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EVALUATING PERFORMANCE CHARACTERISTICS OF X-RAY EQUIPMENT AND
FILM SYSTEMS WITHOUT THE USE OF ELECTRONIC MEASUREMENT AND/OR
SPECIAL INSTRUMENTS
M.F.Bianchi1, C.De Nitto2, A.Liscio1, N.Scala3
1 Avio, Rivalta (TO), Italy; 2 Avio, Brindisi, Italy; 3 Avio, Pomigliano d'Arco (NA), Italy
Abstract: Measurement and control of characteristics of NDT equipment and system that
produce output to be interpreted by inspector is one of the most important tools for NDT
reliability. Control activity should be based on:
* initial accurate measurement and calibration,
* periodical check to assure maintenance of calibration status,
* immediate verification and corrective action when any malfunctioning is suspected.
"Self-calibration" intended as capability of NDT facility to calibrate and control its own
equipment and systems is very important for continuous and reliable activity. Typical approach
based on this philosophy is ASTM E317 "Standard Practice for Evaluating Performance
Characteristics of Ultrasonic Pulse-Echo Examination Instruments and Systems Without the Use
of Electronic Measurement Instruments" that is applicable to shop or field conditions.
Is "Self-calibration" applicable to radiographic system too ? Many characteristics can be self-
determined according to existing practices and methods, but other ones require assistance and
cooperation of supplier both for film system and x-ray equipment.
A certified film system being controlled by pre-exposed film strips can be adopted as
"measurement device" for X-ray output concerning both intensity and contrast.
Basically x-ray equipment manufacturer performs initial accurate measurement and calibration
using electronic measurement and/or special instrumentation as necessary. Then specific film set
on "low-price" blocks and specimens is produced according to standard practice whose guidelines
are supplied by this paper. Film set, blocks, specimens and results referred to specific film
system will be the reference kit for periodical check in NDT facility.
This paper supplies some guidelines for standard practice based on testing using mainly GE
Inspection Technologies radiographic system being available in Avio facilities.
Introduction: Following "Self-calibration" subjects are discussed in this paper:
1. X-ray equipment check based on films independent from processing fluctuation
2. Duty Cycle characterization
3. KV comparison among different X-ray machines
4. Focal spot measurement
5. Concept of equivalent radiograph
6. Introduction of alternate film of other manufacturer in a Certified Film System
Results: This paper shows that "Self-calibration" is possible concerning aspects affecting quality
image as film processing monitoring, Duty Cycle, kV, focal spot, film processed by chemistry of
other manufacturer. Additional electronic measurement instrumentation is not requested to NDT
facility except standard densitometer and light-meter for viewer check. Equipment outside
forwarding may be generally avoided saving money and time. Determinations and parameters
may be used for selection of radiographic equipment and system also. Similarly to Ultrasonic
Testing, issue of "Standard Practice for Evaluating Performance Characteristics of Radiographic
Equipment and Systems Without the Use of Special Measurement Instruments" establishing
standard testing condition could be very useful.
Discussion: Preliminary it is to be note that for an effective "Self-calibration" status,
performances should be evaluated by parameters that are directly measurable by radiologist in
shop or field conditions without use of instrumentation in addition to that normally available in a
good radiographic facility: e.g. variation of film density and contrast measured by densitometer
shall be preferred to mA and kV accuracy measured by electronic measurement instruments
generally reported in equipment brochure. In following subjects directly measurable parameters
are identified.
1. X-ray equipment check based on films independent from processing fluctuation
Parameters: film density (D), Speed and Contrast Index discrepancy according to EN 584-2
(∆S% and ∆C%).
Normally daily X-ray equipment is checked by standard exposure using pre-determined
parameters considering as acceptable D variation within ±15%. Example in Fig.1 concerns a
week where X-ray equipment Isovolt 160HS is daily checked (150 kV, FE.50 and .37 blocks,
Agfa D4, processors Agfa NDT S Eco and NDT1).
