Automated measurement of liquid and solid levels is important to the smooth and safe operation of water and wastewater treatment facilities and their distribution and collection networks.

These devices enable accurate measurement in a wide variety of applications including inventory in bunkers, reactor vessels and silos, volumetric measurement, and others. They meet the requirements of numerous industries, including water and wastewater.

ABB has introduced the LLT100 laser level measurement device, designed to accurately measure level, distance and position over short or long ranges. It is a noncontact instrument suited for industrial applications and harsh environments.

Mohit Manglani, regional manager for ABB Measurement & Analytics, talked about the product in an interview with Treatment Plant Operator.

How does this level measurement device fit into the marketplace?

Manglani: Facility operators need accurate level measurement inside pumping stations, in lift stations, in chemical tanks, in water towers, in screening rooms and in other settings to make sure processes don’t get backed up or clogged. Primary noncontact technologies available include ultrasonic, radar and laser level measurement.

Where might laser measurement devices be found in the water and wastewater sector?

Manglani: They are suitable for water and wastewater treatment plants, water reuse and desalination plants, water distribution networks and wastewater collection systems. The main applications are deep wells, lift stations and pump stations, sludge processing facilities and storage tanks. It can also be used to measure the depth of stormwater ponds and the depth of the water inside the pond.

How does laser level measurement differ from the other two technologies?

Manglani: Laser level measurement technology is not based on waves like radar or ultrasonic methods. It’s based on optical pulses.

In basic terms, how does a laser measurement device function?

Manglani: Laser pulse time of flight is measured to determine distance from measured surface to the transmitter. Among the technologies, this technique yields the best results in the presence of light dust, mist or fog. The sensor has a narrow field of view, and it only detects returns from the surface. The laser beam is narrow, so that surrounding objects do not interfere with it. The devices are inexpensive to install and enable automated measurement in settings that otherwise would be difficult.

What are some of the key advantages of laser measurement?

Manglani: No. 1, it doesn’t require a process called echo mapping. Ultrasonic and radar devices require mapping, where you have to empty out the pump station or vessel and map any pipes or other structures that would be in the way, so that when the device takes the level reading, it ignores them; it filters them out. No. 2, laser devices have greater range as a default, so they can be installed at higher elevations from the surface to be measured — 100 feet for liquids and up to 330 feet for solids, such as in biosolids silos.

What are the benefits of that greater mounting height?

Manglani: When a wave device is mounted down in a pit, then heavy condensation or spider webs can actually block the reading. With the laser, you can mount it up higher and out of the way of those interferences. There’s also a maintenance benefit. When technicians come to maintain and clean the device and make sure it’s reading properly, they don’t have to pull it on a wire all the way out of the pit as with remote ultrasonic or radar devices. They can work on the device where they’re standing.

What kinds of material can a laser device measure?

Manglani: A laser device can detect any material, even low-dielectric material. It can measure clean water. It can measure dirty water. In a pumping station, if there is a foam buildup, the laser will read foam. We’ve even done biogas volume measurement. If a customer has a digester with a biogas balloon tank, we have the capability to do a table build inside the device.  We’re able to correlate the balloon height to the associated volume. 

Is this device suitable to operate in hazardous environments?

Manglani: Yes. It has an explosion-proof rating; so for example, in an application where you may have methane gas coming out of a pit, the device is rated for that hazardous atmosphere.

Are any optional accessories available for specific applications?

Manglani: Yes. There is a dust tube to protect the lens. There is a pivot bracket to be used for mounting inside a vessel, pumping station or lift station. There is a swivel-mount flange for those who want to control the alignment of where the laser beam is hitting. And there is a purge ring that blows air onto the lens to prevent any kind of buildup there.