Apparatus and method for diagnosing deterioration of smokestack

• US 4,768,158 A
• Filed: 01/23/1987
• Issued: 08/30/1988
• Est. Priority Date: 01/25/1986
• Status: Expired due to Fees

• Current Assignee: Kajima Corporation
• Original Assignee: Kajima Corporation
• Inventors: Osanai, Takahito
• Primary Examiner(s): YASICH, DANIEL
• Application Number:
  US07/006,123
• Time in Patent Office: 585 Days
• Field of Search: 374/124, 374/137, 374/4, 374/5, 364/557, 364/507
• US Class Current: 702/34
• CPC Class Codes: G01N 25/72 Investigating presence of flaws

Abstract

The disclosed apparatus and method diagnose deterioration of a steel-reinforced concrete smokestack by taking its infrared ray photograph, thermographically processing the photograph into an outside surface temperature distribution diagram so as to detect a defect as a singular point on the diagram, measuring the circumferential length (L) of the defect from the diagram, finding concrete crack width (W) at the defect based on outside surface temperature difference between sound portion of the smokestack and the defect, and calculating reduction of the strength of the smokestack wall structure due to the defect by using the circumferential length (L) and the concrete crack width (W) of the defect.

Claims

1. An apparatus for diagnosing deterioration of a steel-reinforced concrete smokestack by detecting a defect in the concrete of said smokestack, comprising:

thermal graphic means for producing a diagram of outside surface temperature distribution of said smokestack from an infrared ray photograph;

detecting means for detecting a defect as a spot in said diagram whose temperature discontinuously differs from that of area surrounding the spot;

means for calculating smoke temperature in the smokestack at the defect based upon the temperature difference between the inside and outside of the smokestack at the defect based in turn on the smoke temperature at the inlet of the smokestack and said outside surface temperature distribution;

means for calculating the depth of said defect based upon said temperature difference and the temperature gradient of the wall of said smokestack;

a means for empirically determining a concrete crack width W based on said defect depth; and

means for assessing deterioration of strength of the smokestack based on the concrete crack width W and the area of the defect as measured on said diagram.

2. An apparatus for diagnosing deterioration of a steel-reinforced concrete (SRC) smokestack by detecting a defect in concrete of said smokestack, comprising a thermographic means for producing a diagram of outside surface temperature distribution of said SRC smokestack from an infrared ray photograph thereof, a means for detecting a defect (F) as a spot in said diagram whose temperature discontinuously differs from that of area surrounding the spot, a means for calculating smoke temperature θ

_g in the smokestack at the defect by an equation

space="preserve" listing-type="equation">θ

.sub.2 =θ

.sub.o +(K/α

.sub.2 r.sub.2) (θ

.sub.g -θ

.sub.o)

space="preserve" listing-type="equation">(l/k)=(1/α

.sub.1 r.sub.1)+(1/α

.sub.2 r.sub.2)+(1/λ

)1n(r.sub.2 /r.sub.1)

wherein,

r₁ ;

smokestack inside radius (m)

r₂ ;

smokestack outside radius (m)

θ

.sub. ;

smokestack outside surface temperature on said diagram at said area surrounding the spot with discontinuous temperature

θ

_f ;

smoke temperature (°

C.)

θ

_o ;

outside air temperature (°

C.)

α

₁ ;

inside surface coefficient of heat transfer

α

₂ ;

outside surface coefficient of heat transfer

λ

;

coefficient of heat transfer concrete

K;

coefficient of overall heat transmission,

a means for calculating depth (d) of the defect (F) by an equation

space="preserve" listing-type="equation">θ

.sub.f =θ

.sub.o {K/α

.sub.2 (r.sub.2 -d)}(θ

.sub.g θ

.sub.o)

wherein,

θ

_f ;

smokestack outside surface temperature on said diagram at said discontinuously different spot,

a means for empirically determining a concrete crack width (W) based on said defect depth d, and a means for assessing deterioration of strength of the smokestack based on the concrete crack width (W) and area of the defect as measured on said diagram.

3. An apparatus for diagnosing deterioration of an SRC smokestack as set forth in claim 2, wherein said area of the defect is a product of said concrete crack width (W) and a a length (L) of the defect (F) taken in a circumferential direction of the smokestack on said diagram.

4. A method of deterioration diagnosis for a steel-reinforced concrete (SRC) smokestack by detecting a defect in concrete of said smokestack, comprising steps of producing a diagram of outside surface temperature distribution of said SRC smokestack from an infrared ray photograph thereof, identifying a defect singular as a spot in said diagram whose temperature discontinuously differs from that of area surrounding the spot, calculating smoke temperature θ

_g in the smokestack at the defect (F) by an equation

space="preserve" listing-type="equation">θ

.sub.2 =θ

.sub.o +(K/α

.sub.2 r.sub.2)(θ

.sub.g -θ

.sub.o)

space="preserve" listing-type="equation">(l/K)=(1/α

hd 1r.sub.1)+(1/α

.sub.2 r.sub.2)+(1/λ

)1n(r.sub.2 /r.sub.1)

wherein,

r₁ ;

smokestack inside radius (m)

r₂ ;

smokestack outside radius (m)

θ

₂ ;

smokestack outside surface temperature on said diagram at said are surrounding the spot with discontinous temperature

θ

_g ;

smoke temperature (°

C.)

θ

_o ;

outside air temperature (°

C.)

α

₁ ;

inside surface coefficient of heat transfer

α

₂ ;

outside surface coefficient of heat transfer

λ

;

coefficient of heat transfer of concrete

K;

coefficient of overall heat transmission,

calculating depth d of the defect F by an equation

space="preserve" listing-type="equation">θ

.sub.f =θ

.sub.o +{K/α

.sub.2 (r.sub.2 -d)}(θ

.sub.g -θ

.sub.o)

wherein,

θ

_f ;

smokestack outside surface temperature on said diagram at said discontinuously different spot,

empirically determining a concrete crack width (W) based on said defect depth d, and assessing deterioration of strength of the smokestack based on the concrete crack width (W) and area of the defect as measured on said diagram.

5. A method of deterioration diagnosis of an SRC smokestack as set forth in claim 4, wherein said area of the defect is represented by a product of said concrete crack width (W) and a length (L) of the defect (F) taken in a circumferential direction of the smokestack on said diagram.