Piston pumps solenoid

The flow analyzer involves simple apparatus such as samplers, liquid drivers (peristaltic pumps, piston pumps, solenoid pumps), injection devices (rotary valves, injector-commutators), reactors and flow lines (usually narrow bore tubing), mixing chambers, and flow-through detectors. As a rule, these devices are readily available in most laboratories devoted to chemical analysis. Regarding detection, almost all analytical techniques have been used in flow analysis a small flow cell volume and a short response time that is compatible with system dynamics are important detector parameters. 

In the MiniMed implantable pump, a piston pump drives insulin through the delivery catheter. A patented solenoid motor controls the piston movement, to aspirate insulin from the reservoir chamber into the piston chamber and then push it through the insulin delivery catheter. 

Laminar flows are inherent to most flow analysers, as already recognised in the 1970 s [115], but their exploitation can lead to a pronounced broadening of the sample zone. This shortcoming can be circumvented by resorting to turbulent mixing, which can be achieved when membrane, solenoid or step-wise piston pumps which deliver pulsed flows [116—119] are used. Exploitation of pulsed flows led to the proposal of multipumping flow analysis by Lapa et al. in 1999 [120]. 

These pumps can be designed with or without a diaphragm. Their operation involves the same mechanism as a cam-drive piston pump, but the movements of the piston are achieved by passing (or not) an electric current through a coiled resistor around the piston [29]. As the solenoid-driven displacement is very abrupt, the pump delivers a pulsed flow [30]. 

Solenoid piston pump. (For color version of this figure, the reader is referred to the online version of this book.)... 

The reaction of l-hexene on 1/16 1 Pt/ AlaOj (Engelhard E-302) reforming catalyst extrudates was chosen as the test reaction. Figure 1 shows a schematic of the reactor unit A Waters dual piston HPLC pump rated to provide flow rates between 6 and 600 ml/h with a pressure head up to 414 bar was used to feed 1-hexene (Ethyl Corporation CAS 592-41-6 Lot 851201). By closing the liquid shut-off valve (V3) and opening the gas shut-off valve (V2), either hydrogen or nitrogen gas may be admitted to the reactor unit. The feed gas was selected by a three-way, computer-controlled solenoid valve (VI). 

FIGURE 6.4 Schematic representation of the operation of a solenoid pump. The figure refers to a pump without a diaphragm. 1 — spring 2 — piston around which the solenoid is wound 3 — pump chamber. Left and right portions — full and empty chamber (stroke volume). The check valves are not shown. 

The controlled-release micropump (Figure 2) is a recently invented device that uses the principles of membrane transport and controlled release of drugs to deliver insulin at variable rates (20,26). With a suitable supply of insulin connected to the pump, the concentration and/or pressure difference across the membrane results in diffusion or bulk transport through the membrane ). This process is the basal delivery and requires no external power source. Augmented delivery is achieved by repeated compression of the foam membrane by the coated mild-steel piston. The piston is the core of the solenoid, and compression is effected when current is applied to the solenoid coil. Interruption of the current causes the membrane to relax, drawing more drug into the membrane in preparation for the next compression cycle. 

The solenoid-driven Tracor-Chromatec Model 3000 pump is an exception, as both the piston cycle and distance travelled by the piston are variable. 

The propelling systems normally used in FI are peristaltic, piston, syringe, and solenoid pumps, gravity-driven sources, electro-osmotic flow (EOF) devices, and osmotic pumps. 

This equipment being very expensive, preference is now given to a servo-motor - similar to that employed wnth the pump in Fig. 174-the piston of which is pilot controlled by a solenoid operated slide-valve. The servo-motor is driven by a small gear pump w hich delivers the pressure oil for a 30 to 40 atm control circuit. 

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