fluid handling and fluid power
This section was written by Michael Valenti, Associate Editor. part 1 / part 2
Versatile Switch for Measuring Chemical processors, metal workers, textile manufacturers, and utilities are among the industries that conduct a wide range of mass-flow-, level-, and temperature-monitoring tasks using the VS 5100 Versa-Switch, made by Delta M Corp. in Oak Ridge, Tenn. A single Versa-Switch can be reconfigured in the field to serve as a dual-mass-flow switch, a dual-level interface switch, or a single-level/flow switch with an independent temperature switch. This flexibility eliminates the cost of purchasing separate measuring instruments and their spares to perform different measurement functions.

Within the Versa-Switch are two miniature resistance/temperature detector (RTD) sensors that change resistance in proportion to a temperature change in the fluid they contact. One RTD is heated by electrical current to establish a temperature differential, approximately 50 degrees F, between the sensor and fluid. The second, unheated RTD provides a reference to the ambient process temperature changes, which serves as temperature compensation over the switchÕs entire operating range.

The Versa-Switch sensor detects the change in the temperature differential caused when fluid contacts the heated sensor to measure point level. For measuring flow, the sensor detects the thermal-differential affect of the fluid as well as the thermal differential change proportional to the velocity of the flow across it. Once detected, these changes are used to actuate valves and safety equipment or to notify plant control systems. Engineers constructed all wetted parts of the Versa-Switches of 316 stainless steel to provide corrosion resistance. The switches can operate in temperatures ranging from 100 degrees F to 572 degrees F; they are also capable of monitoring liquid flows 0.01 to 5 feet per second and gas flows 0.1 to 500 feet per second. Georgia Power, Houston Light & Power, and Southern California Edison are among the utilities that use the Versa-Switch. The switch is also used by chemical-processing firms including Akzo, Degussa, and Monsanto; textile-manufacturer end such as Amoco Fabrics, Kimberly Clark, and Russell Corp.; and metal fabricators including ARMCO Steel, Kaiser, and Norande Aluminum.

Conserving Coolness with Responsive Valves Thermal sensitivity is the key characteristic of FR fluid-sensing valves developed by Ogontz Corp. in Willow Grove, Pa. The valves are used to conserve water and provide maximum cooling-system efficiency in air compressors, heat exchangers, and cooling drums found in refineries, metal-working shops, and plastics factories.

The valves are designed to respond to cooling-fluid temperatures inside the valve body by automatically opening when that temperature exceeds a preset limit. This capability eliminates the wasteful discharge of low-temperature cooling fluid found in many industrial cooling systems, saving both energy and fluid.

At the heart of the valve is a solid/ liquid-phase thermal actuator that converts temperature change to mechanical force for valve actuation. This device is filled with hydrocarbon wax to make it more rugged, and it can open and close the valve against line pressure up to 200 pounds per square inch. Engineers built a controlled leakage path through the valve to provide the thermal actuator with a constant, true temperature. The valve can be supplied with any temperature set point from 40 degrees F to 255 degrees F, over an operating differential of 10 degrees F to 15 degrees F. The valve is equipped with a stainless-steel return spring to permit fail-safe operation, and is designed to be serviced in-line with a replaceable plug and seat.

Alcoa, Du Pont, Dow Chemical, and Shell are some of the companies that incorporate the valves in their cooling operations.

Safeguarding Position Sensors Position sensors establish precision control of hydraulic systems by measuring the position and velocity of hydraulic cylinders. They are compromised, however, by the vibration, shock, and high-precision requirements of tough industrial environments. Minneapolis-based MTS Systems Corp. developed its new Temposonics III and L series position sensors to provide accurate measurement in rugged industrial applications.

Both types of sensors are built from three separate modules, each module consisting of the magnetostrictive sensing element, electronics, and application housing. By separating the modules, the designers eliminated the need for the critical alignments found in conventional magnetostrictive sensors. Engineers fully encapsulated the sensing element head and electronics to make the components more resistant to shock and vibration. Applications for the sensors include primary woodworking, metalworking, plastic processing, and hydraulic and pneumatic machinery.

Temposonics L sensors are designed for maximum reliability and durability. These instruments offer repeatability of ±0.001 percent of scale or 0.002 millimeters, whichever is greater, in either analog or digital output form. Temposonics III, designed to serve smart sensor applications where superior speed and precision are required, are 20 times faster than their predecessors, taking up to 10,000 measurements per second with a resolution of 2 microns, or 0.00008 inch. The electronic module of the speedy sensor can provide one of three outputs: analog, serial synchronous interface, or digital-controller-area network bus.

Small but Powerful Hydraulic Pumps Operators of steel mills, power plants, and other industrial facilities are lifting their heavy equipment with single- and double-acting rams powered by the Vanguard 30 series hydraulic pumps developed by Power Team in Owatonna, Minn. These high-volume, lightweight hydraulic pumps weigh only 41 pounds but deliver 30 cubic inches of oil at 10,000 pounds per square inch, so they can lift 5 to 500 tons.

Power Team engineers equipped the two-speed Vanguard 30 pump with a true unloading valve to achieve high pump efficiency. The pump relies on a 1-horsepower motor that has a completely enclosed permanent magnet design. The motor is available in either a 115-volt or 220/230-volt, 50/60-megahertz model and can run at 50-percent voltage.

The motor can start and run when voltage is reduced down to 50 percent of nominal rating. Another energy benefit of the motor is that at the pump's full pressure load of 10,000 pounds per square inch, the motor draws only 13 amperes at 115 volts and 6.5 amperes at 220/230 volts. Versions of the pump equipped with remote control and/or solenoid valves use 24-volt controls.

The Vanguard 30 is adapted to suit a wide variety of heavy-lifting applications by means of optional valves. For example, the Posi-Check style manual valve has improved porting to provide faster single-acting ram return. The pumps can hold 1 to 1 3/4 gallons of hydraulic fluid in their aluminum reservoirs. A 13/16-inch-diameter port facilitates filling, and a roll-cage carrying handle both protects the pump and makes it easy to carry.

Steel mills use the Vanguard 30 pumps in the maintenance of continuous casting of steel bar. Utilities employ the pump to lift turbines for maintenance. Pulp and paper mills, refineries, and construction companies also use the pumps to lift their heavy machinery during installation, replacement, or maintenance.

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