The Necessity of Oil tank level measurement

-In the process of oil and gas storage and transportation, accurately measure the height of the liquid level in the large oil storage tank. This is an important measure to correctly calculate oil storage, determine inventory, and calculate transportation.

-In oil and gas production, especially in oil and gas gathering, transportation, storage, and transportation systems, oil, natural gas, and associated sewage must be separated, stored, and processed in various production equipment and tanks. The measurement and control of the level are essential to ensure normal production and equipment safety. Otherwise, a major accident will occur.

-For example, if the oil tank level measurement is not well controlled, there will be evacuated or oil spill “roofing” accidents. If the liquid level of the oil-air separator is too high or too low, “oil running” and “gas blow-by” accidents will occur. Seriously affect the production and safety of subsequent equipment;

-The high oil-water interface in the electric dehydrator will destroy the electric field. If it is low, it will carry oil in the water and affect production.

The Basic Concept of Level

• Level—refers to the general term of the liquid level of the liquid medium, the level of solids or the level of particles in the container and the interface between two different liquid media.
• Liquid level-the height of the liquid medium in the container
• Material level-the accumulation height of solid or granular substances in the container
• Interface level – the level of the interface of two immiscible liquids medium

Extended Reading: How to Measure Volume of Liquid

Classification of Oil Level Measurement

According to the measurement method, it can be divided into continuous measurement and fixed-point measurement.

According to its working principle, it can be divided into the following types:

1. Direct reading type It measures the liquid level based on the principle of fluid connectivity.
2. Buoyancy type It measures the liquid level according to the principle that the height of the float changes with the height of the liquid or the buoyancy of the liquid to the float (or sinker) immersed in the liquid changes with the height of the liquid. The former is called constant buoyancy, and the latter is called variable buoyancy.
3. Differential pressure type (static pressure type) It measures the level according to the principle of the change in the static (differential) pressure generated at a certain point by the change in the height of the liquid column or the material accumulation.
4. Electrically, it measures the level based on the principle of converting level changes into various changes in electricity.
5. Nuclear radiation type It measures the liquid level based on the principle that when the nuclear radiation of the isotope rays penetrates the material, its intensity changes with the thickness of the material layer.
6. Acoustic It measures the level according to the changes in acoustic impedance and reflection distance caused by changes in the level

Read more about: 7 Level Senors for Tank Level Measurement 

Performance characteristics and selection of common oil tank level gauges

The intermediate tank only monitors parameters such as liquid level, temperature, and pressure (pressure storage tank) to prevent accidents such as roof capping and vacuuming of the oil tank. There is no need for handover monitoring and measurement;

The liquid level, temperature, density, volume, and quality of the medium in the trade tank must be monitored and measured frequently, and the accuracy is very high.

Performance comparison of Oil level measurement

Level gauge	Light oil	Crude oil	Heavy oil	Asphalt	Liquefied gas	Other liquids
Magnetic flap level gauge	ok	ok	ok	poor	No	very good
Float	ok	ok	ok	poor	No	very good
radar	Great	Great	Great	Great	Great	Great
Static pressure	Great	Great	ok	poor	ok	Great
Magnetically induced	Great	Great	Great	poor	Great	Great
Ultrasonic	Great	Great	Great	Great	Great	Great

Extended reading: Radar Oil Tank Level Sensor

Oil Tank level measurement instruments for different media

Level gauge	Level measurement	Temperature deletion	Density deletion	Boundary measurement	Volume measurement	Quality deletion	Installation situation	Cost
Magnetic flap	High precision	Can not be measured	Can not be measured	Small error	Depends on TD	Depends on Tρ	simple	low
Float	High precision	Can not be measured	Can not be measured	Mistaken sheep	Depends on TD	Depends on Tρ	simple	low
radar	High precision	important	Unable to delete	Unable to	Small error	Depends on Tρ	simple	high
Hydrostatic pressure	Big error	unimportant	Small error	Unable to	Big error	Depends on Tρ	complex	Relatively high
Magnetically induced	High precision	important	Unable to delete	High precision	Small error	Depends on Tρ	complex	high
Ultrasound	High precision	unimportant	Can not be measured	Unable to	Small error	Depends on Tρ	complex	high

