Used as high, low, or mid-level sensors, they can assure a continuous supply of material into a production process and prevent downtime. When used in conjunction with an alarm–such as a horn or light–or wired to a PLC, they make the workplace safer by eliminating the need to climb vessels. Point level sensors are easy to install through an existing mounting connection, and many offer varied power supplies, making them convenient to wire to the existing electrical system.
Rotary Level Indicators
Rotaries are a familiar and common device and are versatile enough to use in nearly any material from powders and granules with a minimum bulk density of 2 lb./cu. ft.3 to coarse, lump materials with bulk densities up to 150 lb./cu. ft.3.
There are many options for rotaries applied in new and innovative ways. For high level detection, a vertical rotary with a custom-length rigid or flexible extension can allow it to be extended as far as 12 feet down into the vessel. A wide selection of paddles–including collapsible paddles that can be inserted through a process connection–make rotaries adaptable to many materials and easy to install.
Capacitance sensors can be adapted to a wide array of applications and can easily be customized with different type of probes, lengths, or extensions. Capacitance sensors operate by detecting the presence or absence of material in contact with the probe by sensing minute changes (as low as 0.5 picofarad) in capacitance caused by the difference in the dielectric constant of the material versus the air.
Capacitance probes are available with a wide range of options such as certified for hazardous locations, for use in high temperature environments, outfitted with extended probes or cables, made for applications with excessive vibration, or models that house the electronics and probe in separate enclosures. A flush mounted probe can be used in narrow or space-constrained areas or a bendable probe can be used to avoid obstructions.
The vibrating level sensor or vibrating rod is a piezoelectric driven vibration type level switch. A vibrating level sensor can detect extremely light, fluffy materials as light as 1.25 lb./ft.3 such as powders and flakes or can be used for heavier materials such as granules or pellets. Vibrating rod level sensors vibrate when there is no material covering the active rod. When the rod is covered with material, the vibration is dampened, and an electronic circuit causes a relay to switch and sends an alert. When the rod becomes uncovered, the vibration restarts, and the relay will switch back.
Most vibrating rods do not require calibration or are easily adjusted to the desired sensitivity level. There are models featuring fail-safe alerts, hazardous locations, high temperatures, and remote electronics. Some vibrating rods can be extended to a custom length or used for detecting sediment settled on the bottom of a vessel, such as a brine tank.
A diaphragm—or pressure—switch is very affordable and highly reliable when used in free-flowing dry and granular materials. Models are available for ordinary as well as hazardous environments where there is a risk of combustible dust.
The diaphragm switch works by activating a sensitive micro-switch when material reaches the level of the switch in the bin. It sends an alert that can be used to start or stop a process or alert to a high, medium, or low-level in the vessel. They can be wired to a light, horn, alarm, or into a company’s PLC to indicate an alert status.
A tilt switch is an inexpensive, reliable high-level indicator that is easy to install and requires no routine maintenance. A hanging tilt switch is installed by suspending it from a flexible cable over a control point. Its principle of operation is quite simple–as material rises below the switch, it will tilt and activate a microswitch when the tilt reaches 15 degrees. Tilt switches are routinely used in bins or silos or over a conveyor belt or open pit. A hanging tilt switch can also be used for plugged chute detection.
The Easiest Way to Avoid Mistakes When Selecting a Point Level Sensor
Point level sensors are highly cost effective, easy to use, and are very durable. The key to success is selecting the right one for an application.
Within each type of point level sensor there are so many options it can be overwhelming. Make a phone call or send an email to the manufacturer to get free advice on the best solution for your material, application, and budget.Click here for more information on the point level sensorsClick here for related articles and news
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