Pumps casing

By solving the differential equation above and using the single-pump case (P2 = 0) to detennine a, it can be shown that the photo-current is... 

Axial-Flow (Propeller) Pumps (Fig. 10-44) These pumps are essentiahy very-high-capacity low-head units. Normally they are designed for flows in excess of 450 mVh (2000 gal/min) against heads of 15 m (50 ft) or less. They are used to great advantage in closed-loop circulation systems in which the pump casing becomes merely an elbow in the line. A common installation is for calandria circulation. A charac teristic cui ve of an axial-flow pump is given in Fig. 10-45. 

Bypassing is occurring between volute channels in a double-volute pump casing due to a casting defect or extreme erosion. 

Damage will be confined to the bubble-collapse region, usually immediately downstream of the low-pressure zone. Components exposed to high velocity or turbulent flow, such as pump impellers and valves, are subject. The suction side of pumps (Case History 12.3) and the discharge side of regulating valves (Fig. 12.6 and Case History 12.4) are frequently affected. Tube ends, tube sheets, and shell outlets in heat exchanger equipment have been affected, as have cylinder liners in diesel engines (Case History 12.1). 

Similarly, graphitically corroded cast iron (see Chap. 17) can assume a potential approximately equivalent to graphite, thus inducing galvanic corrosion of components of steel, uncorroded cast iron, and copper-based alloys. Hence, special precautions must be exercised when dealing with graphitically corroded pump impellers and pump casings (see Cautions in Chap. 17). 

Graphitically corroded cast irons may induce galvanic corrosion of metals to which they are coupled due to the nobility of the iron oxide and graphite surface. For example, cast iron or cast steel replacement pump impellers may corrode rapidly due to the galvanic couple established with the graphitically corroded cast iron pump casing. In this or similar situations, the entire affected component should be replaced. If just one part is replaced, it should be with a material that will resist galvanic corrosion, such as austenitic cast iron. 

Metal loss in these areas had produced a smooth surface, free of deposits and corrosion products. The rest of the internal surface was covered by a thin, uniform layer of soft, black corrosion product. The graphitically corroded surfaces of the pump casing provided soft, friable corrosion products that were relatively easily dislodged by the abrasive effects of high-velocity or turbulent water (erosion-corrosion). 

Figure 17.16 Pump casing as received. Note the large perforation near the center.

As you can. see, the pump casing will grow against its shaft almost 0.030 inches with an increase of 300°F. There are many tolerances in a pump that are tighter than 0.030 inches. This means a rotary element will scrape and rub a stationary element. 

Correct Soft Foot. Soft foot exists when one of the four machinery feet is not level with the base. When the base bolts are tightened with soft foot, the effect can distort and misalign the pump casing. 

Mechanical problems. Pipe strain distorting the pump casing. 

Erosion is the wear of the pump internal parts by suspended solid particles contained in the fluid being pumped. The most affected parts are wear rings, shaft sleeves, packing, mechanical seal faces, lip seals, the pump casing and the impeller. 

Pump casings should be made of steel if possible, which, on the smaller compressor systems, will not be practical. Most petrochemical plants live in the fear of fire, and the use of cast iron casings in a hydrocarbon plant is not a good idea. 

Pump and Downstream Equipment - A PR valve is required for a pump when the shutoff pressure of the pump is greater than the design pressure of the discharge piping, downstream equipment, or pump casing. Positive displacement pumps normally require such protection, while in most cases centrifugal pumps do not. 

Analogously to MP methods, coupled cluster theory may also be based on a UFIF reference wave function. The resulting UCC methods again suffer from spin contamination of the underlying UHF, but the infinite nature of coupled cluster methods is substantially better at reducing spin contamination relative to UMP. Projection methods analogous to those of the PUMP case have been considered but are not commonly used. ROHF based coupled cluster methods have also been proposed, but appear to give results very similar to UCC, especially at the CCSD(T) level. 

Pump Casing Impeller Pump Frome Split Gland Shot ... 

The single mechanical seal is made of a rotating element fixed to the shaft (or shaft sleeve), and a stationary element fixed to the pump casing [16]. 

Figure 3-36C. Illustrates exact same pump casing and impellers at two different shaft speeds. (By permission, Goulds Pumps, Inc.)...

The minimum flow simply means that this flow must circulate through the pump casing (not recirculate with no cooling) back to at least the initial temperature of the feed, if excessive temperatures are not to dev elop. The best practice is to request the manufacturer to state tliis value for the... 

Tubular Anodes Tubular anodes are supplied in diameters between 12-5 and 32 mm and have been designed for installations where water conditions on the plant under protection are known to be turbulent. The tubular anode has a number of holes drilled in the active portion of the anode and the nonactive portion is filled with sand to act as a damping agent. As in the case of rod anodes they are supplied complete with mounts ready for installation in the prepared bosses on the plant under protection. They are particularly suitable for internal protection of pump casings and internal protection of pipelines, carrying salt water or other low resistivity liquids. 

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