INTRODUCTION
Definition - What does Environmental Health and Safety (EH&S) (EHS) mean?
Environmental
health and safety (EHS or HSE or SHE) is the department in a company or an
organization involved in environmental protection, safety at work, occupational
health and safety, compliance and best practices. EHS aims to prevent and
reduce accidents, emergencies and health issues at work.
Oil companies are feeling
more and more pressure to reduce environmental pollution caused by their
services or production processes, and reduce accidents in the workplaces
ensuring better health of their employees and the third parties. Some of these
compulsions are required by law, demanded by their customers, or the owner’s
aspirations for higher quality production. EHS ensures a systematic method of
prevention of accidents and emergencies including fire, solid or liquid waste
management, reduction of environmental footprints and use of carbon energy,
improving safety and health of the workers, employee ergonomics and confirming
a risk free workplace. EHS also aims to prevent workers from suffering from
occupational diseases.
Formation of the US
Environmental Protection Agency (EPA) in the 1970s initiated the requirement of
environmental management. Soon after it was followed by other regulatory
systems at the state levels. The Occupational Safety and Health Act of 1970,
required many other compliances for the industries to protect employees. In the
1990s the EHS started functioning at the company level. Professionals were
required to reassess and redesign the production processes to become more
eco-friendly and health risk free. ISO 14001 and OHSAS 18001 have set standards
of EHS internationally.
company leaders are now becoming increasingly
responsible for implementing EHS in their organizations.
HSE also ensures safety of
pipelines in their use for crude oil transportation.Hence the need for pipeline
leak detection and control.
LITERATURE REVIEW
Pipelines
originated over 5,000 years ago by the Egyptians who used copper pipes to
transport clean water to their cities.
The first use of pipelines for transportation of hydrocarbons dates back
to approximately 500 BC in China where bamboo pipes were used to transport
natural gas for use as a fuel from drill holes near the grounds surface. The
natural gas was then used as fuel to boil salt water, producing steam which was
condensed into clean drinking water. It
is said that as early as 400 BC waxcoated bamboo pipes were used to bring
natural gas into cities, lighting up China's capital, Peking.
Today's
pipelines originated in the second half of the 19th century and since their
adoption have grown drastically in size and number. While drilling for water, crude oil was
accidentally discovered in underground reservoirs. This crude oil was not very popular until
simple refineries came into existence.
The oil was
transported to these refineries in wooden vats that were even transported
across rivers via barges pulled by horses.
One alternative method of transport was by way of railway tanker cars.
However, this meant that the oil supply was controlled by the large railway
owners.
So, to make
transport independent and more reasonably priced, pipelines were adopted as a
more economical means of transportation. The transported oil was boiled off in
refineries to obtain the by-products of naphtha, petroleum, heavy crude oil,
coal tar and benzene. The petroleum was used as a fuel for lighting and the
benzene produced was initially considered an unwanted byproduct and was
disposed of.
This situation
changed drastically with the invention of the automobile which instantly
increased the demand for consistent and reliable supplies of gasoline and
resulted in the need for many more pipelines.
Pipelines today transport a wide variety of materials including oil,
crude oil, refined products, natural gases, condensate, process gases, as well
as fresh and salt water. Today there are
some 1.2 million miles of transport pipelines around the world, with some well
over 1,000 miles in length. The total
length of these pipelines lined up end to end would encircle the earth 50 times
over.
The construction
of these longer pipelines with larger diameters also increased the need for
more intelligent leak detection systems to better detect and localize
accidental releases. Where it was once
enough to have inspectors walk the length of pipelines and visually inspect for
evidence of leaks, today this is no longer possible. In many cases, due to the longer lengths and
the rigorous runs of remotely located pipelines, physical access may be
limited. Pipelines can run through snowy
landscapes, across mountain ranges, along bodies of water, or be located
underground or subsea, even at depths exceeding 1 mile.
But why is it
necessary to implement leak detection systems at all? Although they are the most reliable and safe
option compared to other methods of transportation possibilities, accidents and
thefts can and do occur with pipelines.
In such cases, leak detection systems can help minimize damage to
people, the environment, and the company image as well as the high costs for
repair, renovation, indemnity, breakdowns and the lost value of the liquid or
gas that has been released. In addition,
there are also different official regulations related to pipeline leak
detection.
What Causes Leaks
Before we take a closer
look at how leak detection in a pipeline can be done, let's first take a look
at what causes leaks. Fatigue cracks are
one cause. These occur as the result of material fatigue and are often found on
longitudinal welds. Tensile strength can
cause stress tears which can reduce the effectiveness of Cathodic corrosion
protection systems, resulting in corrosion on the pipeline. Stress corrosion is another possible cause. Cracks can also be caused by hydrogen
indexing. In this case, atomic hydrogen
diffuses into the metal grid of the pipe wall, forming molecular hydrogen. This can lead to the pipe material becoming
brittle and prone to early failure.
