Medical air support – striking a balance

André Farysch of BOGE Compressors explains how to make sure compressed air systems are energy efficient and cost effective for hospitals

Safety comes first where human lives are at stake. But, even in a highly-regulated environment like a hospital, the compressed air systems used must also be energy efficient and cost-effective. André Farysch, business unit manager for the medical division at BOGE Compressors, explains how to strike the right balance between these three competing demands

Delivering pure air to hospitals and other medical facilities is far more complex than installing a conventional compressed air supply in, say, a factory. Why? Because the highest priority for medical air is patient safety, and that requires an assurance that breathing air is available 24 hours a day, seven days a week without fail. Without fail means no loss of air supply to the system under any circumstances, and that means guaranteeing outstanding reliability.

By designing compressed air systems with at least triple redundancy, the risk of failure is virtually eliminated

But the challenges for air used in the healthcare sector don’t end there. The system must also be energy efficient and offer the best-possible cost effectiveness. And it must comply with a host of stringent regulations governing the specification and use of medical equipment.

Hospitals contain two distinct types of air that are required to be generated by a compressed air system – medical air for use with patients and medical equipment, and technical air to maintain the facility.

It’s important that the systems supplying this air are kept apart. In other words, air supplied by compressors for the benefit of patients can’t be used for maintenance purposes, or vice versa. To guarantee breathing air is available at all times, redundancy is built into medical air systems by providing multiple sources of compressed air. This ensures that, should one compressor be out of action for, say, maintenance, and a second breaks down at the same time, then there are back-ups able to supply a hospital’s maximum air requirements. Indeed, it’s not uncommon for installations to have three or even four compressed air systems in place, each able to satisfy 100% of the demand placed upon them.

One of the most-critical design criteria for a hospital compressed air system is the calculation of the hospital’s 100% compressed air demand. This is defined as the amount of air that would be required if every conceivable application was being used at the same time, even though this is unlikely to ever actually happen in a real-world situation. By designing compressed air systems with at least triple redundancy, the risk of failure is virtually eliminated.

A compressed air system for a hospital typically comprises at least three compressors, a control system to co-ordinate their operation, and the delivery mechanisms, including pipework.

There is little difference between compressors used for medical air and those for general air in a hospital. Indeed, the compressors themselves are not classified as medical devices; this means there is no restriction on the type of compressor used in healthcare facilities.

The main difference between compressed air systems for medical and maintenance purposes is in the software that controls them. Indeed, the system as a whole, rather than its individual components, is classed as a medical device and the gas that it delivers is classified as a medicine.

Effective filtration is critical to the delivery of 100% medically-pure air. BOGE’s systems, for example, operate a seven-stage filtration process with two chambers to dry the compressed air and remove harmful substances in a ‘pressure swing’ process.

Integrated filter and purification/catalytic stages treat the compressed air efficiently and reliably according to the stringent specifications for the supply of medical compressed air.

The filtration must have at least two redundancies to ensure the output of medical air is delivered to a defined purity, even if one stream is offline for maintenance or has a fault. The filtration process itself must ensure that any residual oil, dust, and humidity are removed as well as limiting the ambient concentration of carbon monoxide.

So, when we design a compressed air system for medical use, we always gear it to the worst-case scenario. That’s why every BOGE compressed air generating system has at least triple redundancy. And compressed air buffers and medical compressed air treatment systems are designed with at least dual redundancy to guarantee a reliable supply no matter what the circumstances.

After all, the primary aim of progressive medical compressor manufacturers is the same as the hospital staff themselves – the best possible care and welfare of those who are receiving treatment or in recovery.

Four critical energy-saving measures

  • Reduce the idle time of the compressors by sizing the system accurately and employing inverter-driven units to vary the speed of the compressors
  • Introduce heat recovery. A heat recovery device like the BOGE DuoTherm can recover up to 80% of the heat energy so that it can, for example, be used for space heating
  • Compressed air needs drying, an energy-hungry process, so it’s vital that this operation is optimised. Intelligent load-dependent controlling of the medical dryers means that up to 50% of the regeneration energy can be saved. This works by continuously adapting the ratio of drying and regeneration to the current moisture status
  • Using simulation software helps in the design of a compressed air system, ensuring the correct compressor technology in the right size system to deliver the best solution, particularly when it comes to energy consumption

A focus on cost-effectiveness

A medical system not only has to deliver the right level of redundancy and make breathing air available, but it must also keep the total cost of ownership – including maintenance and energy consumption – as low as possible. That means specifying the right technology for the job to satisfy current and possible future needs.

A modular system has the benefit of bringing efficiencies both in initial cost of investment and throughout the system’s lifecycle

A modular system has the benefit of bringing efficiencies both in initial cost of investment and throughout the system’s lifecycle.

In the standard control configuration, each compressor will have its own compressor control to govern its operation. If, for example, a compressor needs to run even when it has reached maximum pressure, it features technology which unloads internal systems.

Modern control systems are smarter; they can monitor the internal pressure and as soon as this is unloaded the compressor can be switched off. This saves money as running idle costs 30% of the rated power, even when no compressed air is produced.

For medical systems, BOGE uses a master control system that can control the entire compressor system. By monitoring the system and understanding the demand for compressed air, the control system can decide how many compressors are required, and which of the compressors needs to be running. It can also adjust performance to compensate if one compressor is offline for maintenance or through a fault.

Each single compressor control monitors the master control system and will take over if the master control fails or reacts too late. All this information is provided to the monitoring system of the hospital.