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Open Discussion on Fittings Used in Subsea Applications – Standards and Future Challenges

Open Discussion on Fittings Used in Subsea Applications – Standards and Future Challenges. COIN Soap Box Meeting #4 (SBM#4) Presented by Mark Holder. Fittings – Considerations for Subsea Equipment.

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Open Discussion on Fittings Used in Subsea Applications – Standards and Future Challenges

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  1. Open Discussion on Fittings Used in Subsea Applications – Standards and Future Challenges • COIN Soap Box Meeting #4 (SBM#4) • Presented by Mark Holder

  2. Fittings – Considerations for Subsea Equipment • There are many considerations to keep in mind when determining which fitting to use. Questions to keep in mind in the determination are as follows: • Is the fitting exposed to ambient sea water conditions or dielectric service such as in a SCM? • Is the maximum operating temperature at or below 140F? • Is the fitting tied into the cathodic protection system? • Is the service condition driven by NACE MR0175/ISO 15156 (exposed or potentially exposed to wellbore condition)? • Is the fitting required to be rated to the RWP of the tree?

  3. Other Considerations There are other considerations that must be evaluated in the selection of fittings. These include: • Are there customer expectations for the fittings such as test ports verifying the makeup? (example: tubing hanger fittings) • Are there fitting requirements defined within the customer specification such as “anti back-off” , “anti vibration” or “metal to metal”? • If a fitting is specified by the customer, is it qualified and to what requirements? (PTI, Well Dynamics, Butech, Nova, Production Quest, etc) • Do the other items in the circuit have consistent ports or connections? (Hot stab receptacles, needle valves, etc) • Are there interface requirements/constraints which may prohibit a fitting? • Are there standard practices in installation that have been defined and accepted? • What tubing is to be used to interface the fitting (tube material, hardness, etc)?

  4. Which Fitting? With all of the fitting manufacturers and types of fittings and interfaces available…how do we chose the best fitting for the application? We need to look at the fittings with their pro’s and con’s, review the application to determine the requirement of the fitting, what fittings have been qualified to meet the applications, field and rework considerations, etc. This is not an easy task!

  5. Common Problems To Fittings Fittings have common problems that we must evaluate. These problems include: • Proper make-up and installation –customers are specifying welded connections more frequently as the techniques used to inspect mechanically attached fittings is lacking. There appears to be a lack of trust in how fittings are installed. • Lack of adequate length of tube insertion into compression style fittings • Under or over tightened causing the tube to slip or threaded connections to back off • Cone and threaded fittings have inherent issues • Taper must be machined properly (angle and surface finish) • Alignment of the tube cone to the sealing cone may be difficult with heavier walled tubes • Anti vibration fittings must be used as the standard gland fittings are poor when it comes to vibration resistance • These fittings are labor intensive in the cone and thread operation and make up • Proper lubricants must be used or the torque values specified are invalid • Potential for galled threads with some material combinations

  6. Requirements of Fittings How are fittings qualified and what as an industry should we use as a standard? There are a couple of good standards that can certainly apply to the qualification of a fitting. Two such standards are ASTM F1387 and ISO 19879. FMCTI has standardized on the ASTM standard as it covers all of the tests identified within the ISO document but also includes other important tests. FMCTI has also performed a review of the fittings materials of construction and identified what the material should be as a standard based on service conditions. These service conditions take into account the circuit (Control Line service, Chemical Injection Service, Test Line Service, Tubing Hanger Service) as well as the considerations presented earlier. Taking all of this into account…what do we have?

  7. FMCTI Standard Fittings For lower pressure circuits such as for control line interface to valves, compensation circuits, hot stab interface for lock and unlock of connectors, etc limited to the control system working pressure of 3,000 to 5,000-PSI (207 to 345 bar); the 37 degree SAE J514 metal to metal sealing JIC interface was selected as the standard threaded port and the twin ferrule compression fittings were selected for tube interface. For higher pressure circuits such as for test lines, the medium pressure or high pressure cone and thread interface was selected as it too is a metal to metal sealing fitting. The requirement for “standard” fittings is for subsea ambient temps and exposure, tied in the CP system and has no potential for exposure to production or annular fluids or NACE/ISO requirement. Some equipment does not however have these connections as a standard which introduces difficulty…we have to adapt.

  8. Proper Use and Installation FMCTI recognizes the issues facing everyone with regards to fittings. As a result, FMCTI has contacted the fitting manufacturers and captured their recommended practices for installation, their qualification records or statements, the OEM catalog of fittings accepted within FMCTI, the pressure ratings of the connections present for the fittings; all in an effort to ensure the fittings are used properly and are installed correctly. What about the other fittings (which we will call “specialty” fittings)?

