Welding methods
Trade terms and synonyms in plastics welding
A glossary of the trade's language: from butt fusion and mirror welding via bead, angleich and heat soaking to calibration under DVS 2208. The synonyms also power the site's search field.
See all welding methods in the overview
Why a trade glossary
The plastics welding trade mixes Danish terms, German DVS terminology and English designations from the manufacturers. The same welding method is called butt fusion, mirror welding and heated tool welding, for example. This guide explains what the words mean and which of them you will meet in standards, machine menus and manufacturer tables.
The glossary is also built into the search field of the knowledge base: search for "mirror welding" and you will also find the articles on butt fusion; search for "bead" and you will find the articles on bead evaluation.
The glossary is divided into four groups: welding methods, the phases of the welding process, materials, and control and testing. Sources are holm-holm.dk and plasticwelding.dk, the DVS technical rules, and the industry's machine manufacturers (Hürner, Widos, Georg Fischer, Munsch, Wegener).
Welding methods and equipment
The methods and the equipment used with them.
| Term | Synonyms | Explanation |
|---|---|---|
| Butt fusion | mirror welding, heated tool welding, butt welding | The two pipe ends are melted against a heated plate and pressed together into one homogeneous joint. The standard method for PE and PP pipes from around Ø63 upwards, under DVS 2207-1 (PE) and DVS 2207-11 (PP). |
| Heating element (welding plate) | mirror, heated tool | The flat, temperature-controlled plate that melts the pipe ends in butt fusion. Temperature is typically 200-220 °C for PE and 210 ±10 °C for PP. |
| Electrofusion | EF, electrofusion fitting, coupler welding | A fitting with a built-in wire coil is heated electrically and fuses with the pipe. The fitting's barcode controls voltage, resistance and welding time. |
| Extrusion welding | extruder welding, hand extrusion | Molten welding rod is extruded into a prepared, bevelled seam while the base material is heated with hot air. Used for thick-walled material, tanks and geomembranes. |
| Hot gas welding (hot air welding) | hand welding, hot air gun welding | Welding rod is melted into the seam with a hot air gun. Used for details, linings and repairs. |
| Socket fusion (socket/mandrel welding) | bead welding, "boiler hole" welding | The pipe's outer surface and the fitting's inner socket are heated on a heated tool and joined. For small diameters, typically Ø20-Ø125. |
| Sheet welding | sheet butt welding, sheet seam welding | Welding of plastic sheets, typically with extrusion or hot gas, for tanks, linings and fabrication work. |
| Wedge welding | hot wedge welding, automatic wedge welding | An automatic machine with a heated wedge welds overlapping sheet seams continuously - used for geomembranes and roofing. |
| Extrusion lap welding | lap seam extrusion, fillet seam | Extrusion-welded lap seam where two sheets overlap and the seam is filled with extruded material. |
| Saddle welding | branch welding, saddle fitting welding | Welding a saddle (branch) fitting onto a main pipe, with electrofusion or heated tool equipment. |
| Welding rod | welding wire, filler rod | The filler material for extrusion and hot gas welding. Must always match the base material: PE rod for PE, PP rod for PP. |
| Welding tent (assembly tent) | welding shelter, site tent | A tent around the pipe and machine that keeps wind, rain and dirt away from the welding plane. Standard practice for documented joints. |
| Pipe cutter (guillotine cutter) | pipe saw, cut-off tool | Tool for cutting pipes square. A square cut is a precondition for an even melt layer and a full-contact joint. |
The phases and parameters of the welding process
The phases and variables that control a weld, as found in the welding tables.
