What is system quenching in regard to medical imaging equipment?
System quenching is when liquid helium or cryogen, used to cool the superconducting electromagnet in most medical imaging equipment, becomes overheated and boils to a gas. This gas is then bled out of the system usually through some sort of external vent. A common cause of quenching is equipment malfunction in the cooling system. Other causes include improper cryogen filling techniques and extreme environmental disturbances.
Why is system quenching a problem for medical imaging equipment owners?
If system quenching occurs too rapidly, the helium may not be able to be bled off to an external vent causing the gas to instead enter into the patient scanning room. This creates a risk of asphyxiation and this is why many scanning rooms have oxygen deficiency monitors.
Aside from patient health risks, system quenching is very costly. To replace the cryogen and bring the superconducting magnet back to working order takes time and is costly. In cases of cryogen loss and magnet damage due to overheating, the best solution is prevention. Not only is the cost of repair great, but there is significant lost revenue opportunities with system downtime. On capital-intensive systems such as MRIs down time is extremely undesirable.
How can a medical imaging facility protect against system quenching?
Dual Chiller System – Redundancy equals certainty
Medical imaging equipment is incredibly expensive to purchase and maintain. A dual chiller system can virtually eliminate risk of overheating and cryogen loss due to chiller failure. As helium becomes more and more scarce, dual chiller systems that preserve cryogen and maximize uptime are more and more economical.
A dual chiller system prevents system quenching due to chiller failure by providing a system backup. Essentially you are running the system at 50% capacity and should one of the units experience a failure there can be a manual or automatic switchover to the backup chiller.
In a dual chiller system, the glycol is not purged from the system in the event of chiller failure, the loop is simply switched over via an automatic valve to the backup chiller. This enables maintenance to be performed on the chiller unit without interrupting MRI operation.
Dual chiller systems are more expensive upfront, but greatly reduce the maintenance costs and downtime on MRIs. There are a number of considerations to be made when determining the cost and value of a dual chiller system.
Emergency City Water By-Pass Chiller Systems – Economical Assurance
Another approach we have employed when a customer is interested in options that will improve the protection of and reduce the maintenance on their medical imaging equipment is the use of a city water by-pass. A city water bypass is a series of solenoid valves that allow for the city water to directly cool the cold head compressor (the machine that moves the primary coolant for the medical imaging equipment) while the chiller is down for maintenance or if an error occurs. City water is typically in the right temperature range to work as a temporary fix while the medical chiller is brought back online.
There are two ways, manual and automatic. For more information on our city water bypass system please click here.
Stop Cryogen Loss
If you are having a problem with cryogen loss due to equipment failure our team of chiller experts would be happy to help you determine the best solution for your unique situation. General Air Products can provide customized dual chiller systems and city water bypass systems for multiple 3 Tesla MRI units in large facilities as well as smaller more economical systems for smaller single machine facilities.