APPLICATIONS The most immediate consideration in the UK is compliance with the Pressure Equipment (Safety) Regulations 2016. These regulations implement European Directive 2014/68/EU into UK law and remain the basis for assessment of pressure parts at or above 0.5 bar. Any item that qualifies must undergo conformity assessment and be appropriately marked before being placed on the market. In Great Britain, manufacturers may apply either CE or UKCA marking. In Northern Ireland, CE continues to apply under the relevant rules. The implication is that design, material selection, production route, and final inspection must all be documented to demonstrate compliance. From a technical perspective, there are several issues which are particularly relevant to hydraulics and pneumatics. Porosity is the first, as it affects both leak tightness and fatigue performance under cyclic pressure. Additive processes can leave lack of fusion defects or small internal voids. The accepted way to address this is to apply post-processing such as hot isostatic pressing, followed in many cases by machining of critical surfaces. This combination reduces internal defects and ensures that sealing areas meet the dimensional and surface finish requirements needed for reliable O-ring or metal-to-metal contacts. Cleanliness is another critical issue in fluid power applications. Any loose powder trapped in internal passages represents a contamination hazard to the system. Designers need to provide drain paths or removable sections that allow trapped powder to be evacuated. Cleaning procedures must then be validated, and it is common to use borescope inspection or micro-computed tomography on representative parts. This is not a theoretical concern: contamination control remains one of the most stringent requirements for hydraulic systems, especially in aerospace and offshore sectors. Surface finish of internal channels is also important. While the as-built surface of an additive part is often too rough for efficient fluid flow, various finishing methods are available. Abrasive flow machining, chemical smoothing, and targeted machining can all be applied to improve efficiency and reduce pressure losses. In areas where seals are installed, conventional machining remains the most practical way to achieve the required tolerances. Standards framework The qualification pathway for additive parts is developing quickly. The relevant standards framework begins with BS EN ISO/ASTM 52900, which provides common definitions. More detailed standards exist for feedstock control, machine qualification, and part acceptance. In practice, many companies rely on independent assurance frameworks. Lloyd’s Register has published guidance notes and issues part and facility certification for additive manufacturing, and DNV has developed its own standard for qualification of additively manufactured parts in pressure systems. Both organisations operate in the UK and their involvement can reduce uncertainty when dealing with customers or regulators. Testing remains essential. Non-destructive examination methods are being adapted for additive parts, but they have limitations due to complex geometries. A realistic strategy usually combines non-destructive inspection of critical regions with proof pressure testing on every part and destructive burst testing on a statistical basis. Regulators and independent certifiers expect such evidence as part of the technical file that accompanies the conformity assessment. Technical risk For pneumatics, the technical risk is somewhat lower because working pressures are often reduced. Nevertheless, leakage and cleanliness remain concerns. Polymer additive manufacturing may find a place for low pressure pneumatic housings or fittings, but for pressure-bearing parts the same principles of qualification and testing apply. In hydraulics, where pressures and safety factors are higher, the case for metal additive processes with full post-processing and certification is much stronger. It is also worth recognising the cost and time realities. Additive manufacturing can reduce the number of parts in a manifold and create optimised internal passages, but the production route is not limited to the build itself. Heat treatment, machining, surface finishing, non-destructive testing, cleaning, and certification all add steps. In practice this means additive manufacturing is most competitive where weight reduction, part consolidation, or supply-chain resilience provide a clear benefit. For UK engineers and managers, the conclusion is that additive manufacturing offers genuine opportunities in hydraulics and pneumatics, but only if it is approached with a clear understanding of the regulatory framework and the technical challenges. Compliance with the Pressure Equipment (Safety) Regulations is not optional, and qualification must be based on recognised standards and accepted assurance routes. With these foundations in place, the technology can provide real advantages in performance and supply flexibility, while meeting the demanding requirements of modern fluid power systems. 30 HYDRAULICS & PNEUMATICS September 2025 www.hpmag.co.uk Additive manufacturing is steadily moving from a prototyping technology into a production method for components in demanding sectors. For fluid power engineers in the United Kingdom, the interest lies in the possibility of lighter, more compact hydraulic manifolds, bespoke pneumatic housings, or rapid production of spares. The attraction is clear, but the barriers are equally important to understand, especially where components fall under the legal requirements for pressure equipment. H&P reports. The realities of additive manufacturing for hydraulics and pneumatics
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