Welcome to our third blog installment on level instrumentation for pulp and paper process applications. As pulp and paper operations face increasing competition and heightened demand for conservation and carbon mitigation initiatives, facility managers are actively assessing ways to improve process efficiency. Accurate and reliable level control throughout a pulp and paper plant can be a critical source of process improvement.
In this blog article, we address the application of level instrumentation in plant-wide operations, including Medium Consistency (MC) pump standpipes, water storage, chemicals and additives, and lubrication and hydraulic oils.
MC Pump Standpipes
Application: Designed to move thick fluids, MC pumps are ideal for transporting pulp in a mill. Pulp is often pumped from a standpipe, which is a vertical feed pipe integral to the pump. Pumps with standpipes typically pump to and from washers and thickeners, O2 and CLO2 mixers, extraction towers, bleach storage towers and high-density pulp storage towers.
Challenges: It is important that the proper level of pulp be maintained in the standpipe. A level control in the standpipe does this by actuating a valve downstream of the pump. A malfunctioning level control could result in standpipe overflow, or cause a pump to operate in a no-flow condition in which it would quickly sustain damage through overheating and seal damage.
Level Technologies:
- Thermatel® Thermal Dispersion Switch for point level
- Eclipse® Guided Wave Radar Transmitter for continuous level
Mill Water Storage
Application: Because paper is made in an aqueous vehicle that is up to 99.5% water, water management is essential for productive mill operations. Level controls monitor the storage of cold, warm and hot process water, potable water, boiler feedwater, liquor production water, process wastewater, and open effluent weirs, sumps, and stormwater basins.
Challenges: The vessels holding the process, reclaimed and service water storage may range from small tanks to large bulk tanks with heights of 40 feet (12.2 meters). Level controls are specified according to the size and geometry of the bulk storage vessel. Level controls in open atmosphere reservoirs must withstand punishing weather conditions. Firewater storage must conform to NFPA standards.
Level Technologies:
- Model A15 Series Displacer-Actuated Switch or Echotel® Ultrasonic Switch for point level
- Echotel® Non-Contact Ultrasonic Transmitter, Eclipse® Guided Wave Radar Transmitter or Pulsar® Non-Contact Radar Transmitter for continuous level
- Atlas® Magnetic Level Indicator for visual indication
Chemical and Additive Storage
Application: Chemical stocks stored in mills include acids and alkalies, delignification chemicals, bleaching agents and water treatment chemicals. Chemical additives mixed into the process stream at the wet end of the paper machine include dyes and pigments, drainage aids, defoamers, slimicides, and a broad range of specialty chemicals that improve paper performance.
Challenges: Chemical solution storage and day tanks require stringent level monitoring. Though precise chemical measurement is accomplished by metering pumps, tank level controls actuate tank-filling operations and protect against overfilling. Tank size and geometry, the presence of mixing hardware, and the solution’s chemical nature are prime factors in level instrument selection.
Level Technologies:
- Model A15 Series Displacer-Actuated Switch or Echotel® Ultrasonic Switch for point level
- Echotel® Non-Contact Ultrasonic Transmitter, Eclipse® Guided Wave Radar Transmitter or Pulsar® Non-Contact Radar Transmitter for continuous level
- Atlas® Magnetic Level Indicator for visual indication
Lubrication and Hydraulic Oil
Application: Pulp and paper mills operate many machines that require lubrication. Oil is stored in stainless steel and carbon steel tanks. While gearboxes hold up to 50 gallons, and hydraulic reservoirs up to 200 gallons, a paper machine may contain up to 5,000 gallons of lubricant.
Challenges: Level monitoring of oil reservoirs will ensure the proper functioning of pumps, gearboxes, drives, compressors, bailing presses, materials handling equipment and paper machines. Temperature shifts in oil reservoirs affect media density that excludes some technologies, such as pressure transmitters. Because ISO cleanliness levels increase oil change frequency, controls should be easy to remove.
Level Technologies:
- Echotel® Ultrasonic Switch or Tuffy® II Float-Actuated Switch for point level
- Eclipse® Guided Wave Radar Transmitter or Pulsar® Non-Contact Radar Transmitter for continuous level
- Atlas® Magnetic Level Indicator for visual indication
Explore the full range of benefits that level control can bring to the pulp and paper industry in our comprehensive brochure.
