Document KJE8XbJDLdEEnY39Lpr685mbr

670 CHAPTER 63 K. J&nis: Bibliography on Low Temperature Characteristics of Steels 1904-1954 (The International Nickel Co., New York). A. B. Kizuel, W. Krafts, and J. J. Egan: Fine grained steels for low temperature pressure vessel service {American Institute of Minma and Metalatrgical Engineers Transactions, Vol. 125,1937). V. N. Krivobok and A. M. Talbot: Effect of temperatures on the mechanical properties, characteristics and processing of aus- tenic steels (Proceedings, American Society for Testing Materials, VoL 50, 1950). E. R. Parker: Brittle Behavior of Engineering Structures (John Wiley and Sons, New York). 1962 Guide And Data Boole J. A. Rinebolt and W. J. Harris, Jr.: Effect of alloying elements on notch toughness of pemlitic steels (American Societyfor Metals, P. L. Teed: Properties of Metallic Materials at Lota Tempera tures (Chapman and Hall, Ltd., London, 1950). J. M. Zambrow and M. G. Contana: Mechanical properties, including fatigue, of aircraft alloys at very low temperatures {American Society for Metals Transactions, Vol. 41, 1949). W. T. Ziegler: Properties of metals below 300F (Refrigerating Engineering, August 1952, p. 848). CHAPTER 64 MEDICAL APPLICATIONS Refrigeration in laboratory Medicine, Laboratory Instruments Using Refrigeration, Refrigerated Centrifuge, Freezing Microtome, flection Microscope, Liquid Scintillation Counter, Warburg Apparatus, Freeze-Dry Apparatus, Principles and Systems, Tissue Banks, Virus Preservation and Storage, Blood Banks, Pathology and Anatomy Laboratories, Refrigeration in Clinical Medicine N outlining refrigerating applications in laboratory and I clinical medicine, it is evident that the majority of the equipment used does not vary in any spectacular fashion from that used in any other field. The great emphasis lies in greater stringency of control and closer scrutiny of the permissible temperature variation, since much of the material entrusted to refrigeration preservation or action in the medical area either has an acute bearing on human life, or has its origin from human or ftnimol sources that m-iltft it irreplaceable or highly expensive. By far the most common piece of refrigerating equipment in any medical area is the standard household refrigerator, varying in size within die limits of such equipment and with the same special features of shelving or freezing compartment that make the instrument attractive to any buyer. Specially designed re/rigeratore forlaboratories do exist and are listed in catalogs of laboratory and hospital equipment, but the dif ference in cost above the standard household appliance pre cludes their use in the average medical facility. Following closely in standard medical refrigerating equip ment is the walk-in unit, which may vary in size from the 500 cu ft range .to much larger construction. These areas for preservation of either larger objects such as anatomic cadav ers, or many smallw objects such as unite of banked blood, are fitted with exactly the same type of cooling equipment necessary to meet specifications of any such areas outside die medical scope. Walls, floors, and ceilings,involve the same general principles of construction and insulation familiar to everyone interested in this field. These principles are equally applicable, and indeed die desired equipment is not unlike other cold storage units used industrially in preservation and handling of many perishables. Lastly, there are specially constructed instruments involv ing refrigerating principles such as the cold centrifuge, freez ing microtome and tissue freeze-dry apparatus which are more closely and specifically related to medicine and its allies in the scientific realm, but the cooling principle is the same and construction peculiar to the instrument is but a variation on a general theme that enables a specific temperature to be produced and maintained in a specific area. The important variant that distinguishes the major uses of commercially Hpaign^H refrigeration in the medical field is the wide application of recording thermometers and alarms. In certain medical areas as many as three or four control and recording devices may be integrated in one piece of refrigerat ing equipment and a margin of variation of perhaps only one or two C deg will be the crux of the whole application. Thus in a blood storage refrigerator, systems of recorders both without and within the cooled area, an alarm system of lights or bells or both, and fans to insure air circulation and a con stant temperature throughout a shelved space may be added to an insulated walk-in or large commercial refrigerator. Consequently, a medical refrigerating application calls for concern in exact specifications and a knowledge of ancillary . equipment that informs the user at all times that his specifica tions are met and are continuing to be maintained. Equip ment failure is probably no more common or less common in medical facilities than in any other area of refrigeration use, but the responsibility resting on this refrigeration may be somewhat greater t.han the tangible considerations of cost. A recent article1 by Gage describes the overall refrigeration anH air-conditioning facilities of one major medical institu tion, pmphftair.tng the applications of refrigeration to the building itself. The above commentary on medical applica tions is well supported by Gage both from the standpoint of the equipment described and the emphasis on controls, alarmt and automatic sequence-changing devices which supply a comfortable reserve in areas where equipment failure would prove most critical REFRIGERATION IN LABORATORY MEDIONE General Refrigeration Applications Surveys of clinical laboratories, whether private, in hos pitals, physicians' offices or research areas such as large medical centers, will reveal wide use of standard household refrigerators and freezers, from the small apartment site up to the double-door 17 cu ft box. The majority of this equip ment will be used for three main reasons: to preserve and store by simple cooling or freezing for bacteriostatic action, various sera and biological products, either liquid or dried, *nd common specimens of blood, urine, etc., until proper studies may be mode or confirmed; to preserve by cooling or freezing, for reduction of chemical reaction, various reagents used in the laboratory testing of-specimens mentioned; and the manufacture of ice for use in procedures demanding ice cooling-baths. This last is generally a function of biochemical laboratories, and the common refrigerator ice cube facilities may be replaced by an ice-making machine if the demand warrants. As indicated, these refrigeration needs are ade quately met by common household units, so that materials of one sort or another are both cool and readily accessible. If the maintenance of sharply critical temperature is also expected of these refrigerators, the most dependable device is a simple spring wound seven-day recording thermometer, which can be placed on a shelf in a convenient location within the unit and is easy to maintain and service. The chart is re placed weekly, *nH forms a permanent record of the opera tion of the cooling unit. This is of great value if there are power or mechanical failures which may be corrected without" the knowledge of those using the refrigerator. While the insulation will prevent sudden temperature rises, variations beyond critical limits, both high and low, may have made the material dependent on this critical refrigeration an immediate total loss. Since the recording thermometer is moderately high priced, the purchase and use of such instruments is tempered by the value of the refrigerator contents or by the necessity 671