Understanding Tank Bridle Level Measurement
A bridle is a vertical pipe connected to the side of a storage tank or process vessel, typically with side/side or side/bottom connections. Because the fluid inside the bridle will rise and fall equally with the level of fluid inside the tank or vessel, the bridle has been adapted for level measurement on a broad scale.
The Magnetrol and Orion Instruments use of the term “bridle” refers to a bypass chamber on a larger process vessel on which the level instrumentation for that vessel is mounted. Bridles usually do not have level equipment extending into the bridle itself. Level equipment is typically placed in its own cage or nozzle attached to the bridle.
Tank bridle level measurement has provided industrial users with distinct advantages:
Because a level instrument mounted in a bridle is isolated from the process it can be calibrated or maintained without disturbing the process.
A bridle reduces the number of connections necessary on the process vessel. This is especially important on boiler code vessels that require qualified welders and procedures.
Level instrumentation is often the last consideration on a project. Mounting the instrumentation on a bridle eliminates the need for planning multiple instrumentation connections on the vessel.
Because instrumentation is typically left until the end, ordering a bridle with all the level instrumentation cuts down on the time necessary to add connections and install the instrumentation at the project deadline.
When a tank has mixers, agitators, aerators, ladders, or structural bracing, a bridle avoids any interference between these objects and the level controls.
Reduces Turbulence, Foam:
In a highly agitated vessel, a bridle calms the surface to be measured and reduces foam to improve measurement accuracy.
Here are a few of the most common level instrument technologies used for tank bridle measurement:
Guided Wave Radar:
GWR mounted in a cage is well suited for bridle measurement. Configuration is fast, no calibration is required, and accuracy isn’t affected by changing densities, dielectrics, high temperatures or high pressures. MAagnetrol Eclipse® transmitters are available with a wide range of probes, materials and options.
Magnetic Level Indicators:
Developed for the most demanding industrial applications, MLIs provide local visual indication and remote indication when combined with a transmitter. Highly visible flags magnetically coupled to the moving float provide local level indication. Aurora® (float and GWR transmitter redundancy) and Atlas™ (float-based MLI) can be customized for unique application solutions.
Designed to attach quickly and easily to magnetic level indicators, magnetostrictive transmitters offer high accuracy and high linearity when combined with MLIs. The Orion Instruments Jupiter® magnetostrictive transmitter is available with an innovative dual compartment design.
External Cage Float Switches:
A wide range of float switches suitable for bridle applications with flanged and sealed cage designs include ASME B31.1 construction for boiler and power plant use and B31.3 construction for petrochemical use. HP and HT versions and a selection of switch styles and material options are available.
Displacer Controllers utilize simple buoyancy principles to detect and convert liquid level changes into a stable output signal. Modern displacer controllers serve most liquid level measurement and control applications including those with varying dielectric, vapors, turbulence, foam, buildup, bubbling or boiling and high fill/empty rates. The Magnetrol Digital E3 Modulevel® is an advanced, intrinsically safe, two-wire controller that comes in a variety of configurations and pressure ratings for varied applications.
Ultrasonic Contact Point Sensors:
Nozzle-mounted ultrasonic switches are mounted horizontally on bridles for high or low level alarm applications. The Magnetrol Echotel® Model 961 Level Switch offers advanced transducer designs, extensive hazardous location approvals, and self-test technology. Pulsed signal technology for superior performance in difficult conditions and excellent immunity from electrical noise interference are also featured.
Thermal Dispersion Point Sensors:
Nozzle-mounted thermal dispersion switches provide a high level of performance for level and interface applications on bridles. Magnetrol Thermatel® Model TD1/TD2 switches feature continuous diagnostics with fault indication, temperature compensation, narrow hysteresis, and fast response time.