Pumps and Injection Systems

The function of the pump in hplc is to pass mobile phase through the column at high pressure and at a controlled flow rate. One class of pump (constant pressure pump) does this by applying a constant pressure to the mobile phase the flow rate through the column is determined by the flow resistance of the column and any other restrictions between the pump and the detector outlet. Another type (constant flow pump), generates a given flow of liquid, so that the pressure developed depends on the flow resistance. 

In addition to being able to pump the mobile phase at high pressure and constant flow, the pump should also have the following characteristics  

The earliest form of constant pressure pump in hplc (the coil pump) used pressurised gas from a cylinder to drive mobile phase from a holding coil through the column. This type of pump was used in some of the older hplc instruments, but is now only of historical interest. If you want to know any more about it, there are details in most textbooks. 

The operating principle of the pneumatic amplifier pump is shown in Fig. 2.2b. 

Air from a cylinder at pressures up to about 10 bar (150 psi) is applied to a gas piston that has a relatively large surface area. The gas piston is attached to a hydraulic piston that has a smaller surface area. The pressure applied to the liquid = gas pressure x area of gas piston/area of hydraulic piston. With 10 bar inlet pressure and a 50 1 area ratio, the hydraulic pressure obtained is 500 bar (7500 psi). On the drive stroke, the outlet valve on the pump head is open to the column and the inlet valve closed to the mobile phase reservoir. At the end of the drive stroke, the air in the chamber is vented and air enters on the other side of the gas piston to start the return stroke. On the return stroke the outlet valve closes, the inlet valve opens and the pump head refills with mobile phase. The pump can be started and stopped by operation of a valve fitted between the cylinder regulator and the pump. 

---

Fuel stability is an indication of the sediment- and gum-forming tendency of fuel. Gums and sediment can cause filter plugging and combustion chamber deposits and result in sticking of pumping and injection system components. 

Fuel system corrosion inhibitors must have a low tendency toward emulsification with water and toward foam enhancement in turbulent systems. These properties are especially critical whenever inhibitors are used in jet fuel. The sensitivity of jet fuel pumping and injection systems requires that fuel be free of emulsions and foam. 

For practitioners of in situ technologies, note that U.S. EPA has issued a policy statement that reinjection of contaminated groundwater is allowed under Resource Conservation and Recovery Act (RCRA)35 36 as long as certain conditions are met. This policy is intended to apply to remedies involving in situ bioremediation and other forms of in situ treatment. Under this policy, groundwater may be reinjected if it is treated aboveground prior to reinjection. Treatment may be by a pump-and-treat system or by the addition of amendments meant to facilitate subsurface treatment. Also, the treatment must be intended to substantially reduce hazardous constituents in the groundwater (either before or after reinjection) the cleanup must be protective of human health and the environment and the injection must be part of a response action intended to clean up the environment.37... 

Consider the case of pure methanol for which the values of Cp and a are known. Using a specific volume of 0.00127 m3/kg, a temperature of 25°C (298 K), and a compression pressure of 1000 bar, Equation 13.2 predicts the eluent temperature will increase approximately 15°C assuming adiabatic conditions. In actual practice, the increase in eluent temperature entering the column will be lower than this upper limit due to thermal losses in the pump, connecting tubing, and injection system, as well as entropic changes (AS A 0). 

The essential components of the instrumentation are a solvent reservoir, a solvent delivery system (pump), sample injection system, packed columns, a detector(s), and a data processing system. 

Cost of package boiler plants. Price includes complete boiler, feed-water deaerator, boiler feed pumps, chemical injection system, stack, and shop assembly labor. 

For the first preliminary experiments, a standard fuel oil burner system was purchased. Due to several reasons, however, a new pump and atomisation system was required, viz. a dedicated fuel punqp and a different spray nozzle. In this new set-up, primary air for a proper fiiel atomisation and secondary air for the combustion could be controlled separately. Furthermore, pumping and combustion of heavy fuel oil (sulphur content of 3.35 wt.% and a viscosity of 180 cP) was possible only, when mixed with diesel in a ratio of 60 40 (dicsehheavy firel oil). Besides, the flame tuimel had to be preheated to approx. TSO C using ordinary diesel or ethanol as a start-up fuel. When a steady state operation was observed (after approximately 10 minutes), the diesel flow to the flame tunnel could be replaced by a mixture of heavy fiiel oil and diesel (40 60), and the emissions of SOj are recorded (approx. 400 ppm). Then CEB is injected and subsequently the SO2 levels are recorded every 30 s. Usually, almost instantly a sharp decrease in the SOj concentration was observed, due to the reaction of the Ca wifti SO2. The experiments were carried out at various fiiel flow rates, ranging from 0.5 to 3 kg/hr, and at a CEB flow rate corresponding to Ca S ratios from 0 to 3. 