Processig by Agfa NDT S Eco Processing by Agfa NDT 1
Fig.1
2.3
D
2.1
1.9
1.7
1.5
1.3
Mon Tue Wed Thu Fri
day D.50 z D.37 ∆S% ∆C% day D.50 " D.37 ∆S% ∆C%
Mon 2.07 3.86 +9.9 -3.8 Mon 1.96 3.49 +9.9 -11.7
Tue 2.13 3.89 +10.5 -1.7 Tue 2.00 3.53 +11.0 -12.5
Wed 2.09 3.85 +8.9 -2.9 Wed 1.99 3.48 +8.9 -10.8
Thu 2.20 4.00 +12.0 -2.4 Thu 2.06 3.61 +11.5 -9.0
Fri 2.06 3.83 +9.9 -0.5 Fri 1.98 3.46 +11.0 -13.8
= [D.50]' adjusted by {f1}
{
† = [D.50]' adjusted by {f1}
z= D.37-D.50 "= D.37-D.50
{= [D.37-D.50]' adjusted by {f2} †= [D.37-D.50]' adjusted by {f2}
{} [] [ ] [ ]
2
f
()
D.50
'-
D.37
'
D.50
-
D.37 ⋅
= '
∆C%
-
100
100
() 100
∆S%
-
100
{} []
D.NN ⋅
+
=
0.16
-
D.NN
1
f
0.16
'
Introducing adjustment by {f1} and {f2} based on pre-exposed film strips Agfa PMC processed
together films on the blocks, {
/ †
and {
/ †
are more independent than z
/ "
and z
/ "
from
processing fluctuation and are more convenient to correlate X-ray equipment performances in
different conditions and dates.
2. Duty Cycle characterization
Parameters: 1 Hour Trend (Rh), Standard Deviation (∆D) and Performance Index (PI) as defined
in Fig.2.
Some times brochure declares very optimistic Duty Cycle: for radiologist useful Duty Cycle shall
allow continuously same density when thermal security switches off. So testing concerning
actual performances in the whole operational range should be carried out. Six exposures
4'ON/1'OFF (Duty Cycle 80%) are carried out on standard blocks for penetrameters to obtain 6
films to measure density variation in 30 minutes using as mA as possible for stable emission;
focal to film distance from 50 to 200 cm to obtain initially density in the range from 2.5 to 3.5;
Agfa D4 with lead screens 0.027 mm over 120 kV has been used.
1 Hour Trend
Standard Deviation Performance Index Fig.2
3.0
2.8
2.6
Rh
2.4
2.2
2.0
D
minutes (T)
0 10 20 30 40 50 60
Example Chart
Linear regression
function is used to
obtain
D = f (T) = mT + n
than Rh is
calculated as
Rh = 60 × m
(see Chart also)
∆
Purpose of ∆D is
monitoring excessive
up-and-down by
D
∑ -
=
()
6
x
x
i
2
where:
xi = Di - f (Ti)
x = Σxi /6
i = 1, 2,..,6
(for 6 exposures) PI has been introduced for:
summarizing Rh and
∆D in one parameter
only;
increasing values as
performance increases.
PI is calculated as:
PI ⋅
=
1
∆D
10
Rh
+
Rh = +0.33 ∆D = 0.19 PI = 0.45 Limit: |Rh|<0.60
Limit: ∆D≤0.05
Limit: PI>1.00
*
*
Fig.3 shows results concerning 4 X-ray machines being available in Avio facility in Rivalta.
Values exceeding limits are highlighted by gray background. Last line supplies average values
intended for general comparison.
0
.