| Term | Synonyms | Explanation |
|---|---|---|
| Angleich (heating equalisation) | angleich time, equalisation time | The phase after heat soaking where the pressure is released to zero so the melt can equalise. A DVS 2207-1 term that appears in many machine programmes. |
| Heat soaking time (heating time) | heating time, melt time | The time the pipe ends are held against the heating element, approximately 10 seconds per mm of wall thickness for PE. |
| Changeover time | dwell time, open time | The time from the plate is withdrawn until the ends meet. Must be kept as short as possible so the melt surfaces do not cool. |
| Joining pressure (welding pressure) | fusion pressure, butt pressure | The specific pressure (N/mm²) on the welding plane during joining, converted via the pipe surface area to the machine's hydraulic pressure. |
| Cooling time | cool-down time | The minimum time the joint must be held under pressure while it cools. May not be shortened, and the pipe must not be moved until the joint is cold. |
| Weld bead (bead) | pearl, bead-up | The raised molten material pressed out at the weld. An even, symmetrical bead on both sides is a good quality indicator. |
| Bead remover | internal bead remover, deburring tool | Tool that removes the internal bead after butt fusion to reduce flow resistance and enable pigging. |
| Drag pressure | movement pressure, friction pressure | The hydraulic pressure needed to move the carriage with the clamped pipes. Added to the welding pressure on manual machines; automatic machines compensate for it. |
| Data logging of welding data | welding log, weld data recording | Automatic recording of pressure, temperature, time, operator and location for each joint - the basis of the weld log and the quality document. |
| Facing (facing the pipe ends) | planing, facing tool operation | Machining the pipe ends flush with the facing tool so the welding plane is clean, even and perpendicular to the pipe axis. |
| Scraping (oxide removal) | peeling, oxide layer removal | Removal of the outer oxidised layer, required for electrofusion of PE100-RC: approximately 0.1-0.2 mm removed evenly all the way round. |
Materials and measurements
Pipe and sheet materials and the measurements that determine the welding parameters.
| Term | Synonyms | Explanation |
|---|---|---|
| SDR (Standard Dimension Ratio) | wall series, dimension ratio | The ratio between the pipe's outer diameter and its wall thickness. A lower SDR means a thicker wall and higher pressure rating. SDR11 and SDR17 are the most common for PE pressure pipe. |
| PN (nominal pressure) | pressure class, pressure rating | The pressure the pipe is designed for at the reference temperature, e.g. PN10 (10 bar) for SDR17 and PN16 for SDR11 at 20 °C. |
| MRS | minimum required strength | The material's long-term strength in MPa: PE100 has MRS 10, PE80 has MRS 8 - hence the names. |
| PE100 / PE80 / PE63 | PE 100, PE 80, PE 63 | PE pressure pipe materials graded by MRS. PE100 is today's standard for water and gas; PE80 and PE63 are older classes still found in existing networks. |
| PP-H / PP-B / PP-R | polypropylene H/B/R | PP types: PP-H (homopolymer, stiff and chemical-resistant), PP-B (block copolymer, impact-resistant) and PP-R (random copolymer, for hot water). Welded under DVS 2207-11. |
Control, testing and standards
Documentation, testing and the standards the trade works to.
| Term | Synonyms | Explanation |
|---|---|---|
| Calibration of welding machines | machine calibration, annual calibration | Checking and adjusting pressure and temperature measurement. The standard is every 12 months, under DVS 2208 and the manufacturer's requirements, documented with a certificate. |
| Pressure testing | hydrostatic test, leak test | Pressurising the completed pipeline with water to prove it is tight before backfilling, following DS/EN 805. Never against clamping tools. |
| Spark test | holiday test, spark testing | High-voltage testing of linings and coatings that finds pinholes and voids in the lining. |
| Test weld (destructive test) | trial weld, sample weld | A weld made for testing and cut apart to inspect the bead and fusion. Used for operator qualification and when material or crew changes. |
| DVS 2207 | DVS 2207-1, -3, -4, -11, -15 | The German technical rules behind most welding tables: 2207-1 for PE butt fusion, 2207-11 for PP, etc. |
| DVS 2208 | DVS 2208-1 | Operation, control and calibration of heated tool welding machines, and the dimensions of heated tools for socket fusion. |
| DS 2383 | DS/DS 2383 | Danish standard for welding of thermoplastics - welding personnel and procedures; the Danish counterpart to the DVS qualification practice. |
Sources: holm-holm.dk and plasticwelding.dk (product names and methods), DVS 2207-1/-3/-4/-11/-15 and DVS 2208, Holm & Holm's note on calibration of welding machines (DS/INF 70-6, DS 2383, SBC 243) and Georg Fischer's welding tables.
Need help choosing equipment?
We are happy to help you choose the right method and machine for the job, whatever you call it - butt fusion or mirror welding.
What can be welded together?
Select the two materials you wish to join and see the assessment. The tool is based on generally recognised combinations and notifies you when data is unavailable.
Not recommended
No - not a load-bearing joint
PE and PP are different polymers and cannot be welded together with a load-bearing result. They may appear to hold together, but the joint will fail under load.
The assessment is for guidance only and does not cover load, media or temperature in the specific application. Welding must always follow the manufacturer's instructions and the relevant DVS 2207 part, and a test must confirm the strength before the joint is used in a load-bearing application.