Explore Oil and Gas Flow Meters

Selecting Guide for Oil level measurement

1. Oil tank volume
   • ·For large tanks (10000~100000m3) and relatively large liquefied gas tanks, higher performance level gauges can be used, and general level gauges can be used for medium and small tanks;
   • Read more about: Ultrasonic Tank Level Sensors for Tank Level Monitoring
2. ·Oil tank use
   • High-precision level gauges should be used for trade tanks, and general level gauges can be used for intermediate tanks;
3. Medium characteristics
   • When storing high-viscosity media (such as heavy oil), try to use a level gauge that does not or has little contact with the measured medium. Such as radar type, ultrasonic type and magneto-induced level gauge, light oil can use general level gauge;
4. Actual needs of users
   • ·If the user requires high measurement accuracy and low investment restrictions, a level gauge with good performance can be used. Under normal circumstances, the old tank area can be retrofitted or updated according to the use and maintenance of the original level gauge.

Extended reading: The Secret of Ultrasonic Level Measurement

Featured Oil level measurement devices

Read more about: Capacitive Level Measurement System

Sino-Inst offers over 50 Solutions for Tank Level Sensing. About 50% of these are float liquid level meters, 40% are the level switches.

A wide variety of Solutions for Tank Level Sensing options are available to you, such as free samples, paid samples.

Sino-Inst is a globally recognized supplier and manufacturer of Solutions for Liquid Level Measurement instrumentation, located in China.

Liquid level measurement and monitoring play an increasingly important role. Liquid level measurement and monitoring directly affect the quality of the production process.

8 Types Liquid level measurement methods

1. Floating ball measurement:

This method is the simplest and oldest detection method, and the price is relatively cheap.

Mainly through the up and down movement of the float to detect the change of the liquid level. It is a mechanical detection, the detection accuracy is easily affected by buoyancy, and the repeat accuracy is poor. Different liquids need to be recalibrated.

It is not suitable for viscous or impurity liquids, which can easily cause blockage of floating balls. At the same time, it does not meet the application requirements of the food hygiene industry.

2. Tuning fork vibration measurement:

Tuning fork measurement is only a switch output and cannot be used to continuously monitor liquid height. The most representative one is the tuning fork level switch.

The principle is: when the two vibrating forks are filled with liquid or bulk material, the resonance frequency changes, and the switching signal is sent out depending on the detection frequency change.

It can be used to monitor the height of high-viscosity liquids or solid bulk materials, mainly for anti-overflow alarms, low-level alarms, etc. It does not provide analog output. In addition, in most cases it is necessary to install holes on the side of the container.

3. Ultrasonic measurement:

Since the principle is to calculate the liquid level by detecting the time difference between ultrasonic transmission and reflection, it is susceptible to the energy loss of ultrasonic propagation.

It has the characteristics of easy installation and high flexibility. Usually can be installed in high places for non-contact measurement.
But when used in environments containing steam and powder, the detection distance will be significantly shortened. Therefore, it is not recommended to use it in a wave-absorbing environment with foam.

Read more: Guide: Non-contact Ultrasonic Level Sensing transmitters

4. TDR (time domain reflection)/guided wave radar/microwave principle measurement:

Its name has many different names in the industry, and it has the advantages of laser measurement. Such as: easy installation, calibration, flexibility, etc.

But it is better than laser detection, such as no need to repeat calibration and multi-function output. Suitable for all kinds of liquid level detection with foam. Not affected by liquid color.

It can even be applied to highly viscous liquids, with relatively little interference from the external environment. But its measuring height is generally less than 6 meters.

Extended reading: Radar Non Contact Water Level Sensor

5. Laser measurement:

The laser sensor is based on the principle of optical detection and detects light by reflecting light from the surface of the object to the receiver. The light spot is small and concentrated, easy to install, calibrate, and flexible. It can be applied to continuous or limit alarm of bulk material or liquid level.

But it is not suitable for transparent liquids. Transparent liquids easily refract light, causing the light to not be reflected to the receiver. Use in foam or steam environment (cannot penetrate foam or easily interfered by steam), fluctuating liquid (easy to cause malfunction), vibration environment, etc.

6. Photoelectric refraction measurement:

This detection method emits a light source inside the sensor. The light source is totally reflected by the transparent resin to the sensor receiver.

But when encountering the liquid surface, part of the light will be refracted to the liquid. Therefore, the sensor detects the decrease in the amount of total reflected light to monitor the liquid level. The detection method is cheap and simple to install and debug. But it can only be applied to transparent liquids, and it only outputs switching signals.

7. Capacitive measurement:

Capacitive measurement mainly measures the height of the material level by detecting the change in capacitance value caused by the change of the liquid level or the height of the bulk material.

