Purpose of a VPA Filling & Metering Pump… Imagine having an employee who constantly measures out a precise dose of liquid whenever it’s needed.
But a Series VPA Air-Operated Filling & Metering Pump is much more accurate… …and it doesn’t spill or drip. It also measures a lot faster!
Uses for an Air-Operated Filling & Metering Pump 1.Exact filling of a batch of containers. 2.Adding a precise amount of liquid to a mixture, container, or pipeline. 3.Deliver a regularly timed, repeatable dose. 4.Deliver a precise dose sporadically, when signaled by a control system or an operator.
How it Works: There are three key components to Series VPA Air-Operated Metering Pump… 1.Check Valves 2.Internal Piston 3.Compressed Air, with 4-way air solenoid valve (not shown).
There are two chambers in the pump. The LIQUID chamber, which fills with and discharges liquid. The AIR chamber, where compressed air is used to drive the piston.
Using controlled compressed air, the piston moves to both fill and discharge the pump. Proper flow – filling and discharging – is assured by the check valves. Let’s look at it, step-by-step…
To accomplish this, compressed air is directed into the air chamber on “top” of the piston. First, we need to draw liquid into the pump from the supply source.
The compressed air begins to act on the piston, and the piston starts to move. Notice that the air beneath the piston in the liquid chamber is being forced out through a vent. Likewise, the air beneath the piston in the air chamber is expelled through the 4-way air solenoid valve.
As compressed air forces the piston down, a vacuum is created in the upper section of the liquid chamber. This vacuum draws open the inlet check valve, and liquid is sucked into the chamber.
The piston continues its stroke. Negative pressure in the liquid chamber continues to draw the liquid in.
This negative pressure also draws on the outlet check valve, assuring that it will stay closed during this fill stroke.
The piston moves until it reaches the limit stop. This limit stop is a screw that can be set to change the volume of the dose.
Compressed air flow stops momentarily while the air control valve switches. Both inlet and outlet check valves are closed. Now we see that the pump is fully loaded with liquid, ready to discharge and deliver the precise amount in the liquid chamber.
The 4-way air control valve switches, and now begins to direct compressed air below the piston in the air chamber.
Air pressure beneath the piston begins the discharge stroke.
As the piston moves up, liquid pressure forces open the outlet check valve, and discharge begins.
The piston continues moving, the outlet check valve is fully open…the pump is discharging.
Notice that the air above the piston – the air used to fill the pump – is discharged through the same vent used for filling. (It’s all controlled by the 4- way air solenoid valve.)
Throughout the discharge stroke, the inlet check valve remains closed, even though the inlet pipeline has liquid present.
When the piston reaches the stop in the air chamber, the discharge stroke is complete. The VPA Metering Pump has delivered a precise amount of liquid.
The pump is primed, and ready for the next fill stroke. With liquids similar to water, the pump can cycle up to 10 times per minute. Cycle rate is reduced as liquid viscosity increases.
Series VPA is unlike any other “metering pump.” Each cycle delivers a precise amount Volume is adjustable via built- in Limit Stop Self-priming Controlled by common, inexpensive 4-way air control valve
Plast-O-Matic Series VPA chemical metering pumps are available with maximum per cycle capacities of 7 ounces, 10 ounces, 32 ounces and 128 ounces. Using the Limit Stop, the per cycle discharge capacity can be infinitely adjusted from its maximum to 20% of its maximum. For example: the 128 ounce pump can be adjusted to discharge anywhere between 25 and 128 ounces per stroke. Versatile Sizing…
While the pump discharge adjustment is simple, it is recommended that the discharge amount be physically measured. Once the measured amount is set and checked the accuracy of the discharge repeatability is approximately 1/2 of 1%. To see a brief video of how the pump functions and the limit stop is adjusted, please click here.please click here. (must have internet connection) …and incredible accuracy!
Series VPA pumps are available in PVC, Natural Polypro, and Kynar PVDF. It is also offered with PTFE cap seals, and stainless steel cylinder walls. In lab tests with water, pumps with PVC cylinder walls will last between 100,000 and 300,000 cycles. Over 1,000,000 cycles is achieved in testing with optional stainless steel cylinder walls. Rugged construction…
Proximity sensors are available to verify position on all metering pump sizes. These can be used to power a relay, stage a filling line, signal a computer, signal a fill station counter, or signal virtually any other process control. Switches are ideal to verify that the pump has discharged or retracted, or both.
So what is this pump used for? Applications that need terrific accuracy. Applications where a dose must be delivered – but only when signaled to do so. It’s not a continuous pump, it won’t do what a double diaphragm pump does. But no other pump will do what the VPA does. For example… Deliver an exact amount of additive to paint cans in a filling line. Pump and discharge a preservative/lubricant to railroad ties, as part of an automated system using an electric eye. Fill bags with reactive liquid, causing the bags to expand and control the force of dynamite in mining operations. …the applications for Series VPA are limited only by your imagination!
Series VPA Air-Operated Filling & Metering Pump