International Atomic Energy Agency
Rev. No. 0
PROCEDURE OF RADIOTRACER Date 5 December 2003
TECHNIQUES FOR LEAK TEST IN Page 1 of 18
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CASE STUDIES
1 Study of leakage in heat exchanger at a refinery in Pakistan
PINSTECH Team conducted a Radiotracer Test at an oil refinery in Pakistan.
Radiotracer Br-82 in the form of Di- Bromo-Benzen with an activity of 130 mili Curie was used. A
brief feasibility of experimental set up was carried out and necessary arrangement was discussed
with plant engineers. Experimental set- up was completed and background radiation levels were
recorded before tracer injection. Special arrangements were made to inject radiotracer in the system.
Following monitoring stations were set up to monitor the passage of radiotracer in the heat
exchanger loop. The relative positions of various detectors are shown in figure-1.
Detector-1: At the Tube Inlet --- Just before the tube inlet pipe enters the exchanger
Detector-2: At the tube outlet --- Away from the Exchanger
Detector-3: At the Shell Inlet --- Away from the Exchanger
Detector-4: At the Shell Outlet --- Just after the shell outlet pipe goes away from the Exchanger
Detector-5: At first Platform (near Shell Top) --- against the Shell wall
All the rate meters and computer were time synchronized. Data recording was started at
14:23 hours. The detector-4 placed at Shell outlet to monitor leakage (if any) was connected to
computer for data acquisition. The data from other detectors was recorded manually. The data of
detector-4 was also recorded manually to avoid data loss in case of any problem with the computer.
Data of detector-4 was recorded every 5 seconds while for other detectors, data was recorded for
every 10 seconds.
Tracer Injection: Valves V-1 and V-3 of the Injection Port (see figure-1) were closed.
The Flange at the top of valve V-2 was removed and the valve V-2 was opened. The oil level in the
-1 -3
horizontal pipe between valve V and V was maintained such that 3/4 of pipe diameter was
filled with oil. Specially designed device to crush the silica glass ampoule was inserted vertically in
the pipe through valve V-2. Two glass ampoules containing Radiotracer Br-82 (in the form of Di-
Bromo-Benzen powder) were inserted in the crushing device. Ampoules were crushed and tracer
was mixed in oil in the pipe. The ampoule-crushing device was rinsed (inside the pipe) with
inactive oil before it was taken out and stored safely. The valve V-2 was closed and Valves V-3 and
V-1 were opened. The Radiotracer was injected into the system by starting the pump.
The injection was made at 14:32 hours in the Tube inlet pipe through Injection Port as
described above. The data was recorded from 14:23 to 16:00 hours i.e., for 1 hour & 37 minutes.
Data was analyzed and plotted as shown in figurer-2, 3, 4 & 5.
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PROCEDURE OF RADIOTRACER Date 5 December 2003
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Detector−5
Detector- 2
OIL INPUT Detector- 3
TRACER INPUT
Detector- 4
V2
PUMP Detector-1
V1
Figure-1: Schematics of Experimental Set-up showing Tracer Injection
Port and position of various detectors.
________________________________________________________________________________
Discussion and Results
The data obtained from detector-1,2,4 & 5 is plotted in figure-2. As the Radiotracer did not
appear at detector-3, its data is not plotted. The data from detector-4 with 5-second time base is
plotted in figure-3. The data from detector-1 and detector-4 is plotted in figure-4. The zoom view of
figure-4 near the peak area is shown in figure-5. The timings of tracer-peak arrival and peak
duration are also given in figure-2 and figure-5.
The data from detector-1 (monitoring tracer injection in tube inlet) and detector-4
(monitoring leakage, if any, in shell outlet) is very important and is to be analyzed carefully. Tracer
r
injection was made away f om detector-1 at 14:32 hours. The tracer plume of injection reached
detector-1 at 14:33:50 hours and the tracer plume passed away from detector-1 at 14:34:50 within a
duration of 60 seconds. The maxima of injection peak was recorded at 14:34:00 hours (please see
peak-B, figure-4 & 5). A tracer peak was also recorded by detector-4 placed at shell outlet (leak
detector). The tracer peak arrived at detector-4 at 14:33:05 hours and passed away at 14:34:05 hours
International Atomic Energy Agency
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PROCEDURE OF RADIOTRACER Date 5 December 2003
TECHNIQUES FOR LEAK TEST IN Page 3 of 18
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within 60-second duration. The maxima of the peak was recorded at 14:33:15 hours (please see
peak-A, figure-4 & 5).
The detector-1 and detector-4 recorded the peak for the same duration i.e., for 60 seconds
and the peak maxima reached within 10 seconds of the arrival of tracer peaks on both detectors.
However, detector- 4 recorded the tracer peak 45 seconds earlier than detector-1. That means
detector-4 recorded tracer peak before the tracer entered the exchanger. This indicates that the peak
recorded by detector-4 at 14:33:05 hours is not related to any leakage in the exchanger but this peak
is due the fact that detector-4 has seen activity of injection plume while tracer passed through the
tube inlet pipe in the near vicinity (see figure-1). The detector-5 placed against the shell wall, at the
platform near the shell top (see figure-1) recorded tracer peak maxima at 14:37:10 hours while the
detector-2 placed against tube outlet (see figure-1) recorded the peak maxima at 15:08:10 hours.
