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ANSI B16.5 Process Flange

These are a very common type of flange used throughout the process industry. They bolt into the side of tanks, pressure vessels and piping systems. The flanges are available in Class 150, 300, 450 and 600, which allow operating pressures up to 1,580 Psi.

In level applications, the weight of the liquid above a point creates a pressure that is measured by the diaphragm based sensor. The density of the liquid needs to be known, and this type of measurement is suitable for liquids that are corrosive, have extreme temperature and contain solids.

The flange assemblies can be liquid filled where the diaphragm isolates a delicate sense element, or direct where the diaphragm displacement is calibrated and the motion is used to measure level.

Isolation Diaphragms

Kearflex offers a line of diaphragms specifically used for isolation applications. This is where there is a fluid fill behind the diaphragm which trasmits pressure to a remote, or "isolated" sensor. The sensor can be of any type including strain, gauge, piezo, capacitive, inductive and optic.

Direct Acting Switch

In a direct acting assembly the diaphragm displacement with respect to pressure, and therefore level, is calibrated.  The diaphragm acts like a linear spring and will move a known distance with pressure, and this displacement can be converted into level.

The diagram shows a simple level switch.  This direct acting switch has several advantages.

No Liquid Fill 

There is no liquid fill as used with isolation diaphragms, and therefore no possibility of contaminating a critical process in the event a diaphragm is damaged.

Very Sensitive Diaphragms

A very sensitive diaphragm can be used which can detect down to a few inches of liquid. This allows quick detection if mounted in a spill containment vessel, or overfill protection if mounted at the top of a storage vessel.

Alternative Technology

The switch is not electronic or microprocessor based - it will remain operational in the event of electrical or electronic interference, and is a suitable backup of other technologies.


Direct Acting Mechanical Movement

With the same benefits as the direct acting switch, the mechanical movement provides level indication in tanks as small as 2 feet in size.


Direct Acting Electronic Output

The position of the diaphragm can be detected using a Linear Variable Differential Transformer (LVDT) with either internal signal conditioning, or a straight AC/AC interface.

The sensor can also be of any other type including strain gauge, piezo, capacitive, inductive and optic.

The direct acting diaphragms do not require and oil fill, and eliminate the potential to contaminate the process if the diaphragm is damaged.

Sanitary Style Flanges

Used in the food processing and pharmaceutical industries, the isolation diaphragm provides a sterile sensing interface.  These diaphragms include special internal angles that allow natural drainage for in place cleaning and sterilization.

Industry specific surface finishes include electro-polishing and bio-compatible coatings. The assemblies are installed using standard quick release clamps.

The sanitary flange has the same functionality as the ANSI flanges described above, and can be configured with isolation diaphragms to support liquid filled sensing, or direct acting diaphragms that operate switches, movements or electronic detectors.

The direct acting diaphragms do not require an oil fill, and eliminate the potential to contaminate the process if the diaphragm is damaged.


The purge method of hydrostatic pressure measurement in liquids is commonly called the "bubbler". The bubbler functions by forcing gas out of the bottom of an open tube submerged in the liquid, similar to blowing bubbles through a straw, and the backpressure in the purge line is measured.  This pressure is equal to the hydrostatic pressure at the exit point of the tube.

The isolation provided by the purge of gas down the sense lines makes the bubbler an excellent choice for tanks with corrosive, acidic, volatile, molten, cryogenic, hazardous or radioactive liquids

The bubbler can be located away from the vessel to provide easy and economical access for testing, calibration, certification and maintenance.  The bubbler does not require service at the measurement point, and personnel are not exposed to the measured media.  The remote installation will provide safety with dangerous liquids, and offers containment with EPA controlled media.

The simplicity and reliability of the bubbler also make it a good choice for almost any level application.  By using a differential pressure transducer closed tanks can also be measured.


Custom Features:

Customer specified pressure transducer
Redundant mechanical gauges and switches
Power out operation with bottled gas
Power out indication with mechanical gauges
Measures level as low as 6 inches
Measures level as high as 250 feet
Standard Pump Controls - sequential and load share
Fault monitoring and alarm outputs
Can be configured for very low power consumption


Remotely located
Indirect Measurement
Use any standard transducer
Use any mechanical gauge
Use any mechanical switch
Customized by application
Suitable for hazardous material
Not affected by foam

Level Applications:

Open tank
Closed tank
Open channel flow
Water table monitoring
Well and pump operations
Overfill protection
Containment vessel leak detection
Tide monitoring
Rainfall measurement