Centrifugal Pump Troubleshooting Guideline

orange centrifugal pump

Centrifugal pumps are a sub-class of dynamic axisymmetric work-absorbing turbomachinery – (wikipedia).

It’s a very important device for solids control process. Centrifugal pump is the ideal equipment to provide impetus for shale shaker, desander, desilter and jet mud mixer. Aipu solids control  offers a complete line of centrifugal pumps to accommodate a full variety of drilling applications. Sizes range from 3 x 2 to 8 x 6.

centrifugale pumps for sale
8 * 6 centrifugale pumps

Troubleshooting Guideline

PUMP WILL NOT REACH DESIGN FLOW RATE

A. Insufficient NPSH (noise may or may not be present).

  • Redesign suction piping; possibly enlarge diameter;
  • Keep elbows, and so forth, at a minimum.

B. System head requirements greater than anticipated.

  • Redesign system piping; possibly enlarge diameter;
  • Keep elbows, and so forth, at a minimum;
  • Increase impeller diameter.

C. Plugged impeller, suction line, or pump casing by fibrous or settled solids

  • Clean and install strainer over suction line;
  • For fibrous material, possibly enlarge pump.

D. Entrained air from atmosphere

  • Check suction-line fittings and gaskets for leaks;
  • Repack pump stuffing box;
  • Check suction pit for vortex;
  • Check for minimum suction-line submergence;
  • Check degasser.

E. RPM too slow

  • Check motor speed.

F. Wrong rotation direction

  • Reverse any two of the three leads on a three-phase motor.

G. Impeller worn, has improper clearance, etc.

  • Inspect impeller and reset to proper clearance;
  • If worn, replace.

CENTRIFUGAL PUMP NO DISCHARGE OR FLOW

A. Motor horsepower too small

  • Replace motor with larger size and proper rpm;
  • Motor cannot rotate impeller.

B. Not properly primed

  • Repeat priming operations;
  • Try to have a flooded suction.

C. Suction lift too high

  • Rearrange piping;
  • Increase suction head;
  • May need larger impeller;
  • Check motor speed;
  • May need larger pump for higher suction lift;
  • Check suction line and pump for plugging;
  • Check direction of rotation; if incorrect, change any two leads to motor;
  • Check for entrained air or gas;
  • Move centrifugal pump down to a lower level.

PUMP OPERATES BUT CONTINUALLY LOSES PRIME

A. Insufficient NPSH

  • Redesign suction piping; possibly enlarge diameter.
  • Keep elbows, and so forth, at a minimum.

B. Check for entrained air or gas.

C. If small whirlpools appear on top of liquid level, install baffle plate

EXCESSIVE NOISE—WET END

A. Cavitation—insufficient NPSH

  • Redesign suction piping; possibly enlarge diameter;
  • Keep elbows, and so forth, to a minimum;
  • Abnormal fluid rotation due to complex piping.

B. Impeller rubbing

  • Inspect and reset impeller;
  • Inspect bearing assemblies for end play.

EXCESSIVE NOISE—POWER END

A. Overloaded bearing with races flaking or pitting

  • Suction pressure and/or fluid specific gravity may exceed bearing design.

B.Bearing contamination—raceways scoured, pitted, or rusted

  • Work with clean tools and clean the area around centrifugal pump; provide cover from wash-down water;
  • Clean pump housing before removing;
  • Use clean solvents and flushing oil;
  • Protect bearings from moisture when not in use (wrap in clean paper or clean cloth);
  • Clean interior of pump housing before replacing bearings;
  • Inspect oil lip seals;
  • Inspect plugs and tapped openings for tight closure.

C. Worn bearings

  • Inspect and replace bearings;
  • Improper lubrication including brown or bluish discoloration on races; stiff, cracked grease; failure of ball retainer; dirty or improper amount of lubricant; improper lubricant grade(s);
  • Check shaft straightness;
  • Check bearing alignment;
  • Check housing bore for alignments.

D. Check for electric arcing from static electricity, electrical leakage, or short circuiting.

EXCESSIVE LEAKAGE OF A PACKED CENTERIFUAL PUMP STUFFING BOX

A. Loose packing gland

  • Adjust packing gland while pump is running.

B. Packing excessively worn or improperly lubricated

  • Replace packing and inspect for proper lubrication

C. Bent or scoured shaft

  • Replace shaft and inspect pump for cause.

EXCESSIVE VIBRATION

A. Steady, regular vibration

  • Inspect shaft balance and straightness;
  • Check motor—shaft alignment; inspect coupling;
  • Check baseplate bolting and grouting.

B. Unsteady vibration

  • Bad bearings (largest vibration should be near the bad bearing)

C. Random, extremely high vibration

  • Possible cavitation; improve suction piping layout.

D. Vibration disappears when power is off

  • Check current cps

Note: When mounting a bearing on a shaft, use a proper size ring and apply pressure against the inner rings. When mounting in a housing, press against the outer ring. Apply pressure slowly and evenly.

 

orange centrifugal pump

 

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