CSI pumped venturi metering pumps |
Most piston and diaphragm metering pumps |
|---|---|
| Simple flow rate adjustment: No need to stop the metering pump. Adjust the metering valve and immediately see the effect of the adjustment on the built-in flowmeter. |
Complex flow rate adjustment: Stop the metering pump. Change stroke length. Calibrate. Repeat the procedure until you get it right. |
| Foolproof calibration: Built-in flowmeter provides continuous flow rate information. |
Tiresome calibration procedure: The only way to check flow rate is by timing the emptying of a calibrated cylinder with a stopwatch. |
| Excellent accuracy and repeatability: Pumped venturi injects at constant rate over its whole operating pressure range. |
Flow varies with line pressure: Flow rate fluctuates when pipeline pressure changes, due to diaphragm flexing and/or ball-check seating. |
| Smooth flow: Venturi draws injected fluid into the water stream smoothly, continuously. |
Pulsing flow: Flow starts and stops with each stroke of the pump. |
| No bleed valve: Venturi systems are inherently self-priming — even when the injection lines are dead-dry. |
Bleed valve needed: Most reciprocating metering pumps require bleed valves and manual priming from a dry condition. |
| No backpressure valve needed: All required flow devices are included with the metering pump. |
Backpressure valve adds cost: Injection quill backpressure valve adds to initial cost and adds another component that needs maintenance. |
| Gentle injection: Smooth flow eliminates harmful vibration and mechanical stress in the chemical pipework. |
Pulsing Injection: Vibration is often quite violent in the supply and discharge tubing of diaphragm and piston pumps. |
| Ideal for closed-loop control: Flowmeter can provide a measurement signal for flow verification and process control. Output from a controller can set the injection rate by means of a motive pump VFD. |
Mostly unsuitable for closed loop control: Accurate measurement of reciprocating pump flow is impractical. Thus piston and diaphragm pumps are almost always controlled as open loop devices. |
| Excellent dispersion: Injected materials go through 2 stages of smooth dispersion, the first stage at the venturi and the second stage when the liquid enters the main pipeline. |
Poor dispersion: Concentrated material goes directly into the main pipeline without pre-dilution. Even centerline quills cannot change the pulsating nature of the injection. |
| Simple mechanism: Water from the centrifugal pump drives a venturi. No gears, diaphragms or pistons. Only one wearing part: the centrifugal pump seal. No lubrication needed. |
Complex mechanism: Reciprocating motion has many more moving parts. Oil fill and/or lube points are needed. Repairs require a skilled mechanic. |
| No contact between pump and the injected chemicals: Injected liquid enters the water stream at the venturi — DOWNSTREAM of all moving parts. |
Whole pump is in contact with injected chemicals: All wetted pump components are in continuous contact with injected chemicals. |
| Greater safety: Concentrated chemical is under vacuum. Leaks are less likely, and they are less hazardous if they do occur. |
Less safety: Concentrated chemical is under high pressure between the pump and the pipeline. It can spray out from any leak. |
| Wide capacity range: Single venturi metering pump models allow injection rates from 1 gph to 400 gph. Special designs are available for even higher flows. |
Narrower capacity range: Most piston pumps are limited to flows of 200 gph or less. |
| Excellent turn-down: CSI offers configurations where minimum repeatable flow can be less than 1% of maximum flow. |
Delivery problems at low flow: Accuracy/repeatability of most piston and diaphragm pumps deteriorates badly at flow less than 10% of capacity. |
| Injecting multiple chemicals is easy: Several venturis can be installed in parallel on one centrifugal pump. CSI models are available for smooth simultaneous injection of 1, 2, 3 or 4 chemicals. |
Injecting multiple chemicals is difficult: Some suppliers offer dual head pumps, but these suffer all the same disadvantages as their single-head pumps. |
| More power options: In addition to providing metering pumps for any country’s electrical characteristics, ChemIndustrial offers gasoline, diesel and hydraulic powered versions of most metering pump models. |
Few power options: Only a few piston and diaphragm pump manufacturers offer anything other than electric motors. |
| System capabilities: ChemIndustrial can complete your process integration projects by designing and building process skids to add controls, instrumentation, piping, valves, supports, etc. Specialized applications like blending, batching, pH control, neutralizing and cooling tower treatment are routinely handled by standard CSI designs. |
Component suppliers only: Most piston and diaphragm pump vendors move their iron and leave you or your engineering firm to handle the process integration task. |
| Do it your way: CSI offers you more capacity choices, more simultaneous metering choices, more power choices and more system capabilities than any other metering pump supplier. |
Why do it their way? |
For answers to your questions about pumped venturi metering pumps or systems based on this technology contact ChemIndustrial.