This rig features a Mission 4-by-5 centrifugal pump. Courtesy of Higgins Rig Co.

As I traveled and questioned drillers, I found that opinions of the centrifugal pumps varied. "Best pump ever built," "What a piece of junk" and "Can't drill more than 200 feet with a centrifugal" were typical of varying responses. Because different opinions had confused the issue, I concluded my discussions and restarted my education with a call to a centrifugal pump manufacturer. After that conversation, I went back to the field to continue my investigation.

For the past eight months, I have held many discussions and conducted field visits to understand the centrifugal pump. As a result, my factual investigation has clearly proved that the centrifugal pump has a place in mud rotary drilling. The fact also is clear that many drilling contractors do not understand the correct operational use of the pump. Following are the results of my work in the field.

Some of the primary benefits of the centrifugal mud pump:

• High up-hole velocity - High pump flow (gpm) moves cuttings fast. This works well with lower viscosity muds - reducing mud expense, mixing time and creating shorter settling times.
  
• Able to run a desander - The centrifugal's high volume enables a desander to be operated off the pump discharge while drilling without adding a dedicated desander pump.
  
• Easy to operate - Watch the flow, not the pressure. When flow decreases, reduce bit load. Begin drilling when flow resumes.
  
• Smooth running - Centrifugals pump without the inertia and "sway" effect piston pumps can sometimes generate while running
  
• Lower investment cost - Centrifugals require half the investment of a piston pump.
  
• Rebuild time and cost - Centrifugals are easy to overhaul, with a low parts cost.
  
• Lighter weight - Centrifugals are a fraction of the weight of a piston pump.

Eight key operating tips and considerations for centrifugal mud pumps:

1. Begin drilling with mud rather than clear water to reduce surface wash out.
2. Priming the centrifugal pump can be done with a water injection pump.
3. Attaching a foot valve on the suction end ensures prime being held in the pump.
4. Centrifugals do not pump grouts as well as a piston pump.
5. Centrifugals require a sealed housing and suction hose. Any air suction will greatly reduce pump efficiency.
6. Sticky clays will stall a centrifugal pump's flow. Be prepared to reduce your bit load in these conditions and increase your rpm if conditions allow. Yes, clays can be drilled with a centrifugal pump.
7. Centrifugal pumps cannot pump muds over 9.5 lbs./gal. Centrifugal pumps work best with a 9.0 lbs./gal. mud weight or less. High flow rate move cuttings, not heavy mud.
8. Centrifugal pumps perform best in a vertical position with the intake as low to the ground as possible.

The goal of this article has been to increase awareness of the value of the centrifugal pump and its growing use. Although the centrifugal pump is not flawless, once its different operating techniques are understood, drilling programs are being enhanced with the use of this pump.

If you wish to learn more, please talk directly to centrifugal pump users. Feel free to call me at 314-909-8077 for a centrifugal pump user list. These drillers will gladly share their centrifugal pump experiences.

Links

• Schramm Inc.