High Pressure standards for butt fusion, what you need to know

Overview

The world of butt fusion welding has grown, and countless manufacturers have placed on the market machines for every price range, with differing product and service quality. From a regulatory point of view, individual countries are keeping pace by proposing rigorous welding standards such as the American ASTM F2620, the international UNI ISO 12176-1, or the German standard DVS 2207-1.

The professional welding sector also requires ever more guarantees, such as digital traceability of the welding phases. As a result, the choice of equipment must no longer be taken lightly, but made consciously and without risk.

Butt fusion welding machines for thermoplastic materials that do not comply with strict pressure and temperature guidelines can be dangerous. A single incident can cause serious environmental damage and immeasurable damage to reputation.

This article provides the main differences among high-pressure welding standards and highlights the characteristics that a good machine must have to meet the challenges of the butt fusion welding world.

High-pressure standards

The United States, commonly bases its guidelines on a single high-pressure philosophy (SHP – Single High Pressure). The ASTM F2620 standard sets a heating mirror temperature of 204–232 °C and an interfacial pressure of 0.41–0.62 Mpa [1]. It differs from other welding standards in its jointing pressure and in the cooling time under pressure, which is almost half the cooling time required by other standards [2].

German practice, by contrast, derives from two key national standards which together cover both single low-pressure operation (SLP – Single Low Pressure) and dual low-pressure operation (DLP – Dual Low Pressure).

The SLP (Single Low Pressure) and DLP (Dual Low Pressure) welding techniques are two internationally standardized procedures for butt welding polyethylene (PE) or polypropylene (PP) pipes.

The main difference lies in the management of pressure during the various phases of the welding cycle (heating, removal of the heating plate, and cooling).

The DVS 2207-1 standard of the German Welding Society introduced the SLP method (Single Low Pressure) with a melt temperature of 200–220 °C and an interfacial pressure of 0.15 ± 0.01 MPa [3].

This standard covers thicknesses up to 130 mm and defines the cooling time under pressure as a function of ambient temperature. In DVS 2207-1, the cooling time under pressure is directly correlated with the pipe wall thickness and can be reduced by 50% if the joint is made in a laboratory.

The British standard WIS 4-32-08 indicates an initial pressure of 0.15 MPa, with a plate temperature of 230 °C (+10, −5 °C), and specifies DLP (Dual Low Pressure) for pipes with wall thickness greater than 22 mm, in which the initial pressure is reduced to one-sixth during cooling [4].

It applies to thicknesses up to 71 mm, but unlike DVS 2207-1 it does not allow reduced cooling times, especially for thick-wall pipes. The cooling time under pressure is also set according to the pipe wall thickness.

Several European countries follow similar standards (for example, INSTA 2072 in Scandinavia and France, NEN 7200 in the Netherlands, and DS/INF 70 in Denmark) and adapt holding or cooling times to local climates without leaving the SLP or DLP reference frameworks [5].

China, now a major manufacturer of welding machines, follows its own standard, GB/T 32434-2015, for gas and water distribution systems.

This standard defines two methods: SLP and DLP for pipes with wall thicknesses up to 70 mm. The SLP protocol uses a plate temperature range of 200–235 °C and a dynamic fusion pressure of 0.15 ± 0.01 MPa. For DLP, the temperature rises to 225–240 °C, with an initial fusion pressure of 0.15 ± 0.02 MPa followed by a reduced cooling pressure of 0.025 ± 0.002 Mpa [6].

The international standard ISO 21307 integrates the German SLP profile, the British DLP profile, and the American SHP profile into a coherent three-option matrix. For SLP it specifies 225 ± 10 °C at 0.17 ± 0.02 MPa; for DLP it assigns 232.5 ± 7.5 °C at 0.15 ± 0.02 MPa followed during cooling by 0.025 ± 0.002 MPa; and for SHP it sets 215 ± 15 °C at 0.52 ± 0.10 Mpa [7].

When it was first published in 2009 and in the second version of 2011, the cooling time under pressure for both SLP and DLP procedures was simply defined as wall thickness + 3 min, regardless of wall thickness. In the latest version published in 2017, the cooling time under pressure was defined with a formula for pipe thicknesses greater than 18 mm.

In summary:

Recent comparisons (in A.I. Alhatti et al. 2025, especially Fig. 11) show that each national standard fits within the ISO standard and that time–pressure trends differ either because pressure is kept constant (SLP and SHP) or reduced during cooling (DLP). Machine manufacturers can therefore design a single ISO-compatible profile and implement it worldwide.

This brief overview shows a progression from local to global regulation: American companies operate within the SHP block defined by ASTM F2620 and its derivatives; European operators follow DVS 2207-1 or WIS 4-32-08 within the SLP or DLP blocks; likewise, Chinese authorities refer to GB/T 32434-2015 for SLP or DLP; and ISO 21307 encompasses all approaches in a single international framework by anchoring (heater plate temperature, bead-up pressure, fusion pressure, and cooling protocol) this set of standards within clearly specified tolerances and ensuring the mechanical integrity and long-term reliability of PE joints in water, gas, etc. pipelines, while preserving the climatic, material, and regulatory nuances that originally shaped national practice.

