Mechanical pumps pump size

Combinations of steam jet ejectors operating in conjunction th mechanical pumps can significandy improve the overall s) stem efficiency, especially in the lower suction pressure torr range of 1 torr to 100 torn They can exist beyond the range cited, but tend to fall off above 200 torr. Each system should be examined indhadually to determine the net result, because the specific manufacturer and the equipment size enter into the overall assessment. Some effective combinations are ... 

Although the thermal efficiencies of various mechanical vacuum pumps and even steam jet ejectors vary with each manufacturer s design and even size, the curves of Figure 6-34 present a reasonable relative relationship between the types of equipment. Steam jets shown are used for surf ace intercondensers with 70°F cooling water. For non-condensing ejectors, the efficiency would be lower. 

System component Filter beds, media, backwash mechanism, pumps, and controls. The filter beds were sized for hydraulic loading of 81 L/min/m2 (2gpm/ft2). 

Into a size 6A porcelain boat (88 X 13 X 10 mm.) is placed 10.0 g. (0.0113 mol) of Ag2ReBr6 (as much as 15 g. may be processed readily), and the boat is positioned near the sealed end of a 25 X 300 mm. Pyrex tube fitted with an inner 29/44 S.T. sleeve joint. The tube is connected to a mechanical vacuum pump (capable of reducing the pressure to ca. 50 p) via either a trap cooled by liquid nitrogen or a trap cooled by a Dry Ice-isopropyl alcohol slush, which is in turn connected to an 11-mm. Vycor combustion tube packed with copper gauze and maintained at 600° by means of a furnace. (Either protective system between the tube and the pump will serve to remove bromine, one of the reaction products.)... 

Fluid mechanics. Pump heads, rates, and power piping sizes column tray layout and sizing heat-exchanger tube and shell side bafliing and sizing... 

On the basis of these requirements, a study was initiated by the United States Army Institute of Surgical Research (USAISR) to evaluate nine commercially available tourniquets for applicability to combat use. Of these nine only the seven that were within the mechanical specifications of size and weight were tested. In a report covering the study issued in 2005, Walters et al. concluded that three of the candidate tourniquets met the requirements, the Combat Applications Tourniquet (CAT), the Special Operations Forces Tactical Tourniquet (SOFTT), both are windlass type tourniquets, and the Emergency Military Tourniquet (EMT), which is a hand-operated bulb pump pneumatic type tourniquet. These three were rated as 100% effective in blood flow occlusion. Of these three, the EMT was judged as the least painful, but it was recommended only for medical personnel and not for the field... 

As stated, a medium mechanical pump can only have speeds of 11.7-25 liters/ sec. However, a comparable-sized diffusion pump can achieve speeds of up to 30 liters/sec, but with 2-3 times the vacuum capacity. It is easy to see why the assistance of an auxiliary pump is required to effectively obtain vacuums beyond 10 4 torr, such as those in the high or even ultrahigh-vacuum range. Although it is possible to obtain larger and faster mechanical pumps, the cost/efficiency ratio starts to go down and it becomes less expensive to use a mechanical/diffusion pump combination. For more information on pumping speeds, see page 347. 

If you have a glass system and can achieve a vacuum between approximately 10 to approximately 10"3 torr, then you can use a Tesla coil (sometimes called a sparker ) to look for moderate-size leaks. Because this range is the vacuum range of a mechanical vacuum pump, the Tesla coil provides an excellent tool for examining such systems. 

Compute the size of the connection pipe. In usual vacuum-pump practice, the pressure drop in pipes serving mechanical pumps is not allowed to exceed 20 percent of the inlet pressure prevailing under steady operating conditions. A correctly designed vacuum system, where this pressure loss is not exceeded, will have a pump-down time which closely approximates that obtained under ideal conditions. 

Since the introduction of metered-dose inhalers, nasal solutions have increasingly been formulated as nasal sprays. Initially, aerosol-based systems containing chloro-fluorocarbons were employed however, the Montreal Protocol put an end to this. Thereafter, mechanical pumps or actuators were employed to deliver nasal formulations as sprays. These devices, using actuators, can precisely deliver as little as 25 pL and as much as 200 pL of a formulation. However, various factors must be considered in formulating the spray these include viscosity, particle size, and surface tension, all of which may affect the accuracy of the dose administered. 

