CN1761858A

CN1761858A - System and method in a radar level gauging system

Info

Publication number: CN1761858A
Application number: CN 200480007697
Authority: CN
Inventors: 莱纳特·哈格
Original assignee: Saab Rosemount Tank Radar AB
Current assignee: Rosemount Tank Radar AB
Priority date: 2003-03-21
Filing date: 2004-03-05
Publication date: 2006-04-19
Anticipated expiration: 2024-03-05
Also published as: CN100356145C; SE0300819D0

Abstract

The present application relates to the field of radar level gauging systems for gauging the level of a surface (12) of a product (16) stored in a container (10). The measurement system includes: a radar level measuring device (14) mounted above the surface (12) of the product (16) that transmits microwave signals towards the product surface (12) and receives reflected microwave signals from the product surface (12); a calculating unit for determining the liquid level of the product according to the received signal; means for comparing a predetermined value of the level of the product with said measured value; a second level measuring device (20) mounted near the bottom of the container (10) determines the product level when the measured value is below a predetermined value.

Description

System and method in the radar level gauging system

Technical field

The present invention relates to radar level gauging system, when particularly relating to a kind of liquid level in container, improve the radar level gauging system and the measuring method of the accuracy of measuring the liquid level that is stored in liquid in containers near container bottom.

Background technology

Radar level gauging is generally to be used for now measuring being stored in container, and as the device of the liquid level of the liquid in the oil tank, it receives then from the microwave signal of liquid surface reflection, thereby can determine liquid level by to liquid level launched microwave signal.Importantly, when liquid level during near the bottom, the user can access reading accurately, and can detection receptacle when become empty.

A problem is that when liquid had low specific inductive capacity, the major part of reflected signal was next from the surface reflection of container bottom rather than liquid especially.This can produce distorted signal, removes the filling liquid level height of on-liquid because by the signal of bottom reflection by Liquid Absorption.When liquid is that this problem will constantly increase when hanging down liquid level at large.

Another problem is the bottom section at container, almost total by-product layer, and water for example, its separation owing to liquid, concentrated etc. produces.And when the specific inductive capacity of secondary product is high relatively, a reflected signal that is better than liquid surface will be sent in the interface of secondary product.

Therefore, the radar level gauging device of previously known just has during near the measurement of container bottom in measuring the container of storage of liquids and has limited to.

Summary of the invention

Therefore, when an object of the present invention is to provide the level that a kind of measurement is stored in the surface of the product in the container is the improved method of sky with liquid level and the detection receptacle of allow measuring near container bottom.

Purpose of the present invention realizes that by using following measuring method the method comprising the steps of: the radar level gauging device by being installed in the product surface top is to product surface launched microwave signal; In described radargrammetry device, receive from the microwave signal of product surface reflection; In computing unit, determine the measured value of product liquid level based on the signal that receives; The relatively measured value of this product liquid level and predefined product fluid value; And when this measured value is lower than the predetermined prod fluid value, use second liquid surface measuring device that is installed in container bottom to determine the product liquid level.

Another object of the present invention provides a kind of improved level gauging system, is used for measuring the liquid level on the surface of the product that is stored in container, when is sky with liquid level and the detection receptacle that allows to measure near container bottom.

This purpose realizes by the level gauging system that provides following being used for to measure to be stored in the liquid level of container product, this system comprises: the radar level gauging device that is installed in the product top, this installs to product surface launched microwave signal, and receives the microwave signal of reflection from product surface; Computing unit is used for determining based on the signal that is received the measured value of the liquid level of product; Be used for the device of measured value and predefined product fluid value of comparative product liquid level; With, being installed in second liquid surface measuring device that approaches container bottom, it is used for measuring the liquid level of product when measured value is lower than preset value.

The other objects and features of the invention are from below in conjunction with becoming obvious the detailed description of accompanying drawing.Yet, should be understood that the accompanying drawing purpose only be to explanation of the present invention and, be not to be used for limiting definition of the present invention, the reference of limitation of the present invention should be made by appended claims.Should be appreciated that more accompanying drawing needn't proportionally draw, unless otherwise indicated, otherwise their purpose only is in this description scheme and the conceptual demonstration of step.

Description of drawings

In institute's drawings attached, the identical identical unit of numeric character indication.

Fig. 1 discloses the synoptic diagram that is installed in according to the container in the radar level gauging system of the present invention.

Fig. 2 has shown the synoptic diagram according to the container of Fig. 1, and wherein, the product liquid level in the container is lower than the product liquid level among Fig. 1.

Fig. 3 is the process flow diagram of the creative method of the present invention of execution when being presented at container for sky.

Fig. 4 is the process flow diagram of the creative method of the present invention carried out when being presented at container and being full of.