There are many types, including capacitive level gauges and capacitive proximity switches that can output analog quantities. Capacitive proximity switches can be installed on the side of the container for non-contact detection.

When choosing, it must be noted that capacitance sensors are easily affected by different container materials and solution properties. For example, plastic containers and hanging materials can easily affect capacitance sensors with analog output.

Read more about: Capacitive Level Measurement System

8. Static pressure measurement:

This measurement method uses a pressure sensor installed at the bottom. By detecting the bottom liquid pressure, the liquid level is converted and calculated. The bottom liquid pressure reference value is the atmospheric pressure connected to the top or the known pressure.

This measurement method requires the use of a high-precision, flush-type pressure sensor. At the same time, the conversion process requires continuous calibration.

Its advantage is that the detection is not limited by the height of the liquid level. But the higher the height, the higher the accuracy requirements of the sensor. Repeated calibration is required when using for a long time or changing liquid.

Read more about: Hydrostatic level measurement: Measuring Principle

Featured liquid level measurement devices/instruments

Liquid level measurement in a closed tank

Differential Pressure Level transmitter for closed containers

For airtight containers, the inside is isolated from the atmosphere. When the process fluid fills or empties the tank, the pressure in the tank may change from positive pressure to vacuum. This change in tank pressure will directly affect the measured liquid level unless it is compensated for. This can be done by connecting the low-side pipe of the differential pressure transmitter to the top of the tank. Therefore, when measuring the liquid level of a closed tank, a differential pressure transmitter must be used.

Double flanges are used to measure the liquid level of a closed tank.

The calculation method of the differential pressure range: the height of the liquid level to be measured (unit: m) × acceleration of gravity (9.8) × (the density of the measured medium-the density of the capillary filling liquid) (unit: g/cm3) = differential pressure range (unit: KPa).

The selection must know the measurement medium, measuring range, medium temperature, pressure, capillary length, the size and pressure rating of the process connection flange and the flange standard

If you need to measure river water level, open channel level, etc. The Ultrasonic Liquid Level Sensor can be used for non-contact continuous level monitoring.

Portable Ultrasonic Liquid Level Gauge

Portable ultrasonic liquid level indicator is best choice for tanks or pipes level measurement. It is designed to measure the presence or absence of liquid at a certain height position in a tank or in pipelines. Non-contact ultrasonic detection technology.

SI-ML works perfect for detection of dangerous toxic or corrosive liquids. Under ordinary conditions, the maximum wall thickness of measurable containers is 30mm. The product is suitable for the detection of various types of liquids. Liquids are non-crystalline or other particulate matter. For example CO2 Tank. Thanks to non-contact detection technology, this level indicator is ideal for detecting hazardous toxic or corrosive liquids.

Read more about: 7 Level Senors for Tank Level Measurement

Liquid Level Measurement Converter Tools

Converter Tools used to convert and calculate liquid level values or for calculations that require liquid level measurement to obtain other measurement parameters. Help users choose suitable Level sensors and transmitters!

Liquid Level Transmitter 4-20mA Current Output Calculator	Liquid Depth/Level to Hydrostatic Pressure Calculator	Pressure to Liquid Level Calculator
Specific Gravity Calculator	Horizontal Cylindrical Storage Tank Contents/Volume Calculator	Rectangular Shaped Tank Liquid Volume/Contents Calculator
Vertical Cylindrical Tank Volume/Contents Calculator	Depth/Level Unit Converter	Volume Unit Converter

FAQ

Extended Reading: How to Measure Volume of Liquid

Selection of liquid level measuring sensor

The issues that need to be considered before choosing a level measurement sensor include:

1. Measuring liquid or solid?
2. What is the temperature and pressure range of the application environment?
3. Need point level measurement or continuous measurement?
4. How much liquid level measurement range is required?
5. Is the tested material conductive?
6. Will the tested material cover or accumulate on the surface?
7. Will there be turbulence, foam or steam on the surface of the liquid?
8. Do you need contact or non-contact level measurement?
9. What kind of output is needed, analog, relay, digital display or other?

Extended reading: Ultrasonic liquid level sensors

Sino-Inst offers over 10 Solutions for Liquid Level Measurement. About 50% of these are float liquid level meters, 40% is the level switches.

A wide variety of Solutions for Liquid Level Measurement options are available to you, such as free samples, paid samples.

Sino-Inst is a globally recognized supplier and manufacturer of Solutions for Liquid Level Measurement instrumentation, located in China.