Quenchline exit plenum for a cyrogenic unit |
|||||||
申请号 | US11180604 | 申请日 | 2005-07-14 | 公开(公告)号 | US20060185371A1 | 公开(公告)日 | 2006-08-24 |
申请人 | Stephen Trowell; Keith White; | 发明人 | Stephen Trowell; Keith White; | ||||
摘要 | A quench line and exit plenum configuration for a mobile MRI system housed in a transportable trailer includes an exit plenum with deflector plates that direct the quench flow of cold gases upward and away from surrounding objects. In addition, the plenum also includes dual vents to facilitate optimum gas flow and water drainage. The deflector plates are configured to utilize the Venturi effect to create an auxiliary flow of the ambient air to help deflect the flow of cold gases away from nearby pedestrians, when the magnet is quenching, and to enable service personnel to fill the magnet safely while in the vicinity of the exit plenum. | ||||||
权利要求 | What is claimed is: |
||||||
说明书全文 | The present invention is directed to a quench line and plenum arrangement for a mobile MRI system of the type which is generally housed in a trailer. Magnetic Resonance Imaging (“MRI”) systems require the generation of an extremely strong magnetic field, which is generally measured in units referred to as “Tesla”. (One Tesla=10,000 Gauss.) In order to achieve a magnetic field of this strength, it is generally necessary to employ superconducting magnets, which include coil windings that are cooled to temperatures on the order of a few degrees above absolute zero, using liquid helium as a coolant in the form of a cryogenic bath. Aside from the difficulties posed by the intense magnetic field itself, the handling of large quantities of such extremely cold liquid helium poses certain inherent difficulties. One such difficulty is associated with the quenching of the superconducting coils of the magnet. “Quenching” in this context refers to a sudden loss of superconductivity in the wire that makes up the superconducting coils. As the coils start to exhibit normal resistive behavior, they heat up, causing the process to accelerate, so that the liquid helium “boils” off rapidly, releasing the magnet's stored energy in a process that can become somewhat violent. Moreover, the large volume (thousands of cubic meters) of evaporated liquid helium, which is released rapidly via a quench line remains extremely cold, and can cause injury, including “cold burns”, to anyone who comes into contact with it. Asphyxiation is also a hazard. Quenching may be performed intentionally, such as when it becomes necessary to shut down the magnetic field in order to prevent personnel or patient injury, or it may occur spontaneously due to a failure in the magnet system itself or an external influence. In either case, it is apparent that the manner in which the resulting discharge of evaporated helium gas is guided and vented to the exterior is extremely important. In particular, the design of the so-called “quench line” is significant, and must be configured so as to minimize the risk that people, animals or damageable objects will come into direct contact with the gas discharge. Moreover, it is also essential that the quench line be capable at all times of venting the evaporated helium at a rate that accommodates the rapid boiling in the cryogenic unit. If, for example, the quench line is inadequate or becomes constricted or clogged, a particularly dangerous situation can result. One such possibility is that moisture accumulates in the quench line, blocking it and causing helium gas to be vented into the examination area, which can result in asphyxiation. Mobile MRI systems of the type mentioned previously are subject to all of the considerations described above, and in addition present their own unique design problems as well. For example, there is an increased risk of a spontaneous quench of the cryogenic cooling system due to “jostling” of the mobile MRI device between field locations. In addition to mechanical vibrations, systems are exposed to varying electromagnetic environments during transport which can also induce a quench. In addition, the necessity for movement of the trailer along routes populated by other vehicles is also of concern. For example, if the trailer is in a line of traffic, with a bus immediately behind, passengers at the front of the bus on the upper floor might be at risk of personal injury from cold gas in the event of a magnet quench. Similar risks have been identified to personnel working on ladders or raised platforms behind a mobile MRI system which is installed at a site. In order to address safety risks to service personnel, known mobile MRI systems have been designed to be refilled with liquid helium by service personnel located outside and to the rear of the trailer/housing, beneath the quench line exit. To deal with these considerations, the exit of the quench line for mobile MRI systems must meet the following criteria:
Conventional horizontal quench line exits do not direct quench flow gas away from pedestrians or bus passengers. During magnet depressurization and filling, air cooled by the released helium gas could impinge on service personnel beneath the exit grill. If the inner surface of the quench line exit is not angled downwards, condensation will reside in the quench line, with serious consequences if this migrates to the quench valve assembly. Covers have been fitted to the exterior of horizontal quench line exit grills on previous MRI mobile installations, primarily to prohibit the ingress of rainwater. These designs were not favored by trailer manufacturers since appendages to the trailer are limited by road regulations (maximum trailer width), and compact cover designs can lead to large pressure drops for the quench gas flow. Hinged covers over exit grills are not permitted for any MRI installations (mobile or static) within the guidelines provided by Siemens Magnet Technology for quench line design (830-105HB2). In view of the above safety concerns, one object of the present invention is to provide a quench line and exit plenum for a mobile MRI system, which exhibit an improved design with regard to venting of helium gas. Another object of the invention is to provide such a quench line and exit plenum which reduces the risk to individuals close to the trailer when the cryogenic system quenches. These and other objects and advantages are achieved by the quench line and exit plenum arrangement according to the invention, which includes an exit plenum with deflector plates that direct the quench flow of cold gases upward and away from surrounding objects. In addition, the plenum also includes dual vents to facilitate optimum gas flow and water drainage. The deflector plates are configured to utilize the Venturi effect to create an auxiliary flow of the ambient air, which combines with the cold gas flow, and helps to deflect it away from nearby pedestrians when the magnet is quenching, and to enable service personnel to fill the magnet safely while in the vicinity of the exit plenum. The secondary vent 11b and angled lower surface 11d enable effective water drainage from the plenum ( The plenum according to the invention was fitted to a mobile system, built by Medical Coaches, Oneonta, N.Y. It was mounted inboard so that there were no appendages to the rear of the trailer ( The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof. |