Differential Pressure: A Difference You Can See

From:WIKA
Differential pressure gauges are often found in industrial process systems and yet, they are easily overlooked or misunderstood. In fact, a differential pressure gauge can often times provide multiple solutions to everyday problems.

Differential pressure (DP or ∆p) is the difference between two applied pressures. For example, the pressure at point “A” equals 100psi and the pressure at point “B” equals 60psi. The differential pressure is 40psi (100psi – 60psi).

A differential pressure gauge is a visual indicator, designed to measure and display the difference in pressure between two pressure points in a process system. They typically have two inlet ports, each connected to the pressure points that are being monitored. In effect, the differential pressure gauge performs the mathematical operation of subtraction through mechanical means. This eliminates the need for an operator or control system to watch two separate gauges and determine the difference in readings.

Typical applications for differential pressure gauges in refineries, petrochemical or chemical plants include filter monitoring, liquid level measurement and flow measurement.

Filter Monitoring

Filtration is a vital part of an efficient operation in industrial process systems. A differential pressure gauge can be used to detect a contaminated or clogged filter. As the filter collects foreign materials, the pressure before the filter builds up. The Differential pressure gauge measures the pressure before and after the filter. The more the filter gets clogged with particles, the more the differential pressure increases. Once the differential pressure reaches a maximum value, then the operator knows that the filter needs to be changed.

Liquid Level Monitoring

Sealed tanks often have an atmospheric pressure gas blanket on top of the contained liquid. The pressure of the gas blanket adds to the hydrostatic pressure created by the water column of the content. This makes it difficult to get an accurate level measurement using a conventional pressure gauge. A differential pressure gauge measures the difference in gas pressure from the total pressure, thus translating into a true liquid level reading. Differential pressure gauges can also be used on production and injection wells to measure the difference between reservoir pressure and bottom-hole pressure, or between injection pressure and average reservoir pressure.

 Flow Monitoring

Differential pressure gauges are also used to measure the flow of a liquid inside a pipe. Utilizing an orifice plate, venturi, or flow nozzle to reduce the diameter inside a pipe; the differential pressure gauge measures the pressure before and after the orifice. The pressure drop across the orifice is then mechanically translated by the differential pressure gauge into the flow rate. Differential pressure gauges are an uncomplicated solution for a visual indicator when measuring process flow.

Why WIKA
WIKA Instrument Corporation offers a wide variety of differential pressure gauges that are best suited for industrial processing applications. WIKA's differential pressure gauges offer an assortment of housing materials, wetted parts, dial sizes, connection types, mounting configurations, and custom dial art work. Design options include: piston-style, dual diaphragm and the all-welded/all stainless steel models.

Piston-style differential pressure gauges (Wika Type 700.04) are designed for a long service life. The piston-style differential pressure gauges are best suited for use with clean liquid or gaseous media where low differential pressure ranges and static working pressures are required. Piston-style differential pressure gauges are also available with a separating diaphragm (Wika Type 700.05) for applications that do not tolerate a flow-by, such as liquid level applications. Both feature a 7 year limited warranty.

Dual diaphragm differential pressure gauges are ideal for applications requiring high working pressure in combination with very low differential pressure. The pressurized components are mounted outside the case and face plate for maximum safety. Dual diaphragm differential pressure gauges feature an all stainless steel construction with 316 wetted parts. These gauges are suitable for high working pressures up to 3600 psi regardless of scale range.

The all-welded/all stainless steel construction model (Wika Type 732.51) is best suited for applications with corrosive atmospheres or media, pressure pulsation, system vibration, wide range of ambient temperatures, or high media temperatures.

Don't overlook where a difference can be seen. WIKA Instrument Corporation's differential pressure gauges are available in an assortment of styles, designs, and solutions that are perfect for industrial process systems.

For additional information please visit our website www.forberg.com or contact  Forberg Scientific customer service.
Toll Free: 855-288-5330
Email: mechanicalsales@forberg.com

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