A pipe marked PN16 is not a 16 bar pipe
Thermoplastic pipework specification for hydrogen, carbon capture, nuclear balance of plant and gigafactory projects.
Most thermoplastic systems that fail in service fail for reasons that had nothing to do with the material. An unapplied safety factor. A derating factor nobody carried through. A chemical reduction factor nobody looked up. A fusion joint made outside a qualified procedure.
We have published the calculation chain, the material exclusions and the standards framework in full, in one document, for the design teams who make these decisions once every few years.
14 sections. Sourced from published AGRU, Spears and SwissFluid technical data and the cited standards. Written for design teams, not for procurement.
The number that goes on the drawing
Take PE 100 SDR 11, above ground, 50 year design life. The catalogue figure is 16.0 bar.
| Condition | Calculation | Result |
|---|---|---|
| Tabulated operating pressure, water, 20 °C | AGRU Table A.5 | 16.0 bar |
| Above ground system reduction coefficient | 16.0 × 0.8 | 12.8 bar |
| Same pipe at 40 °C | 11.7 × 0.8 | 9.4 bar |
| Same pipe, hydrofluoric acid at 75 per cent or less, 20 °C | 16.0 / (1.6 × 1.4 × 1.0) | 7.1 bar |
Source: AGRU AGRUCHEM catalogue, Table A.5, calculated with a safety factor of 1.25.
The same pipe, described in a schedule as PN16, is a 12.8 bar pipe above ground, a 9.4 bar pipe above ground at 40 °C, and a 7.1 bar pipe in that acid duty.
The above ground coefficient alone removes a fifth of the pressure capability, and it is the factor most often left out.
A second example makes the point differently. AGRU calculates PE operating pressures with a safety factor of 1.25 for water and 2 for gas. The same PE 100 SDR 11 pipe is a 16.0 bar pipe in water service and a 10.0 bar pipe in gas service, at the same temperature and the same design life. Specifying by SDR alone, without stating the service, is ambiguous.
Why the chain matters
The six decisions
Six things separate a specification that works from one that fails in service.
A stated scope boundary, including where thermoplastics do not apply.
A specification that names its own limits is stronger, not weaker.
Material selection against quantified properties and against specific chemical exclusions.
PVDF is unsuitable for amines and for basic media at pH 12 or above, with a risk of stress cracking. On an amine based capture plant that is a hard exclusion, and PP or PE is the correct starting point for those circuits.
The correct design coefficient.
The safety factor is material specific and temperature banded. PE 100 sits at 1.25 across the range. PP-H moves from 1.6 to 1.4 to 1.25 as temperature rises. PVDF and ECTFE stay at 1.6. There is no single number.
Temperature derating and the above ground system coefficient, both applied.
Derating from 20 to 40 °C at a 50 year design life is a factor of 0.73. Above 45 °C the published tables stop at shorter design lives, which is itself a design constraint.
Thermal movement, support spacing and anchor loads calculated for the material.
A 30 metre PP-H run installed at 15 °C and operating at 60 °C moves 216 mm. The same run in PVDF moves 176 mm. Nothing here carries across from steel.
Jointing procedure control, operator qualification and joint traceability.
A fusion joint is as strong as the pipe wall only when it is made to a qualified procedure, by a qualified operator, with calibrated equipment. On a 40 year asset the joint log is straightforward to produce during construction and impossible to reconstruct afterwards.
Where thermoplastics apply
| Asset type | Typical thermoplastic scope |
|---|---|
| Electrolytic hydrogen production | Feedwater and ultra pure water treatment, electrolyte handling, cooling water, chemical dosing, deioniser skid interconnect, chemical drainage |
| Carbon capture | Solvent make up and transfer, cooling water, wash water, effluent and drainage, chemical dosing |
| Onshore and offshore energy process plant | Cooling water, seawater and firewater distribution, chemical injection, effluent, fume and vapour ductwork |
| Nuclear, conventional island and balance of plant | Cooling water, demineralised water treatment, chemical dosing, drainage subject to classification |
| Battery and gigafactory process | High purity water, electrolyte and solvent handling, fume extract, chemical drainage |
The demanding duty is rarely the headline medium. On an electrolytic hydrogen plant the hydrogen itself is a small part of the pipework scope, and the larger part is ultra pure water, electrolyte, cooling water, chemical dosing and drainage.
On a carbon capture plant the CO2 pipeline is steel, and the amine solvent circuit, cooling water and wash systems are where corrosion drives whole life cost.
And where they do not
Thermoplastic pipework is not a universal substitute for metallic pipework. The guide states these exclusions plainly:
- High pressure hydrogen transmission. Published evidence supports low pressure service only.
- Dense phase or supercritical CO2 transport. Specify carbon steel to the relevant pipeline code.
- Steam and steam condensate.
- Amine solvent service in PVDF.
- Nuclear safety classified duties, which require a qualified supply chain to BS EN ISO 19443.
