Author: joyo

The High Accuracy Servo Tank Gauge is designed specifically for use in Custody Transfer and Inventory Management applications across the full range of modern storage tank designs. The servo tank gauge measures product level, water interface and product density profile in a single microprocessor based unit. Connecting the gauge to one of the range of MCS 3780 Series temperature probes, provides measurement of both product and vapour temperature.

Principle of Operation

The servo tank gauge measures liquid level based on the principle of liquid displacement. A displacer is suspended on a stainless steel wire payed out from a grooved drum housed in the gauge enclosure. A highly sensitive torque measurement devise continuously measures the effective weight of the displacer which, under steady state level conditions, is half immersed in the liquid. Should the level change, the displacer undergoes an apparent change of weight. The gauge microprocessor senses this change in weight and causes a servo motor to rotate the measuring drum until balance is restored.

Density is determined by measuring the effective weight of the displacer when completely immersed. Sample readings, recorded at configurable intervals as the displacer travels down through the liquid, provide density profiling.

Water interface level and tank base measurement are achieved by recording the point at which the gauge recognises the effective displacer weight in water and at the tank base respectively.

The Servo Tank Gauge Features and Key Benefits:

Intrinsically Safe (EEx ia IIB T4) with the added benefit of no electronics exposed to the tank atmosphere.

•Low Power requirements enable both power and communications to be safely distributed via one 4-wire cable running around the tank farm.

High visiblility large LCD provides selectable Level, Temperature, Interface or Density readings at all times.

•Optional display for mounting at tank base.

•Non-volatile memory that restores itself to full operation in the event of a power loss.
•Operates across a wide range of process and enviromental conditions.

•Range of installation options to suit all tanks, including high pressure applications and a flexible coupling installation for tanks with undefined deformation characteristics.

•User friendly local control by single push-button.

•Remote control and monitoring via industry standard multi-drop serial communications that includes extensive diagnostic information.

•Lightning protection through galvanic isolation.

•Extensive installation reference list in a wide variety of applications and low maintenance requirements.

PERFORMANCE

•Level Accuracy: ± 1mm

•Water/Interface Accuracy: ± 2mm

•Level Measuring Range: 0-20 meters (Optional: 0-40 meters)

•Density Accuracy: ±5kg/m3

•Ripple Damping: Adjustable, typically 4 seconds

•Temperature Accuracy: ± 0.1°C (from Spot/ Multiple Averaging/ Multiple Spot Probe)
•Temperature Measuring Range: -50°C to +125°C (Optional: -200°C to Ambient or -20°C to +280°C)

Materials:

•Gauge Housing: LM25-M Aluminium Alloy (Option: 316 SS)

•Measuring Drum: Anodised Aluminium (Option: 316 SS)

•Measuring Wire: AISI 316 Herdened SS (Option: Hastalloy)

•Displacer: Carbon Loaded PTFE; 90mm or 140mm diameter

This article comes from indmac edit released

The Automatic Servo Tank Gauge, with 4 mm level gauging accuracy per SIRA Report E1588583, provides continuous liquid level measurement of products stored in above- and below-ground vessels.

The servo tank gauge can be installed on atmospheric or low pressure (2.5 psig) fixed cone roof, floating roof, fixed roof with internal floating pan, or underground tanks. It can be mounted above the storage vessel or at grade.

Other versions include float check knob or float hoist, gauge head/counter for oil filling, negator motor or cartridge motor models, and stilling well and water interface models. Standard, moderate, severe, and extreme service kits are available.

This article comes from chemicalonline edit released

Intelligent hybrid servo tank gauge combines the field proven high accuracy and reliability of servo gauge technology with the advantages of average density and mass measurements of the hydrostatic gauge.

Displacer weight is used to find the product level. The addition of one or two high accuracy pressure transducers to the servo tank gauge provides highly accurate product weight and level measurements, giving all the advantages, and eliminating all the shortcomings, of both Servo and HTG technologies.

Features:

• Minimal Moving Parts (3) Ensure Reliability
• Accuracy/Repeatability of +/- 1/32 inch (0.8mm)
• Product and Interface, Custody Transfer
• Handheld Infrared Calibration
• Ground Level Display Eliminates Tank Climbing
• Temperature, Pressure and Density
• Product and BS&W Level Gauging in Process Industries

This article comes from chemicalonline edit released

Tank gauging is essential for the assessment of tank contents, tank inventory control and tank farm management. Our servo tank gauges help in accurate level gauging for refineries, tank terminals and petrochemical industries. Our servo tank gauges are suitable for custody transfer as well as inventory control and are designed to be used in SIL-3 loops to prevent spillage.​​​​​​​​

How Does It Work?