Embodiment

With reference to figure 1 and Fig. 2, be often referred to and be shown 10 container and be full of liquid 16, the height of liquid or liquid level are determined with radar level gauge 14.Radar level gauge 14 is preferably installed and is sealed on the container port on container 10 tops and with respect to its sealing.Radar level gauge 14 comprises an antenna 18, and antenna 18 is to liquid surface 12 launched microwaves, and receives the reflected microwave signal from liquid surface 12, thereby the indication of the liquid level of liquid 16 in the container 10 is provided.The radar level gauge 14 that is used for launched microwave and reception reflected microwave signal is known, and only schematically shows at this.

An interface determinator 20 is mounted close to the bottom of container 10.Interface determinator 20 is used to measure the liquid level or the level 24 of secondary product 22, and this liquid level is for example because the separation of liquid 16 or concentrate and raise.Radar measuring device 14 and interface determinator 20 interconnect (not shown).In the time of the reflected signal poor quality that receives when radar level gauge or when the level gaging value of liquid surface 12 reaches predetermined value, for example, when the filling liquid level of liquid is low, it is such that image pattern 2 is represented, installation radar measuring device is used for instructing interface-measuring device to recalibrate and comes work as liquid surface measuring device rather than as interface-measuring device.In this article, and term " measured value " be meant with rice the value of the liquid level that is the unit measurement, that is, and the height of tested liquid level.

Preset value is based on experience, and is stored in the radar level gauge 14.When the filling liquid level of liquid 16 was low, the operator was from interface determinator 20 rather than obtain the information of relevant liquid level from radar level gauge 14.The change of this determinator is sightless to the operator.Perhaps, if the operator needs, can provide the liquid level information that obtains from these two level gauge simultaneously.

Interface determinator 20 is reference point (its value preferably is stored in the interface-measuring device 20) by the specific inductive capacity that uses air, and have how many interface-measuring devices 20 to be immersed in the liquid (value that provides by radar level gauge 20), thereby come the liquid level rather than the interface 24 between secondary product 22 and liquid 16 of calibration measurement liquid surface 12 as the range calibration point by use.

In a preferred embodiment of the invention, container is the oil tank that oil is housed.Oil, particularly crude oil all can comprise some water usually, and these water will separate and accumulate in tank bottom from crude oil.In order to determine that how much water is arranged in the oil tank, a water interface gauge is installed in tank bottom.Water interface gauge in the preferred embodiment of the present invention is a capacitance probe.

Capacitance probe uses a kind of like this relation, i.e. electric capacity change and specific inductive capacity are directly proportional.For example, the example of some specific inductive capacity is air-1, oil-4, ethanol-25, water-80.Capacitance probe is known to those skilled in the art, does not go through in this application.Radar level gauge 14 and capacitance probe 20 preferably communicate by the HART agreement.

Usually, capacitance probe knows that the specific inductive capacity of product is necessary.This can have problems when product is the situation of profit mixing, because can not learn specific inductive capacity from bad measurement data result.But in this application, do not need to know in advance specific inductive capacity.This is that promptly, capacitance probe is calibrated by the range calibration point (detector is immersed in the length in the product) that is provided by radar level gauge, thereby can calculate the specific inductive capacity of liquid at an easy rate because of a kind of like this fact.

In the preferred embodiment of the application, when container 10 when empty in the measuring vessel 10 storage liquid 16 liquid surface 12 step as shown in Figure 3, as follows:

1. radar level gauge 14 is by measuring the liquid level (step 31) of liquid surface 12 from the microwave reflection of liquid surface 12 to liquid plane 12 launched microwaves and reception.

2. measured value X compares (step 32) with the predetermined value Y that is stored in the radar level gauge 14.If measured value X is higher than predetermined value Y, then radar level gauge 14 is equal to or less than predetermined value Y according to the height of step 31 measurement liquid surface 12 up to measured value X.

3. when measured value X is equal to or less than predetermined value Y, radar level gauge 14 instruction capacitance probe 20 calibration measurement liquid surfaces 12 rather than water terminations 24 (step 33).Water interface gauge 20 is by using dielectric constant of air as neutral point (this value preferably is stored in the capacitance probe 20), what and have water termination detectors 20 to be dipped in the liquid (value that provides by radar level gauge 20), thereby calibrate as the range calibration point by use.

4. capacitance probe 20 is measured the liquid level (step 34) of liquid surface 12, that is, the interface of air and liquid, this measuring process is to change the fact that is directly proportional with the specific inductive capacity of liquid 16 by the electric capacity that utilizes detector 20 to realize.

