Diaphragm Vacuum Pump

Glass column, diameter 4 cm 50 mL Erlenmeyer flask Rotary evaporator Diaphragm vacuum pump High-vacuum (oil) pump... 

Positive displacement pumps diaphragm vacuum pumps, liquid ring vacuum pumps, rotary vane and rotary piston vacuum pumps as well as Roots vacuum pumps (dry compressing claw and screw pumps are not yet mentioned here but also belong to this group of pumps). 

A diaphragm vacuum pump is an oscillating type of positive displacement vacuum pump in which the wall moving to and fro is a diaphragm (Figure 5.4). Today, diaphragm vacuum pumps have become a popular environment-friendly alternative to water jet vacuum pumps (kinetic vacuum pump) at low and medium pumping speeds especially in chemical laboratories and in connection with pilot... 

Piston displacement driven by electric motor Figure 5.4 Principle of modern diaphragm vacuum pump. 

In accordance with DIN 28 400 (Part 2) a dry compressing vacuum pump is a positive displacement vacuum pump which operates without an oil seal (as the liquid seal). A diaphragm vacuum pump is a dry compressing pump, a type of pump which chiefly has its role in connection with laboratory apphcations. Here the diaphragm vacuum pump replaces the universal laboratory water jet pumps, the water consumption of which and thus the high operating costs due to the generation of contaminated waste water are factors which are not desired. 

The diaphragm vacuum pump which in connection with chemical production facihties is practically of no great significance is not covered here. Information on this kind of pump can be found in [2]. 

Many different materials can be used to build bilayer artificial muscles. Here, for simplieity, we will focus on doped polypyrrole electrogenerated and characterized in presenee of LiClOVcommercial (office) tape bilayer artificial muscles. For that, pyrrole (Fluka) was purified by distillation under vacuum using a diaphragm vacuum pump MZ 2C SCHOTT and stored under nitrogen atmosphere at -10 °C. 

Any commercially available vacuum pump is perfectly fine for the underground chemist s needs but the best kind to buy is a diaphragm pump, which is more resistant to the often-harsh chemical vapors that are sucked through it. Most vacuum pumps cost about 100- 200. However, the stronger the vacuum the better. If a chemist is looking to pull 1mm of Hg (don t ask) like the girls in the chemistry papers do then she can be looking at a turbovac that can run well over 5000. 

The most used mechanical vacuum pumps or compressors are reciprocating, liquid-ring, rotary-vane, rotary blower, rotary piston, and diaphragm. 

Many control problems can be better solved with a diaphragm controller. The function of the diaphragm controller (see Fig. 3.27) can be easily derived from that of a diaphragm vacuum gauge the blunt end of a tube or pipe is either closed off by means of an elastic rubber diaphragm (for reference pressure > process pressure) or released (for reference pressure < process pressure) so that in the latter case, a connection is established between the process side and the vacuum pump. This elegant and more or less automatic regulation system has excellent control characteristics (see Fig. 3.28). 

DC Diaphragm controller P Vacuum pump M Measuring and switching device PS Pressure sensor V1 Pump valve V2 Gas inlet valve TH Throttle... 

The diaphragm controller is therefore closed. When the system is started up, the connecting line between the vacuum pump and pump valve V2 is first evacuated. As soon as the pressure drops below the maximum switching point, valve V1 closes. When the pressure falls below the minimum switching point, valve V2 opens. 

Depending on the quantity of vapor that accumulates, the throughput of the diaphragm controller is set by increasing or decreasing the reference pressure in each case so that the maximum permissible partial water vapor pressure at the inlet connection of the vacuum pump is never exceeded. 

If the pump is protected using a diaphragm-type pressure switch, then the pump will be switched on automatically. If a combination of roots pump and roughing pump is to convey highly volatile substances such as liquids with a low boiling point, then it is advisable to use a roots pump which is equipped with an integral bypass line and a valve which will respond to a pre-set pressure. Example Roots vacuum pumps RUVAC WAU / WSU. 

Figure 4.3. Schematic diagram and sectional views of the autoclave of the pressure-jump apparatus of Knoche and Wiese (1974) 1, conductivity cells 2, potentiometer 3, 40-kHz generator for Wheatstone bridge 4, tunable capacitors 5, piezoelectric capacitor 6, thermistor 7, 10-turn helipot for tuning bridge 8, experimental chamber 9, pressure pump 10, rupture diaphragm 11, vacuum pump 12, pressure inlet 13, heat exchanger 14, bayonet socket. [From Knoche and Wiese (1974), with permission.]...

Figure 8.4l. Apparatus for the parallel recording of DTA. T, TG. DTG. TGT- and DTGT curves (86). 1. compressed test piece 2. compressed reference substance 2. furnace 4. silica bell 5, inlet tube for carrier gas 6. tube for eas extraction 7. silica tube S. suka tube with stirrup-shaped end 9. thermoelement 10. diaphragms 11. light cell 12- lamps l3. optical slit 14. magnet l5. coil 16. galvanometer 17. photographic paper 18. damns transformer 19, absorber 20. electrodes 2l, amplifier 22. vacuum pump 23. automatic burette 24. potentiometer 25. servomotor.

Figure 5.8b shows the components assembled and ready for forming. The spacer ring has vents in one or more places so that a vacuum pump can remove air from the volume between the diaphragms. This pressure differential applies a consolidation pressure to the laminate that helps it remain a contiguous laminate as its shape changes. Once the laminate has melted, the autoclave applies pressure to the assembly and the operator vents the tool to external pressure at one atmosphere. Driven by the applied pressure, the diaphragms and laminate move into the tool. 

---