GTWS selection, field joints on coated line
Pipeline sleeve size chart, 159 to 1016 mm
A sleeve that will not reach around the coated joint cannot be closed, and the trench has no remedy for it.
The joint disbonds along one line. A code ordered a size down reached around the steel and stopped short of the coating, so the crew stretched it, laid the lap thin and trimmed the patch to suit. The excavation years later finds film lifted either side of that longitudinal seam, with the corrosion sitting under it.
None of that is repairable once the sleeve is on the pipe. Length is cut before the part leaves the factory, and no amount of torch time adds circumference to it.
So size on circumference and on the cutback, never on nominal bore. The GTWS code carries the pipeline outside diameter it is cut for, then the width. GTWS Ø 610 x 500 is a sleeve for 610 mm outside diameter, 500 mm wide, supplied flat with a separate closure patch. That is what lets it go onto a weld already lowered into the trench.
The sleeve is three-layer cross-linked polyethylene over a hot-melt adhesive that bonds to bare steel and to the pipeline's own PE coating. Its cathodic disbondment figure is 3 rad. The standard is ISO 21809-3.
This page carries pipeline dimensions and nothing else. Cable and conductor codes are selected on supplied and recovered diameter instead, and not one column below transfers to them.
GTWS selection chart, all fifteen codes
| Gala code | Sleeve length | Sleeve width | Closure patch length | Closure patch width |
|---|---|---|---|---|
| GTWS Ø 159 x 500 | 620 | 500 | 100 | 500 |
| GTWS Ø 219 x 500 | 830 | 500 | 100 | 500 |
| GTWS Ø 273 x 500 | 1000 | 500 | 100 | 500 |
| GTWS Ø 325 x 500 | 1200 | 500 | 120 | 500 |
| GTWS Ø 377 x 500 | 1370 | 500 | 120 | 500 |
| GTWS Ø 406 x 500 | 1500 | 500 | 150 | 500 |
| GTWS Ø 426 x 500 | 1560 | 500 | 150 | 500 |
| GTWS Ø 457 x 500 | 1660 | 500 | 150 | 500 |
| GTWS Ø 508 x 500 | 1840 | 500 | 170 | 500 |
| GTWS Ø 529 x 500 | 1900 | 500 | 170 | 500 |
| GTWS Ø 610 x 500 | 2160 | 500 | 170 | 500 |
| GTWS Ø 711 x 500 | 2480 | 500 | 170 | 500 |
| GTWS Ø 720 x 500 | 2500 | 500 | 170 | 500 |
| GTWS Ø 813 x 500 | 2800 | 500 | 170 | 500 |
| GTWS Ø 1016 x 500 | 3430 | 500 | 200 | 500 |
All dimensions in millimetres. Sleeve width and closure patch width are 500 mm on every code, and no other width is published. Reproduced from the manufacturer's three-layer corrosion protection sleeve page.
What is left over after one full turn
| Gala code | Pipe OD | Circumference at π × OD | Published sleeve length | Remainder |
|---|---|---|---|---|
| GTWS Ø 159 x 500 | 159 | 500 | 620 | 120 |
| GTWS Ø 219 x 500 | 219 | 688 | 830 | 142 |
| GTWS Ø 273 x 500 | 273 | 858 | 1000 | 142 |
| GTWS Ø 325 x 500 | 325 | 1021 | 1200 | 179 |
| GTWS Ø 377 x 500 | 377 | 1184 | 1370 | 186 |
| GTWS Ø 406 x 500 | 406 | 1275 | 1500 | 225 |
| GTWS Ø 426 x 500 | 426 | 1338 | 1560 | 222 |
| GTWS Ø 457 x 500 | 457 | 1436 | 1660 | 224 |
| GTWS Ø 508 x 500 | 508 | 1596 | 1840 | 244 |
| GTWS Ø 529 x 500 | 529 | 1662 | 1900 | 238 |
| GTWS Ø 610 x 500 | 610 | 1916 | 2160 | 244 |
| GTWS Ø 711 x 500 | 711 | 2234 | 2480 | 246 |
| GTWS Ø 720 x 500 | 720 | 2262 | 2500 | 238 |
| GTWS Ø 813 x 500 | 813 | 2554 | 2800 | 246 |
| GTWS Ø 1016 x 500 | 1016 | 3192 | 3430 | 238 |
Circumference is π multiplied by the outside diameter in the code, rounded to the nearest millimetre. The remainder is the published sleeve length minus that circumference. Both of those columns are worked out here from the published figures; neither appears on the manufacturer's own chart, and both are calculated on bare steel rather than on a coated pipe.
Reading the remainder column
Follow that last column down. It climbs from 120 mm at Ø159 to 244 mm at Ø508, and then it stops climbing. Every code from Ø508 to Ø1016 carries between 238 and 246 mm of extra length, whatever the diameter. A sleeve for a metre-diameter line gets no more spare material than a sleeve for a half-metre one.
What the allowance is spent on is not published. Two demands are certainly inside it. The coating already on the line raises the real wrapped diameter above the bare steel figure printed in the code, and the sheet has to lap past itself before any patch goes over the seam. The manufacturer states neither share.