In this preferred embodiment of the application, when container 10 was filled with, as shown in Figure 4, the step of the liquid level of the liquid surface 12 of liquid 16 was as follows in the measuring vessel 10:

1. capacitance probe 20 is measured the liquid level (step 41) of liquid surface 12, that is, the interface of liquid and air, this process is to change the fact that is directly proportional with the specific inductive capacity of liquid 16 by the electric capacity of using detector 20 to realize.

2. measured value X compares (step 42) with the predetermined value Y that is stored in the radar level gauge 14.If measured value X is equal to or less than predetermined value Y, then capacitance probe 20 is according to the liquid level of step 41 measurement liquid surface 12, till measured value X is higher than predetermined value Y.

3. when measured value X is higher than predetermined value Y, radar level gauge 14 instruction capacitance probes 20 calibration measurement water terminations 24, i.e. the interface of water 22 and liquid 16, rather than measure the liquid level (step 43) of liquid surface 12.Capacitance probe 20 is calibrated by the calibration point (neutral point and range calibration point) (these preferably manufactured merchants of point are stored in capacitance probe 20) that use is used for water termination 24 measurements.

4. radar level gauge 14 is by also receiving the liquid level (step 44) of measuring liquid surface 12 from the microwave reflection of liquid surface 12 to liquid surface 12 launched microwaves.

Therefore, though the novel features of being implemented by preferred embodiment of the present invention is shown and describes and points out, but should be understood that, the various forms of omissions of the details of the design shown in those skilled in the art can make under the situation that does not break away from spirit of the present invention and form and their enforcement replace and change.For example, clearly all within the scope of the invention, these combinations have been carried out same function in fact, used with quadrat method and have been obtained same effect in the combination of these key elements and/or method.And, will be appreciated that, among any form disclosed by the invention and the embodiment disclosed structure and/or key element and/or method step can be included in any other open describe or the form of suggestion or embodiment in as the routine of a design.Therefore, the present invention is only limited by appended claim.

Claims

1. A method of measuring the liquid level on the surface of a product stored in a container, comprising the steps of:

Send microwave signals to the product surface with a radar liquid level measuring device installed above the product surface;

receiving microwave signals reflected from the product surface in the radar liquid level measuring device;

Determining a measured value of the product level in the computing unit based on the received signal;

comparing the product level measurement with a predetermined value for the product level;

The product level is determined using a second level gauge mounted near the bottom of the container when the measured value is less than or equal to the predetermined product level.

2. The method of claim 1, further comprising the step of measuring the level of the interface between the product and the by-product in the container by a second level gauge when the product level is higher than a predetermined value of the product level.

3. The method of claim 1, further comprising the step of using the dielectric constant of the product and the dielectric constant of air to determine the product level.

4. The method of claim 1, further comprising the step of determining the product level by the capacitive probe for calculating the dielectric constant of the product surrounding the capacitive probe.

5. The method of claim 4, further comprising the step of calibrating the capacitive detector, the step being accomplished by:

Use the dielectric constant of air as the neutral point;

The value of the length of the probe immersed in the product is provided by the radar level gauge;

Calculation of the actual value of the permittivity via a capacitive probe; and

Use the calculated permittivity as a range calibration point corresponding to the length.

6. A radar level measurement system for measuring the liquid level on the surface (12) of a product (16) stored in a container (10), comprising:

A radar liquid level measuring device (14) installed above the surface (12) of the product (16), the radar liquid level measuring device (14) is configured to transmit microwave signals to the product surface (12) and receive signals from the product surface ( 12) Reflected microwave signals;

Calculation unit for determining the measured value of the product level from the received signal;

means for comparing the measured value of the product level with the predetermined value of the product level;

A second liquid level measuring device (20) mounted near the bottom of the container (10) is arranged to determine the product liquid level when the measured value is lower than or equal to a predetermined value of the product liquid level.

7. The radar liquid level measurement system according to claim 6, wherein the second liquid level measuring device (20) is arranged to measure the product (16) in the container (10) when the product liquid level is higher than a predetermined value of the product liquid level ) and the liquid level of the junction (24) between the by-product (22).

8. The radar level measurement system of claim 6, wherein the product level is determined using the dielectric constant of the product (16) and the dielectric constant of air.

9. The radar liquid level measurement system of claim 7, wherein the second liquid level measurement device is a capacitive probe (20) arranged to determine the liquid level of the product by placing the capacitive probe (20) from the arranged to measure the interface (24) between the product (16) and the by-product (22) in the container (10) calibrated to be arranged to measure the product level for said determination, wherein neutral as the dielectric constant of air points, as well as range calibration points which are the calculated dielectric constant values provided by the radar level measuring device corresponding to the value of the probe (20) immersed in the product (16), are applied in said calibration step.