Procedures and Specifications - Pipe Testing
The following is a detailed specification
of testing procedures, equipment, and reporting methods used in our ultrasonic
pipe testing investigations. It is fundamentally based upon the testing methods
established by the American Society of Mechanical Engineers and the American
Petroleum Institute, as well as our own testing experience. Such testing and
reporting procedures have evolved over many years based upon our response to
the needs and requests of our customers. Changes in our procedures will be
reflected in this specification.
This specification is in use by various
consulting engineers requesting such nondestructive testing services.
Preliminary Investigation
Prior to the actual testing, and where
the locations make it possible, East Coast Industries, Inc. shall conduct a
full walk through of the subject location, and review the operation of the
piping system(s) in question. Specifics such as material type, pipe size, pipe
construction, operating pressure, and general physical condition shall be
determined. Operating parameters such as previous mechanical maintenance
history, hours of operation, internal fouling, accumulated deposits, quality of
water treatment, etc., shall be noted.
A review of each system layout shall be
made based upon existing piping specifications and blueprints, as well as any
supplemental information available through the engineering department. An
historical review of any prior leaks, obstructions, or failures at the subject
piping system(s) shall be made with the engineering department. Areas where a
specific concern for the integrity of the piping exists by building operators
shall be noted as probable test locations.
Visually observed examples of outer pipe
corrosion or leakage shall be highlighted as probable test locations. Based
upon the number of piping locations to be tested, a general outline of
investigation shall be proposed, and testing fees quoted. Locations at the top
and bottom extremes of the piping system shall be selected, as well as at
horizontal extremes of the piping layout.
Any existing procedure or outline for
pipe testing established by the client or client's engineering representative
shall be reviewed for suitability in gaining the desired diagnostic
information. In such cases, and where the proposed testing procedure is
acceptable, testing will proceed according to the client's specifications, and
the results noted as based upon an alternate procedure.
Sufficient testing shall be performed in
all pipe testing investigations as judged acceptable by ECI - the high volume
of data sought being critically necessary in order to produce an accurate
general assessment of the piping condition, and to identify any pitting or low
wall thickness conditions which may exist.
In all cases, effort shall be made to
evaluate the various size pipes comprising the system, and of all methods of
construction such as welding, threading, or grooving, unless otherwise advised
by the client. Test points shall be spaced as evenly as possible throughout the
piping system.
Testing Equipment
Field testing shall be performed using a
Panametrics 36DL Plus ultrasonic thickness gauging device or its diagnostic
equal. The instrument shall have an on-board waveform display allowing its
operator to instantly evaluate the validity of each and every wall thickness
measurement taken (See below illustration). All wall thickness measurements
which do not show an acceptable waveform pattern shall be discounted, and
further investigation made to identify the cause for the problem.
Measurements showing an acceptable
waveform display and indicating an accurate wall thickness value shall be saved
for later download and analysis. Both the wall thickness value and the
accompanying waveform display shall be saved in the memory of the 36DL Plus for
future reference and re-evaluation, if necessary.
The instrument shall feature "echo
to echo" technology allowing the measurement of coated or painted pipes
without scraping, sanding, grinding, or otherwise potentially removing any
outer metal from the test surface.
A Panametrics D794 dual crystal element
straight probe transducer, or equal, shall be used in order to provide the
highest wall thickness measurement accuracy possible, and to locate interior
pitting. This probe shall have a frequency of 5.0 MHZ and a tip diameter of 7.2
mm. A coupling agent of glycerine or its acoustic equal shall be used to
facilitate the transmission of the ultrasound signal into the test surface. The
appropriate high temperature couplant (based upon operating temperature) shall
be used for hot water, steam and steam condensate piping.
Instrument calibration shall be performed
at the beginning of the test session and at regular time intervals throughout
the investigation. A calibrated test block of the same material to be
evaluated, and having reference thickness steps above and below the minimum and
maximum anticipated pipe wall thickness to be tested, shall be used. The test
block and instrument probe shall always be allowed to equalize to the
temperature of the test medium before calibration.
Re-calibration of the equipment shall be
performed whenever a change in the temperature of the medium occurs.
Re-calibration of the instrument and probe shall also be performed after each
hour of use, whenever the instrument is turned off and on, or when pipe of a
significantly different diameter and wall thickness is measured.
Testing Procedure
A preliminary review of each test
location shall be performed to generalize the condition of that particular
area. A minimum of 12 wall thickness readings shall be taken and saved to
memory for use in the final analysis of the test location. When possible, those
12 measurements shall be taken at 3, 6, 9, and 12 o'clock positions around the
circumference of the pipe, and at three cross sections along the length, each
separated by approximately 3-4 inches. See below diagram.
Under conditions where the entire pipe
circumference is not available, measurements shall be taken at random, but with
evenly spaced intervals. Measurements shall be identified as being taken at
random or based upon the above referenced standard grid in the final report.
A photograph of each test location shall
be taken in order to illustrate the general test area and supplement the
written description; documenting the location and specific piping condition, or
to document a failure event or condition. All relevant information regarding
the location, operating conditions, observed problems, etc. shall be noted on a
formal worksheet for incorporation into the final report. All observed piping
related problems such as thread leakage, outer surface corrosion, weld failure,
and insulation failure, etc. shall be noted for incorporation into the final
report.
Small 8 in. to 12 in. sections of
insulated or covered pipe surfaces shall be removed in order to provide access,
if necessary. The removal, replacement, and re-painting of the insulation or
pipe covering shall be the responsibility of the engineering or property
management. Asbestos covered pipe will not be tested until properly
abated.