Material manufacturing
errors can also cause leaks, e.g. when cavities are rolled into the material
during production of the pipe. Lastly,
leaks can also occur when an external force acts from the outside. This is the
case when backhoes dig up a pipeline or seismic ground movements cause shifts in
the ground surrounding a pipeline.
PIPELINE
LEAK DETECTION METHODS
PIPELINE HYDRO TEST
Hydrostatic (Hydro) Testing is a process where components, such as piping or pressure vessels are tested for strength and leaks by
filling the equipment with pressurized liquid. For pipelines, hydro tests are conducted while the pipeline
is out of service. All oil and/or natural gas is typically vented off, and the
line is mechanically cleaned prior to testing.
Hydrostatic testing
works by completely filling the component with liquid (usually, but not always,
water), until a specific pressure is reached. The hydro test pressure often exceeds
the designed working pressure of the equipment, sometimes by over 150%,
depending on the exact regulations and code requirements, as applicable. The
pressure is then held for a specific amount of time to inspect visually for
leaks. The visual inspection can be enhanced by applying either tracer or
fluorescent dyes to the liquid, as required or needed.
Hydrostatic testing
is often required as a final proof test after repairs are completed and
equipment is returned to service. While it can tell you whether or not leaks
are present, a hydrostatic test does not necessarily ensure the integrity of
the component beyond the time period of the actual test. On-going equipment integrity
is best managed by an effective, integrated fixed
equipment mechanical integrity (FEMI) program.
There are two
additional methods of hydrostatic testing: water jacket testing and the direct
expansion method. These are more often used for cylinders or vessels.
- With water jacket testing, the vessel to be examined is
filled with water, after which it is placed in a sealed container which is
itself filled with water and connected to a calibrated gas tube. It is at
this point that the vessel is pressurized for a period of time before
being subsequently depressurized. Pressurizing the vessel forces water out
of the test jacket and into the tube. Operators can then determine how
much the vessel expanded. This method does cause some slight, yet
permanent stretching to the vessel.
- With
the direct
expansion method, the
vessel being examined is completely filled with water. Then additional
water is pumped in until it reaches the test pressure. The amount and
weight of the water forced into the vessel, along with the amount not
expelled from the vessel upon the release of the pressure allows the
inspector to determine how much the vessel expanded.
Hydrostatic testing
can be used to examine many different types of equipment, including pipelines,
fire extinguishers, storage tanks, and gas cylinders. It is particularly
useful for pipelines in situations where the use of inline inspection tools are not feasible.
Prior to conducting
a hydrostatic test, one should consider the specific gravity and chemistry of
the hydro test fluid both in terms of loads and corrosivity (e.g., chloride
content of water), and how this may impact the equipment. For example, some
equipment foundations and piping supports may not be designed to handle the
loads. When hydrostatic loads are unacceptable, alternative test methods should
be considered such as pneumatic testing or other gas leak testing. When using
gasses (e.g., air or nitrogen), special caution should be paid to safety as gas
pressurization results in significantly higher amounts of stored energy in the
test subjects, which can result in catastrophic failures. It is best to use a
customized procedure, created by competent personnel, for this type of testing.
EQUIPMENT USED IN
PIPELINE LEAK DETECTION
Hydrostatic testing of
systems or components is most times referred to as “H” pressure tests. These
tests of piping systems should be at a pressure of 135 percent above the maximum
system design pressure, but in no case less than 50 psi. The line drawing in
fig 1 shows a simple hydrostatic test setup and associated equipment.
Fig 1
Hydrostatic
testing of piing systems or components should be conducted in an area that can
be secured from all distractions.
The
area should also provide the operator protection in event of component failure.
When hydrostatic testing the piping system,set the equipment in an area that
can be secured from all unwanted distractions.
The
equipment required for hydrostatic testing includes a pump, two pressure
gauges, two relief valves, a cutoff valve, blank flanges, gaskets and clamps.
PUMPS: There is no specific
requirements for the type of pump to be used for hydrostatic testing. The pump
must be large enough to deliver the required pressure and water volume to the piping system being
tested. Pneumatic pumps are the most common type of pump used for hydrostatic
testing .
Fig
2 and 3 show different pumps that can be used during
hydrostatic testing.
Fig
2
Fig
3
PRESSURE GAUGES:When
performing hydrostatic tests, use two independent pressure gauges. These two gauges will indicate actual hydrostatic
test pressure. One of the two pressure will be the master gauge and the other
will be the backup gauge. The master test gauge readings are used as the true
hydrostatic test pressure throughout the test.
·
Master Gauge: Master gauges are used to indicate the actual hydrostatic test
pressures. The scale range of the master test gauge are usually greater than
the maximum test pressure but should not
be more than 200 percent of the maximum test pressure. Master test gauges shall
have a valid caliberation label according to standard.
