Custom pneumatics upgrades oxygen concentrator

Edited by K. Korane, contributing editor

The customized air valve from Bosch Rexroth was designed to meet Nidek’s requirements for compact size, light weight, precise oxygen flow, cost-effectiveness, and most of all, reliability.

Nidek Medical Products, Birmingham, Ala., makes oxygen concentrators that are widely recognized as setting the global standard for performance when it comes to delivering medical oxygen to patients. The company’s Nuvo concentrators are used in homes and small clinics — locations where on-site medical resources are limited, making reliability critical.

To meet the growing demand for outpatient and at-home care, Nidek recently rolled out a smaller, lighter unit — the Nuvo Lite — that offers the traditional advantages of precise oxygen delivery and high reliability in a smaller, lighter, and more economical package.

The product rollout, however, had to meet a precisely orchestrated schedule for creating a prototype, testing the device, and ramping up production in conjunction with FDA medical-device listing. A delay in submitting the new version for FDA approval would also delay market introduction and create potential supply-chain difficulties. That meant a narrow window for designing and manufacturing the components needed to create Nuvo Lite on-schedule.

Heavy demands for the valve
One of the most important components — and challenging to develop — was the solenoid-operated, pneumatic directional-control valve that helps turn ordinary air into 95% pure oxygen for respiration. Nuvo Lite technology depends on this valve to deliver a precise amount of oxygen each cycle and, equally important, to continue functioning even if the valve encounters particulate contamination.

The concentrator works by compressing filtered, ambient air and sending it to the directional-solenoid valve. The valve then directs compressed air into one of two molecular sieve beds. These adsorb nitrogen at pressure but let oxygen pass. The oxygen-enriched gas then flows to a pressure-reducing valve and through a bacterial filter located near the outlet fitting.

As one adsorbent column generates oxygen, the other purges trapped nitrogen from the previous cycle. This regeneration process can pose problems because particles from molecular sieves can enter the directional valve. The control valve must deliver a precise amount of oxygen each cycle and work even if subject to particulate contamination. Should the valve fail, the concentrator shuts down, forcing patients and clinicians to use backup oxygen supplies.

This makes reliability and contamination resistance a must. But the directional-control valve also must ensure precise oxygen delivery to patients and handle frequent cycling (ordinary air in, oxygen out, approximately every 13 sec). And it had to be lightweight, tailored to the Nuvo Lite design, cost-effective, and available on demand.

Off-the-shelf valves were quickly eliminated from consideration due to cost and specialized engineering and production demands. That meant exploring a customized valve.

With experience in valve engineering, and in the medical device industry in particular, Bosch Rexroth – Pneumatics, Lexington, Ky., was one of several manufacturers Nidek engineers considered to deliver a custom solution.

Coming up with a solution
According to Nidek engineers, Rexroth developed a fully integrated, electronics-driven, compact valve based on proven technology, yet tailored to the exact specifications of the Nuvo Lite. This eliminated the headache of adjusting the concentrator design and production schedule to the capabilities of the valve. In addition, Rexroth technicians were able to meet a series of challenging deadlines, which included designing and creating a prototype for FDA submission, plus testing and production, within several months.

The Nuvo Lite concentrator precisely delivers medical oxygen at 0.125 to 5 lpm with the help of a contamination-resistant air valve.

But acceptance ultimately hinged on the valve itself meeting the challenge of Nidek’s application testing. That meant functioning flawlessly under actual operating conditions — and outperforming a range of other valves from other global suppliers. During this test, when particles of sieve material eventually entered the Rexroth directional-control valve, it continued to operate – and so did the Nuvo Lite—unlike other valves tested. It proved to be the best suited and most reliable of all the products tested, according to Nidek engineers.

The customized Rexroth valve is also light, which contributed to trimming the new design to only 30 lb, about 20 lb less than conventional units. This is important in a medical device that is frequently transported in cars by an individual person or moved around by a patient.

Rexroth also proved capable of handling logistical demands – another aspect of production that was crucial to a successful launch. Nidek production lines were geared up to begin delivering product as soon as the Nuvo Lite met regulations approved by various agencies in the U.S. and around the world without creating a backlog of inventory. This required a steady supply of components exactly when needed for smooth and rapid manufacturing – with little or no excess inventory.

Rexroth’s experience with lean manufacturing ensured a dependable supply of valves to the production line. Worldwide shipping of the Nuvo Lite was on schedule, providing unrivaled reliability and performance to patients needing medical oxygen.

Information for this article was provided by Bosch Rexroth Corp., Pneumatics Div., (859) 254-8031, www.boschrexroth-us.com/BRP. For more details on Nidek Medical Products, call (205) 856-7200 or visit www.nidekmedical.com.