Application Digest

Solid-state pressure switch can replace multiple components

Raymond R. Williams, P.E.,
Product Manager, Barksdale, Inc., Los Angeles, CA

The measurement and control of multiple pressure points is a common application. Typically, four pressure points would require as many as twelve different pieces of hardware. Engineers can now accomplish the same task with a single, solid-state pressure switch.

A duplex pump control system, for example, requires control logic based on four pressure settings with low- and high-pressure alarms and activation of either the leading or lagging pump. Traditional systems have used either four individual or two duplex electromechanical pressure switches.

Current solid-state technology can improve accuracy, extend life, and reduce installed cost. An example of this would be Barksdale's PS-3 Solid-State Pressure Switch that provides an accuracy of ±0.1% FSO over its 100-million-cycle life.

Four independent switches and deadbands are set via the keypad. A four-digit LED displays either the settings or process condition. The entire system has keypad security and is mounted in a NEMA 4X enclosure.

An electromechanical system might run more than $1,500. Its solid-state counterpart costs less than half that.

To speak with a Barksdale applications engineer, call (800) 835-1060.

O-ring design software saves time and money

Dale M. Ashby, Technical Director Parker Seal, Lexington, KY

O-Rings have been used for years as a cost-effective method of preventing leakage in a variety of applications. This versatility, however, creates a challenge for designers trying to select the correct O-ring seal for the job.

Typically, engineers select the O-ring size and material from graphs, charts, and tables found in a manufacturer's design handbooks. They then calculate such factors as the percent compression (squeeze), installed stretch, volume-to-void ratios, maximum pressure rating, and min/max tolerance. A typical O-ring design may require two hours or more, if the designer performs a number of "what if" studies.

Recently, the power of the computer has been applied to help in the design of O-ring glands and select materials.

One fully integrated Windows-based software package designed exclusively for the O-Ring design and material selection is inPHorm, from Parker Hannifin. It allows the experienced O-ring designer to rapidly perform the following:

Select appropriate O-ring materials for single or multiple fluids. Examine a wide range of O-ring material test reports. Choose appropriate gland dimensions for static and dynamic O-ring seal applications. Select O-rings to fit standard and non-standard O-ring glands. Save and print proposed O-ring seal designs. Access documentation from the Parker O-ring Design Handbook.

All of these activities take just minutes as opposed to hours when done by hand.

To speak with a Parker Seal applications engineer, call (606) 269-2351.