Inspection, testing and standards
Documentation, testing and the standards used in the industry.
| Technical terminology | Synonyms | Explanation |
|---|---|---|
| Calibration of welding machines | calibration, machine calibration, pressure characteristics | Verification of the machine's temperature and pressure control. Holm & Holm calibrates according to DVS 2208 with pressure characteristics, and works according to DS/INF 70-6, which is planned to be reclassified to an actual DS standard. Certification to DS 2383 and SBC 243 (Annex E-F). |
| Pressure testing | pressure test, pressure testing, pressure test, leak test | Testing of completed pipelines with water or air according to applicable guidelines. Provides final documentation that the joints hold. |
| Spark testing | spark tester, spark test, spark testing, holiday detector | High-voltage testing of welded membranes and linings: pores and leaks in the weld seam generate a spark and can thus be detected. |
| Test weld (destructive test) | test weld, test piece, test coupon, bend test, tensile test, destructive test | A test joint is welded and mechanically tested, typically by bend or tensile testing, to verify the machine, parameters and welder prior to the main work. |
| DVS 2207 | dvs 2207-1, dvs 2207-3, dvs 2207-4, dvs 2207-11, dvs 2207-15, dvs rules, dvs regulations | DVS technical codes for welding thermoplastics: 2207-1 butt fusion of PE, 2207-3 hot gas welding, 2207-4 extrusion welding, 2207-11 butt fusion of PP and 2207-15 PVDF. The most widely used references in the plastics welding industry. |
| DVS 2208 | dvs 2208, calibration standard, 2208 | DVS code of practice for the calibration and verification of plastic welding machines, used in Denmark as the basis for machine calibration until DS/INF 70-6 is reclassified as an actual standard. |
| DS 2383 | ds 2383, sbc 243, certification, annex e-f | Danish standard and SBC certification schemes under which Holm & Holm is certified (Annex E–F), used to document quality in welding work. |
| DVGW GW 332 | gw 332, dvgw gw 332, abquetschen regulations, squeeze-off of gas pipes | DVGW worksheet on squeeze-off (Abquetschen) of gas mains made of PE 80 and PE 100 – the primary reference for tool requirements, squeeze stops set by SDR, removal of jacket in the squeeze zone, squeeze zones, squeeze time and post-inspection. Also used outside Germany as a technical reference framework. |
| DS/EN 12132 | en 12132, ds/en 12132, 12132, squeeze-off standard | European standard on squeezing-off PE pipes: principles, squeeze bar geometry and tool requirements. The foundation together with DVGW GW 332 and the tool manufacturer's instructions. |
| DS/EN 805 | en 805, ds/en 805, water supply standard, test pressure standard | European standard (Danish version DS/EN 805) specifying requirements for water supply pipelines, including test pressure method, holding times and evaluation. The revised edition explicitly mentions viscoelastic pipes such as PE; pipe end closures must be dimensioned for the test pressure – therefore never apply test pressure against squeeze-off tools. |
| DVGW W 400-2 | w 400-2, dvgw w 400-2, contraction method, pe test pressure | German DVGW regulations with detailed test pressure procedures for PE pipelines, including the contraction method. Often used as a practical reference in Denmark as well. |
| DS/INF 70-6 | inf 70-6, ds/inf 70-6, danish plastics welding guidance, sbc | Danish informative guidance document on practical plastics welding, used as a professional reference framework (not an actual standard). Forms the basis together with the DS 2383/SBC 243 certification under which Holm & Holm operates. |
| EN 12201 / EN 1555 | en 12201, en 1555, pipe standard, water pipe standard, gas pipe standard, pe product standard | European product standards for PE piping systems: EN 12201 for water supply and EN 1555 for gas supply. Specifies requirements for materials (e.g. PE100), dimensions with SDR/PN and marking on the pipe – which is why the standard is shown on the pipe marking. |
Sources: holm-holm.dk and plasticwelding.dk (product names and methods), DVS 2207-1/-3/-4/-11/-15 and DVS 2208, DVGW GW 332 and W 400-2, DS/EN 805 and DS/EN 12132, EN 12201/EN 1555, as well as Holm & Holm's note on calibration of welding machines (DS/INF 70-6, DS 2383, SBC 243) and Georg Fischer's welding tables.
Need help with the equipment?
We are happy to help select the right method and machine for the job, whether you call it butt fusion or mirror welding.