A glass level gauge is a device that allows the liquid level in a
Vessel to be visually inspected. It is useful in many applications, such as monitoring the amount of flows in tank.


Reflex glass is a most common and has prisms molded into the process side. Level indication will show black for liquid and white for gas. Level indication is obvious and illuminators are rarely required. Reflex gauges have glass on the viewing side only, and the single cover per section is held in place with U-bolts. Shields may not be used, as the shield will prevent liquid from filling the spaces between prisms. Reflex gauges are less expensive than transparent gauges and are suitable for most process condition. Do not specify for steam above 300 PSIG (21kg/cm2)

Transparent glass is flat on both sides. Level indication depends on the color of liquid or meniscus. Transparent gauges have glass on both sides of the chamber to allow sufficient light to enhance viewing. Illuminator1 is usually used to supplement ambient light. Point 1: Illuminators used to improve level indication for transparent only.

1. Place seal gasket in chamber seat and cushion gasket in cover seat. Do NOT lubricate gasket or cushion.

2. Locate the glass centrally in the chamber seat and cover to avoid glass-to-metal contact at the ends or sides. (This is best done with the gauge lying flat on a bench.) If the gauge must be reassembled in the vertical position, use a small strip of gasket material as a spacer at each end of the glass. This will prevent any glass-to-metal contact.

3. Inspect bolt and nut threads. If the nut cannot be freely spun down the length of the Bolt threads, then the nut and/or bolt should be discarded. If nuts and bolts show signs of excessive corrosion, they should be discarded.

4. Apply Molykote or similar molybdenum disulfide lubricant to the bolt threads and nut seating Surface.

5. If the gauge includes an option for Belleville spring washers, Reference figure 4 for proper orientation of the washer stacks.

6. Tighten nuts finger-tight, working from the middle set, alternating outward Next, Tighten with a torque wrench in the same sequence in 5 ft.-lb. (6.7 N-m) increments

7. Note: New gaskets often become permanently compressed after a short time in service (especially if the gauge operates hot). This causes slight leaks or apparent loosening of bolts. If the gauge has not been provided with spring washers, isolate and relieve the gauge and re-torque to the original value after the gauge has been in hot operation for 30 minutes.

1. Isolate gauge from service, relieve internal pressure, and drain

2. Remove the gauge from the vessel (if conducting rebuild in a workshop).

3. Loosen end bolts first, then work towards center, alternating from top to bottom And following the sequence for tightening in reverse

4. Remove glass, gaskets, cushions, and shields from assembly. Promptly dispose of all used components.


5. Clean chamber gasket surface and cover cushion seating area. Remove all debris or residual gasket material.

6. Thoroughly inspect chamber gasket surface seating area. Remove any pitting damage, Steam cuts, gouges, or scars on a milling machine


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