Pipeline Corrosion Protection with Isolation - Monolithic Joints

Summary of "W" Style Insulated Joint design. 

Tube Turns developed and started manufacturing Insulated Joints in the early 1960’s. The basic design was comprised of two flanged hubs, separated by a nonmetallic insulating gasket all held together with a split yoke. The assembly was sealed with two o-rings, one in each flange face. In response to customer requests, Tube Turns Technologies instituted a program in 1994 to develop a new style of insulated joint. The bolts used on the “L” and “R” designs made it difficult to “wrap” these joints with mastic before they were buried in the ground. Joining the yoke halves by welding rather than bolting produced a smooth outside configuration which made the mastic wrapping much easier. This new style of the insulated joint was designated the ”W” style as shown above. 

The hydrostatic testing of the “W” style insulated joints is the same as the “L” style, in that the hubs and yoke are exposed to the longitudinal force due to the internal pressure. The “W” style overall length is between the “L” and “R” style. 

 The “R” and “L” style joints utilized gasket material 1/8 inch thick. To improve the resistance to arcing and breakdown voltage properties of these joints, a 1/4 inch thick gasket material is used on the “W” style joint. The use of the thicker material allows the gasket to be cut to match the ID of the joint and dispense with the epoxy putty utilized on the previous designs

All of the dimensions affecting the strength of the insulated joints are unchanged. The only difference between the “R” and “L” and the “W” joint is the overall length and the dimensional changes required by the use of the 1/4 inch thick gasket material. 

 To sum up, the “W” style insulated joint is identical in strength to the previous designs, but has superior electrical characteristics and provides a smooth outer configuration, which is easier to coat in the field.

Prototype and Design Information 

 PROTOTYPE TESTING 

 Tube Turns has conducted a detailed prototype testing program on the “W” style line of insulated joints. Both 6” and 24” joints were tested. A summary of the testing is listed below followed by test details. 

 Specifically, the testing was composed of: 

? Internal pressure - The 6” joint was pressurized to 5,000 psi for thirty minutes. The 24” joint was pressurized to 3000 psi for thirty minutes.    

? Pressure fatigue - Both joints were subjected to 25 rapid pressure cycles from 0 to 2230 psi and back to 0. The pressure (2230 psi) was held for 5 minutes during the 15 th cycle on the 6” and for 15 minutes during the 15th cycle on the 24” insulated joint.  

? Bending - Both joints were exposed to a bending moment in a four-point loading fixture sufficient to produce a stress in the attached piping of at least 75% of 65,000 psi or 50,700 psi concurrent with an internal pressure of 1500 psi. 

? Torsion - The 6” joint was exposed to a torsional moment sufficient to produce a stress in the attached piping of approximately 10% of 65,000 psi or 6320 psi. 

 Both joints successfully passed all of these tests with no evidence of permanent distortion or leakage. All of the testing was witnessed by an independent third-party inspection agency.  

The 6” joint was built with a 6.065” ID. After assembly was completed, 120” long pipe pups (.280” wall) were welded to each end of the joint and caps were welded to the ends of the pups. Similarly, the 24” joint assembly was built with a 23.000” ID and 120” long (.500 wall) pipe pups. Strain gages were attached to the top and bottom of both joints and they were placed in a bending fixture as shown in Figure 1. The load P was applied by a hydraulic press and measured by a load cell. The resulting load/stress calculations are shown in Table 1. 

 The 6” insulated joint was then subjected to a pure torsional torque of 107,376 in-lbs. The shear stress induced in a 6” standard wall pipe by this torsional moment is 6,320 psi. Careful examination of match marks placed on the hub(s) and the yoke before the test indicated that there was no relative rotation or “spin” between the hub(s) and the yoke. 

Table 1 clearly shows that, while under full rated internal pressure, these insulated joints are capable of withstanding an external bending moment greater than that permitted by ASME B31.8, paragraph 833.3 for 65,000 minimum yield pipe.  