The data acquisition was continued for 1 hour and 37 minutes after the tracer injection, but detector-
4 did not record any leakage. The absence of any tracer at detector-3 placed at shell inlet (see
figure-1) shows that tracer is diluted and adsorbed somewhere in series of reactors and did not
appear afterwards at the she ll inlet.
RESULT: The Tracer Test reveals that there is NO LEAKAGE in the
Exchanger.
Radiation Safety Aspects
All necessary radiation protection aspects were taken into account during all stages of the
experiment (radioisotope production, transportation, injection, etc.). Nobody except PINSTECH
personnel was allowed to stay within 10 meters diameter around the injection port during tracer
injection till the area was checked at the end of experiment. The injection port and the area around
were checked and no radiation contamination was found. However, there was still little activity
inside the pipe at the injection port and that too was safe at 1 meter distance. The process engineer
at site, his staff and Inspection Engineer were briefed about the necessary precautions in this regard.
It may be noted that continuous oil flow was taking place at the injection port leading to dilution of
activity besides radioactive decay process. All other points in the experimental loop were checked
and found safe. Next day, PINSTECH team checked injection port again and radiation level was
found within safe limits. No radioactivity was recorded by Detector-3 placed at the shell inlet. That
means that there is no question of any radioactivity in the refined product.
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PROCEDURE OF RADIOTRACER Date 5 December 2003
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LeakTestin103-E-6(NRL)
14000
D-4(ShellOutlet)
Counts (per 5 second)
ActivityseenbyDetectorfrom
12000
Injection Plume from Tube Inlet pipe
10000 Sensitivity Test of Detector
8000
6000
4000
2000
0
14:24:00 Detectors - with 15:21:36 15:36:00 15:50:24 16:04:48
Response of 14:38:24 14:52:48 415:07:12 5 second counting ti
-2000
i e
Tm
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PROCEDURE OF RADIOTRACER Date 5 December 2003
TECHNIQUES FOR LEAK TEST IN Page 5 of 18
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LEAK TEST IN 103-E-6 (NRL)
600000
(Tube inlet)
(Shell outlet)
500000
Peak-B (Tube Inlet)
COUNTS (per 10 second)
( at 14:34:00 )
400000
Injection Time: 14:32
300000 PEAK POSITION TIMINGS
Detector at Peak Duration Peak max. at
Tube Inlet 14:33:50 to 14:34:50 14:34:00
200000 Shell Outlet 14:33:05 to 14:34:05 14:33:15
Peak-A (Shell Outlet)
( at 14:33:15 )
100000
0
14:24:00 14:38:24 14:52:48 15:07:12 15:21:36 15:36:00 15:50:24 16:04:48 16:19:12
TIME
Figure- 4: Response of Detector-1 & Detector- 4
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PROCEDURE OF RADIOTRACER Date 5 December 2003
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LEAK TEST IN 103-E-6 (NRL)
30000
Peak-A (Shell Outlet) Peak-B (Tube Inlet)
( at 14:33:15 ) ( at 14:34:00 ) (Tube inlet)
(Shell outlet)
25000
COUNTS (per 10 second)
Injection Time: 14:32:00 Hours
20000
PEAK POSITION TIMINGS
15000
Detector at Peak Duration Peak max. at
Tube Inlet 14:33:50 to 14:34:50 14:34:00
Shell Outlet 14:33:05 to 14:34:05 14:33:15
10000
5000
0
14:24:00 14:31:12 14:38:24 14:45:36 14:52:48 15:00:00 15:07:12
TIME
Figure- 5: Response of Detector-1 & Detector- 4 ( Zoom view near peak area )
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2 Inspection report on-stream radiotracer leak test of the Heat Exchanger tower of the
petrochemical Plant, Thailand
DESCRI The Heat Exchanger tower as a tube and shell heat exchanger is expected leaks from
PTI tube side into shell side as indicate by contaminants found from laboratory analysis.
To identify the problem, radiotracer technique has been applied by injection of
gamma emitting radioactive tracer into the tube side inlet and monitor gamma
radiation at the tube outlet and shell outlet to find the residence time of process
stream flow in the vessel and the leakage, if any.
OPERAT The equipment setting as showed in figure 1. Radiotracer Dibromobenzene-82 of
ION half- life 35 hours in liquid form is injected into the process line going to the vessel at
tube inlet. Collimated detectors installed as the following:
- Detector 1 about 5 meter down stream of the injection point
- Detector 2 at tube inlet
- Detector 3 at tube outlet
- Detector 4 at shell outlet (for leak detection)
The detectors are connected to data logging system at 0.05 seconds interval. Two
injections are performed with approximately 15 mCi Br-82 each at 15 bars into the
process stream of 8 bars. Transmitted gamma ray intensities at each position is
recorded and processed by Excel as gamma intensity VS time graph for
evaluation/interpretation. Detector 4 in located at the shell outlet and about 10 meters
away in the first and second injection respectively.
