Engineering Springs for the Next Generation of pMDIs with Low-GWP Propellants

The pharmaceutical industry is undergoing a significant transition as pressurized metered-dose inhalers (pMDIs) move toward low-global-warming-potential (LGWP) propellants such as HFA-152a and HFO-1234ze(E). This shift, driven by the U.S. AIM Act and similar global regulations, is essential for sustainability – but it also brings significant engineering challenges.

LGWP propellants have different vapor pressures, densities, and chemical profiles than legacy HFA-134a or HFA-227ea. These changes impact every aspect of pMDI performance – especially the valve system and the springs inside it. Factors such as dosing uniformity (DDU), actuation force, chemical compatibility, and lifetime stability must be re-engineered to maintain patient safety and regulatory compliance.

RPK Medical’s solution: Precision-engineered springs for LGWP pMDIs

Our engineering teams work closely with OEMs and device developers to deliver custom spring designs that meet the unique demands of LGWP-based inhalers:

• Optimized spring constants, preload, and geometry – including conical, barrel, and helical configurations – to match new pressure profiles and maintain consistent actuation force throughout the product’s life.
• Advanced material selection – from 17-7PH and 316L stainless steels to Elgiloy® and Hastelloy® – for enhanced corrosion resistance and ultra-low extractables in the presence of new co-solvent blends.
• Surface finishing for performance and cleanliness – precision passivation + electropolishing to improve corrosion resistance, control surface roughness (Ra), and reduce particulate generation; optional shot-peening for fatigue life optimization.
• Dimensional and fatigue validation under real-world LGWP conditions, including stress relaxation, creep testing, and performance verification across temperature extremes and propellant chemistries.
• Integration with valve seat design to ensure compatibility between spring force, seal integrity, and actuator geometry, minimizing dosing variability over the product’s lifetime.
• Special cleanroom packaging – customized to the client’s assembly process, preventing tangling and ensuring springs arrive contamination-free and ready for integration.

From concept design and prototyping to high-volume manufacturing, RPK Medical provides a complete spring engineering and production solution. We integrate decades of spring manufacturing expertise with in-depth knowledge of drug delivery requirements to ensure your pMDI devices are ready for the regulatory, performance, and sustainability standards of the future.

Your pMDI innovation starts here. Contact us to learn how RPK Medical can help you meet the challenges of the low-GWP transition with confidence.