Centrifugal Pumps Design and Application 2nd ed - Val S. Lobanoff, Robert R. Ross (Butterworth-Heinemann, 1992)
Figyre 13-7, (courtesy Pumps, Inc.).
240 Centrifugal Pumps: Design and Application of the real pressure prevailing at the stuffing box, which results in excessive use of gland water and increased maintenance. Built into some slurry pump designs are methods to reduce pumped pressure at the stuffing box by hydrodynamic means. (For example, see Figures 13-7 and 13-8 for diagrams of pump out vanes on impellers and expellers.) The side-suction-pump configuration is subjected only to suction pressure and has an advantage over end-suction pumps, one not fully recognized by users. By proper application of impeller pump out vanes and expellers, the pressure at the box can be reduced to almost zero. This is called a dry box arrangement. In these cases, weep-type seal is satisfactory, with either water or grease being injected into the cavity formed by the lantern ring. Sump Design Many slurry pump problems will be eliminated if proper attention is given to the sump design. Design considerations are: • The suction feed box should be placed as close to the pump as possible. • The slurry level in the feed box above the pump center line should be at least seven times the pump suction nozzle size. • The feed box should always have a hopper bottom sloping to the pump suction as shown. See Figure 13-9. » The suction pipe should always have a minimum slope of at least 30°; this particularly important when handling settling-type slurries. • The feed box should be sized so there is a minimum retention volume of slurry equal to or greater than two minutes of pump flow. If the slurry is frothy, then a greater retention time is required (e.g. eight minutes of pump flow). • A dump gate should be provided at the bottom of the feed box. « Turbulence near the feed box walls should be avoided to prevent excessive wear. Pump Drive Generally slurry pumps are belt driven because it is almost impossible to match the pump to the system by trimming the diameter of rubber and hard metal impellers, due to their design and materials of construction. Traditionally slurry pumps are driven by V-belts so that pump performance can be adjusted to meet actual conditions of service in the field, thereby saving power and reducing wear. As wear increases, pump output is reduced. This can be easily and inexpensively rectified by increas-
- Page 204 and 205: High Speed Pumps 189 Figure 11-5. I
- Page 206 and 207: High Speed Pumps 191 Figure 11-7. I
- Page 208 and 209: High Speed Pumps 193 Figure 11-9. R
- Page 210 and 211: High Speed Pumps 195 Figure 11-10.
- Page 212 and 213: High Speed Pumps 19? Figure 11-11.
- Page 214 and 215: High Speed Pumps 199
- Page 216 and 217: High Speed Pumps 201 Figure 11-13.
- Page 218 and 219: High Speed Pumps 203 nal bearings a
- Page 220 and 221: High Speed Pumps 205 Barske, U, M.,
- Page 222 and 223: Double-Case Pumps 207 jected to ext
- Page 224 and 225: Double-Case Pumps 209 Figure 12-3.
- Page 226 and 227: Double-Case Pumps 211 Figure 12-4.
- Page 228 and 229: Double-Case Pumps 213 ally by split
- Page 230 and 231: Double-Case Pumps 215 The throttle
- Page 232 and 233: Figure 12-11. pump for 4,000 psi In
- Page 234 and 235: Double-Case Pumps 219 so that the t
- Page 236 and 237: Double-Case Pumps 221 Figure 12-12.
- Page 238 and 239: Doubte-Case Pumps 223 Volute Casing
- Page 240 and 241: Double-Case Pumps 225 5. Survey of
- Page 242 and 243: Slurry Pumps 227 An approximate com
- Page 244 and 245: Slurry Pumps 229 Figure 13-2. Nomog
- Page 246 and 247: Slurry Pumps 231 Table 13-2 Alloys
- Page 248 and 249: Slurry Pumps 233 Figure 13-3. Class
- Page 250 and 251: Figure 13-4, (A) (B) (C)
- Page 252 and 253: Slurry Pumps 237 There is little to
- Page 256 and 257: Flgyr« 13-8, with (courtesy Goulds
- Page 258 and 259: Slurry Pumps 243 ing the pump speed
- Page 260 and 261: Slurry Pumps 245 Where there exists
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- Page 280 and 281: Figure 14-14. Internally adjustable
- Page 282 and 283: Hydraulic Power Recovery Turbines 2
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- Page 298 and 299: 15 by Frederic W. Buse Ingersolf-Ra
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240 <strong>Centrifugal</strong> <strong>Pumps</strong>: <strong>Design</strong> <strong>and</strong> <strong>Application</strong><br />
of the real pressure prevailing at the stuffing box, which results in excessive<br />
use of gl<strong>and</strong> water <strong>and</strong> increas<strong>ed</strong> maintenance.<br />
Built into some slurry pump designs are methods to r<strong>ed</strong>uce pump<strong>ed</strong><br />
pressure at the stuffing box by hydrodynamic means. (For example, see<br />
Figures 13-7 <strong>and</strong> 13-8 for diagrams of pump out vanes on impellers <strong>and</strong><br />
expellers.) The side-suction-pump configuration is subject<strong>ed</strong> only to<br />
suction pressure <strong>and</strong> has an advantage over end-suction pumps, one not<br />
fully recogniz<strong>ed</strong> by users. By proper application of impeller pump out<br />
vanes <strong>and</strong> expellers, the pressure at the box can be r<strong>ed</strong>uc<strong>ed</strong> to almost<br />
zero. This is call<strong>ed</strong> a dry box arrangement. In these cases, weep-type<br />
seal is satisfactory, with either water or grease being inject<strong>ed</strong> into the<br />
cavity form<strong>ed</strong> by the lantern ring.<br />
Sump <strong>Design</strong><br />
Many slurry pump problems will be eliminat<strong>ed</strong> if proper attention is<br />
given to the sump design. <strong>Design</strong> considerations are:<br />
• The suction fe<strong>ed</strong> box should be plac<strong>ed</strong> as close to the pump as possible.<br />
• The slurry level in the fe<strong>ed</strong> box above the pump center line should be at<br />
least seven times the pump suction nozzle size.<br />
• The fe<strong>ed</strong> box should always have a hopper bottom sloping to the pump<br />
suction as shown. See Figure 13-9.<br />
» The suction pipe should always have a minimum slope of at least 30°;<br />
this particularly important when h<strong>and</strong>ling settling-type slurries.<br />
• The fe<strong>ed</strong> box should be siz<strong>ed</strong> so there is a minimum retention volume<br />
of slurry equal to or greater than two minutes of pump flow. If the<br />
slurry is frothy, then a greater retention time is requir<strong>ed</strong> (e.g. eight<br />
minutes of pump flow).<br />
• A dump gate should be provid<strong>ed</strong> at the bottom of the fe<strong>ed</strong> box.<br />
« Turbulence near the fe<strong>ed</strong> box walls should be avoid<strong>ed</strong> to prevent excessive<br />
wear.<br />
Pump Drive<br />
Generally slurry pumps are belt driven because it is almost impossible<br />
to match the pump to the system by trimming the diameter of rubber <strong>and</strong><br />
hard metal impellers, due to their design <strong>and</strong> materials of construction.<br />
Traditionally slurry pumps are driven by V-belts so that pump performance<br />
can be adjust<strong>ed</strong> to meet actual conditions of service in the field,<br />
thereby saving power <strong>and</strong> r<strong>ed</strong>ucing wear. As wear increases, pump output<br />
is r<strong>ed</strong>uc<strong>ed</strong>. This can be easily <strong>and</strong> inexpensively rectifi<strong>ed</strong> by increas-