Secondary pump

Figure 22. Central multiple heat pump system with ground loop and primary/secondary pumping...

The operation and control of this system will be complex and maintenance cost will be higher. As an alternative, secondary pumps are eliminated and primary only pumping is considered (Section 6.3.6). 

The term ion pump, synonymous with active ion-transport system, is used to refer to a protein that translocates ions across a membrane, uphill against an electrochemical potential gradient. The primary pumps do so by utilization of energy derived from various types of chemical reactions such as ATP hydrolysis, electron transfers (redox processes), and decarboxylations, or from the absorption of light (Table 1). Secondary pumps are symport and antiport systems that derive the energy for uphill movement of one species from a coupled downhill movement of another species. The electrochemical gradient driving the latter movement is often created by a primary pump. 

To reach lower pressures, a secondary pump is used, such as a diffusion pump or a sublimation pump (both must remain connected to a primary or "roughing" pump). There are two kinds of diffusion pumps. A mercury diffusion pump can reach 10 6 Torr, but the toxicity of mercury vapor has decreased its use dramatically. A silicone oil diffusion pump can reach 10-7 Torr. For even lower pressures, a Ti sublimation pump is used it can reach about 10 11 Torr. It is usually connected to a sorption primary pump. The ultimate low pressure attained in a laboratory on earth is about 10 13Torr. 

The body of these cells is connected to a dual primary and secondary pumping system. An initial primary pumping system is used to evacuate the reactive gases in order to avoid excess contamination of the secondary pumping system which can be used to obtain vacuums of approximately 10" mbar if required. 

The arrival of hydrophobic synthetic fibres created interest in dyeing, under pressure, at temperatures above 100°C. The machine illustrated in Fig. 13.16 has a secondary pump which is brought into operation to create a static high pressure in the d e vessel when it is desired to apply the dyes at temperatures above 100°C. A constant elevated pressure cannot be maintained satisfactorily by the main pump alone because it would vary according to tbe density of the winding of the padcages and other factors, including the speed of the motor. The secondary pump extracts extra dye liquor from the expansion tank and introduces it into the pressure vessel in such a manner that a static pressure is maintained. 

Apparatus. High performance liquid chromatographic separations were achieved on a binary gradient microbore HPLC systems primary pump (A) Model 305, secondary pump (B) Model 306, monomclric module Model 805, and a dynamic mixer Model 811C from Gilson Inc. (Middleton. Wl). Sample injections were achieved with a 20 pL loop on a Model EQ-36 injection valve from Valeo Instruments Co. Inc. (Houston, TX). A stainless steel Y-splitter also from Valeo was used in order to achieve a post-column split of the mobile phase Dow to the CLND. A Supelcosil LC-18S analytical HPLC column was purchased from SUPELCO Inc. (Bellefonte. PA). The Y-splitter was attached to the analytical column by a SLIPFREE connector, available from Keystone Scientific Inc. (Bellefonte, PA). Analyses of nor-dihydrocapsaicin, capsaicin and dihydrocapsaicin in spices as well... 

Solvents of greater eluting power should not be used to dissolve the sample as this disturbs the system equilibrium. The sample solution can be applied via a six-port valve of the Rheodyne type fitted with an appropriate sized loop. Loops up to 10 ml are commercially available. Alternatively the sample can be applied to the column via a small volume secondary pump, though this has the disadvantages associated with stopped-flow techniques (discussed previously in this chapter). This complex subject has been reviewed by Guichon [101]. 

T0 reduce the quantity of sodium leakage, the drain system was found to require two improvements. One is the addition of a new drain line pipe at the inlet of the secondary pump. The other is the replacement of all drain lines by pipes of larger diameter. In the existing system, each drain line has two drain valves in series to prevent accidental draining by single valve action error. In future so as to assure the draining, each drain line will have double drain valves in parallel. After these improvements, the drain time will be shortened from approximately 50 minutes to 20 minutes. It is estimated that it takes 40 minutes from the occurrence of sodium leakage to finish the drain for the secondary circuit. The modified drain system is shown in Fig.9. 

Secondary pumps BCS C and 0 were driven by the auxiliary motors... 

It is envisaged to have one primary pump, one secondary pump and a SG as spare. 

The probe is attached by a tube, to a pumping system consisting of a primary two-stage pump of flow rate 80 m /h and a secondary pump of the ROOTS type of flow rate 500 m /h. The attachments are carried out using tubes of diameter 40 mm in order to avoid pressure drops. 

The secondary circuit is composed of two loops, each one includes one secondary pump, one steam evaporator, one steam-water separator, one superheater, one expansion tank, valves and draining tank and emergency draining tanks. The steam generators will produce 96.2t/h dry steam with die temperature 480 C and the pressure 14 MPa for a 25MWe turbine generator. The heat in the condenser will dissipate to the air by a cooling tower. 

This steady state was also interrupted for a few days by a rapid shutdown that occurred on August 6, following a trip of a secondary pump due to the failure of an electric module of the pump speed regulation system. 

Various transients analysed are one primary or secondary or boiler feed water pump trip, one primary or secondary pump seizure, rupture of one primary pump discharge pipe, offsite power failure, uncontrolled withdrawal of a control and safety rod, total loss of feed water to SG, one primary or secondary pump acceleration from 20 % power and feed water flow increase to 125 % in one loop. Based on these studies reactor scram and LOR parameters are identified. Reactor is scrammed, i.e., by gravity drop of all control safety rods (CSR) and diverse safety rods (DSR), only for events involving fast transients and flow blockage in the core. For all the other events LOR (lowering of all the control and safety rods) is used for the reactor shutdown. The safety criteria is to ensure the availability of two diverse reactor trip parameters for every DBE (fig 9). 

Roughing pump n. In high-vacuum work, e.g., vacuum metallizing, a mechanical pump that removes most of the air from the chamber, leaving the remainder to a secondary pump, usually a diffusion pump, capable of reducing the pressure to about 0.13 Pa absolute. 

Position Normal operation Secondary pumps loss of power Valve shut in 2 s Seconday pumps Loss of power Valve shut in 3 s... 

For the roof-slab, a radial beam structure of eight box-beams 2.5m high and 0.5m wide of 38mm thick carbon steel are used based on the results of a 3 dimensional eigenvalue analysis. This number of beams conforms with the arrangement of the SGs and the secondary pumps. 

Reactor core d) Steam generator Primary vessel Q) Secondary pump (D Secondary vessel (D Roof slab Intermediate heat (D Top dome exchanger Air cooler... 

The setup at the Universitat Rostock utilizes an ACIS to produce a continuous cluster beam (see Fig. 3.9). The metal vapor plasma is created in the cylindrical cathode of target material. The fabricated clusters, neutral and charged are expanded through an exit nozzle and collimated by an aerodynamic lens attached to the source. The clusters then flow through a secondary pumping stage bracketed by two skimmers and are size selected by an electrostatic quadrupole deflector for deposition. 

In the Twinflow VR (variable ratio) the metering pumps are here also driven by a lever system (Fig. 86). By moving the secondary pump (for the hardener), the mixing ratio changes. The total volume delivered is controlled by the displacement of the pistons. In the Twinflow FR (fixed ratio), one single pneumatic jack drives... 

Fermi (USA) power set back to 67%, secondary pump in same loop stopped... 

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