Correct electrofusion coupler sizing starts with the pipe outside diameter, then checks the permitted SDR and PN range, material family and manufacturer instructions. Matching only the number printed on a fitting box is not enough for a controlled fusion joint.
Use this checklist during estimating, receiving and setup. The approved welding procedure specification (WPS), project engineer and current manufacturer documentation remain authoritative.
Start with outside diameter, not a guessed nominal size
Electrofusion fittings are selected against the pipe outside diameter (OD). Read the pipe stamp and the fitting label. If either is damaged or unclear, measure with the appropriate tool and resolve the discrepancy before scraping or clamping.
A pipe described informally by service, bore or legacy naming can still have an OD that differs from what the buyer assumed. A correct purchase order should state the OD explicitly, for example 110mm, 160mm or 355mm, together with the relevant pressure information.
Check SDR and PN compatibility
SDR relates outside diameter to wall thickness. PN identifies nominal pressure class under defined conditions. Both affect whether a fitting is approved for the pipe and duty.
Our catalogue includes electrofusion families labelled SDR11/PN16, SDR17/PN10, SDR21/PN8 and SDR26/PN6 or PN6.3. Those labels help buyers filter the range, but they are not permission to mix families. Confirm the fitting datasheet covers the pipe’s actual wall thickness and the project conditions.
Thin-wall or lower-pressure pipe needs particular care because clamp force, melt behaviour and manufacturer limits may differ from a familiar SDR11 installation.
Choose the correct fitting function
The fitting type must match the geometry as well as the size:
- Straight coupler: joins pipe of the same OD in a straight run.
- Reducer: transitions between two stated outside diameters.
- Elbow: changes direction at the angle shown on the fitting.
- Equal tee: creates a branch with matching run and branch ODs.
- Reducing tee: uses different run or branch dimensions; read all three sizes.
- End cap: closes a compatible pipe end.
- Saddle: creates a branch from a main and requires its own approved installation sequence.
For a reducer or tee, write every connection size in the take-off. “One 160 fitting” is not enough when the other socket may be 110mm or 90mm.
Confirm the system before site setup
Before accepting the fitting, compare:
- Pipe OD and fitting socket size.
- Pipe material designation and fitting approval.
- Pipe SDR/PN and the fitting’s permitted range.
- Manufacturer, barcode and batch information required by the WPS.
- Fusion machine capability and connector compatibility.
- Clamp and restraint range.
- Scraping, cleaning and cooling requirements.
- Traceability or datalogging records required by the client.
Keep questionable items separate rather than letting them reach the weld station.
Preparation is part of sizing
A correctly sized fitting can still fail when preparation is poor. Mark insertion depth, remove the oxidised pipe surface with an approved scraper, keep the prepared area clean, align and restrain the joint, and follow the barcode or manual parameters allowed by the WPS.
Do not shorten cooling time to recover programme delay. Keep the clamp in place for the specified period and record the joint information required by the project.
For equipment selection and records, see choosing an EF machine and datalogging basics. For method selection, see electrofusion vs butt fusion.
Printable sizing checklist
Before ordering, write down:
- pipe OD;
- pipe material;
- SDR and PN;
- fitting type and every connection size;
- manufacturer or approved-equivalent rule;
- machine and clamp range;
- WPS reference;
- quantities, spares and delivery date.
Browse the high-pressure and electrofusion line or contact the trade desk with pipe-stamp photos and the approved take-off. We can help map the request to catalogue options while leaving engineering approval where it belongs.