Nearly any unit operation in the process industry can be fabricated as a self-contained, modular skid system. Modular fabrication has increasingly become a viable alternative to field construction for owner/operators, OEMs and plant engineers. This post discusses level and flow instrumentation for liquid gravity separator skids and is part of an occasional Magnetrol® blog series on modular skid systems.
Liquid separation is essential to all processing industries. Skids vary according to the separation technology, including: distillation, gravity separator technology, coalescence, crystallization, adsorption, membrane processes, absorption and extraction. Pre-separated mixtures can combine two or more states: solid-solid, solid-liquid, solid-gas, liquid-liquid, liquid-gas, gas-gas or solid-liquid-gas mixtures.
Featured Skid Application: Oil-Water Separation
An oil-water separator is designed to separate oil and suspended solids from the wastewater effluents in chemical and petrochemical processing plants and other industrial settings.
Gravity separator design is based on the specific gravity difference and immiscibility of the oil and the wastewater. The oil will rise to the top of the separator, and the wastewater will settle beneath the oil. Each layer is then drawn off.
Level and Flow Applications
The interface level measurement monitoring level within the gravity separator should provide accurate and reliable level control during liquid separation, despite the presence of an emulsion layer between the oil and water layers.
Continuous Level: E3 Modulevel® Displacer Transmitter; Eclipse® Model 706 Guided Wave Radar Transmitter
Point Level: Float or Displacer Level Switches; Thermatel® Model TD1/TD2 Thermal Dispersion Switch
- Pump Protection
Whether caused by a closed valve, a plugged line downstream or by pump cavitation, pumps operating in a reduced or no-flow condition can overheat and rupture the pump’s seal causing a dangerous deviation in process pressure and temperature. A flow switch along a pump’s discharge piping will actuate an alarm and shut down the pump when liquid flow drops below the minimum flow rate.
Flow Alarm: THERMATEL Model TD1/TD2 Thermal Dispersion Switch for low-flow cutoff
- Waste Oil Tank
When volumes of separated oil are large, they are collected in a waste oil storage tank. When the collected oil reaches a pre-determined level, it is discharged for transport to treatment facilities for reclamation.
Continuous Level: ECLIPSE Model 706 Guided Wave Radar Transmitter; Pulsar® Model RX5 Radar Transmitter or Model R82 Radar Transmitter
Point Level: Tuffy® II Float Switch or Echotel® Model 961/962 Ultrasonic Switch
- Wastewater Tank
Industrial plants generate water waste from separators, runoff, washing units, sumps, and other processes. When the collected liquid reaches a pre-determined level in waste tanks, it is discharged for transport to the treatment plant or to disposal facilities.
Continuous Level: ECLIPSE Model 706 Guided Wave Radar Transmitter; PULSAR Model RX5 Radar Transmitter or Model R82 Radar Transmitter
Point Level: Model B35 External Cage Float Level Switch or ECHOTEL Model 940/941 Ultrasonic Switch