 The strain gage measurements for the 6” showed a maximum strain in the hub of 1,125 μ inches, which corresponds to a stress of 33,188 psi. Similarly, the maximum yoke strain was 640 μ inches or 18,880 psi. The 24” results were; a maximum strain recorded in the hub of 460 μ inches, which corresponds to a stress of 13,570 and a maximum yoke strain was 520 μ inches or 15,340 psi. These stresses are obviously lower than those in the connected piping. 

 Cyclic Pressure Testing 

 In addition to the above testing, Tube Turns has conducted an extensive cyclic pressure testing program on a 24 Class 600 W style insulated joint. 

 A summary of the testing is listed below. 

 SUMMARY 

 Two 24” welding caps were welded to the 24 CL600 W insulated joint as shown in Figure 1. The test was set up in this manner so that the insulated joint would “see” the full end load due to the internal pressure. 

An air powered diaphragm pump was used to provide pressure for the test. A simple control system was designed and built to perform the cyclic test. The pump would increase the internal pressure until it reached the setpoint of the high-pressure limit. The pump would then stop and the water control solenoid would trip, reducing the pressure to the low-pressure limit setpoint. The cycle would then restart. 

The intent was to cyclic test the joint at the hydro test pressure for a CL600 unit, 1.5 times the design pressure of 1480 psi or 2220 psi for a minimum of 2000 cycles. To ensure at least 2220 psi the high-pressure limit was set at approximately 2300 psi. Testing was started on 2/1/00 and completed on 2/4/00 and 2199 cycles were actually performed and charted. 

 After completion of the above, the insulated joint was hydrostatically at 3340 psi for 15 minutes. 

 There was no evidence of any leakage during the above testing. The unit was then disassembled and the components inspected. The o-rings showed no evidence of extrusion or any other type of damage. Similarly, there was no evidence any of change to the other components. 

 This cyclic fatigue test verifies the incredible durability of the Tube Turns Insulated Joint. The 24” CL600 was actually cycled 2000 times at hydro test pressure and then passed a hydro test of 2.25 times design pressure. 

Standard Materials (Carbon Steel)

Insulated Joints (W-Style): 

 Hubs: Pipe (2” thru 6”) – SA106 Br. B/C; 52,000 PSI Min Yield; Hardness = Rockwell C22 Max (NACE); Heat Code Identified; Test Reports with Shipment Forging (8”+) – SA105/SA350 LF2 Class 1/A694-F52 (dual certified); Heat Code Identified; Test Reports with Shipment 

 Yoke: Pipe (2”, 4”, 6”) – SA106 Br. B/C; 46,000 PSI Min Yield; Heat Code Identified; Test Reports with Shipment Forging (3”, 8”+) – SA105/SA350 LF2 Class 1/A694-F46; Heat Code Identified; Test Reports with Shipment 

 O-Rings:  FKM (Viton) 

 Insulated Gasket Material:  Epoxy Base/Glass fiber reinforced high strength laminate (NEMA Gr. FR-4)

Filler Material: The internal cavities of each completed joint are filled with a liquid epoxy resin that fills all voids and, when cured, achieves very high adhesion to the metallic components and provides high electrical resistance. 

Coating: The surface of the metallic parts are blast cleaned and all internal and external surfaces are coated with a non-conducting epoxy primer and topcoat with a total thickness of about 4 mils. For special orders, coal tar epoxy coating or special paints can be provided.

Dimensions 

 The dimensions provided below are for ASME Class 600 Rating and below. ASME Class 900 Rating dimensions are available upon request. 

Codes & Standards 

 ANSI/ASME B31.8 Gas Transmission and Distribution Piping Systems. ANSI/ASME B31.4 Liquid Petroleum Transportation Piping Systems. ASME SECTION IX Qualification Standards for Welding and Brazing Procedures. ASTM - Applicable Material Standards. 

Bore and End Preparation 

 The Insulated Joints shall have a smooth, clear bore suitable for the uninterrupted passage of Pigs, Spheres and On-line inspection tools (Intelligent Pigs). 

 The Weld End internal diameter to match that of the attached pipe and the weld end shall be beveled to an angle of 30°, +5°/-0°, 1/16" Land. 