The connection of the pumping system to the manifold should be by way of a large-size trap (Fig. 3-10), which is cooled with liquid nitrogen in order to remove contaminants. In operation, the mechanical pump is started first, the pressure in the system is reduced below 100 /X, and the diffusion pump is turned on. Once a low pressure has been attained, the pumps are not ordinarily shut off unless this becomes necessary for maintenance or repair. If the system to which the pumps are connected is to be raised to atmospheric pressure regularly, a bypass system should be supplied so that the system may be evacuated... 

The heart is an electromechanical system, in which mechanical pumping function is initiated and coordinated by automatic rhythmic cardiac electrical activity. Transient electrical disturbances m this activity (cardiac arrhythmias) can immediately cause death. The implantable cardioverter defibrillator (ICD) is a medical device that can be implanted in a human body and will automatically detect and treat cardiac arrhythmias. Mirowski et al. [1] first reported on a demonstration of a functioning ICD in 1970. In his demonstration, he induced a fatal ventricular tachyarrhythmia in a dog. The dog was then successfully and dramatically rescued by the automatic operation of a previously implanted ICD. The first report of successful ICD implantation in humans soon followed [2]. In subsequent decades, advances in ICD technology have reduced ICD size from more than 200 cm, originally, to as httle as 25 cm, while markedly improving functionality, reliability, and longevity. ICDs are now considered as standard of care for patients at risk for ventricular arrhythmia and are implanted in more than 150,000 patients per year in the United States alone [3]. 

Discussions of allometry (e.g., Schmidt-Nielsen, 1984) focus on the mechanical consequences of size differences. The skeletal system changes with increased size because of the added stress of increased weight. The heart increases with size because of the increased demands of pumping a greater volume of blood. In these examples, the functional consequences of scaling seem obvious. When the number of receptor neurons contributes to the performance of a sensory system, the effect of changes in size seem less clear. This conundrum had not escaped earlier researchers who wondered how adult humans, with an olfactory epithelial surface area of lOcm, are considered microsmatic while a rabbit, with 9.3cm of olfactory epithelium are considered macrosmatic (Moulton and Beidler, 1967). 

Low-pressure plasma systems operate at 13 Pa to 133 Pa (0.1 Torr to 1 Torr) with a continuous gas flow into the reactor. Therefore, the vacuum system must be able to maintain this pressure/flow regime. However, the moderate vacuum level does not require sophisticated pumps. Two stage mechanical pumps are satisfactory. The pump package is usually sized to allow pumpdown in less than 1 minute and to maintain an inlet gas flow of 50 cc/min to 1000 cc/min, depending on the size of the reactor. The most expensive part of the vacuum system is the perfluorinated lubricant required if an oxygen plasma is to be used. 

The turnings are then placed in a stainless-steel, perforated basket of sufficient size to take the whole batch, i.e. about 36 in. deep by 24 in. diameter. The basket is placed inside the vacuum distillation retort shown in Fig. 6.11. This is about 8 ft deep and is divided into a lower, mild-steel portion, heated by a furnace, joined by a cooled neoprene gasket to an upper, stainless steel portion, which acts as a condenser. The furnace is in the form of an evacuated bell with a rating of 50 kW, although only about 20 kW is used in a distillation. The retort is capable of evacuation to a pressure of 100 /Li mercury equivalent by means of an oil diffusion pump, and the furnace can be evacuated to 1 mm mercury equivalent by a high-capacity mechanical pump, which serves five furnaces. 

Mechanical vacuum pumps are more efficient than steam jets. Typical calculated efficiencies of various pumps are shown in Figure 23-10. These curves represent estimates, because efficiency is a function of pump size and because there are significant variations in the efficiencies of pumps offered by different manufacturers. However, Figure 23-10 is generally representative of vacuum pump efficiencies. 

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