- Hazardous area service without an electrostatic assessment and a conductive grade.
Three issues that invalidate a specification
Hydrogen permeation
Hydrogen permeates polyethylene faster than methane. Published testing puts PE 100 permeation at approximately 1.5 times that of PA 12, with clear temperature dependence, so a buried line at 10 °C and an above ground line at 30 °C are not the same case. Permeation is a loss and accumulation issue rather than a structural integrity issue, and it has to be assessed for confined spaces, ducts, chambers and buildings.
Electrostatic charge accumulation
Standard grades are insulators, with surface resistance above 10¹³ Ω for PE 100 and PP-H. Flowing dry gases and particulates generate charge that cannot dissipate through the wall. In a hazardous area that is an ignition risk. Conductive grades bring three consequences with them: PE 100-el is not MRS classified, both conductive grades carry higher safety factors, and PPs-el operating pressure reduces to 60 per cent of the standard figure. Earthing then becomes part of the jointing scope, including a final bleeder resistance evaluation.
Fire performance
The polyolefins are combustible. AGRU publishes UL 94 94-HB and DIN 4102 B2 for PE 100 and PP-H, and UL 94 V-0 for PPs, PVDF and ECTFE. A UK or European building or process safety case will normally ask for EN 13501-1 reaction to fire classifications instead, and those certificates have to be obtained for the specific range being specified.
These three are the issues most likely to invalidate an otherwise sound thermoplastic specification on an energy site.
Book a specification reviewFourteen sections, every table sourced
Fourteen sections, written to be used at concept and outline design rather than read once.
- Scope, application map and exclusions, including the metric ISO and US Schedule sizing classifications and where they cannot be mixed.
- Material selection against quantified properties, with a comparative table for PE 100, PE 100-el, PP-H, PVDF, ECTFE and PVC-C covering classification, density, mechanical, thermal, fire, electrical and approvals, with the test basis named where the sources differ.
- Material exclusions, stated plainly, for PVDF, PP and PE, including the concentration thresholds at which diffusion begins for hydrochloric and hydrofluoric acid.
- Pressure rating, reduction factors and design life, with the full reduction chain for water endangering media, buckling and external pressure, and surge.
- Thermal movement, supports and anchor loads, with expansion leg sizing, support spacing to 80 °C and minimum bending radii.
- Jointing method selection and procedure control, with the governing document for each method and what a defensible fusion specification requires.
- Chemical resistance in practice, including swelling and its effect on restrained systems.
- Hydrogen specific considerations, presenting the published evidence and its limits.
- Valve specification, including ISO 15848-1 tightness, endurance and temperature classes, and why "TA-Luft compliant" is not a specification.
- Closed sampling and secondary containment.
- Whole life performance and total cost of ownership, with a framework for the assessment and the supply continuity questions that belong in a specification rather than a purchase order.
- Standards and approvals framework, mapped by area.
- A specification checklist that, completed, is a duty schedule.
Every data table names its source.
Get the full technical guide
Specification guide for consulting and specifying engineers, EPC design teams and asset owners.
AGRUCAD libraries: from material selection to bill of materials
The guide settles the engineering decisions. The AGRUCAD Digital Libraries carry those decisions into the model.
AGRU publishes centralised access to digital models and technical data for around 10,000 products, covering pipes, fittings, instrumentation, control components and valves. There are two libraries, and they serve different design environments. AGRU publishes both under AGRUCAD Digital Libraries.
AGRU BIM and Plant Design Library
For Autodesk Revit and AutoCAD Plant 3D. Revit families are supplied at LOD 500, the highest level of detail, with complete metadata.
The routing function, available in Revit from the 2020 version onwards, works in the order a designer actually thinks:
- 01Select the material. Everything in the AGRU range, from PE through to ECTFE.
- 02Select the SDR or pressure rating for the project.
- 03Route. The library places suitable AGRU pipes and fittings automatically.
- 04Dimension. Fittings and reductions adjust or are added automatically.
- 05Add components such as valves and end caps within the design process.
- 06Export the bill of materials. Every component in the routed system is collected, and the bill of materials exports for enquiry.
Automated tagging logic and quality checks run alongside, so the model, the schedule and the documentation stay consistent with each other.
Pipe classes available
- AGRULINE: PE 100-RC, including the FM 215 psi and FM 250 psi classes.
- AGRUCHEM: PP, PE 100-RC, PVDF, ECTFE, and the double containment system.
- PURAD: PVDF-UHP, PP-Pure, PolyPure.
- Backing rings, accessories and seal clean gaskets.
Reference: AGRU BIM and Plant Design Library request page and the product sheet (PDF).
AGRU MultiCAD Library
For everything outside the Autodesk environment. Thousands of validated 2D and 3D models in formats including Allplan, AVEVA, Bentley AECOsim, Inventor, Solid Edge, SolidWorks and Trimble SketchUp, so AGRU components drop into whichever CAD environment the project runs in. The models are hosted on AGRU PARTcommunity.
