How to choose the shell material of a radar level gauge depends not only on reducing costs for low pressure, but also on ensuring the protection rating, corrosion resistance, and compatibility with the actual site environment. For a level measurement system, the shell of a radar level gauge is both an external barrier and an important foundation for stable operation. If the shell is chosen incorrectly, it may lead to seal aging and surface corrosion at best, or affect circuit reliability and increase downtime and maintenance costs at worst.

First, understand what task the radar level gauge shell is meant to handle

When discussing model selection, many discussions focus only on the probe, antenna, and measuring range, and easily overlook the shell. In fact, the shell of a radar level gauge is not just an outer cover; it must protect the internal electronic module, wiring terminals, and sealing structure, and also withstand dust, water vapor, temperature differences, chemicals, and mechanical impact.

If the site is located in petrochemical, environmental protection, municipal water treatment, or general industrial process control scenarios, the outer shell is exposed to a complex environment for a long time, and the stability of the shell material and structure often determines the subsequent failure rate of the whole device.

Xi'an Shenghongchuang Instrument & Meter Co., Ltd. has long been involved in pressure, flow, displacement, temperature and humidity sensors and intelligent instruments. In actual projects, the common question is often not “can it measure,” but “can it measure stably and for how long.” This is also why shell materials are receiving more and more attention.

Material selection usually revolves around 304 stainless steel, 316 stainless steel, and engineering plastics

From the perspective of industry applications, the common materials for radar level gauge shells mainly include 304 stainless steel, 316 stainless steel, and some high-performance engineering plastics. There is no absolute superiority or inferiority; the key is whether they are suitable for the site.

304 stainless steel: suitable for conventional industrial environments

304 stainless steel has relatively controllable cost, mature processing, and is suitable for ordinary drainage, conventional storage tanks, building automation, and general humid environments. If the medium has weak corrosiveness and the site has no obvious salt mist or acid/alkali vapors, 304 is often sufficient.

316 stainless steel: more suitable for high-corrosion-risk conditions

When the site is near the sea, or when there are acid/alkali vapors, chemical fumes, or chloride-containing media, 316 stainless steel is more stable. Its resistance to pitting and crevice corrosion is stronger, making it more suitable for wastewater treatment, petrochemical, pharmaceutical, and highly humid, highly corrosive scenarios.

Engineering plastics: lightweight, but boundary conditions matter

Some non-metal shells have advantages in weight reduction, anti-condensation, and cost, but their resistance to high temperature, impact, UV aging, and long-term sealing must be carefully evaluated. If the installation point has severe vibration or large temperature differences, engineering plastics are not necessarily the preferred solution.

Protection rating cannot be judged by numbers alone; installation method must be considered

When discussing radar level gauge shells, the protection rating is often mentioned first. Common ratings such as IP65, IP66, IP67, and IP68 look similar, but their actual performance in use may be completely different.

Under normal circumstances, indoor general-duty applications have relatively high requirements for dust and water spray protection, and IP65 or IP66 can cover most needs. If the equipment is located on an outdoor platform or tank area, and there is exposure to rainstorm, washing, or condensation accumulation, at least a higher level of protection should be considered.

What is more worth noting is that the protection rating is not just about the nameplate. The direction of the cable entry, the material of the sealing ring, the quality of the cable gland, and the locking structure of the cover all affect the actual protection performance of the radar level gauge shell. A sufficient rating is not enough; if the installation is not done properly, problems will still occur.

Corrosion resistance depends on the “environment,” not just the “medium”

Many projects only analyze the medium inside the tank and ignore the external air environment. In fact, what the radar level gauge shell comes into contact with is often a more complex external source of corrosion.

For example, there may be sulfur-containing gases above a wastewater tank, acid mist in a chemical area, salt mist on an offshore platform, or frequent rinsing and detergent residue in a food workshop. These factors do not directly enter the measuring cavity, but they continue to act on the shell, screws, seals, and cable entry.

In other words, when selecting a radar level gauge shell, you cannot only look at “what fluid is being measured”; you must also look at “where it is installed.” If the site environment has long-term corrosion sources, 316 stainless steel usually has more margin than 304, and the long-term maintenance pressure is also lower.

Shell selection ideas are not the same in different scenarios

To make the judgment more practical, you can place the radar level gauge shell into typical operating conditions instead of comparing material parameters in isolation.

• Clear water, raw water, constant-pressure water supply scenarios: prioritize water resistance, anti-condensation, and basic corrosion resistance; 304 is usually sufficient.
• Wastewater and environmental protection treatment scenarios: pay more attention to corrosive gases and frequent washing conditions; 316 is more common.
• Petrochemical, metallurgy, and thermal power unit scenarios: in addition to corrosion resistance, also pay attention to temperature difference, vibration, and maintenance cycles.
• Outdoor storage tanks and high-level installation points: the radar level gauge shell must take into account sun exposure, rain, dust, and cable-entry reliability.

If the site also uses pressure and level measurement equipment, the material selection logic can remain consistent. For example, in level measurement and control, petrochemical, and environmental protection operating conditions, using a domestic general-purpose pressure transmitter N-10 threaded connection high-frequency pressure sensor with a 304 or 316 outer shell emphasizes that the contact material and shell material should be matched with the actual environment; this selection logic also applies to radar level gauge shell evaluation.

In addition to the material itself, these details also matter

On-site problems are often not caused by a single material parameter, but by a combination of details. When judging a radar level gauge shell, the following points are often underestimated.

Whether the seals are compatible with the environment

A 316 shell does not mean the whole instrument is corrosion-resistant. If the sealing ring, breathable parts, and terminal pad are not suitable for the temperature and chemical environment, they may fail first.

Whether the surface treatment is suitable for long-term exposure

Some sites are not sensitive to appearance, but are sensitive to cleanliness and adhesion. Surface roughness, coating integrity, and welding treatment will affect the subsequent cleaning and the speed of corrosion expansion.

Whether temperature and vibration exceed the shell boundary

High-temperature equipment, compressor areas, and pump platforms may subject the radar level gauge shell to continuous thermal shock and mechanical vibration. When selecting, the overall adaptability of the outer shell and internal electronic components should be verified.

A similar idea is also common in pressure measurement. For example, domestic general-purpose pressure transmitter N-10 threaded connection high-frequency pressure sensor will clearly specify the environmental temperature, medium temperature, stability, and outer shell material range; in essence, it is to place the question of “whether it can be used for a long time” at the selection stage.

Establish a practical evaluation sequence

During actual evaluation, information can be collected in order, which is more effective than simply comparing quotations.

• First confirm the installation location: indoor, outdoor, tank top, or pipe gallery platform.
• Then confirm environmental exposure factors, including salt mist, acid mist, water vapor, dust, and washing frequency.
• Check the protection rating and cable entry structure to avoid only looking at nameplate parameters.
• Compare the expected service life and maintenance cycle of 304, 316, or non-metal shells.
• Finally, return to procurement cost and evaluate the full lifecycle input.

In simple terms, the selection of a radar level gauge shell is not an isolated action, but part of the reliability design of level measurement. As long as environmental conditions, shell material, protection rating, and maintenance method are considered together, many subsequent failures can actually be avoided in advance.

A more practical next step is to classify existing projects by medium type, installation environment, cleaning method, and maintenance cycle, and build your own shell selection checklist. In this way, when facing different radar level gauge shell solutions, judgment will be faster and closer to real working conditions.