5
Theory of Operation
The MV250-LL is a rod displacement style metering valve designed to dispense small volumes of fluid
with the highest degree of accuracy. This true positive displacement valve will dispense one small dot of
fluid with each full cycle. Fluid volume is determined by the micrometer adjustment setting and cannot be
affected by changes in fluid viscosity due to temperature or changes in fluid delivery pressure.
MV250-LL volumetric fluid displacement range:
(0.0001 cc – 0.012 cc)
The MV250-LL has a divorced design comprising of two major sections. These include:
•
Air section (red anodized portion)
•
Fluid section (stainless steel portion)
Air Section
The air section is an aluminum body with a simple piston/cylinder combination used to cycle the valve. A
micrometer adjustment in the upper air body controls how far the piston and needle assembly can retract
thus altering the volume of fluid that can be metered and dispensed during each cycle.
Fluid Section
The fluid section is a stainless steel body, which includes a needle, seat, and two integral check valves to
make up the metering chamber. The metering chamber fills as the needle retracts away from the seat, then
dispenses as the needle moves back toward the seat. Such fluids may include but are not limited to;
solvents, epoxies, UV adhesives, silicones, RTV, grease, etc.
Wetted parts on the MV250-LL include:
•
303, 304 stainless steel
•
Teflon
®
•
Kalrez
®
Safety
Due to material contents being under pressure eye protection is required for operators. Refer to MSDS
sheets on material being dispensed for other precautions.
Setup
The MV250-LL requires a 2-position, 4-way air solenoid valve to actuate the air section. The valve should
be operated with clean, dry air between 60-100psi. Two #10-32 threaded air ports are located on the air
section of the valve. The port located closest to the mid-section of the valve is air actuating to fill the fluid
chamber. The port located furthest from the mid-section of the valve is air actuating to dispense material.
Quick connect air fittings are typically supplied with the MV250-LL to fit 5/32"od tubing. Note that the
valve should be normally in the filled and ready to dispense position.
Fluid is supplied to the MV250-LL through the 1/8"npt port located on the stainless steel fluid section of
the valve.