Drilling

The Modern Mud Pump







  



	Since the modern mud (or slush) pump was built approximately 60 years ago, the industry has widely accepted the three cylinder or triplex style pump. 


	
	
by Shaun White, White Star Pump Company


	

	



	

	
Triplex mud pumps are manufactured worldwide, and many companies have emulated the original design and developed an improved form of the triplex pump in the past decade.


The triplex pump has a basic, simple design (see Figure 1).

	Figure 1a. Triplex pump side view


Figure 1b. Triplex pump plan view


As in all single acting pumps, the piston exerts a load on the crankshaft. The load is then transmitted to the crankshaft main bearings, which are set in their retainers in the pump frame or housing (see Figure 2).

	

	Figure 2. Loads on crankshafts


The middle piston often exerts seven times greater bending moment on the crankshaft than either of the outer two pistons, causing the crankshaft to bend or flex. Where the force is directed along either of the outer two piston rods to their respective outer two crankshaft cams, the force is close to the bearings and the bending moment is considerably less. However, when the center piston is under pressure and the forces are directed down the middle connecting rod to the central cam, the distance of that central cam from either main bearing is large (sometimes 850 mm or 33 in), thus allowing for a large bending moment and resulting in significant flex in the crankshaft.


	
	







			
	

  


  

    

          
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