Pilot pressure pump

Fig. 82 illustrates the hydraulic circuit diagram of an oil-hydraulic extrusion press operated by a variable-delivery pump (see p. 212). The control stand accommodates a hand-wheel connected linkage which sets the press to advance or return, as well as two rotary slide valves which serve to lock and shift the die-carrier with the die. The linkage acts on a servo-control (see p. 215), which is arranged directly at the pump the servo-control is connected to a geared pump, also called pilot pressure pump. 

The apparatus equipped with Sunflower CeRam Inside (23-8-1178), characterized in Table 25.10, was used in pilot plant tests. The plant consisted of feed tank (1) and is equipped with cooler (2), membrane module housing (3), pretreatment filters (4), pressure pump TONKAFLO (5), circulating pump Grundfos (6), nonreturn valve (7), and two needle valves and four ball valves (Figure 25.14). 

Fixed-volume and variable-volume pumps are the two types commonly applied in the press application. Fixed-volume pumps are normally vane type and are used for fixed-speed presses and for auxiliary circuits such as filtering, cooling, and pilot pressure. Variable-volume pumps are normally radial or axial piston type and are used for variable pressing speeds and pressure compensated circuits. 

Auxiliary circuits are those not directly producing the activity of the main slide of the press. Usually, these circuits have dedicated pumps to provide hydraulic pressure and flow to accomplish an auxiliary task or function that is independent from the main press action. Some examples include pilot pressure, filtering, cooling, cushion, ejector, blankholder, or other auxiliary actions. As with the main circuit, the auxiliary circuit can be equipped with a fixed-volume or a variable-volume pump, depending on the requirement. 

When human strength is no longer sufficient to adjust the cradle, a servo-motor with piston-valve h and slide-valve i is used. The servomotor is driven by a small gear pump which produces a pilot pressure of about 20 atmospheres and is rated for 2 to 3 H.P. 

When the system pressure decreases to a point slightly below 600 psi, the spring forces the piston down and closes the pilot valve. When the pilot valve is closed, the fluid cannot flow directly to the return line. This causes the pressure to increase in the line between the pump and the regulator. This pressure opens the check valve, causing fluid to enter the system. 

Figure 6. Block drawing of the pilot installation for the production of trichloromethyl chloroformate by exhaustive photochlorination [39] 1 Dryer for gaseous Cl2 (H2S04 cone.). 2 Safety tank. 3 Thermoregulated immersion-type photochemical reactor. 4 Raschig column. 5 Cl2 detection system (1,2,4-trichlorobenzene). 6 Neutralization tank (20% NaOH). 7 Reservoir of 20% NaOH. 8 Buffer to atmospheric pressure (20% NaOH). 9 Active carbon filter. 10 Reservoir of crude trichloromethyl chloroformate. 11 Buffer to normal atmosphere via CaCl2 filter and direct entry for trichloromethyl chloroformate to be distilled. 12 Distillation flask with Vigreux column. 13 Exit to vacuum pump. 14 Solid NaOH filter before pump. 15 Cooling water alarm linked to power supply of the light source. 16 Medium pressure mercury arc. 17 Heater for distillation apparatus. 18 Magnetic stirrers. /T thermometer /P manometer.

The third factors to control and keep constant are the gas pressure and superficial gas velocity. This probably will involve gas recirculation with either a small compressor, or through a hollow shaft or some other pumping device. As seen before, the bubble diameter, the mass transfer area, the gas hold-up, and the terminal bubble-rise velocity, all depend on the superficial velocity of the gas and the power input per unit volume. When these are kept constant, the various mass transfer resistances in the pilot plant and in the large unit will be the same, hence the global rate will be conserved. The last factor is the input power to the agitator. As required for mass transfer, the scale-up must be made on the basis of constant power input per unit volume. If turbulent conditions and geometrical similarity prevail, this rule imposes the following relationship ... 

Table 8.3-2 shows heat duties in the different pieces of equipment, and the solvent makeups needed to run the plant, as a function of pressure and temperature in the flash drum, D200. The data reported are computed by assuming efficiencies for heaters and coolers equal to 0.7, and 0.6, respectively, to account for thermal inefficiencies [4]. From analysis in the pilot plant, which is probably more accurate than the results from the process simulator, an accurate estimate was that 20 kW is needed to pump all the fluids in the final plant. 

The feed-stream is pressurized to the operation pressure by a metering pump, and the air which is used as oxidant in the oxidation reaction, is compressed to the operational pressure in a four-stage compressor. Both streams are mixed in a static mixer inside the reaction chamber as it is shown in Fig. 9.4-10. The reactor has been described in the section 9.4.4.I. A more etal ed description of the pilot plant can be found in reference [7]. 

The NF/LPRO pilot plant was supplied by Sepratech (Separation Technoloy, INC, US), and consisted of a feed tank, a pump and planar module, as detailed in Fig. 5. All studies were done using a low conversion rate (5%) and a high tangential flow rate ( 4 ms-1) in order to minimize the polarization concentration effects. The applied transmembrane pressures were in the range of 0-25 bar. The temperature was maintained at 25°C. 

Experience indicates that an important part of a normal process development is definition of solutions to operability and reliability problems that have been identified. The EDS process development is no exception. Potential mechanical problems associated with feed slurry preheat, slurry pumping, high pressure letdown valves and vacuum bottoms pumping have been identified and will be addressed in the 250 T/D pilot plant program. In addition, several process problems associated with the variety of coals processed have been identified and solutions defined. The status of both pilot plant construction and definition of solutions to process problems is presented in this paper. 

The pilot plant is able to treat 25 L/h of wastewater with an organics content between 10% and 15% w/w. Wastewater is presurized with a plunger pump to 27.5 MPa. Air is used as oxidant previously pressurized in a four stages compresor to 28.0 MPa. 

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