Density 1
30 minutes
kV
300
200
250
150
100
50 150
100
50
kV kV
300
200
250
150
100
50 kV
300
250
150
100
50
200 kV
200
150
100
50
Fig.3 Isovolt320HS Wmax Eresco65 Wmax
Eresco65 3mA Smart225X 4mA Isovolt160HS Wmax
kV
Rh
∆D
PI
Rh
∆D
PI
Rh
∆D
PI
Rh
∆D
PI
Rh
∆D
PI
300 0.01 0.01 6.95 -0.46 0.04 1.79 -0.46 0.04 1.79 N/A N/A N/A N/A N/A N/A
250 -0.05 0.02 3.90 -0.52 0.02 1.43 -0.54 0.02 1.33 N/A N/A N/A N/A N/A N/A
200 0.11 0.03 2.28 -0.62 0.04 1.37 -0.43 0.03 1.98 0.23 0.02 3.71 N/A N/A N/A
150 0.01 0.01 8.20 -1.77 0.02 0.50 -0.24 0.03 1.98 0.14 0.01 5.74 -0.03 0.02 3.78
100 0.05 0.03 3.27 -1.82 0.04 0.45 -0.13 0.04 1.93 0.27 0.02 3.03 0.01 0.02 5.37
50 -0.21 0.03 1.98 -1.12 0.02 0.74 -0.49 0.02 1.37 0.43 0.03 2.00 -0.14 0.01 3.77
Ave -0.01 0.02 4.43 -1.05 0.03 1.05 -0.38 0.03 1.73 0.27 0.02 3.62 -0.05 0.02 4.31
Eresco 65MF2 shows unstable X-ray output until 200 kV where maximum Wattage is used (e.g.
900W=6mAx150kV). So operational limit of 3 mA is introduced for further testing.
3. KV comparison among different X-ray machines
Parameters: Steel Half Value Layer (HVL) that reduces X-ray intensity to 50% as defined in
Fig.4.
KV calibration knowledge is very important to obtain equivalent radiographs in terms of contrast
using different equipment. So testing to compare different X-ray machines have been carried out
in range from 50 to 150 kV. Steel filter is placed on X-ray window in order to cut low energy
spectrum. Six steel blocks at least are placed on film Agfa D7 to determine HVL besides filter.
No intensifying lead screen is used under 100 kV.
First short exposure (from 30 to 60 seconds) shall performed at Source to Film Distance of 50
cm. mA shall be maintained in stability range as determined in para.2. SFD and/or mA can be
adjusted in order to obtain film density from 1.0 to 2.5 where filter only is crossed through. Then
further 3 exposures are performed each one using double time referred to the previous one (e.g. 2,
4 and 8 minutes where first exposure is 1 minute). Density shall be measured as close as
possible to X-ray beam axis (beam within angle ±6° is used only). 3 HVL shall be determined so
that increment doesn't exceed ±15% (see Fig.4). Where increment between consecutive HVLs
exceeds ±15%, exposures shall be repeated after increasing filter thickness.
kV
Steel
Filter
SF0
(mm) 6 Blocks
Steel
Range
(mm) Lead
Screen
0.027
mm Fig.4
(mm)
80
60
0
SF
40
20
0
kV
0 100 200 300 400
SF0 amount from EN 12544-2
150 18 3.2÷18.0 yes 4
3
2
1
SF0
0
s
ity
n
3 HVL over Filter
(e.g. Smart 125 kV)
HVL2
HVL1
HVL3
DSteel (mm)
e
nute
s
m
i
8
4
1
2
10 12 14 16 18
50 1 0.1÷1.0 no
75 3 0.3÷3.0 no
100 7 1.3÷7.0 yes
125 10 1.9÷10.0 yes
Reference HVL is calculated as following:
HVL
HVL
HVL
HVL
=
+
3
2
+
3
≅
2.7
e.g.
2.8
+
+
2.9
1 =
2.8
3
mm
Fig.5 shows results concerning 3 X-ray machines: Isovolt 320HS was not available at the
moment of the test.
Fig.5
50 kV HVL 75 kV HVL 100 kV HVL 125 kV HVL 150 kV HVL
Isovolt 160HS 0.33 mm steel 0.93 mm steel 2.0 mm steel 3.3 mm steel 4.5 mm steel
Eresco 65MF2 0.43 mm steel 0.87 mm steel 2.1 mm steel 3.2 mm steel 4.3 mm steel
Smart 225X 0.28 mm steel 0.77 mm steel 1.7 mm steel 2.8 mm steel 4.1 mm steel
New Seifert Isovolt HS is selected as reference equipment due to standard provided with special
electronic device for measurement and evaluation of X-ray tube voltage by divider method
according to EN 12544-1 allowing periodic control. HVLs exceeding ±10% from Isovolt 160HS
are highlighted by gray background.
