IR vs RAM PEXa Crosslinking: Which Technology Wins for Production?

If you’re planning to invest in a PE-Xa production line, the crosslinking technology you choose will influence nearly every aspect of your operation, from production capacity and factory space to maintenance requirements and cost per meter of pipe. The two leading peroxide crosslinking technologies are infrared (IR) crosslinking and RAM extrusion, commonly known as the Engel process. Both produce high-quality, standards-compliant PE-Xa pipe, but they differ significantly in throughput, production efficiency, and the total investment required to achieve the same output.

This comparison draws on production data from Intelligent Extrusion Systems, the leading PEXa extrusion line manufacturer specializing in infrared (IR) crosslinking technology, with over 25 years of experience developing high-output PEXa production systems, alongside established knowledge of the RAM process as the market’s longstanding alternative.

What Is PEXa Crosslinking?

PE-Xa is produced by triggering a chemical reaction that converts linear polyethylene chains into a three-dimensional crosslinked network. During extrusion, peroxide added to the polymer decomposes under heat into free radicals, which bond adjacent PE chains together (C–C crosslinks). The result is a material that behaves like a thermoset rather than a thermoplastic — it doesn’t remelt under heat, and it gains the thermal memory, freeze resistance, and mechanical performance that make PEXa the preferred choice for underfloor heating and pressure plumbing applications where PE-Xb and PE-RT alternatives fall short.

Industry standards (ISO 15875, DIN 4726, ASTM F876) generally require a minimum crosslinking degree of 70% for PEXa to qualify as such — the exact minimum threshold should be checked against the specific standard and application in question, as this can vary by region and pipe class.

What standards don’t dictate is how you get the polymer to that crosslinking degree during extrusion. That’s where IR and RAM diverge.

Method 1: Infrared (IR) Crosslinking

In IR crosslinking, the pipe is extruded through a counter-rotating twin-screw extruder and then passed through an infrared oven immediately after extrusion, where the crosslinking reaction is driven to completion in a continuous, single-pass process.

This continuous design is the source of IR crosslinking’s speed and efficiency advantage. In practice, IR lines are capable of:

• Single-step production of multilayer PEXa/EVOH pipe (3- or 5-layer barrier construction) without a secondary processing stage
• Achieves guaranteed minimum line speeds of approximately 35 m/min for Ø16 mm pipe, providing around 11.6 times higher output than conventional RAM-based systems, which are limited to a maximum speed of 3 m/min for the same pipe size.
• A smooth, mark-free surface finish, since the pipe passes through the oven without mechanical contact during crosslinking
• Produces the equivalent output of approximately 11 conventional RAM-based lines while requiring only approximately 220 m² of factory floor space.

Method 2: RAM Extrusion

RAM extrusion remains one of the most widely used technologies for PEX-a pipe production. The process uses a ram (plunger) extruder to push batches of molten, peroxide-compounded material through the die under high pressure and extended residence time, rather than employing a continuous screw-fed extrusion process.

• Relative to IR, the batch nature of this process is where the speed and efficiency gap shows up. The RAM/Engel process is characterized by:
• Lower production speed for equivalent pipe dimensions, requiring more than 11 RAM lines operating in parallel to match the annual output of a single IR line.
• Requires a secondary reprocessing stage for PEX-a/EVOH multilayer pipes, rather than a true single-pass production process.
• Requires significantly more factory space to achieve the same production capacity due to the additional reprocessing equipment.
• Greater likelihood of surface waviness, a characteristic associated with the batch/plunger process compared to IRs continuous extrusion process.
• More frequent PTFE tooling recoating. RAM lines typically require recoating approximately once per day, whereas IR technology extends this interval to around five days at comparable production volumes, improving uptime and reducing consumable costs.

IR vs RAM/Engel: Side-by-Side

Why IR Generally Wins for High-Volume PEXa Production

For manufacturers targeting meaningful production volume, IR crosslinking tends to come out ahead on the metrics that matter most to a plant’s economics over its operating life:

1. Higher throughput per production line. A single IR line can deliver the same annual production capacity as more than 11 RAM lines producing the same pipe dimensions. This reduces the number of production lines to operate, simplifying staffing, production management, maintenance, and quality control.
2. True single-pass multilayer production. PEX-a/EVOH oxygen-barrier pipes are produced in a single continuous process, eliminating the secondary reprocessing stage required by conventional RAM technology. This reduces material handling, labor requirements, production time, and the risk of quality losses associated with additional processing.
3. Lower total investment for equivalent production capacity. Although a RAM production line has a lower initial purchase cost, achieving the annual output of a single IR line typically requires more than 11 RAM lines operating in parallel. As a result, the combined investment in machinery, factory space, utilities, and supporting infrastructure can exceed that of a single IR production line.
4. Improved process stability and pipe quality. The continuous IR extrusion process minimizes the process variations associated with batch/plunger extrusion, reducing the likelihood of surface waviness while improving dimensional consistency and overall product quality.

When RAM Still Makes Sense

IR isn’t the right call for every scenario, and a fair comparison should say so:

• Lower initial capital availability. If your volume target is modest and you’re not planning to scale output significantly, a single RAM line’s lower entry investment may fit your budget and demand curve better than committing to IR capacity you won’t use.
• Smaller-batch or specialty runs. For lower-volume or highly specialized product runs where line utilization won’t approach IR-line capacity anyway, the throughput gap matters less.

The right choice ultimately depends on your target volume, product mix (monolayer vs. EVOH multilayer), available floor space, and growth timeline.