Qualifying additive manufacturing for fluid power

Aaron Blutstein 17 September 2026  

Additive manufacturing is opening up new ways to design and produce hydraulic and pneumatic components. For pressure-bearing parts, however, moving from a proven design to repeatable production brings questions around process control, inspection, qualification and regulatory compliance. Smart Machines & Factories reports.

For hydraulic engineers, some of the most convincing arguments for additive manufacturing can be found inside the component rather than on its surface. A conventional manifold may require intersecting drilled galleries, plugged drillings and compromises imposed by the need to get a cutting tool into the material. Additive manufacture can remove some of those restrictions, allowing internal passages to follow more direct routes and potentially reducing weight, part count and the number of potential leakage points. What is considerably more difficult is establishing the evidence that a pressure-bearing component made this way can be manufactured repeatedly and safely.

This is becoming an important distinction as additive manufacturing moves from development work towards series and replacement production. Demonstrating that a prototype can withstand pressure is useful, but it is not the same as establishing a qualified production route capable of delivering components with consistent properties over successive builds.

The regulatory position also needs to be understood accurately. In Great Britain, the Pressure Equipment (Safety) Regulations 2016, usually referred to as PE(S)R, regulate the design, manufacture and conformity assessment of pressure equipment and assemblies with a maximum allowable pressure, PS, greater than 0.5 bar, subject to specified exclusions. Pressure equipment is defined to include vessels, piping, safety accessories and pressure accessories, the latter being devices with an operational function and a pressure-bearing housing.

That does not mean every hydraulic component operating above 0.5 bar should simply be labelled as pressure equipment of a particular category. The manufacturer first has to determine whether the particular product falls within scope and how it is classified. Equipment type, the intended fluid and its group, maximum allowable pressure and, depending on the equipment, volume or nominal size can all be relevant to classification and the resulting conformity assessment requirements.

Additive manufacturing does not create a separate exemption from that process, nor does it automatically create an additional regulatory category. Where the regulations apply, the manufacturer still has to demonstrate that the relevant requirements have been met. What AM changes is the nature of the manufacturing process and, consequently, some of the evidence required to support that demonstration.

This matters because a metal additively manufactured component is not defined by its geometry alone. With processes such as laser powder bed fusion, feedstock condition, machine performance, process parameters, build orientation, position within the build and subsequent thermal processing can influence the properties of the finished part. ISO/ASTM 52909:2024 specifically addresses the evaluation and reporting of orientation and location dependence in the mechanical properties of additively manufactured metals.

For fluid power manufacturers, that should change the qualification conversation. A drawing and material designation remain important, but they cannot by themselves describe everything that determines the characteristics of the finished AM component. The manufacturing route becomes an important part of the product definition.

Pressure testing illustrates the problem particularly well. A proof or burst test can provide valuable evidence about the component tested, but many fluid power components spend their working lives experiencing repeated pressure changes. A component surviving its initial test does not, on its own, demonstrate how an internal defect, adverse surface condition or other manufacturing discontinuity might behave after a large number of cycles.

ISO/ASTM 52908:2023 is relevant here because it addresses qualification, quality assurance, post-processing, inspection and testing of metallic parts produced by powder bed fusion. The wider standards framework increasingly recognises that AM quality cannot be established solely by inspecting dimensions at the end of production.

A more defensible approach is to establish control over the complete manufacturing route.

That begins with feedstock and continues through machine condition, the qualified build parameters, component orientation, support strategy, removal from the build platform, heat treatment and any subsequent machining. For a hydraulic component it can also include the finishing of sealing faces and threaded ports, removal of residual powder from internal galleries, cleanliness requirements, dimensional inspection and appropriate non-destructive examination.

BS EN ISO/ASTM 52920:2023 provides a useful framework for this type of thinking. It establishes requirements for industrial AM processes and production sites and defines quality assurance measures along the manufacturing process. Importantly, it is concerned with the production environment and manufacturing process rather than suggesting that successful inspection of one finished component is sufficient to qualify everything that follows.

The significance becomes obvious when production is repeated. Suppose a manufacturer develops an optimised manifold, establishes suitable build parameters, produces test pieces and components, carries out the necessary mechanical, dimensional and pressure testing and obtains satisfactory results. Eighteen months later the same geometry is required again, but it is manufactured on another machine or at another site, using a different feedstock batch and perhaps a revised heat-treatment route.

The CAD geometry may not have changed, but that does not necessarily mean the original qualification remains valid. A robust qualification system therefore needs to identify which variables are significant, what limits are permissible and which changes require review, additional validation or requalification. This is particularly important to the prospect of digital inventories and distributed manufacture. Sending an approved geometry file to another AM machine does not necessarily reproduce the qualified manufacturing process that originally sat behind it.

