Criteria for Choosing a Reliable Level Meter

Submersible pressure transmitters, also called level sensors, are designed for underwater use, so they must withstand long-term exposure to the working environment. If the advice described in this article is neglected, when measuring clean water, wastewater, as well as during monitoring in tanks, moisture can penetrate through the sensor housing, the cable itself, or its termination.

Failure of the sensor due to moisture ingress can be prevented by carefully selecting the device suitable for specific conditions. Therefore, it is recommended to choose a sensor that best fits the application, which has been specially designed for these conditions and tested in them. The use of "standard" pressure sensors with minor modifications, such as cable output, should be avoided, despite the fact that such pseudo-submersible pressure transmitters are widely available on the market. To prevent chemical decomposition and corrosion of the device, it is necessary to carefully select housing and sensitive element materials that can withstand the environmental impact. For use in standard non-aggressive environments, a sensor with a housing made of stainless steel 316L is sufficient (such as 26Y). For non-standard applications or use in aggressive environments, it is recommended to use devices made of suitable materials such as Hastelloy or titanium (for example, the special version of the sensor 36XW made of titanium or the 36XKY sensor with a Kynar diaphragm).

The risk of moisture penetration into the sensor through the cable requires making another difficult choice. When purchasing a submersible pressure transmitter, the nature of the working environment and the technical characteristics of the sensor cable should be taken into account. Depending on the aggressiveness of the liquid, an appropriate cable material must be selected. In standard conditions, polyurethane (PUR) cables can be used, while for use in aggressive environments, a cable made of fluorinated ethylene propylene (FEP) should be chosen, which has the highest chemical resistance and can ensure safe operation even in the most aggressive environments. All Keller level transmitters can be supplied with either polyethylene/polyurethane cable or FEP cable.

It is also extremely important to consider the immersion depth, which determines the pressure. This is especially relevant for standard applications such as wells, since any cable will remain impermeable to water only up to a certain immersion depth. Thus, a cable resistant to water pressure up to 10 bar may begin to allow liquid penetration at higher pressure, i.e., at depths greater than 100 meters. Our range of level transmitters includes sensors that can operate continuously and stably at depths up to 300 meters and even up to 500 meters in special versions.

One should not neglect the tensile deformation characteristic of this cable. At great depths, the weight of the submersible pressure transmitter along with the cable may be sufficient to stretch the latter, causing sheath wear. Sheath wear, in turn, can cause liquid to penetrate into the cable and further into the sensor itself.

Finally, physical damage to the cable sheath should be avoided. Cable abrasion or even the formation of nicks from sharp edges or improper use of tools during installation can lead to moisture entering the sensor through the damaged sheath. Proper cable laying using auxiliary means such as clamps that protect the cable from bending can reduce cable tensile deformation and prevent sheath abrasion. Clamps can be ordered as accessories together with any level transmitter.

If the level sensor is used in flowing water, for example, in rivers or tanks equipped with a mixing device, it is recommended to pass the cable through protective pipes or an inspection well to avoid mechanical stresses caused by cable abrasion or sudden level rises.

You can select a level sensor suitable for your application in the product catalog or by contacting our technical specialists.