Monday, July 11, 2016

Armored Liquid Level Gauges With Specialty Indicators

armored liquid level gages guages for process measurement and control
Armored liquid level gauges provide protection from
mechanical stress and impact
Courtesy Jerguson / Clark Reliance
Sight glass liquid level gauges are a mainstay of fluid processing operations that store raw materials, intermediate, or final product in tanks and other vessels. Having a direct visual indication of fluid level at the tank enhances safety and provides the all important data point about what is happening inside the tank.

These level gauges are installed on the exterior of the tank, exposed to whatever environmental or operational hazards existing or occurring at the location. Armored level gauges are appropriately named because of their construction. They are designed to resist impact and mechanical stress, as well as a range or environmental conditions.

There are generally two versions of armored level gauges, reflex and transparent. The names refer to way in which light is handled by the gauge to reveal the liquid level. One manufacturer of armored level gauges and other level instruments, Clark-Reliance, provides a good description of the two gauge types. Their brand of armored level gauges is Jerguson, and I provide their description here of the two types (source)

Jerguson® Reflex Level Gauges are ideal for clean total level indication applications for refining, petrochemical and general use applications. The reflex prisms are molded and polished to provide a crisp black-silver bi-color indication of the fluid level. As light passes into the reflex glass, if there is fluid present, the light continues through the glass and reflects off the back of the level gauge, providing a black color for fluid level regardless of the actual color properties of the process fluid. If fluid is not present, the light is reflected off the glass back towards the user, providing a shiny silver or mirror-like appearance to indicate vapor space.

Cross section of reflex level gauge 
Jerguson® Transparent Level Gauges are selected for interface level indication, dirty service or any application that requires the use of a shield to protect the glass from corrosion. A transparent gage is also known as a “thru-vision” gauge since the gauge is constructed with two pieces of flat polished glass assembled on opposite sides of the level gauge chamber. Since the user can see straight through the gauge, it is also easy to view the fluid properties, such as color, whereas this would not be possible with a reflex gauge. The use of an illuminator is always recommended on a transparent gauge.
transparent glass liquid level gauge cross section
Cross section of transparent level gauge
Selecting an armored level gauge is an exercise in preparing for known and unknown events that might disable your ability to directly read fluid level. Armored level gauges are employed extensively in chemical, petrochemical, and other industries where reliability under challenging conditions is essential. Wherever there are mechanical hazards, an armored level gauge may ultimately prove to be cheap insurance against downtime or delay.

Share your level measurement challenges with a product application specialist. Combine their product expertise with your process knowledge to produce an effective solution. Below is a data sheet for one of several series of Jerguson armored level gauges, so you can explore more detail. Contact the product application specialists for more information about larger sizes, higher vessel operating pressures, and optional configurations that will best suit your application.