence level for critical sour service that has been independently validated, please refer to the section of this website covering Electrochemical Impedance Spectroscopy (EIS) testing that was conducted at the Southwest Research Institute, San Antonio, Texas.
All joints are installed compliant to the Stealth-Lock engineered standards and specifications including but not limited to; surface preparation, elongation dimensions, compliant insertion depth requirements, and visual inspection.
Once the pipeline is completed and ready for handover, all projects are hydrotested prior to hookup and hydrotests are performed in accordance with the specific client specifications and standards governing the project. Typical hydrotest maximum pressures are set at either 125% or 150% of the pipeline designed Maximum Allowable Operating Pressure (MAOP).
The fact that no expensive, time-consuming and hazardous radiography is required also improves the commercial and safety values of each and every Stealth-Lock project. More importantly perhaps is the fact that as a company, Stealth-Lock not only engineers and manufactures it’s own pipe joining equipment but the company is also ultimately responsible for the installation and quality compliance of each and every joint, in every field of operations, in every part of the world.
Our diameter range is from 2 inches to 16 inches with the wall thickness ranging from schedule 20 to schedule 80. Typical projects work with API 5L or X52. In almost all cases, we work with free issued, Client pipe but however there are occasions where we perform our prepping service at the supply chain source within the pipe mill itself.
Again, that is the versatility of the Stealth-Lock System in that we can set up our mobile prepping units at the pipe mill, coating plant, project yard or just about anywhere that suits the project logistics and limitations.