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1.2 PRINCIPLES OF OPERATION DRIVE ASSEMBLY(SEE FIGURE 1-2)

The pump consists of two major assemblies; the drive and the liquid end. Pump delivery is a function of the

drive's stroke rate, liquid end size and stroke length. Stroke length can be increased while the pump is running

by counterclockwise turning of the stroke adjustment knob. The drive assembly works on the principle of a

variable eccentric. The rotational motion of the motor is transmitted by the worm (1) to the worm gear(2) which

is linked to an eccentric system (3). The eccentric system then converts the rotary gear motion into linear

reciprocating motion of the connecting rod(4). At 0% capacity setting, the connecting rod axis (B) is aligned

with the gear axis (A) and no movement of the connecting rod takes place. At 100% capacity setting, an

eccentricity exists between the connecting rod axis (B) and the gear axis (A) which results in linear movement

of the connecting rod and resulting pumpage.

Mechanically Actuated Diaphragm Liquid End(See Figure 1-2)

The diaphragm assembly (5) is mechanically linked to the connecting rod (4) and has the same reciprocating

motion. As the diaphragm starts back on the suction stroke, the pressure immediately drops inside the liquid

end. When the pressure in the liquid end drops below the suction line pressure, the suction ball check is

"pushed" upward and the process uid in the suction line ows into the liquid end chamber (diaphragm head).

When the suction stroke ends, the diaphragm movement momentarily stops and the pressure in the liquid end

equalizes with the pressure in the suction line causing the suction ball check to reseat.

NOTE:

It is important that the pressure in the liquid end remain above the vapor pressure of the process

uid during the suction stroke. If the uid pressure drops below the vapor pressure, cavitation will occur

which will have a negative impact on the performance of the pump. If you suspect the possibility of

cavitation, contact your dealer for assistance.

Figure 1-2

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Milton Roy GM Series User Manual

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