Fig.6
kV Isovolt
160HS
| Eresco
65MF2
" Smart
225X
< 160
kV
120
80
40
Steel HVL (mm)
1 2 3 4 5
0 Plotting kV versus HVL
from Fig.5, Fig.6 is
obtained that allows kV
correlation among Smart
225X, Eresco 65MF2 and
Isovolt 160HS: e.g. 150kV
for Isovolt 160HS is
equivalent to 150-(-
6%)=159 kV for Smart
225X.
Curves in the chart
represent steps of 5% kV.
kV variations over ±3%
are highlighted by gray
background.
150 ref.0% -3.0% -6.0%
125 ref.0% -2.0% -9.0%
100 ref.0% +2.0% -7.5%
75
ref.0% +2.5% -8.0%
50
ref.0% +7.5% -7.5%
Ave * ref.0% +1.4% -7.6%
* Average values intended for
general comparison among
different X-ray machines.
What about limit of kV discrepancy ? Following requirements have been found:
ASTM E2104 para.7.12 establishes that no resubmittal for approval is requested for X-ray
technique where kV change is within ±15% or within ±5% with mAs within 10%;
EN 12544-1 page 5 establishes 1% of max kV in case of highly stabilized constant potential for
sophisticated applications (e.g. tomography or dosimetry) and 3% for general applications.
For equivalent radiographs purpose kV variation could be taken into account where over ±3%
against reference equipment that shall be certified by manufacturer according to EN 12544-1 or
equivalent.
4. Focal spot measurement
Parameters: Diagonal of spocal spot (Ø).
Normally pinhole camera method is used according to ASTM E1165. Fig.7 shows some
determinations carried on by Avio RT Lab. To be noted that, as requested by ASTM E1165 para.
7.1, actual size parallel to tube axis is determined multiplying the measured size in the picture by
a correction factor of 0.7.
Focal
spot
shape
Fig.7
Isovolt 160HS
(std focal spot) Isovolt 160HS
(mini focal spot) Eresco 65MF2 Smart 225X Old damaged
focal spot
Size
Ø
3.20x3.12 mm
4.47 mm 0.83x0.76 mm
1.13 mm 1.80x1.61 mm
2.41 mm 1.95x1.78 mm
2.64 mm 1.85x1.44 mm
2.34 mm
Pinhole camera device requiring 3 platinum-gold diaphragms is more expensive than edge
method according to EN 12543-4 that requires a steel cylinder only. Fig.8 shows method and
results obtained on Isovolt 160HS whose focal spot shapes are supplied in Fig.7.
Fig.8
4
3
2
1
0
ity
ns
e
D
0 1 2 3 4 5
mm Measure
chart
4
3
2
1
0
nsi
t
y
De
mm
0 1 2 3 4 5 4
3
2
1
0
it
y
ns
De
mm
0 1 2 3 4 5 4
3
2
1
0
ity
ns
e
D
mm
0 1 2 3 4 5
Isovolt 160HS (std focal spot)
Isovolt 160HS (mini focal spot)
Axis transverse to tube axis parallel to tube axis transverse to tube axis parallel to tube axis
Size
Ø
2.65x3.05 mm
4.04 mm (-9.6% of pinhole measure) 0.70x0.70 mm
0.99 mm (-12.4% of pinhole measurement)
Discrepancy between pinhole and edge method can be disregarded taking into account that
ASTM E1165 para. 9.1.2 attributes to this method a measurement tolerance of ±30% for nominal
focal spot size from 0.3 to 1.2 mm, ±25% from >1.2 to 2.5 mm and ±20% from >2.5 mm. The
only advantage of pinhole method against edge method is information about focal spot status: e.g.
the old damaged focal spot shown in Fig.7 finished to work after few weeks from determination
detecting craters (2 white spots in the picture).
5. Concept of equivalent radiograph
Parameters: reliable Duty Cycle (DC) and minimum Exposure Time (ExpT) producing same
Contrast (Co) and same Geometrical Unsharpness (Ug) by different X-ray machines.
Now we are able to self-establish reliable Duty Cycle per para.2, to self-evaluate kV discrepancy
per para.3 and to self-measure focal spot size per para.4, so we are ready to speak about
equivalent radiograph using an example concerning radiograph of two steel blocks .50 and .37 by
Agfa D4 at about 150 kV.
