Canned pumps

There are four (4) major types of pumps (I) positive displacement, (2) dynamic (kinetic), (3) lift, and (4) electromagnetic. Piston pumps are positive displacement pumps. The most common centrifugal pumps are of dynamic type ancient bucket-type pumps are lift pumps and electromagnetic pumps use electromagnetic force and are common in modern reactors. Canned pumps are also becoming popular in the petrochemical industiy because of the drive to minimize fugitive emissions. Figure 10-24 shows pump classification ... 

The most common maintenance problem with centrifugal pumps is with the seals. Mechanical seal problems account for most of the pump repairs in a chemical plant, with bearing failures a distant second. The absence of an external motor (on canned pumps) and a seal is appeahng to those experienced with mechanical seal pumps. 

There are trade-offs for magnetic drive and canned pumps versus centrifugal pumps with double-mechanical seals. The former have no seals to leak, but need active interlocks to prevent high temperature for temperature sensitive materials. Similarly, diaphragm pumps, that have... 

In canned pumps the rotor (the moving part of the electric motor) is immersed in the process liquid the stator (the fixed part of the electric motor) is separated from the rotor by a stainless steel can. If there is a hole in the can, process liquid can get into the stator compartment. A pressure relief plug is therefore fitted to the compartment and should be used before the compartment is opened for work on the stator. One day, an operator opened the pump without using the pressure relief plug. There was a hole in the can which had caused a pressure build-up in the stator compartment. When the cover was unbolted, it was blown off and hit a scaffold 6 feet above. On the way up it hit a man on the knee and the escaping vapor caused eye irritation. The worker was not familiar with canned pumps and did not realize that the pressure relief plug should be used before opening the compartment. 

Fig. 2 The Harvey O. Banks pumping plant, which pumps Delta water into the California aqueduct, is shown. The plant can pump up to 300 m /s and lifts the water about 73 m to begin the transit southward through the 710 km of canals, tunnels, and pipelines that constitute the California aqueduct...

Reaction with construction materials, e.g. nitric acid can produce nitric oxide gas on contact with copper in pipes or copper windings in motors of canned pumps ... 

The drive motor and pump are enclosed in a single casing and the stator windings and armature are protected by metal cans they are usually referred to as canned pumps. The motor runs in the process fluid. The use of canned pumps to control environmental pollution is discussed by Webster (1979). 

A pump installed on a well can pump at a maximum rate of 100 gallons per minute. If the town requires 15,000 gallons of water in one day, how long would the pump have to continuously run at 75% of its maximum rate to meet the town s need ... 

Canned pumps are used to transfer chlorine to the packing plant and to the vaporiser for feed to the chlor-paraffin plant. 

In the event a well is pumped dry, the pumps can pump air without damage. Pumping air also induces the vacuum-enhanced fluid entry into the well. 

The use of traditional rod and piston pumps continues at many LNAPL recovery locations, particularly at refineries and distribution terminals. These units are usually powered by single-speed electric motors and have adjustable stroke lengths to control the pumping rate. When installed with the intakes set at the optimum pumping depth, they function fairly well. The primary advantage of rod and piston pumps is that the smooth slow stroke rate can pump mixtures of product and water without creating a significant emulsion. 

In many real lasers, the upper laser level, 2 in Figure 2.6(a), is a metastable level that is, it has a long lifetime compared to the lower laser level (t > ti). If we can pump efficiently into such a longer-lived upper level, and provided that there is a lower energy level, E in Figure 2.6(a), with a short lifetime, then a population inversion is very likely to be established. 

For example, if a two-stage vented extruder has a screw that was designed for resins with an Mi range of 2 to 20 dg/min, and plant personnel are asked to manufacture a resin with an MI of 100 dg/min, the extruder may not process the resin acceptably. For this case and flood feeding, the extruder is likely to have resin flowing into the vent because the first stage can deliver more resin than the second stage can pump. One practical solution to this problem is to operate the slide valve in a partially open manner such that it controls the rate of the extrusion process. This will allow the extruder to operate at a lower specific rate and allow operation without the flow of resin into the vent. 

Laboratory results may be reported on an as received by volume basis or dry matter by mass basis, depending on whether the sample is considered to be a solid or a liquid. Samples >10% DM are generally treated as solids, and <10% DM as liquids. However, there are frequently exceptions to this rule, e.g. some fibrous samples <10% DM are difficult to pipette, so are analysed on a weight basis, but reported on a volume basis. Some customers can pump thick samples with >10% DM, so need the fertilizer values reported as liquids on a volume basis. Routine determination of density values facilitates calculation and reporting of fertilizer values in either mass or volume units. 

That is, the cotransporter can pump glucose inward until its concentration within the epithelial cell is about 9,000 times that in the intestine. As glucose is pumped from the intestine into the epithelial cell at the apical surface, it is simultaneously moved from the cell into the blood by passive transport through a glucose transporter (GLUT2) in the basal surface (Fig. 11-44). The crucial role of Na+ in symport and antiport systems such as these requires the continued outward pumping of Na+ to maintain the transmembrane Na+ gradient. 

A particular illustration of this cross-cultural influence is the question of whether one can pump states directly coupled to the transition state. In the Rydberg problem the answer is very much yes because these are often the states that are optically excited. They are directly coupled to the continuum but are also coupled to other Rydberg series, where n is lower and the core is more excited. 

Not all proton pumps are driven by electron transport. ATP synthase is reversible, and if Ap is low, hydrolysis of ATP can pump protons out of mitochondria or across bacterial plasma membranes.268 Cells of Streptococcus faecalb, which have no respiratory chain... 

A leak rate of 0.8-0.9 mbar L/s is already larger than could be pumped off by a reasonable pumpset in this size of freezedrying plant. The partial pressure of air, p.m, must be small compared with the water vapor pressure. At 0.28 mbar total pressure pair should be 0.03-0.04 mbar. A vacuum pump which can pump 0.8-0.9 mbar L/s at 0.03-0.04 mbar must have a pumping speed of -100 m3/h, which is unusually large for a 200 L chamber. A vacuum pump with a 40 m3/h pumping speed will theoretically evacuate a chamber and condenser (total 500 L) in -6 min down to 0.1 mbar. Even if it takes 10 min with the loaded chamber, the pumping speed of the pump is sufficient. With this pump, the leak rate of the plant should not exceed 0.4 mbar L/s, which would be pumped at -0.04 mbar. 

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