·
Backup Gauge: A backup gauge is used to check and certify the accuracy of te master
test gauge. Just like the master gauge, the backup gauge is also in line to the
actual test pressure, but should not exceed 200 percent of the maximum test
pressure. Backup test gauges shall also have a valid caliberation according to
standard.
·
Relief Valves: Relief valves provide for over pressure protection of the system or
component, equipment and also the safety of the personnel.
The fig 4 below shows a
hydrostatic gauge for measuring pressure during leak detection using
hydrostatic testing method.
Fig
4
NON-DESTRUCTIVE
TESTING OF OIL AND GAS PIPELINES
Non-destructive testing
(NDT) is common testing techniques in engineering used in the oil and gas
industry the properties of a material, component or system without damaging it.
This can also be called Non-destructive inspection (NDI). This is because NFDT
does not permanently destroy the material being tested, hence it saves both
time and money in the cause of engineering testing.
Popular NDT methods
used in the oil and gas industry includes;
Ø Ultrasonic magnetic –particle testing,
Ø Remote
Visual Inspection (RVI)
Ø Eddy-current testing
Ø Low coherence interferometry
NDT can be applied in
the following field of engineering;
Ø Petroleum engineering
Ø Forensic engineering
Ø Mechanical engineering
Ø Electrical engineering
Ø Civil engineering
Ø Medicine such as in;
·
Medical
imaging
·
Echocardiography
·
Medical
ultrasonography
·
Digital
radiography
Ø Systems engineering and
Ø Aeronautical engineering.
Engineering
applications of NDT in the oil and gas industry
NDT is used in so many
oil and gas settings that covers a wide range of industrial activities, with
new NDT methods being developed at an advanced speed. NDT methods are usually
applied in industries where a failure of a component would cause a lot of hazard
or economic loss, such as in transportation equipment, pressure vessels,
building structures, piping systems and in hoisting equipment.
Pipeline
weld testing
In pipeline
engineering, welds are used commonly to join two or more metals parts together.
This is because these connections may encounter loads and fatigue during the
material lifetime. What this implies is that there is a chance that they may
fail if not created to proper specifications. For example , the base metal must reach a certain temperature during
welding process, must cool at specific rate, and must be welded with compatible
materials or the joint may not be strong enough to hold the parts together, or
cracks may form in the weld causing it to fail. The welding defects such as
lack of fusion of the weld to the base metal, cracks or porosity inside the
weld, and variations in weld density
could cause the pipeline to break.
To avoid this breakage,
these welds may be tested may be tested using Non-destructive techniques such
as industrial radiography, x-rays, ultrasonic testing or by magnetic particle
inspections.
In a proper weld, these
tests would indicate a lack of cracks in the radiograph, show clear passage of
sound through the weld and back or indicate a clear surface without penetrants
captured in cracks.
Levels of certification
Most
pipeline Radiographic personnel certification schemes above specify three
"levels" of qualification and/or certification, usually designated as
Level 1, Level 2 and Level 3.
The roles and responsibilities of personnel in
each level are generally as follows (there are slight differences or variations
between different codes and standards.
Ø Level
1
are technicians qualified to perform only specific calibrations and tests under
close supervision and direction by higher level personnel. They can only report
test results. Normally they work following specific work instructions for
testing procedures and rejection criteria
Ø Level
2
are engineers or experienced technicians who are able to set up and calibrate
testing equipment, conduct the inspection according to codes and standards
(instead of following work instructions) and compile work instructions for
Level 1 technicians. They are also authorized to report, interpret, evaluate and
document testing results. They can also supervise and train Level 1
technicians. In addition to testing methods, they must be familiar with
applicable codes and standards and have some knowledge of the manufacture and
service of tested products.
Ø Level
3
are usually specialized engineers or very experienced technicians. They can
establish Radiographic techniques and procedures and interpret codes and
standards. They also direct the laboratories and have central role in personnel
certification. They are expected to have wider knowledge covering materials,
fabrication and product technology.
OIL AND GAS PIPELINE RADIOGRAPHIC TESTING
Pipeline radiography
is the use of ionizing radiation to view pipelines in a way that cannot be seen
otherwise. radiography's purpose is strictly viewing. Industrial radiography
has grown out of engineering, and is a major element of nondestructive testing.
It is a method of inspecting materials for hidden flaws by using the ability of
short X-rays and gamma rays to penetrate various materials. One of the major
ways to inspect materials for flaws is to utilize X-ray computed tomography.