Fig.9 explains concept of equivalent radiograph and allows some comparison among different X-
ray machines.
Fig.9
Isovolt 160HS
(std focal spot) Isovolt 160HS
(mini focal spot) Eresco 65MF2 Smart 225X
Ø (see para.4)
↓
4.47 mm
1.13 mm
2.41 mm
2.64 mm
Reliable DC
(see para.2) ↓
↓ No limitations
(20 mA max) No limitations
(4 mA max) 3 mA max
No limitations (4.0 mA max)
Preliminary exposure for
density 2.16 on Fe.50
block using Agfa D4 Pb
↓
↓
↓ 150 kV 20 mA
SFD 80 cm
0.8 min (0'48") 150 kV 4 mA
SFD 80 cm
4.0 min (4'00") 150 kV 3 mA
SFD 80 cm
4.6 min (4'36") 150 kV 4 mA
SFD 80 cm
4.9 min (4'54")
Adjustement for same Ug
SFD· Ø / Ø Smart
(Ug.50≅ .043 mm) ↓
↓
↓ 150 kV 20 mA
SFD 135 cm
2.3 min (2'18") 150 kV 4 mA
SFD 34 cm
0.7 min (0'42") 150 kV 3 mA
SFD 73 cm
3.8 min (3'48") 150 kV 4 mA
SFD 80 cm
4.9 min (4'54")
KV discrepancy
(see para.3)
↓
↓ 0%
150 kV 0%
150 kV -3%
150+3%≅155 kV -6%
150+3%=159 kV
Adjustement for same Co
(time from diagram below)
Equivalent Radiographs ↓
↓
← 150 kV 20 mA
SFD 135 cm
2.3 min (2'18")
150 kV 4 mA
SFD 34 cm
0.7 min (0'42")
155 kV 3 mA
SFD 73 cm
3.2 min (3'12")
159 kV 4 mA
SFD 80 cm
3.7 min (3'42")
Same Co and same image
distortion on film edge
(SFD = 100 cm) 150 kV 20 mA
(Ug.50≅ .057 mm)
1.3 min (1'18") 150 kV 4 mA
(Ug.50≅ .015 mm)
6.1 min (6'06") 155 kV 3 mA
(Ug.50≅ .031 mm)
6.0 min (6'00") 159 kV 4 mA
(Ug.50≅ .034 mm)
5.8 min (5'48")
ExpT
Rel.
300%
250%
200%
150%
100%
50%
0%
120 130 140 150 160 170 180
kV Diagram on the left is intended to
calculate Exposure Time for kV
variation in the range 150±15% in
order to maintain density 2.0 on
steel block .50 (thickness 12.7 mm).
This diagram is obtained
experimentally using Eresco
65MF2, Agfa D4, lead screens
0.027 thick and SFD 120 cm.
Rel.ExpT 100% corresponds to
12.5 mA·minutes.
6. Introduction of alternate film of other manufacturer in a Certified Film System
Parameters: Contrast (Co), Penetrameter Detectability (PeD) and Crack Detectability (CrD).
Normally Certified Film System (CFS) from one manufacturer only is used. However technical
reason for use of Alternate Film System (AFS), where film and chemistry manufacturers are
different, may be the following:
* film manufacturing artifacts can be occurred with manufacturer unable to supply same class
films for many months (typically concerning not-large production film types);
* film manufacturers do not produce any size and/or package for any film type;
* generally processors with different chemicals are not available (and practical) for a
radiographic facility.
Generally no specific requirement forbids AFS but there is not standard procedure substantiating
a satisfying AFS use. Typical undefined requirement is supplied by ASTM E2104 para.6.2.2
"Only film system having cognizant engineering organization approval or meeting requirements
of Test Method E 1815 Class I, Class II, or special shall be used.". ASTM E1815 and equivalent
EN 584-1 standards classify film and associated processing using objective signal and noise
parameters as Gradient G at net density 2.0 and 4.0 (signal), Granularity σD at net density 2.0
(noise), G/σD (signal to noise ratio). Unfortunately G, σD and G/σD cannot be easy measured by
RT facility and, practically, this kind of classification is applicable to CFS only where
manufacturer measures performances of its proper Film System. Otherwise which practical
criteria should be followed by a RT Level 3 of cognizant engineering organization to approve an
AFS ?
