Low-pressure pump

Process and Equipment. Rigid polyurethane foam processes use the same high or low pressure pumping, metering, and mixing equipment as earher described for flexible foams. Subsequent handling of the mixture is deterrnined by the end product desired. 

MLOCA range from 6 to 18 inches they are mitigated by 2 out of 3 accumulators and I [Pg.211]

In general, rotary pumps with discharge pressure of up to 100 psi are considered low-pressure pumps. Rotary pumps with pressure between 100 and 500 psi are considered moderate-pressure pumps. Pumps with pressure beyond 500 psi are considered to be high-pressure pumps. 

Most of the chromatographic techniques described thus far are usually performed under relatively low pressures, where flow rates through the column are generated by low-pressure pumps (i.e. low-pressure... 

Vacuum filtration has many advantages, not the least being the fact that the feed slurry, often containing abrasive solids in a corrosive liquid, can be delivered by gravity flow or by low pressure pumps which need only to overcome the resistance in the feed pipework. In addition, vacuum filtration equipment does not have to withstand high pressures... 

Consider a steam power plant operating on the ideal regenerating Rankine cycle 1 kg/sec of steam flow enters the turbine at 15 MPa and 600°C and is condensed in the condenser at lOkPa. Some steam leaves the high-pressure turbine at 1.2 MPa and enters the open feed-water heater. If the steam at the exit of the open feed-water heater is saturated liquid, determine (1) the fraction of steam not extracted from the high-pressure turbine, (2) the rate of heat added to the boiler, (3) the rate of heat removed from the condenser, (4) the turbine power produced by the high-pressure turbine, (5) the turbine power produced by the low-pressure turbine, (6) the power required by the low-pressure pump, (7) the power required by the high-pressure pump, and (8) the thermal cycle efficiency. 

The process of fuel injection first involves movement of fuel from the fuel tank by the fuel delivery pump. This low-pressure pump supplies fuel into the fuel delivery port of each plunger and barrel assembly. As the plunger moves past and clears the fuel delivery port, fuel flows into the barrel filling the chamber above the top of the plunger. Continuous rotation of the camshaft then forces the plunger in the opposite direction, closing off the flow of fuel into the barrel and trapping fuel within the barrel chamber. 

For reasons that will be explained in a subsequent chapter, the team found that the application of a technology known as bioflitration was considered the best remediation method. The contaminated gas is pumped through a column packed with a material that performs two functions (1) it provides for efficient contact between the air passing through it and water, and (2) it serves as a scaffold for the development of a bacterial colony. Figure 1.7 shows a typical biofiltration arrangement. The team must develop a system that has a very low pressure drop so that the process can be constructed from plastic tanks and low-pressure pumps to save money. In a further effort to save money, the process should have a small footprint. 

Column chromatography apparatus, including a suitable low-pressure pump, online UV monitoring at 280 nm and a fraction collector. 

Figure 4.43. Plant layout for reactive processing. 1 - tanks for reagents 2 - heat exchangers 3 - low-pressure pumps 4 - high pressure metering pumps 5 - low-pressure recycling line 6 - high-pressure recycling line 7 - chamber for shock mixing 8 - mold.

The criteria used to judge the performance of a low-pressure pump include compositional accuracy, ripple, flow accuracy, and pressure accuracy. Compositional accuracy is tested by following the American Society for Testing and Materials (ASTM) procedure E-19.09.07.5 In this procedure, two bottles of eluent are used, one containing 100% methanol (eluent A) and the other containing methanol with a low concentration of acetone... 

The mobile phase can be allowed to flow under the force of gravity, a low pressure pump can be used, or compressed gas can be used to pressurize a solvent reservoir. The linear velocity should be about one-third of that used in analytical columns. The sample can be applied to the top of the column with a microsyringe or pipet using the stop-flow method, or an inexpensive, low-pressure valve can be used. The eluent is usually collected in separate tubes using an automated fraction collector. Inexpensive UV detectors with large solvent volumes are available, or flow cells can be fitted to conventional UV/visible instruments. 

Less downtime Low pressure pumps can be used Coarse particle size not obtainable... 

The principal types of vacuum pumps will be discussed in this section. The water aspirator is a crude but useful pump for many routine operations. Rotary oil pumps are used for pumping on refrigerant baths and as the forepump for backing low-pressure pumps. For most high-vacuum work, diffusion pumps are utilized to achieve pressures... 

Column chromatography apparatus, including a suitable low-pressure pump, on-line UV monitoring at 280 nm and a fraction collector. Chromatography media Sephacryl S-200 (SF), Sephadex G-25 (SF) (Pharmacia). 

Flash chromatography, a technique for sample purification using disposable glass NPC columns and mobile phase driven by gas-pressure or low-pressure pumps. 

Open the column outlet valve and adjust the flow rate to 2-4 mL/min (for the 200-mL column). The desired flow rate for this type of gel should be such as to give a contact time of approx 50-100 min. This is equivalent to a linear flow rate of approx 10-15 cm/h Such slow flow rates can usually run perfectly well with gravity flow, as these columns generate little back pressure. However, it is generally preferable to use a low-pressure pump. Pumping the solvent through the column allows for better flow-rate control throughout the separation. 

Some simple classic systems are shown in Fig. 4.2.1. These columns have to be repacked after being used only once or a few times. The application of the sample is made directly onto the column, whereupon the flow of the mobile phase is started. The mobile phase may flow either by gravity or may be delivered by a low pressure pump. Detection and quantitation are achieved by photometry (flow-through cell) or by discrete analysis of the individual fractions after fraction collection. 

Fig, 2. Atmospheric pressure, two-solvent gradient mixer. Independently controlled flows, a = low-pressure pump, b, c = valves, d = magnetic stirrer, e = to high--pressure pump. 

Pumps are required in the feed system either to transfer product within the feed systan or to supply product to the atomizer. The pumps in the spray-dryer feed system are sized and selected for each application depending on the type and properties of the feed material and also depending on the atomizer incorporated in the feed system. When rotary atomizers or two-fluid nozzles are used, low-pressure pumps are also usually used. When pressure nozzles are employed, high-pressure pumps are required [34]. Various types of pumps are used because of the variety of feed materials that are encountered (see Table 52.6). A water tank for dryer startup and shutdown is mounted on the atomizer feed pump. 

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