CN202284963U

CN202284963U - Liquid level measuring system of sealing container

Info

Publication number: CN202284963U
Application number: CN2011203269327U
Authority: CN
Inventors: 李毅; 李世元
Original assignee: China National Offshore Oil Corp CNOOC; CNOOC China Ltd Tianjin Branch
Current assignee: China National Offshore Oil Corp CNOOC; CNOOC China Ltd Tianjin Branch
Priority date: 2011-09-01
Filing date: 2011-09-01
Publication date: 2012-06-27
Anticipated expiration: 2021-09-01

Abstract

The utility model relates to a liquid level measuring system of a sealing container, which belongs to the technical field of liquid level measurement, and comprises a first pressure sensor measuring air pressure of the upper part of the liquid in the sealing container, and a calculating unit. The side wall of the sealing container is provided with a second pressure sensor. The measuring signals of the two pressure sensors are sent to the calculating unit, and the liquid level of liquid in the sealing container can be calculated by the calculating unit. The liquid level measuring system of a sealing container is advantageous in that cost can be saved; the structure is simple and the calibrating is easy and more reliable.

Description

A kind of closed vessel liquid level measuring system

Technical field:

The utility model belongs to the level gauging technical field, relates to a kind of closed vessel liquid level measuring system.

Background technology:

In commercial production, the measurement of the liquid level of closed container is extremely important, but the user is often not high to the accuracy requirement of level gauging instrument, more value be the reliability of instrument and after instrument breaks down found complexity.Liquid level is controlled bad and the root of the accident occurred often because liquid level instrument fault occurred and in time do not judged in accident case in the past! Therefore select for use reliability high and be easy to judge the liquid level instrument that whether has fault, seem particularly important!

In liquid level instrument, come the method for measuring liquid level to use more extensive through differential pressure transmitter.Its principle is a (see figure 1): the pressure differential deltap P of pressure P 0 that measures pressure P h and the container top of a certain fixed position in the container through differential pressure transmitter (1).According to static pressure measurement principle Δ P=ρ g Δ h, can get Δ h=Δ P/ ρ g (wherein ρ is a fluid to be measured density, and g is a local gravitational acceleration, and Δ h is the degree of depth that transmitter immerses liquid), measure the liquid level of measured medium at last indirectly.

But the composition mechanism of this method is complicated; The risk that also exists connecting pipe obstruction, leakage, equalizing valve to leak in addition; And the failure judgement difficulty is (when low-pressure side appearance measurement is inaccurate; Be easy to be left in the basket, and can not in time find fault), demarcate difficulty (need positive and negative pressure all to suppress demarcate just reliable), use difficulty shortcomings such as (needs are operated three valve groups or five valve groups), lead to serious security incident easily.

The utility model content:

The purpose of the utility model is to improve the deficiency of existing differential pressure type level gauging mode, provides that a kind of failure rate is low, reliability is high and demarcate to be easy to the closed vessel liquid level measuring system.For this reason, the utility model adopts following technical scheme.

A kind of closed vessel liquid level measuring system; Comprise first pressure transducer and the computing unit of measuring liquid level upper gas pressure in the closed container; The sidewall of said closed container is provided with second pressure transducer; The measuring-signal of two pressure transducers is admitted to computing unit, is calculated the liquid level of liquid in the closed container by computing unit.

As preferred implementation; The closed vessel liquid level measuring system of the utility model; Described liquid level measuring system also comprises the 3rd pressure transducer, is arranged on the closed container sidewall with the second pressure transducer differing heights, and its measuring-signal is admitted to computing unit; By the measuring-signal calculating fluid density of computing unit, and revise the liquid level measured value in view of the above according to second pressure transducer and the 3rd pressure transducer.

The utility model need not have devices such as connecting pipe, equalizing valve, can not only practice thrift cost, and have simple in structure, demarcate simple, use simple advantage, the correction of increase also has reference value with the measured value of pressure transducer (transmitter).What need to propose emphatically is, the reliability of pressure unit is high than differential pressure transmitter and other fluid level transmitter, even and pressure unit break down; Also can be through the contrast of pressure; Find fault easily, thereby take to arrange, execute the generation of avoiding accident.

Description of drawings:

Fig. 1 is the application legend of prior art;

Fig. 2 is the application legend of the utility model.

Embodiment

Below in conjunction with accompanying drawing and embodiment the utility model is further specified

The closed container measuring principle of the utility model is the same with existing differential pressure transmitter survey liquid level, and different is that the utility model utilizes two or more pressure units (sensor) to replace differential pressure transmitter.On central control system, carry out configuration then, calculate the height of liquid level.