First of all a good technical reason is necessary to adopt an AFS, otherwise CFS is preferable: e.g.
ASTM E1815 special or EN 584-1 Class 1 films in lead vacuum package should be used for high
sensitivity on low steel thickness where fine cracks are possible; until 2004 the only film standard
produced in lead vacuum package has been Fuji Ix25; being Avio provided with Agfa CFS, what
about Fuji Ix25 performances in Agfa processing ?
So five D4, five D3, five D2 and five Ix25 were produced on cracked steel welded specimen 5
mm thick using Yxlon Smart 225X. Fig.10 shows crack image and exposure parameters.
Fig.10
Exposure Time for kV mA SFD (cm) Lead screen
(see Note 1) Density range on
cracked area
D4
D3
D2
Ix25
160 4 130 0.027 mm from 2.85 to 3.05 1'44" 2'20" 4'15" 4'15"
Note 1 - In order to simulate same tighten screen-film contact, Agfa D2 has been
introduced in lead screen and envelope normally used for D4 or D3; then it was placed in
rigid cassette; D4, D3 and Ix25 in standard lead vacuum pack was introduced in the same
rigid cassette being used for D2 to assure same conditions.
EN 462-1 13EN wire penetrameter, TAM/ASTM E1742 .20 step-hole penetrameter and shim 2
mm thick were placed on specimen to measure image quality. Films were identified by lead
numbers from 1 to 20 randomly so that examiner cannot recognize film type. Fig.11 shows
contrast between thickness 5 and 7 mm on 20 films.
Fig.11
Sample film 1 Sample film 2 Sample film 3 Sample film 4 Sample film 5 Co
Average ∆
Film
5
7
∆
5
7
∆
5
7
∆
5
7
∆
5
7
∆
D4
2.88 1.99 0.89 3.02 2.07 0.95 2.95 2.02 0.93 3.00 2.05 0.95 2.96 2.04 0.92
0.93
D3
2.95 1.93 1.02 2.88 1.89 0.99 2.94 1.92 1.02 2.95 1.93 1.02 2.93 1.91 1.02
1.01
D2
2.88 1.87 1.01 2.99 1.93 1.06 2.96 1.90 1.06 3.01 1.93 1.08 2.92 1.87 1.05
1.05
Ix25 2.87 1.85 1.02 2.88 1.85 1.03 2.84 1.83 1.01 2.93 1.92 1.01 2.88 1.85 1.03
1.02
Fig.12
Sample film 1 Sample film 2 Sample film 3 Sample film 4 Sample film 5 PeD
average
EPS
Film
nw nh EPS % nw nh EPS
% nw nh EPS
% nw nh EPS
% nw nh EPS
%
D4
4.50 2.00 3.2 4.50 2.00 3.2 4.50 2.00 3.2 4.75 2.25 3.0 4.25 2.50 3.0
3.1%
D3
5.00 2.00 3.1 5.25 2.50 2.8 5.00 2.75 2.7 5.00 2.25 2.9 5.25 2.50 2.8
2.8%
D2
5.50 3.00 2.5 5.50 2.75 2.6 5.00 2.50 2.8 5.25 2.75 2.6 5.25 2.50 2.8
2.7%
Ix25
5.25 2.75 2.6 5.50 2.75 2.6 5.25 2.75 2.6 5.25 2.50 2.8 5.50 3.00 2.5
2.6%
Fig.12 shows evaluation of detectable wires (nw) and holes (nh) by two examiners (see Note 2 &
3).
Fig.13
Sample film 1 Sample film 2 Sample film 3 Sample film 4 Sample film 5 CrD
ave.score
Film
score
score
score
score
score
D4
2.75
3.50
2.75
4.25
2.75
3.20
D3
10.75
8.25
9.50
10.75
9.50
9.75
D2
15.50
13.00
13.00
16.75
11.75
14.00
Ix25
18.50
17.75
9.50
14.75
18.50
15.80
Fig.13 shows evaluation of crack detection by two examiners (see Note 2 & 4).
