Sight Glass Plate Reflex Level Gauge
The reflective liquid level gauge is a device that utilizes compression U-bolts for connection and employs a light-transmitting glass plate to directly indicate and observe changes in the liquid level of the medium within a vessel.
This liquid level gauge is primarily composed of the main body, upper valve (vapor valve), lower valve (liquid valve), drain plug (or drain valve), and safety steel balls. When the glass plate is damaged due to breakage or other reasons, the safety steel balls will automatically seal the valves on the vapor and liquid sides, thereby preventing or reducing the leakage of the medium, while also facilitating the manual closing of the root valves of the liquid level gauge for subsequent handling. This series of products is sturdy, reliable, and easy to install, making it an ideal instrument for liquid level observation in various medium- and low-pressure vessels.
The liquid level gauge is connected to the upper and lower flanges of the vessel via its own upper and lower flanges, forming a communicating vessel structure to achieve direct observation of the liquid level.
Caractéristiques principales
For the reflex monochromatic liquid level gauge, the gas phase appears white (silvery) and the liquid phase appears black; for the reflex bicolour (or dual-color) liquid level gauge, the gas phase appears red and the liquid phase is black (or shows the natural color of the liquid depending on the specific manufacturer’s design/model spec).
1.Direct Visual Liquid Level Indication
The glass level gauge provides a true, real-time visual indication of the actual liquid level inside tanks and vessels. Unlike electronic sensors, it displays the liquid position directly through the sight glass, allowing operators to immediately identify level changes, foaming, or abnormal conditions.
2. Integrated Quick Shut-Off Safety Device
Designed with a built-in quick shut-off mechanism, the gauge automatically isolates the process in the event of glass breakage or leakage. This safety feature effectively prevents vapor or liquid escape, enhancing operator safety and minimizing process risks.
3. Robust & Practical Structural Design
The sight glass level gauge features a compact and well-engineered structure, ensuring easy installation on existing tanks or pipelines. Standard process connections allow for fast commissioning, while the modular design simplifies routine inspection and part replacement.
4.Low Maintenance & Cost-Effective Operation
With no power supply or signal components required, the glass level gauge offers long-term stable operation with minimal maintenance. The durable glass and metal components reduce downtime and spare part costs, making it an economical solution for continuous level monitoring.
Caractéristiques techniques
| Recommended C-C distance: | 500, 550, 800, 850, 1150, 1450, 1750mm |
| Visible length: | 260, 560, 860, 1160, 1460mm |
| Material: | Carbon steel, SS304, SS316L |
| Nominal pressure (MPa): | 1.6, 2.5, 4.0, 6.4, 10.0, 16.0, 20.0, 26.0MPa |
| Température de travail : | ≤450℃ |
| Connection flange: | DN25 HG/T 20592-2009 |
| Steel ball closing pressure: | ≥0.3MPa |
| Light: | LED, 24VDC, 220VAC, non-explosion proof |
Sight Glass Plate Reflex Level Gauge Application
With its robust structure, resistance to high pressure and high temperature, intuitive and clear readings (gas phase appears white/red, liquid phase appears black), and freedom from complex circuitry, the reflex level gauge (Reflex Level Gauge) is widely used for liquid level observation in various medium- and low-pressure vessels across industrial fields.
- Petrochemical and Refining Industry
- Power and Energy Industry
- Water Treatment and Environmental Engineering
- Pharmaceuticals and Fine Chemicals
- General Industry and Mechanical Manufacturing
FAQ
How to handle a reflective level gauge when dealing with dirty media?
When dealing with dirty or contaminated media during the operation of a reflex level gauge (such as suspended solids, impurities, oil, crystals, or sediments adhering to the glass plate or safety steel ball), the following treatment and response measures are typically adopted:
1. On-Site Operation and Maintenance
Regular Flushing via the Drain Valve (or Drain Plug)
Method: The bottom of the level gauge is usually equipped with a drain valve or drain plug. By periodically opening the drain valve slightly, the pressure of the medium within the vessel can be used to flush out dirt, impurities, or sediments accumulated at the bottom.
Remarque : Operators must exercise caution regarding safety protection against high-temperature and high-pressure media, and wear appropriate anti-scalding and anti-corrosion gear.
Isolation and Disassembly Cleaning Using Root Valves
Method: If stubborn dirt adheres to the inner side of the glass plate, causing blurred vision, the upper and lower root valves (vapor and liquid valves) can be manually closed first to isolate the level gauge from the main vessel. Then, open the drain valve to relieve pressure, and remove the level gauge body for manual cleaning.