What the libraries do, and what they do not
This distinction matters, and it is the reason the libraries and the guide belong together.
The libraries give you verified manufacturer geometry, a routed model that is dimensionally correct, and a bill of materials that matches what was drawn. That removes the coordination effort and the transcription errors.
What the libraries do not do is make the specification decision. Selecting material and SDR is an input to the library, not an output of it. The chemical exclusion, the safety factor at the design temperature, the above ground coefficient, the water endangering media chain and the jointing regime all sit upstream of the model.
Get those right first, then let the library hold them consistently across every drawing, schedule and bill of materials on the project.
Request the AGRUCAD libraries
Tell us the design environment and the materials in scope and we will set you up, including a walkthrough of the routing and bill of materials workflow. You can also go direct to AGRU for the BIM and Plant Design Library or the MultiCAD Library.
Request goes to AGRU for the BIM and Plant Design Library. For the MultiCAD formats, go to AGRU PARTcommunity.
When to bring IPS in
The reduction factors and the jointing requirements are inexpensive to resolve at concept and outline design, and expensive to resolve on site.
Three decisions are worth settling before the specification is issued:
- The pressure class, after every reduction factor has been applied.
- The jointing method, procedure standard and operator qualification regime.
- The conductive grade requirement, wherever any part of the plant is a classified hazardous area.
Alongside those, two supply questions belong in the specification rather than in the purchase order: which items are held in UK stock against which are indent, for the specific dimension and SDR rather than for the range in general, and whether fittings, spares and repair couplers will still be obtainable in year 20 and year 35. Large diameter AGRULINE and the fluoropolymer ranges are the usual pinch points, because dimension and SDR combinations multiply quickly.
What to send
A duty schedule is enough to start:
- Medium and concentration, at normal and upset condition
- Temperature range
- Pressure
- Design life
- Installation environment
- Hazardous area classification
Section 13 of the guide is structured to produce exactly that. Send it in and we will confirm material selection against the chemical duty, the pressure class after all reduction factors are applied, the jointing and qualification regime, and the stock and lead time position, before the specification is issued.
Book a specification reviewRanges and support
IPS Flow Systems supplies thermoplastic pipework, valve and fitting systems across the UK and Ireland.
IPS Flow Systems is part of the Indutrade Group, a listed industrial group holding a portfolio of technical supply businesses.
Frequently asked
Is a fusion joint really as strong as the pipe wall?+
Only when it is made to a qualified procedure, by an operator qualified by independent examination, using calibrated equipment. DVS 2207-1 specifies heated tool temperature, interfacial fusion pressure, maximum misalignment, and heating and cooling times tabulated by diameter and SDR. It also recommends that welding data be recorded in welding protocols. Specify the procedure standard, the qualification framework and the joint log as a handover deliverable.
Can thermoplastics be used for hydrogen?+
For the balance of plant on a hydrogen production asset, yes, and that is where the larger thermoplastic scope sits. For hydrogen transmission, the published evidence supports low pressure service only. Testing on PE 100-RC at Groningen Seaport concluded suitability up to 2 bar, while noting that the characteristics distinguishing hydrogen from methane must be taken into account in design and maintenance. For natural gas the ISO 4437 and EN 1555 ceiling is 10 bar. Neither figure supports general high pressure hydrogen service.
Why does design life matter to the pressure rating?+
Because the published envelopes differ by material and the tables are calculated to a design life. AGRU's PE 100 and PVDF tables run to 50 years, and the PP-H and PP-R tables run to 100 years. Where the asset design life exceeds the published envelope, the case goes to the manufacturer rather than being extrapolated.
Can I mix metric and US Schedule pipework on one system?+
Spears advises that classifications based on different outside diameters are not interchangeable, although they can often be connected with specialty adapter fittings. Specify one sizing classification per system and identify every transition point. Mixed classifications discovered during construction cause delay and rework.
What is the difference between PE 100 and PE 100-RC?+
Resistance to slow crack growth, and it is quantified. AGRU gives a stress cracking resistance to FNCT of at least 300 hours for PE 100 and at least 8,760 hours for PE 100-RC. That is what permits sand bed free and trenchless installation, with reuse of excavated material where the grain size limits are met.
Is a pressure test the same as for steel?+
No. Viscoelastic creep means pressure decays during a thermoplastic pressure test without a leak being present. Use a test procedure written for thermoplastics, with the correct relaxation period and acceptance criteria. Do not apply a metallic pipework test procedure.
Get the calculation chain in full
The weakness in most thermoplastic specifications is not the material. It is an unapplied safety factor, an unapplied derating factor, a chemical reduction factor nobody looked up, or an unqualified fusion joint.
Fourteen sections, every data table sourced, and a specification checklist that doubles as a duty schedule.
Already know the duty? The most useful point to make contact is before the specification is issued, while the pressure class, the jointing regime and the conductive grade requirement are still open.