Pumps

Recommendations on the choice of pumps
In the further pumping system when the pressure in the established and maintained at a certain level, there is a steady flow of gas. Steady flow of gas will be, for example, in the case when the pumped volume is allocated or accumulate it from the outside is the same amount of gas during this time is removed from the expansion pump system.

Design of a expansion unit, usually begins with the selection of high-expansion pump, which largely determines the speed of pumping system when the Taco Circulator Pumps & Flanges is its inlet can be directly attached to the Grundfos Pumps & Flanges without any pipeline or by using a relatively short and broad pipeline. As an example, expansion systems, in which the object can be pumped directly attached to the pump, it should be expansion furnaces for various purposes, equipment for the calcination of metal parts by high frequency currents to their outgassing and devices for cathode sputtering, coating under expansion, etc .

In the case where the pumping of any appliance is accompanied by intense heating of its parts, the speed of the pump is often chosen on the basis of the required time of degassing. To determine the rapidity of dilution expansion system in this case it is necessary to calculate the total amount of gas (in liters or cubic meters. Centimeters) allocated from the surface of glass or ceramic parts and the thickness of the metal and cause that amount to the pressure and temperature, which is pumped out, and divided by the required time of degassing.

Calculating the speed of expansion expansion system and the conductivity of the connecting pipeline, it is easy to calculate how quickly action must have the Little Giant Pumps. Need to pump managed to pump off gases or you may be increasing pressure in the device, which significantly affects the process of gas recovery. It should be borne in mind that gas separation is often irregular (peaked, depending on the speed of rise of temperature), so the pump should be chosen with some margin performance.

With regard to pre-expansion pump, designed to work together with the high expansion pump, by securing the mainly two requirements:
1. Creation of dilution required for the normal operation of high expansion pump.
2. Rapidity of the pre-dilution pump at permissible outlet pressure must be at least sufficient to remove the gas ejected by high-expansion pump.

If pumped device attached to the pump through the pipeline with a narrow waist, the diameter of which is usually chosen from the conditions of comfort soldering device after evacuation, it is essentially the speed expansion expansion system in this case is mainly determined by the speed of the pump is not, and bandwidth of the narrowest part of the pipeline (banners). Since any of the used pumps usually have fast action, several times the bandwidth of the neck, in this case, the high expansion pump is selected with such rapidity that the utilization rate of the pump was possible maximum.

Steady flow of gas has also been under continuous pumping of such devices as electron microscopes, mercury rectifiers, collapsible generator tubes, mass spectrometers, etc., which is necessary to maintain the lowest possible pressure at steady rate of leakage and outgassing. Since these devices are mostly made of metal and have welded seams, as well as rubber or metal seals, it should be borne in mind that demountable expansion systems of this kind are never completely sealed, and the penetration of gas through the leak creates an additional burden on the pumps.

For example, through a hole with an area of only 0.0003 mm 2, enters the apparatus 0.1 g of air per hour. When choosing the size of the connecting plumbing pipeline in stationary equipment to pump large volumes should also be guided by considerations of efficiency. The presence of high-expansion communication may reduce the speed of the pump by 40-60%, while in nizkovakuumnyh communications should not be allowed to reduce the speed of the mechanical pump more than 5-10%.

The fact that the mechanical pumps are much more expensive than ordinary communication, usually consisting of pipes with a diameter of 20-60 mm. With regard to the cost of steam jet pump, it is approximately equal to a high-value communications, typically consisting of an expensive high-expansion valve and a nitrogen trap, a significant increase in overall dimensions are not appropriate.

As already indicated, in the case when using a expansion pump removes the bulk of the gas and pressure in the system quickly falls, there is a so-called quasi-steady flow, as exemplified by the process of pumping gas from atmospheric pressure to ultimate expansion of values created by the mechanical pump . The choice of a mechanical pump in this case is quite simple. For this purpose, based on the total volume of the entire system, select the pump with such rapidity of action, to a certain time could be obtained in the desired expansion.