​In the most challenging circumstances such as dome roofs and bad stilling wells, servo tank gauge maintains its ultra-high performance level on a wide range of applications and various tank conditions. The Enhanced Performance Signal processing enables the radar tank gauge to provide an accurate level reading even in difficult applications (close to the tank shell) and prevents the need for a costly stilling well. The servo tank gauge has been certified for use in SIL-2 and SIL-3 applications by the TÜV which allows it to be used in overfill protection applications. Additional diagnostics have been added to detect hardware failures, while a 2004D voting algorithm will detect, report and isolate failures on the boards without interrupting the loading or unloading of a tank.

What Problems Does It Solve?

​The servo tank gauge offers high flexibility that can be used for dedicated tank applications such as independent overfill protection, floating roof monitoring, rim fire detection, roof immersion compensation, etc. The servo tank gauge wireless option reduces the cost for wiring infrastructure and increases flexibility as various instruments can be added to the network without adding cables. The radar tank gauge is also certified for use in custody transfer applications.

This article comes from honeywellprocess edit released

Working principles of servo tank gauge

The principle of servo tank gauge measurement is based on Archimedes law, which states “any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object.”

Typical servo tank gauges consist of three compartments: drum compartment, drive compartment, and power supply compartment. The drum compartment contains a precise machined drum on which the measuring wire is wound. The displacer is suspended by this wire into the tank. The drive compartment contains the drive train (servo tank gauge motor and electronics) and the measurement electronics.

A magnet coupling is used to convey torque between the drive train and the drum and forms the isolation between the process and the electronics and environment. The displacer is moved by a stepper motor in the drive compartment.

As soon as the displacer reaches the surface of the liquid in a tank, buoyancy reduces the apparent weight of the displacer. This is measured by the servo tank gauge electronics using the force transducer. By also keeping track of the exact position of drum and number of revolutions, the length of the expanded wire can be measured. In combination with the known position of the gauge (gauge reference height, GRH), the exact product level can be calculated. This level is then corrected for several typical tank uncertainties, such as product temperature, tank shell effects, changes in GRH due to hydrostatic tank bulging, etc.

This article comes from tanotocentre edit released

First, is the low-accuracy pulse radar units, now these are only “low accuracy” when compared to units designed for servo tank gauge. These are excellent general purpose radar units, but they are limited in use to materials with dielectric coefficients greater than about 8 or so. It generally rules them out for low viscosity hydrocarbons.

Second is the various radar-by-wire designs, such as Alliant(Bindicator-Celtek) and Magnetrol, etc. These are mostly used for solids, but could be used in hydrocarbons. They are also relatively inexpensive.

Next are the FMCW units, these are moderately high accuracy, and can be used in gauging fluids with a dielectric of 3-5 or so. The compromises made in the designs of these units in order to make them look through small (4″<100 mm> to 6″ <150 mm>) vessel ports reduces the accuracy and the ability of these units to see lower dielectric constants. These are designed as process servo tank gauges, not tank farm designs.

The highest level of accuracy are the units designed specifically for Tank Farm Gauging, they were designed to compete specifically with servo tank gauges and with hydrostatic level gauging and are designed to be used specifically for tank farms. These servo tank gauges consistently outperform their competition but are very expensive.

This article comes from control edit released

The intelligent servo tank gauge Proservo NMS81 is designed for high accuracy liquid level measurement in custody transfer and inventory control applications with NMi- and PTB-approvals. It meets the relevant requirements according to OIML R85 and API 3.1B. It fulfills the exact demands of tank inventory management and loss control and is optimized in regards of total cost saving and safe operation.

• Hardware and software developed according to IEC 61508 up to SIL3 (in homogeneous redundancy) for high level of safety
• Maximum reliability through accuracy up to ±0.4mm (± 0.02″)
• Developed according to international metrology recommendations such as OIML R85 and API MPMS
• Local and country-specific certifications like NMi or PTB for custody transfer applications
• Superior corrosion resistance with 316L materials in the process compatible with sour applications such as crude oil
• Measurement of interfaces between up to three liquid layers, tank bottom, spot, and profile densities
• Best fit for LNG/LPG applications without influence of dc value or Boil Off Gas

This article comes from endress edit released

Our servo tank gauge operates on the principle of displacement measurement. A small displacer on a measuring wire is unwound from a drum and accurately positioned in the liquid medium using a servo motor.

The weight of the displacer is precisely balanced against a magnetic coupling and the wire drum. When the displacer is lowered and touches the liquid, the weight of the displacer is reduced because of the buoyant force of the liquid. As a result, the torque in the magnetic coupling is changed and this change is measured. The signal, an indication of the position of the displacer, is sent to the motor control circuit. As the liquid level rises and falls, the position of the displacer is automatically adjusted by the drive motor.

This system provides an outstanding accuracy of our servo tank gauges. Servo tank gauges are ideally suited for light and middle distillates of petroleum.

This article comes from motherwelltankgauging edit released