For the polymer mixing and injection system in Daqing, polymer solution was transferred in the mode of one transfer pump-one pipeline-one injection station in the early days. These days it is in the mode of one transfer pump-one pipeline-two injection stations. Thus, the cost to deliver polymer solution is reduced. Plus, the system of one injection pump (station)-one well is replaced by the system of one injection pump (station)-several injection wells (Li et al., 2005d). 

Figure 5.21. Bifok/Tecator FIAstar 5020 Analyzer (center) shown with the 5032 Detector System (left) and the 5007 Sampler (right). Comprising two independently programmable peristaltic pumps and injection valves, the analyzer applies small dedicated, ready-to-use chemical manifolds with fixed designs (Chemifolds), which are easily interchangeable. The compartment of the analyzer can be thermostated.

Accuracy Double, triple etc. injection volume results in double triple etc. peak area Prerequisite pump and detection system OK gravimetric e.g. 500 fll of a solute with a known and large specific weight (e.g. bromine benzene), 20 pi injection, one more weighting 0.2-0.5 %... 

Other uses are found in plastic surgery, artificial skin and blood substitutes. An unique field is found in membranes for dialysis. PE, mostly linear (including UHMW), serves in many implants or in artificial joints. PVC is the most useful polymer in medicine, in plasticized form for flexible tubing, dialysis and infusion systems. PP is offered for disposible injections and, together with ethylene (copolymer), in blood bags. PS serves as a substitute for glass in tubes, bottles and petri dishes, and as the copolymers SAN or ABS in a wide host of uses. Polyester (PET) is used in sewing threads or nets in prostheses. PC is used (as a replacement for cellophane) in membranes for dialysis as well as in blood pumps and other systems. 

A possible remedy for CHC dense non-aqueous phase liquid (DNAPL) is to install an in-creased-efficieney pump-and-treat system based on introducing surfactants into the aquifer to increase the solubility of CHC and the rate at which it transfers into the water phase. In this type of system, groundwater is extracted, DNAPL is separated (if present), dissolved CHC is air-stripped or steam-stripped from the water, surfactant is added to the groundwater, and the surfactant-rich water is re-injected into the aquifer up-gradient of the suspected DNAPL deposit. As the surfactant-laden groundwater passes across the DNAPL zone it is capable of reaching a CHC saturation level that is many times the natural CHC solubility, thus removing DNAPL more efficiently. 

Figure 1 General scheme of an FI configuration. S denotes sample, PP peristaltic pump, IS injection system, D detector, W waste, and PC personal computer.

Displacement actuators (converse piezoelectric effect) This class contains various actuators - loudspeakers, camera shutters, buzzers, ink-jet printers, microrobots, relays, pumps, fuel injection systems, and others. 

The equipment for the SBLC system is located in the reactor building and consists of a stainless steel storage tank a pair of full capacity positive displacement pumps and injection valves a test tank and the necessary piping, valves, and instrumentation. 

Gan, W. E., L. Yang, Y. Z. He, R. H. Zeng, M. L. Cervera, and M. de la Guardia. 2000. Mechanism of porous core electroosmotic pump flow injection system and its application to determination of chromium(VI) in waste-water. Talanta 51 667-675. 

An iajection mol ding machine is operated by hydrauHc power and equipped with an electric motor and hydrauHc pump. The maximum hydrauHc oil pressure is ca 14 MPa (2000 psi). A hydrauHc cylinder opens and closes the mold and holds the mold closed duriag iajection another cylinder forces the screw forward, thereby injecting the melt iato the mold. A separate hydrauHc motor turns the screw to plasticate, homogenize, and pressurize the melt. Control of these movements is a combined function of the hydrauHc and electrical systems (35—37). 

---