Results from Fig.11, Fig.12 and Fig.13, show that FujiIx25+AgfaG135 AFS can be considered
as equivalent to AgfaD2+AgfaG135 CFS for specific Avio application concerning high
sensitivity on low steel thickness where fine cracks are possible: to be noted in fact that Fuji Ix25
performances are always better than Agfa D4 and D3.
This confirms results reported during 15wcndt in Rome in 2000 where Agfa D2 (named β1) and
Fuji Ix25 (named α1) supplied the best equivalent performance among 14 film types processed
by 3 different chemistry. To be noted that, where AFS is used, periodical performance check is
important because film manufacturer cannot monitor possible variation of chemistry produced by
other manufacturer: in the case of CFS manufacturer is continuously monitoring his proper Film
System according to both ASTM E1815 and EN584-1.
Note 2 - Two different skilled radiologists examined the set of 20 films. Values in the tables
(nw, nh and score) are averages between evaluations of two radiologists on the same film.
Note 3 - As detailed in Fig.14, Equivalent Penetrameter Sensitivity EPS for step-hole
penetrameters has been computed according to ASTM E1025 App.X1.1; for wire penetrameters
same computation has been used after determination of equivalent hole diameter and thickness of
step-hole penetrameter according to ASTM E747 App.X1.1. Values for PeD in Fig.12 are
averages between EPSW and EPSH.
100
EPSH
=
h
T
X
⋅
⋅ Fig.14
X=5mm
= X=5mm, T=0.1016 mm
100
EPS ⋅
4 3
W d
1.193
X
⋅
T penetrameter thickness 2
nw = number of wires min wire ∅ d (mm) EPSW nh = number of holes min hole ∅ h (mm) EPSH
4
0.100
3.7%
1
1.016
4,5%
5
0.080
3.1%
2
0.508
3,2%
6
0.063
2.6%
3
0.254
2.2%
Note 4 - Following example details CrD score system taking into account that Group 1 shows the
best crack detection: Gr.1, 3 films, each film score 19=(20+18)/2 - Gr.2, 4 films, each film score
15.5=(17+14)/2 - Gr.3, 2 films, each film score 12.5=(13+12)/2 - Gr.4, 10 films, each film score
6.5=(11+2)/2 - Gr.5, 1 film, score 1. Fig.15 gives different crack detection levels from EN 584-1
Class 1 (on the left) to Class 4 film (on the right).
Fig.15
Conclusions: So question «Is "Self-calibration" applicable to radiographic system too?» can be
answered YES.
Practically no special device or instrument is necessary in addition to what is standard for a good
radiographic facility. Cooperation with film and X-ray equipment manufacturer is very important
also to have available reliable pre-exposed film strips for processing control and reference
equipment for kV discrepancy evaluation. In this connection Avio radiologists should thank
Italian GE Inspection Technologies Representative for more than 15 years of continuous and
effective technical cooperation using both Agfa films and Seifert equipment.
References: Following documents are referenced in this paper:
ASTM E747 Design, Manufacture and Material Grouping Classification of Wire IQI Used for
Radiology
ASTM E1025 Design, Manufacture and Material Grouping Classification of Hole-Type IQI Used
for Radiology
ASTM E1165 Measurement of Focal Spots of Industrial X-Ray Tubes by Pinhole Imaging
ASTM E1742 Radiographic Examination
ASTM E1815 Classification of Film Systems for Industrial Radiography
ASTM E2104 Radiographic Examination of Advanced Aero and Turbine Materials and
Components
EN 462-1 IQI (wire type) - Quality image determination
EN 584-1 Industrial radiographic film - Classification of film systems for industrial
radiography
EN 584-2 Industrial radiographic film - Control of film processing by means of reference
values
EN 12543-4 Characteristics of focal spots in industrial X-ray systems for use in non-destructive
testing - Part 4: Edge method
EN 12544-1 Measurement and evaluation of the X-ray tube voltage - Part 1: Voltage divider
method
EN 12544-2 Measurement and evaluation of the X-ray tube voltage - Part 1: Constancy check
by the thick filter method
"Evaluation of Film System by a Radiographic Facility" Bianchi, Liscio, Piazza, Baratta,
15wcndt, Rome 2000.
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