New Feed System Equalizes Gas Flow Rates

May 1, 2004
A new system from USFilter Wallace & Tiernan Products increases safety, eliminates waste and reduces labor associated with traditional manifolding of vacuum regulators...

A new system from USFilter Wallace & Tiernan Products increases safety, eliminates waste and reduces labor associated with traditional manifolding of vacuum regulators commonly used for water treatment gases such as chlorine and sulfur dioxide. The patented system equalizes the gas that flows from several connected gas supply containers under vacuum for maximum safety, and can be used to retrofit existing gas feed installations where unequal withdrawal rates continuously occur or vacuum-manifolded upgrades are desired.

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Adjusted to any gas feed system, the company's Equa-Draw™ system can link up to six 150 lb. cylinders or one-ton gas containers. The system can also be paired with USFilter's Series 55-400 remote vacuum, non-isolating switchover unit to provide an uninterrupted supply of gas for critical drinking water applications.

Whereas standard manifolded vacuum systems require extensive labor to ensure equal withdrawal rates, the new Equa-Draw system automatically equalizes gas flow rates for all vacuum regulators, eliminating the need for rate valves and constant monitoring and adjustment. The system prevents temperature variations, friction loss and vacuum regulator manufacturing tolerances from causing the vacuum-manifolded containers to switch over prematurely and waste chemicals due to uneven withdrawal rates.

The corrosion-proof system uses a standard vacuum supply as its sole power source. By simplifying and encouraging vacuum-manifolded installations, the system eliminates all pressurized gas lines, allowing for the use of smaller gas abatement systems.

How It Works

Installed in the gas outlet line from a vacuum regulator, the Equa-Draw system monitors the pressure drop across a fixed, metering orifice. This pressure drop varies in proportion to the gas flow through the orifice. Each Equa-Draw module has an identical metering orifice at the outlet just before the individual gas feed lines are manifolded together.

An increased or decreased flow through any one of these orifices, in relation to the adjacent orifice, indicates an uneven withdrawal rate between the gas supply containers. When this occurs, an internal throttling valve is used to equalize the flow rates. This valve is connected to a diaphragm that compares the pressure of the monitored module with the adjacent module. Therefore, any pressure differential between the two modules results in repositioning the throttle valve to equalize the flows and rebalance the pressure.

Additional modules can be added, as required, when more containers are added to the supply bank. Since the modules are interconnected, each one is referenced to the adjacent module so the flow is equalized in all modules. External tubing is used to connect the end modules to complete the balance loop. A second, separate set of modules is connected to the other supply bank of gas containers for switchover installations.

To learn more about the Equa-Draw system, please contact Gary Schaeffer at 908-851-6919 or [email protected].

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