The utility model seems a differential pressure transmitter will using two pressure units to replace prior art, and reality is not.Because at container top; One all is designed with pressure unit 2 and comes container pressure is measured; Only need replace differential pressure transmitter 1 with a pressure unit 5 so implement the utility model in the bottom of container; On central control system, carry out configuration then, the measured value of pressure unit 2,5 is introduced to calculate just can accomplish measurement, referring to Fig. 2 to liquid level.The utility model is actual to be to have replaced a differential pressure transmitter to carry out the measurement of liquid level with a pressure unit, aspect cost, also can reduce to some extent.

Measuring principle:

Measure the pressure P h of a certain fixed position in the container through pressure unit 5; Measure the pressure P 0 of container top through pressure unit 2, calculate pressure differential deltap P through Δ P=Ph-P0 again, according to static pressure measurement principle Δ P=ρ g Δ h; Can get Δ h=Δ P/ ρ g wherein ρ be fluid to be measured density; G is a local gravitational acceleration, and Δ h is the degree of depth that transmitter immerses liquid, calculates the liquid level of measured medium at last.

In the practical application of Petroleum Production, be designed with 2,3, one 2 Process Control System PCS that insert central control system of two pressure units on the container usually, be used to control pneumatic control valve; The ESD of emergency shutdown system of another 3 access central control system is used to produce emergency shutdown and uses.So enforcement the utility model can all be introduced the measured value of two pressure units 2,3 of tank deck the calculating of liquid level.When the pressure unit 2 or 3 at any one top broke down, the surveying work of liquid level all can also normally carry out, and can compare mutually.In addition, when the transmitter 2 or 3 of pressure damaged, the pressure unit 5 that uses on the liquid level can also for reference use.Because one all also has other level gauging instrument such as being installed in on-the-spot liquid level gauge on the container; Can estimate the pressure of container top through the force value of base pressure transmitter 5 measurements and the liquid level of container, supply the measured value of container top pressure unit to judge reference so also be equivalent to many manometers.

Mode through measuring differential pressure is come measuring liquid level, all can influence the precision of measurement because of the variation of Media density.In order to revise, in the practical application of traditional Petroleum Production, be designed with temperature transmitter 4 on the container usually because of the influence of variable density to measuring accuracy.Because there are certain functional relation in fluid density and temperature, therefore revise density of medium, thereby improve measuring accuracy through introducing temperature calculation.But because the funtcional relationship between fluid density and the temperature and the component of liquid itself have relation, this kind scaling method need be confirmed different funtcional relationships to different liquid.Different with traditional modification method; The utility model provides the method for indirect measurement: on container, increase a pressure unit 6 again at line density; Because the difference in height between the pressure unit 5 and 6 is a fixed value Δ h, the measured value through pressure unit 5 and pressure unit 6 can calculate pressure differential deltap P.According to static pressure measurement principle Δ P=ρ g Δ h, the online density p=Δ P/g Δ h that can get liquid wherein ρ is a fluid to be measured density, and g is a local gravitational acceleration, and Δ h is the degree of depth that transmitter immerses liquid.Obviously, compare with traditional modification method, the utility model needs the pressure units of installing more; Cost also increases; But also brought benefit thus, made the liquid level correction be independent of liquid components and character, become simple and level gauging more accurate.

In addition, can also improve the measuring accuracy of liquid level: during one, to the pressure unit type selecting, need to select the pressure unit of suitable range through the measuring error that reduces pressure unit; Two, because the range of instrument is more little, absolute error is more little.So can be about 90% of container shutoff value lower limit with the Zero calibration of one of them pressure unit 2; With range designation is about 110% of the shutoff value upper limit; Can reduce the range ability of pressure unit so greatly; And then reduce the measuring error of pressure unit, reach the purpose that improves the measuring liquid level precision.

Claims

1. closed vessel liquid level measuring system; Comprise sensor and computing unit; It is characterized in that; Described sensor comprises first pressure transducer and second pressure transducer, and described first pressure transducer is used to measure first pressure transducer of liquid level upper gas pressure in the closed container, and described second pressure transducer is arranged on the sidewall of said closed container; The measuring-signal of two pressure transducers is admitted to computing unit, is calculated the liquid level of liquid in the closed container by computing unit.

2. closed vessel liquid level measuring system according to claim 1; It is characterized in that; Described liquid level measuring system also comprises the 3rd pressure transducer that is used to revise the liquid level measurement result; Be arranged on the closed container sidewall with the second pressure transducer differing heights, its measuring-signal is admitted to computing unit.