Full Encirclement Sleeve (Full Wrap)
5.9.1 A full encirclement sleeve (full wrap) is a metal wrap installed around pipe for reinforcement and containing pressure. The full sleeve is produced by welding together two half sleeves around pipe. Sleeves are only permitted to be installed on pipe having a wall thickness between .188 and .750 inches.
There are two types of full wrap encirclement sleeves:
• Type A is longitudinally welded along its connecting edges but not welded to the pipe at the ends.
• Type B is welded on the ends to the carrier pipe in addition to the longitudinal weld. Type B is the recommended installation because it is pressure containing.
Sleeve material is listed in the Pipe Welding procedure (MIP-407) by pipe material/sleeve material classification. See Section 5.9.10 and 5.9.11 for girth weld and long repair lengths. For assistance, contact the Asset Integrity Team (Pipeline Integrity Technologist).
5.9.2 The sleeve material wall thickness must be calculated to accommodate the full design pressure of the mainline pipe on which it is installed. Use the following formula:
T=………..
Where:
Ts= Minimum sleeve thickness in inches (at full design pressure)
Tp= Minimum pipe thickness in inches (at full design pressure)
Ss= SMYS for the sleeve material in psi
Sp= SMYS for the pipe material in psi
Dp= Outside diameter of the pipe in inches
The sleeve thickness must be greater than or equal to the pipe wall thickness. Sleeve material of higher SMYS than the pipeline shall have a wall thickness equal to or greater than the original pipeline design thickness. No credit shall be taken for the increased SMYS of the sleeve. If the sleeve thickness is greater than
the pipe thickness, the ends of the sleeve must be chamfered at a 45 degree angle to a thickness equal to the pipe.
5.9.3 Inspect the wall thickness.
The integrity of the pipe at the fillet weld location must be verified. This may be done using an ultrasonic thickness gage and by visual inspection.
The minimum pipe wall thickness at the location where the sleeve will be welded to the pipe is .188 inches.
5.9.4 Prepare the pipe as described in section 5.6 of this procedure.
5.9.5 Prepare the sleeve and fit it to the pipe.
5.9.5.1 Wire brush the internal surface of the sleeve to remove dirt, rust, scale, and other foreign materials.
5.9.5.2 A factory manufactured half sleeve is usually ten feet long and may be cut to the required length in the field. The minimum length for a sleeve is four inches per DOT.
5.9.5.3 A backing strip is recommended at the longitudinal butt weld to protect the pipe from weld damage. The strip must be a minimum of 16 gauge (.0625 inch thick) mild carbon steel cut to the length of the half sleeve. Tack weld the strips to the bottom half of each side, with welds approximately a half inch long and spaced twenty-four inches apart. Follow the sleeve manufacturer’s instructions, if available.
5.9.5.4 When sleeves are used to repair dents, fill the dent with a hardening filler material such as epoxy or automobile body putty before installing the sleeve.
5.9.5.5 Place the bottom sleeve, with the backing strips attached, under the pipe with the edges of the strip barely touching the sides of the pipe. Position the top sleeve over the pipe using wedges on the ends of the top sleeve’s longitudinal seam to provide clearance for the backing strip to fit underneath the top half.
5.9.5.6 Plate clamps can be used for positioning the top sleeve and can be removed when the proper position is obtained. Spreader bar rigging may be used when handling long half sole sleeve sections.
5.9.5.7 Once the half sole sleeves are in close proximity to the pipe, position the chain clamps around the half sole. Chain clamps should be fabricated of a diamond, double roller type chain. The tightening mechanism must be supported by a metal shoe contoured to the shape of the half sole/pipe.
5.9.5.8 Tighten the clamps at an equal rate on each clamp until the top half sole has cleared the backing strips. At this point, the wedges can be removed. Continue tightening the clamps until the half sole is firmly in position.
5.9.5.9 Remove any hydrocarbon film on the sleeve and pipe at the fillet weld location with a suitable solvent. This is an important step and integral to ensuring a low-hydrogen weld!
5.9.6 Reduce the pressure by one third of the normal operating pressure to allow the sleeve to share hoop stress. In cases where the product or operation does not allow the pressure to be dropped by one third, consult the Asset Integrity Team (Pipeline Integrity Technologist) or Technical Services before continuing.
5.9.7 After the pressure is reduced, complete final tightening of the sleeves.
The gap of the longitudinal weld groove is critical. The gap must be 1/16 inch on each side. Reposition the sleeve or grind the edges to achieve the proper gap.
5.9.8 Weld the sleeve per the Pipe Welding procedure (MIP-407).
The sleeve installation welding procedure is a low hydrogen API-1107 process. Use absolutely dry low hydrogen electrodes and carefully control the size and shape of the circumferential fillet weld. The leg of the fillet weld should equal 1.4 times the wall thickness of the pipe. Strive for a concave faced fillet weld, with streamlined blending into both members; avoid notches and undercuts. The smoother and more streamlined the weld, the greater the resistance to fatigue. The longitudinal welds must be completed before welding circumferentially type “B” full encirclement sleeves.
5.9.10 If the area to be sleeved contains a girth weld that may provide difficulty with fitting a plain sleeve, an expanded sleeve (sometimes called a pumpkin) can be installed providing the material meets the requirements listed in MIP-407.
5.9.11 If the area to be sleeved is longer than the sleeve material and additional pieces must be used, use one of the following methods:
• Butt weld the sleeves together at each end and radiographically inspect the butt welds prior to installing the sleeve halves on the pipeline.
• Leave a minimum of ½ pipe diameters (or 4” minimum) between the two sleeves.
• Butt the sleeves together and install another sleeve over those using the proper sleeve weld procedure listed in MIP-407. The overlapping sleeve must be at least 12” long and centered over the primary sleeve ends. The overlapping sleeve must be oversized (larger inside diameter) and be able to cover the entire circumference of the primary sleeve. The overlapping sleeve material and thickness must be calculated using the larger outside diameter of the primary sleeves.
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