Treat the column as a sanity check on the row, not as a specification you can design to. If π multiplied by your measured coated diameter comes out above the published sleeve length, that code cannot be closed on your joint at all. If it lands within a few tens of millimetres of it, there is nothing left for the lap and you are on the wrong row.
Checking a row against the pipe in front of you
This sequence is our arithmetic on the manufacturer's published chart, not a manufacturer's instruction. Whatever is supplied with the sleeve overrides it.
Measure over the coating, not the steel
Take the outside diameter across the parent coating either side of the cutback, at the band where the sleeve ends will bond down. On a coated line that figure sits above the nominal diameter printed in the code, and it is the diameter the sleeve actually has to travel around.
Turn the diameter into a circumference
Multiply by π. On a Ø610 line the bare steel circumference is 1916 mm. The published length for GTWS Ø 610 x 500 is 2160 mm, so 244 mm of sleeve remains after one full turn, before the coating build is taken out of it.
Spend that remainder before accepting the row
The remainder absorbs coating build first and lap second. On the Ø610 row the closure patch is 170 mm long, so a bonded band of 170 mm sits over the seam and about 74 mm of the bare steel remainder is still unaccounted for. Work it through on your own measured diameter rather than on the nominal one.
Check the cutback against 500 mm
Width is fixed. Measure the exposed steel, then add the bonded land you need on sound parent coating at both ends. If that total runs past 500 mm, a single sleeve does not cover the joint and the order changes shape.
Confirm the patch that ships with it
Patch length is fixed per code and steps five times across the range. Read it off the row before the order goes out, and refuse a substitution from a smaller code, because the patch is the only material bridging the seam.
Closure map, GTWS Ø 610 x 500
| Dimension | Value | Where it comes from |
|---|---|---|
| Pipeline outside diameter | 610 | The code itself |
| Circumference of the bare steel | 1916 | Computed, π × 610 |
| Sleeve length as supplied | 2160 | Published chart |
| Length beyond one circumference | 244 | Computed, 2160 minus 1916 |
| Sleeve width | 500 | Published chart |
| Closure patch, length by width | 170 by 500 | Published chart |
| Patch length as a share of circumference | 8.9 percent | Computed, 170 divided by 1916 |
The sleeve drawn flat, every figure in millimetres, each with its provenance. Lay out a rectangle 2160 by 500, mark the seam where the two ends meet after 1916 mm, and centre a 170 by 500 patch on that seam.
The patch steps five times across fifteen codes
Closure patch length is not proportional to diameter. It holds flat over several codes, then jumps.
- 100 mm on Ø159, Ø219 and Ø273.
- 120 mm on Ø325 and Ø377.
- 150 mm on Ø406, Ø426 and Ø457.
- 170 mm on Ø508, Ø529, Ø610, Ø711, Ø720 and Ø813, six codes spanning 305 mm of diameter.
- 200 mm on Ø1016 alone.
What cutting a patch down actually removes
The patch is the only bonded material lying over the longitudinal seam, and that seam is the one place on the joint where the sleeve has an edge underneath itself. A larger sleeve recovers around a flatter curve and pulls harder on that edge, which is what the steps answer. The manufacturer prints the steps and not the reasoning.
Trimming a patch takes bonded land off both sides of the seam at once. A 170 mm patch cut back to 120 mm loses 25 mm of adhesive on each side of the line. Peel on this system is published per centimetre of bonded width, so trimming removes holding force in direct proportion, and it does so at the hottest part of the duty where the published PE figure has already dropped to 30 N/cm. The method is ASTM D2671.
There is no patch that fits a diameter it was not cut for, and no field test that will tell you afterwards that the seam was short. Order the patch with the code.
Three figures this chart does not publish
Get these in writing before the order is placed. The split of the length allowance. The remainder after one circumference runs 120 to 246 mm, and no source states how much is coating build and how much is lap. The sleeve-to-sleeve overlap. Where a cutback is wider than 500 mm more than one sleeve is needed, and no overlap dimension between adjacent sleeves is given for GTWS anywhere in the chart or the specification. Any width other than 500 mm. All fifteen codes are published at 500 mm, so a wider single sleeve is a question for the manufacturer and not a selection off this page.
Where the rest of this sizing lives
Two substrates route away from here. Everything above is pipeline, and it stays on this URL.
- Cable and conductor codes, 5 to 192 mm ODGWS and GMRS are chosen on supplied and recovered diameter. No column on this page applies to either family.
- Pre-insulated pipe endsA casing and its service pipe are sized together, and the part is a moulded cap rather than a cut sheet with a patch.
- The GTWS sleeve in fullConstruction, adhesive, and the published mechanical, thermal and chemical figures with their test methods.
- Cathodic disbondment at 3 radThe single result that decides whether a field joint coating is acceptable on a cathodically protected line.
- Wrapping and shrinking itPreheat, torch pattern, and the order the sleeve and the patch go on in.
- What excavations find under a failed sleeveWhy the seam is where it starts, on buried pipeline and on buried cable alike.
Send the coated diameter and the cutback width
A GTWS enquiry comes back right first time when it carries the outside diameter measured over the parent coating, the width of the exposed cutback, the coating type as PE or FBE, the line's operating temperature and the number of joints. Quote the code you read off this chart, and say which diameter you measured it against.