Text version of the page 
Text version of the page 
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Liquid End Designs | | | | | | | | | | tures in common. First, the liquid is drawn into the wetted end by the rearward motion of a piston, and expelled by the forward motion. To achieve this, the metering pump is supplied with check valves at the suction and discharge connection points. The check valves contain and release the chemical based on system conditions and gravity. During the suction portion of the stroke, the motion of the piston lifts | | | | | | ■he liquid end, which is referred to as the wetted part of the pump, is selected to meet the specific service conditions of the application. Required flow and pressure ratings are considered, as well as the physical and chemical properties of the liquid. The liquid end's ability to protect the environment is also a major consideration when dealing with toxic or hazardous chemicals. All liquid ends have several fea- | | | the suction ball check from its industrial seat allowing liquid into the pump. At the same time, the piston's motion and system back pressure hold the upper check valve (discharge) closed. This is then reversed during the discharge stroke. Check valves are available in several different designs and configurations. The choice of ball or poppet style is determined by Milton Roy's Engineering department based on capacity of the specific pump. | | | | | | | | | | 4 | | | | | | | | | | | | Ball Checks | | | | | | | | | | | | | | Seat | | | | | | Ц r-----P | | | | | | | | | | | | | | Single Ball Check Valve | | | | | | Double Ball Check Valve | | Poppet Style Check Valve | | | | | | | | | | | | | | | | | 1 rvn 1 I | | | | | Piston | .^^■SL__L ^ Discharge —Suction ' | | | | | | MX1__L | 1 | | | | | | | | | | | | | | | | | | | | | | | Most pumps feature either single or double ball configuration as standard. The user can also select single or double ball when the application is better served by one or the other. For example, slurries or liquids with large fibers or particles can cause a single ball to leak if particles are trapped between the ball and seat. Therefore, a double ball check offers more stability and accuracy. On the other hand, since each check valve causes some resistance in the flow path even when open, viscous fluids are better handled with a single ball suction check valve. | | | | | | | | | | Process Fluid | | | | | | | | | | Suction Ball Check Valve | | | | | | | | | | | | | | Packed Plunger The packed plunger style liquid end is the only liquid end in which the piston is in direct contact with the process fluid. This direct contact offers a number of advantages, including: high suction and discharge pressure capabilities; high temperature resistance, and lowest NPSH requirements. The reciprocating piston requires packing to industrial seal the wetted parts from the atmosphere. This simple design is effective, but places limitations on the use of packed plunger pumps in certain applications. Because a small amount of controlled leakage past the packing must be expected, this style liquid end should not be used with hazardous or toxic chemicals. Additionally, the friction between the piston and the packing results in wear that increases leakage. Periodic packing adjustment is necessary to maintain volumetric efficiency. To avoid problems associated with leakage, consider a diaphragm style liquid end. The packed plunger can handle pressures up to 15,000 psi, and temperatures to 600oF (with special modifications). | | | | | | Discharge Ball Check Valve | | | | | | | | | | Available on: Milroyal B, Milroyal C, Milroyal D, Centrac, and Maxroyal. Standard Materials of Construction: 316 SS, Alloy 20, Cast Steel (larger models) | | | | | | | | | | | | | | 4 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
|