Cleaning Method: Use warm water, neutral detergent, or a suitable solvent to remove oil and attachments from the inner wall of the glass plate. For stubborn crystals or sediments, use a soft cloth or specialized tool to clean them. The use of hard metal tools to scrape the glass surface is strictly prohibited to avoid scratching or damaging the reflective grooves.
2. Design and Selection Prevention (Reducing Contamination at the Source)
If the process medium contains dirt, is prone to scaling, or is viscous over the long term, consider the following strategies during equipment selection or subsequent retrofitting:
Installing Flushing or Purge Connections
Design auxiliary flushing connections on the upper/lower valves or the body, and equip the line with steam, compressed air, or clean water purge pipelines during shutdown maintenance to periodically flush the interior online.
Opting for Special Materials or Anti-Adhesion Coatings
For media prone to scaling, choose glass plates with specially treated surfaces (such as anti-adhesion coatings) to reduce impurity attachment.
Switching to Alternative Level Gauge Types (When Severe Conditions Prevail)
If the medium is extremely turbid, contains a large amount of solid particles, and easily clogs the level gauge passage or safety steel ball, the reflex level gauge may require frequent maintenance. In such cases, evaluate whether to switch to a magnetic flap level gauge (isolated measurement, unaffected by medium transparency and dirt adhesion) or radar/ultrasonic level gauges and other non-contact instruments.
What causes a false liquid level indication?
A false liquid level indication in a reflex level gauge (as well as other gauges based on the communicating vessel principle)—meaning the liquid level shown on the gauge does not match the actual level inside the vessel—is typically caused by the following main reasons:
1. Blockage, Scaling, or Partially Closed Valves in the Vapor or Liquid Connection Pipes
Cause: If the upper valve (vapor valve) or lower valve (liquid valve) is not fully opened, or if the interior of the pipe is blocked by impurities, crystals, or sediments from the medium, the pressure inside the vessel cannot be properly transmitted to the level gauge.
Manifestations: * If the lower liquid pipe is blocked, the liquid inside the gauge cannot flow out as the liquid level in the vessel drops, creating a false indication that the level remains high.
If the upper vapor pipe is blocked, the vapor pressure cannot balance, forming a closed air cavity inside the gauge, which prevents the liquid from truly rising or falling due to differential pressure.
2. Automatic Sealing by Safety Steel Balls (Malfunction or Jamming)
Cause: Reflex level gauges are usually designed with internal safety steel balls (when the glass plate suddenly breaks, the high-speed escaping medium blows the steel ball up to automatically seal the channel). If severe water hammer, pressure fluctuations occur, or if the steel ball gets stuck in a semi-closed state due to long-term scaling, the steel ball will abnormally obstruct the normal flow of the medium.
Manifestations: The liquid inside the level gauge cannot flow freely in and out, causing the indicated height to stagnate or react sluggishly.
3. Changes in Medium Density or Temperature Differences (Density Difference Caused by Thermal Differentials)
Cause: Exposed to the external environment, the temperature of the medium inside the level gauge often differs from the actual temperature inside the main vessel (especially in high-temperature or freezing environments, or when thermal insulation/tracing is absent).
Manifestations: Temperature differences lead to changes in medium density, causing physical deviations in the height of the liquid columns on both sides of the communicating vessel (according to the hydrostatic balance principle, different densities lead to unequal heights), thereby producing a slight visual false liquid level.
4. Internal Leakage of the Drain Valve
Cause: If the drain valve (or drain plug) at the bottom fails to close tightly due to wear or impurity jamming, resulting in a trace internal leak.
Manifestations: This will cause the liquid inside the level gauge to slowly drain away, showing a false liquid level lower than that actually inside the vessel.
5. Glass Plate Contamination or Optical Illusion (Failure of Bicolour/Monochromatic Refraction)
Cause: Although this does not involve a physical error in liquid level height, severe oil stains or crystals adhering to the inner wall of the glass can cause the light refraction principle to fail (the reflection contrast between the gas and liquid phases disappears or blurs).
Manifestations: Operators may mistake blurred stains for the liquid surface or fail to distinguish the gas-liquid interface, leading to a “reading-type” false judgment of the liquid level.
Troubleshooting and Handling Recommendations: When a suspected false liquid level is detected, check according to the following steps:
Verify Upper and Lower Root Valves: Confirm whether the vapor and liquid valves are in the fully open state.
Flush and Drain: Slightly open the drain valve for a brief flush to remove impurities at the bottom and reset any safety steel balls that may be stuck (exercise safety precautions).
Isolate and Inspect: Close the upper and lower root valves, open the drain valve to relieve pressure, and then disassemble to inspect whether the interior is blocked or check the condition of the glass plate and steel balls.
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