  9. FMCTI Specialty Fittings Specialty fittings are those that are exposed to elevated temperatures, have the potential for exposure to production or annular fluids, orare installed in systems that lack cathodic protection, etc. These fittings typically have material of construction changes required to meet the service conditions. These fittings require greater scrutiny, for example those used in tubing hangers. Materials of construction review is required for temperature and/or level of exposure. Service conditions define the level of qualification required to ensure the fitting meets design life criteria. Accessibility and installation may also pose a problem if a condition should arise in testing.

  10. Specialty Fittings Specialty fittings can be as simple as an alloy 625 compression fitting (for elevated temperature or lack of CP) or as complex as a fitting used in a tubing hanger with test ports and multiple seals. Tubing hanger fittings pose some interesting challenges. The fitting materials are required to be NACE/ISO compliant which typically are lower hardness materials but are required to bite or seal on tubing. The preferred method of interface to the tube is via swaging as it is quick and simple. The issue is twofold. The tube has to be NACE/ISO compliant, have thin enough wall to be swaged and yet thick enough to maintain the pressure. In most cases, this means the tubing used does not maintain the same safety factors applied to the industry tubes such as ASME B31.3 (4:1) and/or reaching the hardness limits with higher strength materials. The ferrules used to bite on the tubes are meant to be higher in hardness to ensure the ferrules bite into the tubes and do not deform around the tube but again may be limited due to NACE/ISO.

  11. Specialty Fittings – cont. Not to be negative, but to open the discussion… The ferrules used by companies manufacturing tubing hanger fittings in most cases are not of their design; but of companies such as Swagelok. This means they are manufacturing a fitting body and using another companies ferrules. Swagelok does not condone using their ferrules nor do they warrant to the pressures indicated; indicating that the pressure rating limit is to the ASME B31.3 rating of the tube. Discussions with Parker and Swagelok in development of these fittings have not so far been very productive. This requires the fittings manufacturers to fully warrant their products inclusive of other companies components. When you ask these same companies how they have qualified their fitting designs, you get mixed results. Remember, these companies did not establish the original ferrule to body design and have re-engineered the interface. What do we do?

  12. Future Challenges Fittings and fitting interfaces are reaching a critical point. We as an industry have yet to define a fitting that everyone is comfortable with either in performance or in installation. This applies to both low and higher pressure applications. Because we have reached this point with limited solutions, some customers have imposed welding as a solution using RT as a criteria with which to grade the weld. This may not be possible for tubing hanger interface. Field maintenance and repair then becomes a challenge potentially requiring re-weld and NDE in environments that do not support or allow these activities… For 20K applications…where do we go from here? Do we use cone and thread HP connections? Will the tubing support this downhole?

  13. Potential Solutions FMCTI has been evaluating different fittings and connection methods in an effort to not only meet requirements; but to provide a solution that is efficient and easy to install, has a way to measure the installation to ensure it has been assembled properly and is robust to meet the future demands. The SAE J518 code 62 4-bolt flange is being investigated for the lower pressure (6KSI or less) circuits such as for control and compensation circuits. The code 62 flange has an extensive history on heavy machinery and is extremely rugged in design. Incorporation of a metallic seal would alleviate any concerns for elevated temperatures or other issues in the use of elastomers if needed. It requires torque of 4 bolts which can be measured, not questioning the tube interface as it can be welded. There are still challenges with OEM providers meeting this interface…

  14. Potential Solutions – cont. For higher pressure applications, FMCTI is evaluating “permanent” solutions which are not defined as welded. These permanent solutions could be shaped memory alloys, swaging fittings such as Parker’s Phastite and Tube-Mac’s Pyplok…or other fittings as they are being developed. All fittings reviewed to date have pro’s and con’s which is why a clear winner hasn’t been established. We may be in a situation where we need to determine what the market is willing to tolerate in light of the current problems we face with fittings. There may not be a perfect fitting out there for every applications which means… What are we willing to accept?

  15. Open Discussion Can we drive establishing a standard in interfaces similar to what ISO 13628-8/API 17H is doing with ROV tooling? What performance criteria do we establish or accept as a standard in evaluating a fittings performance? How do we better communicate or relay information with regards to fittings across the industry so we all benefit from the experiences? Have painful or costly experiences driven the market to define the requirements we see in specifications today or is it a case of a consultant or consulting group making their recommendations to better leverage their position? IDEAS?

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