Recording welding data

The ASTM F3124 standard states that, to be compliant, an HDPE pipe fusion machine must record the operator ID, the machine ID, and the joint number, and provide a graph of the welding cycle showing temperature, time, and pressure (TTP). This record provides proof that the plate remained within 400 °F–450 °F (204 °C–232 °C) and that fusion pressure remained stable throughout the entire cooling cycle. Operating without a data record violates standard F3124 and exposes operators to risks.

Automatic CNC (computer numerical control) butt fusion welding machines made by T2 WELDING eliminate these problems. The computer manages the process according to the chosen standard (ASTM or ISO) and the pipe parameters, automatically calculating the drag pressure, fusion pressure, and cooling time.

If an operator attempts to shorten the cooling time, the machine interrupts the recording or flags it as an error. Automation shifts responsibility from the operator’s judgment to a verified algorithm.

A valid alternative to the CNC control unit is T2 WELDING’s new Datalogger data reader. It enables monitoring and recording of data directly from the standard hydraulic control unit installed on PT series welding machines. This system is calibrated to meet all the main international welding standards. The file with the welding report can be exported as a PDF and transmitted directly to project managers so they can verify weld quality remotely. This integration ensures that “as-built” documentation is generated automatically as work progresses, simplifying final handover to the client.

THE PT – HP SERIES BY T2 WELDING

The PT models have been adapted to meet the force requirements of high-pressure welding regulations. Modifications of varying degrees of substance have been made, particularly to the basic machine and hydraulic unit. The PT 500 model, for example, has been completely redesigned, with new (wider) clamps and tie rods, as well as a new, stronger facing tool. On the other hand, the base body of the PT 250 has undergone only minor modifications.

It’s not just a matter of increasing the pressure. The machines must withstand forces three to five times greater, without bending or breaking. T2 welding machines have been tested according to the most stringent criteria and at the maximum of the declared range.

Advanced engineering and scrupulous choice of the materials make our machines the best choice in terms of performance, reliability and durability.

High Pressure welding standards allow to reduce cooling time by almost 50%, compared to classic stardards like DVS. This means much higher productivity!

Write us for more info: info@t2welding.com

[1] ASTM International; ASTM F2620-24 – Standard Practice for Heat Fusion Joining of Polyethylene Pipe and Fittings https://doi.org/10.1520/F2620-20 (2020).

[2] A.I. Alhatti et al. 2025: Ahmed I. Alhatti, Suleyman Deveci, Imad Barsoum, Abdelrahman I. Hosny,

Advancements in butt fusion jointing of HDPE pipes: A comprehensive review of fusion conditions and joint integrity assessment techniques, in Polymer Testing, Vol. 150, Article 108909, online at:

https://doi.org/10.1016/j.polymertesting.2025.108909 (Accessed 15 May 2026).

[3] German Welding Society (DVS) DVS 2207-1 – Welding of Thermoplastics – Heated Tool Welding of Pipes, Pipeline Components and Sheets Made of PE-HD (2005).

[4] U.K. Water WIS 4-32-08 Issue 4: Specification for the Fusion Jointing of Polyethylene Pressure Pipeline Systems Using PE80 and PE100 Materials, London, United Kingdom (2016), online at:

https://standards-board.water.org.uk/document/wis-4-32-08-issue-4-specification-for-the-fusion-jointing-of-polyethylene-pressure-pipeline-systems-using-pe80-and-pe100-materials/ (Accessed 15 May 2026).

The European Plastic Pipes & Fittings Association (TEPPFA), Butt fusion jointing of polyethylene pressure pipes, Brussels, online at:

https://www.teppfa.eu/wp-content/uploads/Butt-Fusion-Jointing-of-Polyethylene-Pressure-Pipes.pdf (2021) (Accessed 15 May 2026).

[5] The European Plastic Pipes & Fittings Association (TEPPFA), Butt fusion jointing of polyethylene pressure pipes, Brussels, online at:

https://www.teppfa.eu/wp-content/uploads/Butt-Fusion-Jointing-of-Polyethylene-Pressure-Pipes.pdf (2021) (Accessed 15 May 2026).

[6] Standardization Administration of China. GB/T 32434-2015; Plastics Pipes and fittings—Butt Fusion Jointing Procedures for Polyethylene (PE) Pipes and Fittings used in the Construction of Gas and Water Distribution Systems (2015).

[7] International Organization for Standardization ISO 21307:2017, Plastics pipes and fittings—butt fusion jointing procedures for polyethylene (PE) piping systems, online at:

https://www.iso.org/standard/63773.html#amendment (2017) (Accessed 15 May 2026).