The Pump Casing

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. 

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). 

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. 

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. 

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]. 

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... 

The pressure at the inlet to a pump must be high enough to prevent cavitation occurring in the pump. Cavitation occurs when bubbles of vapour, or gas, form in the pump casing. Vapour bubbles will form if the pressure falls below the vapour pressure of the liquid. 

You have purchased a centrifugal pump to transport water at a maximum rate of 1000 gpm from one reservoir to another through an 8 in. sch 40 pipeline. The total pressure drop through the pipeline is 50 psi. If the pump has an efficiency of 65% at maximum flow conditions and there is no heat transferred across the pipe wall or the pump casing, calculate ... 

A pump roller bearing failure in a crude oil refinery initiated the fracture of the motor shaft and the pump bearing bracket. The pump casing then broke, releasing hot oil, which au-toignited. Secondary pipe and flange failures contributed fuel to the fire. Plant damage totaled over 15 million. 

Steel and alloy steel horizontal pumps, and their baseplates, and vertically suspended pumps shall be designed for satisfactory performance when subjected to the forces and moments in Table 2-1A (2-IB). For horizontal pumps, two effects of nozzle loads are considered Distortion of the pump casing (see 2.2.8) and misalignment of the pump and driver shafts (see 3.3.5). 

In addition to being stamped on the nameplate, the pump serial number shall be plainly and permanently marked on the pump casing. 

When specified, the vendor shall test to demonstrate that the pnmp and its baseplate assembly, when anchored at foundation bolt hole locations with any bearing housing support discoimected, are in compliance with 3.3.5. The pump casing shall be snbjected to moments MYq and MZ applied to either nozzle, bnt not both, snch that the corresponding shaft displacements can be measnred and recorded. MY and... 

Piping components shall have a pressnre-temperature rating at least equal to the maximum discharge pressure and temperature of the pump casing, bnt in no case less than ISO 7005 PN50 (300 pound ANSI Class) flange at ambient temperature (2.2.2)... 

When the pump casing is of alloy material, piping and components subject to the process fluid shall have a corrosion/erosion resistance eqnal to or better than that of the casing. Otherwise, all components shall be steel. 

Glands shall be retained by studs in the pump casing. Where spht glands are nsed, the halves shall be bolted—or positively locked—together. 

A Roots vacuum pump (see Fig. 2.17) Is a rotary positive-displacement type of pump where two symmetrically-shaped Impellers rotate Inside the pump casing past each other In close proximity. The two rotors have a aoss... 

The entire scope of a refrigerator cryopump is shown in Fig. 2.65 and consists of the compressor unit (1) which is linked via flexible pressure lines (2) - and thus vibration-free - to the cryopump (3). The cryopump itself consists of the pump casing and the cold head within. Helium is used as the refrigerant which circulates in a closed cycle with the aid of the compressor. 

Roots pumps must be exactly level. When attaching the pump it is necessary to ensure that the pump is not under any tension or strain whatsoever. Any strains in the pump casing caused by the connection lines shall be avoided. Any strain to which the pump is subjected vi/ill endanger the pump since the clearances inside the roots pump are very small. 

The turbomolecular pump may, for example, be used unprotected inside magnetic fields if the magnetic induction at the surface of the pump casing does not exceed B = 3 10 T when radially impinging and B = 15 10 T at axial impingement. 

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