 Design Advantages of Tube Turns Insulated Joint 

•  EXPERIENCE Tube Turns has over 35 years of successful experience in the Insulated Joint business. 
•  LIMITED NUMBER OF WELDS The Tube Turns Insulated Joint Design contains only two (2) longitudinal groove welds in the yoke and there are no pressure containing welds on the Tube Turns Insulated Joint. 
•  COMPACT DESIGN Tube Turns Insulated Joints are designed to produce a relatively compact overall length without the use of expensive pipe pups. The heat from normal welding does not affect the mechanical or electrical integrity of Tube Turns Insulated Joints. This has been verified by actual prototype testing performed at the Tube Turns facility and 35 years of successful field experience. 
•  BOLTLESS The “W” series insulated joint is designed to satisfy customers that require a boltless construction for ease of final wrapping and coating after final installation of the pipeline. 
•  SINGLE PIECE CONSTRUCTION The Tube Turns insulated joint is of monolithic construction designed specifically with regard to the mechanical stresses. This design ensures the precompression of the sealing gasket during assembly and enables a perfect seal to be formed against internal and external environments. 
•  TRIPLE PROTECTION 

  →Insulated gaskets prevent metal-to-metal contact across the insulated joint. 

  →All internal cavities of the insulated joints are filled with a special dielectric compound to provide an additional electrical barrier. 

  →Each metal component is individually coated with a minimum of two coats epoxy paint. 

? STRENGTH AGAINST BENDING MOMENTS The Tube Turns insulated joint is designed to withstand an externally applied bending load producing a maximum bending stress of 72% of the minimum yield strength of the attached pipe. 

MANUFACTURING 

The following list outlines the standard manufacturing, test and inspection requirements for insulated joints (special requirements are often added to meet customer specifications): 

Manufacturing of a Pipeline insulating joint before the hubs are sandwiched together.

1. Order or select raw material as defined below: a. Hub(s) and yoke forgings to be A105 or A694 as specified on order. Material to be heat code identified with mill test reports. b. Insulating gasket material per TT grade 2.068. c. O-rings to be Viton. 

2.1 Rough machine (2) hubs in preparation for ultrasonic examination. Transfer heat numbers to maintain material identification. 

3.1 UT examine (2) hubs for a distance of 4" back (or entire forging if desired) from weld prep per TT-04-059. 

4. Finish machine (2) hubs and (1) yoke in accordance with the appropriate drawings. Transfer heat numbers to maintain material identification. 

5. Abrasive blast clean (2) hubs and (1) yoke to a white metal finish. 

6. Coat (2) hubs and (1) yoke with one coat of epoxy base primer. After the primer has cured apply one coat of epoxy base finish. After assembly, touch-up paint. 

7. Assemble insulated joint. 

8. Weld yoke halves together using approved Welding Procedures. All welders shall be qualified in accordance with ASME Section IX. 

9. Ultrasonic test welds per procedure TT-04-068. 

10. Hydrotest at pressure shown on shop packet for 15 minutes with tap water. Fill out and sign hydro test certification. 

11. Fill all internal cavities with an epoxy base compound. 

12. Steel stencil stamp marking defined by shop packet on OD of yoke in line with terminal connections. 

13. Electrically test for a resistance of 25 Megohms at 1000 VDC. Generate test certification. 

14. Final inspect for general visual appearance, material identification (heat numbers on hubs and yoke), marking and dimensional conformance with appropriate Tube Turns drawing. 

1These steps are optional and not requested by some customers 

QUALITY CONTROL 

Tube Turns Technologies Quality Control System meets the requirements of the American Society of Mechanical Engineering Boiler and Pressure Vessel Code, Section VIII, Division I, Appendix 10 and is audited by an Authorized Inspection Agency. 

Monolithic Insulated Joints ready for shipment coated in a two-part epoxy coating.

The system covers Order Analysis, Drawing Control, Procurement Control, Receiving of Materials, Process Control, Welding, Nondestructive Examination and Inspection. 