Internal inspection

Internal inspection presents a related difficulty for fluid power. The ability to manufacture complex internal passages is one of AM’s strongest advantages, yet it removes some of the access available for conventional inspection. Powder removal and internal cleanliness need particular attention because contamination that remains inside a hydraulic component can subsequently enter the system. The appropriate inspection strategy has to reflect the material, geometry, manufacturing process and defects that could realistically occur, rather than relying on a generic inspection requirement applied after printing.

There is another regulatory distinction worth making because it is sometimes confused in discussions about pressure equipment. PE(S)R concerns equipment being placed on the market or put into service and covers its design, manufacture and conformity assessment. The Pressure Systems Safety Regulations 2000, PSSR, concern qualifying pressure systems in use at work and the hazards associated with stored energy. They are not interchangeable regimes.

HSE specifically notes that hydraulic oils are not relevant fluids under PSSR and that hydraulic systems, while operating at high pressures, are not covered by these regulations. Pneumatic pressure systems containing compressed air can, by contrast, fall within PSSR where the applicable conditions are met.

Manufacturers also need to distinguish equipment requiring conformity assessment from equipment falling under Regulation 8 of PE(S)R. Equipment and assemblies within the regulations but at or below the specified classification limits must be designed and manufactured in accordance with sound engineering practice to ensure safe use and be accompanied by adequate instructions. Unless another applicable piece of legislation requires it, such equipment must not carry a UKCA or CE conformity assessment marking under PE(S)R.

For equipment requiring conformity assessment, Great Britain permits relevant products to use either the UKCA or CE route, provided the applicable requirements are satisfied. Recognition of CE marking for pressure equipment in Great Britain has been extended indefinitely. Where independent third-party assessment is required, however, the body involved matters. UK Approved Bodies and EU Notified Bodies have different roles depending on the conformity marking route being followed. This is something an AM business entering pressure equipment production needs to establish early, rather than attempting to resolve once the component has already been designed and validated.

Standards development is meanwhile moving closer to the particular issues raised by AM pressure components. Work on EN 13445-14, covering additional requirements for pressure equipment and pressure components fabricated using additive manufacturing methods, remains in development. BSI’s standards development programme currently records the project in comment resolution. It should therefore not be treated as a published standard that solves today’s compliance questions, but the work itself is significant. It demonstrates that the relationship between AM process control and pressure equipment manufacture is receiving specific standards attention.

None of this makes additive manufacturing unsuitable for hydraulics or pneumatics. Quite the opposite. Fluid power contains applications where the freedom to redesign internal passages, consolidate components and remove manufacturing constraints offers unusually tangible benefits. The danger is assuming that because AM can manufacture a geometry that conventional machining cannot, qualification can somehow be reduced to proving that the finished shape is correct and that the first few examples hold pressure.

A manufacturer considering a production AM pressure component should instead decide at the development stage what constitutes the qualified product and process. That means defining operating conditions and credible failure modes, establishing material and process controls, determining the required inspection and test evidence, identifying the applicable regulatory route and deciding what changes would require revalidation. Where third-party conformity assessment is applicable, early discussion with the appropriate body is likely to be considerably more productive than presenting it with an already frozen design.

There is a useful change of perspective here for the fluid power industry. The challenge is not really how to certify a 3D-printed manifold. It is how to establish a repeatable and adequately documented manufacturing route that produces a component with known characteristics and supplies the evidence required for its particular application.

Once additive manufacture reaches production, the digital model is only one part of that evidence. The feedstock, machine, process parameters, post-processing, inspection and validation history matter as well. Treat those as part of the engineering from the outset and qualification becomes something that can be designed into an AM programme. Treat them as paperwork to be assembled after a successful print, and some of additive manufacturing’s most attractive fluid power applications may prove much harder to industrialise than they first appeared.

Reader note: This article is provided for general information and discussion purposes only and should not be relied upon as engineering, regulatory, compliance or legal advice. Reasonable care has been taken to ensure that the information is accurate at the time of publication (September 2026), but regulations, standards and guidance may change and their application will depend on the particular equipment and circumstances. Readers should therefore verify current requirements from the relevant legislation, standards and authoritative sources and, where appropriate, obtain advice from suitably qualified specialists or the relevant conformity assessment body before making design, manufacturing, safety or compliance decisions.

Pictured: Additive manufacturing allows complex internal flow paths to be incorporated into fluid-power components, but qualification extends beyond the geometry to the material, manufacturing process, post-processing and inspection.