Level measurement method and apparatus

Patent metadata

Field	Value
Publication number	US-9891091-B2
Application number	US-201214130378-A
Country	US
Kind code	B2
Filing date	Jun 29, 2012
Priority date	Jul 1, 2011
Publication date	Feb 13, 2018
Grant date	Feb 13, 2018

Abstract

A method and apparatus for determining the location of a phase boundary such as a fill level, in a vessel. The method includes: providing at least one source of radiation capable of emitting radiation through a portion of the interior of the vessel; providing a plurality of radiation detectors, each detector being capable of detecting, within a part of the measurement range, radiation emitted by the source; and providing a data processing unit for calculation of the position of the phase boundary from the amount of radiation detected by the detectors, wherein the data processing unit calculates the position of the phase boundary from the amount of radiation detected by the detectors by:
(i) in a first step, determining within which detector stage the phase boundary is located; and then (ii) in a second step, determining the position of the phase boundary within the detector stage determined in (i).

First claim

The invention claimed is:

1. A method of determining a location, within a measurement range of a phase boundary between a first material phase and a second material phase within a vessel,
the first and second material phases having different radiation attenuation characteristics, and the first material phase being denser than the second material phase, the method comprising the steps of:

a) emitting radiation from at least one source of radiation through a portion of an interior of the vessel,
b) detecting the radiation using a plurality of radiation detectors,
each radiation detector being capable of detecting an amount of the radiation within a corresponding detector stage of the measurement range, the corresponding detector stage being associated with the radiation detector and the corresponding detector stage having a top and a bottom and over which corresponding detector stage the said radiation detector is capable of detecting the radiation emitted by the source,

c) calculating the location of the phase boundary from the amount of radiation detected by each of the plurality of radiation detectors by
(i) in a first step, determining, with a data processing processor, within which detector stage the phase boundary is located by comparing the amount of radiation received by each of the plurality of radiation detectors with:
(a) an amount of radiation detected by the each of the plurality of radiation detectors when the phase boundary is located at the top of the corresponding detector stage; or
(b) an amount of radiation detected by the each of the plurality of radiation detectors when the phase boundary is located at or below the bottom of the corresponding detector stage; or
(c) both (a) and (b),

and then
(ii) in a second step, determining, with a data processing processor, the location of the phase boundary within the detector stage determined in (i).

2. The method according to claim 1 , wherein the first material phase comprises a liquid phase and the second material phase comprises a gas phase.

3. The method according to claim 1 , wherein the first material phase and the second material phase comprise two liquids having different densities.

4. The method according to claim 1 , wherein in step (i), a smoothed count rate produced by each of the plurality of radiation detectors is compared with:
(a) a count-rate produced by each of the plurality of radiation detectors when the phase boundary is located at the top of the corresponding detector stage; or
(b) a count-rate produced by the each of the plurality of radiation detectors when the phase boundary is located at or below the bottom of the corresponding detector stage; or
(c) both (a) and (b).

5. The method according to claim 4 , wherein, in step (i), said comparison is made in two adjacent detector stages.

6. The method according to claim 5 , wherein step (i) is carried out using a method comprising the steps of:
a) for each radiation detector n, where n varies from 1 to N and N is the number of radiation detectors, acquire a current smoothed and decay-corrected count-rate Q n
b) calculate:

Q
nf

+

XQ
n

2
⁢

Q
n

⁢

T
c

for all N radiation detectors,
where Q nf is a smoothed count rate when the phase boundary is just at the top of the detector stage corresponding to radiation detector n, Tc is a time constant and X is a number ranging from 0 to 5,
c) starting with a lowest radiation detector (n=1), establish whether:

Q
n

≥

Q
nf

+

XQ
n

2
⁢

Q
n

⁢

T
c

(

Algorithm
⁢

⁢
A

)

d) if algorithm A is not satisfied, increment for n until a lowest radiation detector p is reached where algorithm A is satisfied such that:

Q
p

≥

Q
pf

+

XQ
p

2
⁢

Q
p

⁢

T
c

e) determine that the phase boundary is located in the detector stage corresponding to radiation detector p.

7. The method according to claim 6 where X=0.

8. The method according to claim 5 , wherein step (i) is carried out using a method comprising the steps of:
a) for each radiation detector n, where n varies from 1 to N and N is the number of radiation detectors, acquire a current smoothed and decay-corrected count-rate Q n
b) calculate:

Q
nf

+

XQ
n

2
⁢

Q
n

⁢

T
c

for all N radiation detectors,
where Q nf is a smoothed count rate when the phase boundary is at the top of the detector stage corresponding to radiation detect

Assignees

• Sanchez Galicia Edgar Ramon
• James Kenneth
• Roe Stephen John
• Johnson Matthey Plc

Inventors

• Sanchez Galicia Edgar Ramon
• James Kenneth
• Roe Stephen John

Classifications

• G01F23/2885 Primary

  for discrete levels · CPC title

• G01F23/288 Primary

  X-rays; Gamma rays {or other forms of ionising radiation} · CPC title

• G01F23/284 Primary

  Electromagnetic waves · CPC title