Raw materials are inspected for dimensional acceptability and proper heat code identification. Mill test reports are checked to ensure proper physical and chemical properties.   

A serial number is assigned to each joint at order entry and is permanently stamped on the joint. The actual heats of material used for the individual joint are permanently recorded for this serial number in addition to being stamped on the hub and yoke. This provides traceability to the material test reports for every joint. 

Each joint manufactured by Tube Turns Technologies is completed factory assembled and hydrostatically tested to 1.5 times design pressure before shipment. In addition, each joint is electrically tested to verify its insulating capability. For acceptance, the joint must show a minimum electrical resistance of 25 megohms when tested at 1000 VDC. When specified, the following can be furnished for each joint: 

Certified Material Test Reports Hydrostatic Test Certification Electrical Test Certification   

Tube Turns Technologies is fully qualified in house to provide Magnetic Particle, Ultrasonic and Liquid Penetrant examination along with the required NDE test reports to meet customer requirements 

Welding and Repair 

 All Welders and Welding Procedures used in the fabrication of insulated joints shall be qualified in accordance with ASME Section IX.

Coating and Marking 

 Insulated Joints are coated as follows: 

 Abrasive blast clean (2) hubs and (1) yoke to a white metal finish. Coat (2) hubs and (1) yoke with one coat of epoxy base primer. After the primer has cured apply one coat of epoxy base finish. After assembly, touch-up paint. 

 Each Insulated Joint shall be marked by low-stress steel stencil on the outside of the Yoke with the following: 

 Manufacturer's Name or Trademark Size and Class Material Heat Number (marked on Hubs and Yoke). Insulating Joint Serial Numbers 

Testing and Inspection 

CHEMICAL/MECHANICAL ANALYSIS 

 Supplier Material Test Reports are reviewed by Quality Control to ensure the required chemistry and mechanical properties are met and a Tube Turns Material Test Report is generated. 

 Options available: Tube Turns can supply Supplier Material Reports per Customer request. 

ULTRASONIC TESTING 

 The only welds (groove welds on yoke) are UT tested per TT-04-068 and an Examination Report is generated. 

 Options available: Tube Turns can supply Examination Reports per Customer request. In addition, Tube Turns can UT forgings and/or weld ends per customer request. 

MAGNETIC PARTICLE TESTING (OPTIONAL) 

 Optionally, Tube Turns can MP Test finished hubs and yoke and provide an Examination Report. 

PRESSURE TESTING 

 Insulated Joints are hydro tested at 1.5 times design pressure for 15 minutes with tap water and a Test Certificate is generated. 

 Options available: Tube Turns can supply Test Certificate per customer request. Chart recordings and various test hold times are available upon request. In addition, Tube Turns can pneumatically test Insulated Joints per customer request. 

Cut away view of a Monolithic Insulated joint used for pipeline corrosion protection.

ELECTRICAL TEST 

 Insulated joints are Electrically tested for a resistance of 25 Megohms at 1000 VDC and a Test Certificate is generated. 

Options available: Tube Turns can supply Test Certificate per customer request. In addition, Insulated Joints can be electrically tested for no breakdown at 5000VAC per customer request. 

FINAL INSPECTION 

 Final Inspection for general visual appearance, material identification (heat numbers on hubs and yoke), paint, marking and dimensional conformance with appropriate Tube Turns drawing. 

Options available: Tube Turns can supply a Certificate for Dimensional Inspection per Customer request. Also, Holiday Testing and Coating Records can be provided for special coatings. 

Packing Specifications 

 Insulated Joints are strapped to pallets with bevel ends closed and protected. 

Have Questions or Need Pricing?Contact Us

For Sales Support and General Questions Contact:

Robert Stanton- Owner/Sales 

CELL (219-851-3333)

[email protected] 

Nick Stanton- Sales Manager 

CELL (219-363-3949)

[email protected] 

Stanton Sales & Service LLC

2397 E Division Rd, La Porte, IN 46350, US

Office Phone- 219-363-3949 [email protected] 

Website- www.stantonsales.net