Reporting Procedure
A final written report shall be produced
following the completion of the field testing, and incorporate all compiled
data.
No measured data derived from the field
testing shall be discounted, amended, or falsified. Excepting clear examples
where error on the part of the ultrasound technician has produced a false wall
thickness measurement, as verified by a review of the saved waveform, all test
data shall be incorporated into the final report. An attempt shall be made to
explain all data anomalies.
The report shall be available within 14
days following completion of the actual field testing. The report shall be
separated into sections of summary and detailed information in order to suit
the information needs of various potential readers.
The final report shall be written in a
clear and easily understandable format, be arranged in a logical progression,
and provide a full explanation of all accumulated data and derived statistics.
Specifically requested information from the client falling outside the general
scope of the report shall be incorporated into the final report.
An executive summary shall be produced
condensing the most important findings of the report, as well as any specific
highlights of the investigation. An introductory report section shall be
provided detailing the testing procedure and instrumentation used. It shall
also include a listing and explanation of any assumptions made during the
testing and reporting procedure, as well as any investigative limitations
created by either the testing procedure, pipe material, or actions of the
client.
Definitions of any technical terms and
labels used in the report shall be provided. A preliminary summary section
shall be provided showing overall measured corrosion rates, pipe loss,
remaining pipe life and retirement dates of all test locations. A breakdown of
the number of locations tested per each piping system tested shall be provided.
A detailed section for each individual
test location shall be compiled providing all measured and calculated data.
Full physical identification of the pipe and piping service shall be provided.
A photograph of the location shall be included with highlighted indication of
the general test area. All 12 measured ultrasonic test values shall be graphed
to provide a visual representation of the variation at the interior pipe
surface.
The report shall be printed in color in
order to best display the subject location, and illustrate the wall measurement
data. The original wall thickness of the pipe shall be determined, and
estimated to be at industry specification, or above or below industry
specification. It shall be noted as such in the report.
The minimum allowable wall thickness for
each individual location shall be calculated based upon the particular pipe
diameter, operating pressure, construction (E value), material strength (S
value), thickness schedule, and pipe service provided.
Two alternate corrosion rate and
remaining life prediction scenarios shall be calculated for each test location.
An average case scenario shall be presented based upon the average of all
measured wall thickness values, and provide estimates for the following
parameters:
- Wall Tickness
- Pipe Metal Loss
- Corrosion Rate
- Percentage Of Allowable Loss
- Remaining Pipe Life
- Estimated Retirement Date
- Overall Pipe Condition
An alternate worst case scenario shall
also be presented based upon the single lowest measured wall thickness value
found within the 12 measured values, and shall provide minimum estimates for
the same parameters as highlighted above.
A block graph showing the relationship
between original pipe wall thickness, minimum allowable wall thickness, average
measured wall thickness, and minimum measured wall thickness shall be provided
for each test location.
A comments section offering any
additional information, details, or explanation about the test location or
results shall also be provided. All data points shall be graphed together in
order to show the relationship (or lack thereof) of the accumulated wall
thickness measurements and calculated corrosion rate and remaining life
estimates.
Graphs shall utilize both average and
minimum measured wall thickness values and be presented in color in order to
clearly display the relationship between each series of values. Summary graphs
shall be produced showing the following trends and relationships:
- Original Pipe Thickness vs. Measured Values
- Corrosion Rates
- Remaining Pipe Life
- Percentage Of Allowable Pipe Loss
- Actual Pipe Loss
- Overall Pipe Status
Depending upon the scope of the testing
program and piping layout, modeling scenarios shall also be provided to show
relevant comparisons and relationships such as:
- Corrosion Rate vs. Pipe Size
- Corrosion Rate vs. Physical Floor Location
- Corrosion Rate vs. Piping Service
- Corrosion Rate vs. Horizontal &
Vertical Orientation
- Corrosion Rate vs. Supply & Return
Piping
- Corrosion Rate vs. Pipe Age
A calculation shall be made for each test
location and set of 12 wall thickness measurements for the purpose of
indicating the level of pitting which may exist. Since any spot check of a
piping system is not likely to locate the one lowest wall thickness value of
that area, the standard deviation of all measurements shall be produced, from
which a theoretical minimum wall thickness can be estimated.
A priority worksheet of all test
locations shall be provided listing those locations having the highest amount
of metal loss first. This worksheet will offer writing space for engineering or
building personnel to note any corrective actions or further testing performed
at each location. A written summary section shall be provided to review the
entire report and consolidate its contents into the major generalizations. The
most important findings of the investigation will be highlighted.
Recommendations specific to the findings
in the report shall be provided. General recommendations for good corrosion
control in HVAC related piping systems shall also be provided.
An explanation of all mathematical
calculations used in the preparation of the report shall be provided in order
that interested individuals can verify and reproduce the calculations of
corrosion rate and retirement date predictions used throughout the report.
An appendix section shall provide all
supplemental information relative to the accumulation of data, and preparation
of the report. Observed problems or other information noted during the course
of the testing process shall be photo documented. Overall, and fundamental to
the purpose of any investigation, the report shall be clearly written and
presented in a bound format with the primary objective of providing the
greatest amount of useful information about the subject piping system to the
client.
The final report shall be archived in its
original computer format for a period of ten years, or longer if requested.
Additional copies of the report shall be available for as long as the data is
on archive. Follow-up investigations at the same locations shall include test
data from the most previous report; with a series of calculations performed
showing differences in wall thickness and corrosion rate.
Testing
Services