RESULT
Arrival times after injection (seconds)
S
First injection Second injection
Range Center Peak area Range Center
D1 7.4-35.4 8.8 D1 5.8-24 10
D2 13-34 21.6 23182 D2 13-34 23
D3 34-72 42 D3 31-63 42
D4 11-26 and 28-55 16.8 and 41 1735 D4 6.4-18 16
Ratio of sum peaks D4/D2 = 1735/23182 = 7.5 %
Comment:
- The first peak of D4 at the shell outlet is the interference from the nearby inlet
pipe as it arrives before the peak of D2 at tube inlet. The second peak is the leak.
The ratio of peak area D4/D2 is approximate leak e.g. 7.5%. The figure will be
less if the data is corrected with background subtraction. As detector 4 is situated
further away (10 meters from shell outlet) in injection 2, no leak peak is observed
because tracer is too diluted by the process stream.
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3 Onstream Radiotracer technique leak test of the Hydrocraker unit combined feed
Exchager of The Petroleum Refinery, Thailand
PURPOSES The combined feed heat exchangers unit is operated at high temperature
(200-300°C) and at high pressure(100-200bar). It has been expected small
leakage of about 5% from reactor feed at shell side into reactor effluent at
tube side. The main purpose of this study is to identify/pin-point the
p r o b l e m .
DESCRIPTIO The on- stream radiotracer technique is based on injection of gamma
N emitting radioisotope into the process to observe the process
parameters/behavior. The technique is applicable for flow rate, RTD and
l e a k a g e .
OPERATION J a n u a r y 3 1 - F e b r u a r y 1 , 2 0 0 2
- Organic Bromine-82 radioactive tracer (half- life 35 hrs) is prepared by
neutron activation of inactive Di-bromobenzene power in the Nuclear
Research Reactor for 2-4 hours at neutron flux 1012 neutrons per square
c e n t i m e t e r p e r s e c o n d .
- After dissolution in gasoline the stock solution of 30 ml 120 mCi is
stored in a bottle inside the lead container for transportation at
maximum allowance dose rate of 200mR/Hr
- Injection unit comprises nitrogen/diesel oil chamber, tracer vessel and
line connector is installed at low pressure (3bar) P-9501A/B reactor
feed pump. Tracer solution each of 20 mCi Br-82 is injected into the
p r o c e s s l i n e a t 1 0 - 1 5 b a r .
- Collimated scintillation detectors installed at the following:-
Flow/Injection Test (to optimize the injection procedure)
D - 1 a t E- 9 5 0 1 A S h e l l s i d e r e a c t o r f e e d i n l e t
D - 2 a t E- 9 5 0 1 D S h e l l s i d e r e a c t o r f e e d i n l e t
D-3 reactor feed pipe at a few meters after P-9501A/B injection point.
D - 4 a t E- 9 5 0 3 A T u b e s i d e r e a c t o r f e e d i n l e t
Combined Leak Test (to identify which series leaks E-9501D-F or E-
9 5 0 1 A - C )
D- 1 at E- 9 5 0 1 A S h e l l s i d e r e a c t o r f e e d i n l e t .
D - 2 a t E- 9 5 0 1 D S h e l l s i d e r e a c t o r f e e d i n l e t .
D- 3 a t E- 9 5 0 1 A T u b e s i d e r e a c t o r e f f l u e n t o u t l e t .
D- 4 a t E- 9 5 0 3 D T u b e s i d e r e a c t o r e f f l u e n t o u t l e t .
- Gamma intensity is logged by PM4 program at 0.05-0.5 seconds
interval. Data is processed by Excels.
F e b r u a r y , 0 5 , 2 0 0 2
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The combined leak test is repeated with 50 mCi Bromine- 82 tracer
i n j e c t i o n .
RESULTS/ I n j e c t i o n T e s t
COMMENTS - Graph 1 injection test at 15 bar represents detector responses at E -
9503A Tube side reactor feed inlet and at reactor feed pipe after P-
9501A/B injection point at 16 seconds and 79 seconds respectively.
Injection parameters could be optimized however, the gamma intensity
of 10 mCi Br-82 tracer solution at both positions found very low. No
responses at shell side reactor feed inlets of E-9501A and E-9501D at
100 meters from injection point as due to very high dilution effect
f r o m t h e p r o c e s s f l u i d f l o w s .
C o m b i n e d l e a k T e s t
- Graph 2 the combined leak test using 25 mCi Br-82 represents detector
responses at shell side reactor feed inlets of E-9501A and E -9501D
both at 126 seconds. The gamma intensity still found too low to allow
o b s e r v a t i o n o f l e a k a g e .
- Graph 3 the combined leak test using 55 mCi Br- 82 represents
detector responses at shell side reactor feed inlet of E -9501A and E-
9501D both at145 seconds with peak height of 700 counts. The
responses of the side reactor effluent out lets both at 190 seconds with
peak- height of 27 and 501 counts for A and D respectively. The
estimated leakage observed at 3% for A and D series respectively.
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