Pump, capacity

Many initiators attack steels of the AISI 4300 series and the barrels of the intensifiers, which are usually of compound constmction to resist fatigue, have an inner liner of AISI 410 or austenitic stainless steel. The associated small bore pipework and fittings used to transfer the initiator to the sparger are usually made of cold worked austenitic stainless steel. The required pumping capacity varies considerably from one process to another, but an initiator flow rate 0.5 L / min is more than sufficient to supply a single injection point in a reactor nominally rated for 40 t/d of polyethylene. 

If extreme pumping capacities ate provided, supeduminescence can occur. For a cyanine dye solution, this phenomenon was observed and described for the first time in 1969 (100). 

The Mid-America Pipeline System (MAPCO) (77) for ammonia transportation contains 1763 kkometers of 101 mm, 152 mm, and 203 mm pipe having a pumping capacity of 3885 metric tons per day and supporting terminal storage fackities. Peak dehvery from the system is 4,216 metric tons per day. 

The Gulf Central Pipeline system (78) contains 3220 km of 152 mm, 203 mm, and 254 mm pipe and has a pumping capacity of 2545 metric tons per day and supporting terminal storage fackities. The Tampa Bay Pipeline network services several ammonia plants along a 133 km route. 

Elevated Tanks These can supply a large flow when required, but pump capacities need be only for average flow. Thus, they may save on pump and piping investment. They also provide flow after pump failure, an important consideration for fire systems. 

Shelf area, m Floor s ace, m Weight average, kg Pump capacity, mVs Pump motor, kW Condenser area, m Price/m (1995) ... 

Large tanks tend to develop a recirculation pattern from the impeller through the tank back to the impeller. This results in a behavior similar to that for a number of tanks in a series. The net result is that the mean circulation time is increased over what woiild be pre-dic ted from the impeller pumping capacity. This also increases the standard deviation of the circulation times around the mean. 

Radial-flow impellers include the flat-blade disc turbine, Fig. 18-4, which is labeled an RlOO. This generates a radial flow pattern at all Reynolds numbers. Figure 18-17 is the diagram of Reynolds num-ber/power number curve, which allows one to calculate the power knowing the speed and diameter of the impeller. The impeller shown in Fig. 18-4 typically gives high shear rates and relatively low pumping capacity. 

There is the possibihty of misinterpretation of the difference between circulation time and blend time. Circulation time is primarily a function of the pumping capacity of the impeller. For axial-flow impellers, a convenient parameter, but not particularly physically accurate, is to divide the pumping capacity of the impeller by the cross-sectional area of the tank to give a superficial hquid velocity. This is sometimes used by using the total volume of flow from the impeller including entrainment of the tank to obtain a superficial hquid velociW. 

However, when comparing different impeller types at the same power level, it turns out that impellers that have a higher pumping capacity will give decreased circulation time, but all the impellers, regardless of their pumping efficiency, give the same blend time at the... 

Feed Slurry Temperature Temperature can be both an aid and a limitation. As temperature of the feed slurry is increased, the viscosity of the hquid phase is decreased, causing an increase in filtration rate and a decrease in cake moisture content. The limit to the benefits of increased temperature occurs when the vapor pressure of the hquid phase starts to materially reduce the allowable vacuum. If the hquid phase is permitted to flash within the filter internals, various undesired resiilts may ensue disruption in cake formation adjacent to the medium, scale deposit on the filter internals, a sharp rise in pressure drop within the filter drainage passages due to increased vapor flow, or decreased vacuum pump capacity. In most cases, the vacuum system should be designed so that the liquid phase does not boil. 

Air Rate Air rate through the cake, and thus vacuum pump capacity, can be determined from measurements of the air flow for various lengths of di y time. Figure 18-105 represents instantaneous air rate data. The tot volume of gas passing through the cake during a di y period is determined by integrating under the cni ve. 

Vacuum pump capacity is conventionally based on the total cycle and expressed as mVh-m" (cfi7i/ft ) of filter area measured at pump inlet conditions. Thus, the gas volumes per unit area passing during each dry period in the cycle are totaled and divided by the cycle time to arrive at the design air rate. Since air rate measurements in the test program are based on pressure drop across the cake and filter medium only, allowance must be made For additional expansion due to pressure drop within the filter and auxiliary piping system in arriving at vacuum pump inlet conditions. 

Required vacuum pump capacity = 2.65/4.29 = 0.62 mVmiu X m of total filter area. AUow for pressure drop within system when specifying the vacuum pump. See next example. 

Erequent start/stop Minimize frequent start/stop by proper sizing of of equipment may equipment (e.g. pump capacity) lead to equipment, Implement mechanical integrity program failure. Develop procedure to investigate causes for frequent reset of control Minimize frequent start/stop of equipment ... 

Pump is operated Match pump capacity to the service at a fraction of, Install minimum flow recirculation line to heat capacity. Possihil- ensure adequate cooling of the pump ities of excessive internal interlock to shutdown pump on mini-recirculation, fre- indication quent seal and Implement procedural controls to avoid operat-bearing failure ing at too low a flow resulting in loss of, Provide deadhead protection containment. CCPS G-23 CCPS G-29... 

The larger the ratio of impeller diameter to tank diameter, the less mixer power required. Large, slow speed impellers require a low er horsepow er for a given pumping capacity, and solid suspension is governed by the circulation rate in the tank. 

In some applications (usually high pressure compressors using oil film seals) alternative pump schemes should be considered. It may be that the desired seal pressure is not achievable by one set of pumps or the quantity required by the seal is small relative to the main pump capacity. There are (imes when booster pumps are needed however, if the reason is energy, it would be worth reviewing the economics very carefully, because reliability tends to suffer with the booster. The booster pumps are paired into a main and standby and are configured to take suction fro lower pressure system. Sufficient interlocks have to be supplied drivers so that if the main pumps shutdown, the boosters come ... 

Pumping Capacity the amount of discharge flow from an impeller. It is frequently correlated on the basis of the dimensionless impeller discharge coefficient, Nq = Q/ND, where Q == volumetric discharge rate. 

Other positive displacement pumps, such as rotary, gear, and diaphragm pumps, normally require PR valve protection for both the pump and downstream equipment. PR valves for all positive displacement pumps should have a capacity at least equal to the pump capacity. 

The primary pumping capacity of an impeller is determined by the impeller diameter, the Pumping number, and the rotational speed. The Pumping number Nq is defined by [13]... 

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