In Radiography Testing the test-part is placed between the
radiation source and film (or detector). The material density and thickness
differences of the test-part will attenuate (i.e. reduce) the
penetrating radiation through interaction processes involving scattering and/or
absorption. The differences in absorption are then recorded on film(s) or
through an electronic means. In industrial radiography there are several
imaging methods available, techniques to display the final image, i.e. Film
Radiography, Real Time Radiography (RTR), Computed Tomography (CT), Digital
Radiography (DR), and Computed Radiography (CR).
There are two different radioactive sources available for
industrial use; X-ray and Gamma-ray. These radiation sources use higher
energy level, i.e. shorter wavelength, versions of the electromagnetic waves.
Because of the radioactivity involved in radiography testing, it is
of paramount importance to ensure that the Local Rules is strictly adhered
during operation.
(A) A pipeline undergoing radiographic testing
(B) experts conducting
a radiographic test on pipelines
(c) A pipeline undergoing radiographic testing with
an x-ray generator
Applicability
Radiographic
testing is used extensively on castings and weldments. Radiography is well suited
to the testing of semiconductor devices for cracks, broken wires, unsoldered
connections, foreign material and misplaced components. Sensitivity of
radiography to various types of flaws depends on many factors, including type
of material, type of flaw and product form. Both ferrous alloys can be radio
graphed, as can non-metallic materials and composites.
Limitations
Compared to
other NDT methods, radiography is expensive. Relatively large capital costs and
apace allocations are required for a radiographic laboratory. Field testing of
thick sections is a time consuming process. High activity sources require heavy
shielding for protection of personnel. Tight cracks in thick sections usually
cannot be detected at all, even when properly oriented. Minute discontinuities
such as inclusions in wrought material, flakes, micro- porosity and
micro-fissures cannot be detected unless they are sufficiently segregated to
yield a detectable gross effect. Laminations are impossible to detect with
radiography, because of their unfavorable orientation. Laminations do not yield
differences in absorption that enable laminated areas to be distinguished from
limitation free areas.
It is well
known that large doses of X-rays or gamma rays can damage skin and blood cells,
can produce blindness and sterility, and in massive doses can cause severe
disability or death. Protection of personnel not only those engaged in
radiographic work but also those in the vicinity or radiographic testing is of
major importance. Safety requirements impose both economic and operational
constraints on the use of radiography for testing.
Personnel
Training, qualifications and certifications for radiographic testing
Successful and careful
application of Radiography depends heavily on personnel training, experience
and integrity. Personnel involved in Radiographic testing and interpretation of
results should be certified and in most oil and gas industries, certification
is usually enforced by law or by the applied standards usually according to
international Standard Organizations (ISO).
The terms usually
associated with this includes;
·
Certification: Procedure used by the certification body to confirm that the
qualification requirements for radiography has been fulfilled, leading to the
issuing of certificates.
·
Qualification:Demonstration of
physical attributes, knowledge, skill, training and experience required to
properly perform radiographic tasks
·
Training
Radiographic testing training is provided for people
working in many oil and gas industries. It is generally necessary that the candidate
successfully completes a theoretical and practical training program, as well as
have performed several hundred hours of practical application of this
particular method they wish to be trained in. At this point, they may pass a
certification examination. While online training has become more popular, many
certifying bodies will require additional practical training.
Certification schemes
There are two approaches in personnel certification;
1. Employer Based Certification: Under this concept the employer
compiles their own Written Practice. The written practice defines the
responsibilities of each level of certification, as implemented by the company,
and describes the training, experience and examination requirements for each
level of certification. In industrial sectors the written practices are usually
based on recommended practice.
2. Personal
Central Certification: The concept of central certification
is that a Radiographic test operator can obtain certification from a central
certification authority that is recognized by most employers, third parties
and/or government authorities.
REFERENCES
Kwake, Prof.
quoted in Mordell, D. L. and J. F. Coales (1983). A Proposal for the Developing
Commonwealth. The Need for Engineers and Technicians and How to Meet It
Effectively and Efficiently. Commonwealth Secretariat, London.
1973 – 1991:
An Appraisal of Its Effectiveness and Efficiency. COREN-CODET Workshop on
“Future of Engineering Education in Nigeria”. ASCON, Badagry, Nigeria.
Mafe, O. A.
T. (1997). Harnessing the Potentials of the Students’ Industrial
Work-Experience Scheme (SIWES) for National Development. First National
Workshop on University SIWES for SIWES Coordinators, National Universities
Commission, Abuja.
Mafe, O. A. T (2002). A Framework for Engineering
Manpower Development in Nigeria. Conference Proceedings, National Engineering
Conference on “Engineering Education and Practice in Nigeria”, Nigerian Society
of Engineers. pp. 108 – 124.
Mafe, O. A. T
(2003). Empowering Nigerian Engineers for Entrepreneurship. Conference
Proceedings, National Engineering Conference on “The Engineer in the Nigerian
Society”, Nigerian Society of Engineers. pp. 257 – 268.
please like us or share in facebook
