Page 189 - CW E-Magazine (12-12-2023)

Special Report Special Report

 Local-level public awareness train- damage can progress much faster. Over of diffi cult access. The safety of inspec- tandem with cathodic protection to Popular coating materials used ers and FBE with heavy duty impact
ing, mock drills and audits. the years, the corrosion eats away the tors in examining these coupons is also ensure the safety and economical today include: liquid epoxy and fusion resistance, cavitation resistance, abra-
thick wall and pipes can rupture, caus- a critical issue. Probes used for measur- operation of pipelines in the long run. bonded epoxy (FBE); polyolefi ns; sion protection and gouge protection.
Detecting internal corrosion ing gas leaks, fi re and explosion. ing resistance suffer from similar limi- polyesters; polypropylene (PP); poly- Dual-layer FBE coatings normally
Corrosion of internal surfaces of a tations. Internal surface coatings also con- ethylene (PE) and butyl rubber. Diffe- have thicknesses varying from 550-850
natural gas pipeline can be detected by Monitoring techniques tribute to the hydraulic fl ow effi ciency rent nano-materials are also mixed with microns, but for heavy duty piping, the
many different techniques: Detection and monitoring of gas Non-intrusive techniques of gas pipelines, along with the mitiga- the resins to enhance the anti-corrosion thickness may go up to 1,050 microns.
 Visual inspection of the inside pipelines for internal corrosion is done Ultrasonic devices are the most tion of metal loss due to corrosion. properties.
surface of the gas pipe after it is by: popular non-intrusive systems. Pipe Advanced plastic coatings used on the The three-layer polyolefi n FBE
opened;  In-line detection techniques; thickness is measured by applying a internal surfaces of pipes ensure a lower Today’s gas pipelines are mostly coatings can have a thickness ranging
 Measuring the wall thickness of the  Intrusive techniques; voltage to the outer metallic surface of surface roughness, as compared to the coated with FBE. This coating requires from 1,275-3,000 microns for moderate

pipeline externally by using specifi c  Non-intrusive techniques; and the pipe, across a piezo electric crystal, surface of the metallic pipes they pro- adequate surface preparation to ensure to heavy duty applications. The system

instruments;  Combination systems, comprising generating a sound wave in the ultra- tect. Friction encountered by the fl ow- strong long-term adhesion to the pipe includes: FBE bottom adhesion layer
 Critical examination of installed both intrusive and non-intrusive sonic band. The time required for travel ing gas is reduced due to the coating, surface. Key advantages of FBE coat- (150 micron) with strong adhesion to
corrosion coupons; systems. of the wave through the metal and back and there are energy-savings in driving ings include: excellent physical pro- the metallic substrate; a bonded poly-
 Examination of probes installed in to the device is indicative of the pipe gas compressors. When pipes are stored perties, such as fl exibility; as well as olefi n mid layer (12-150 micron) with
the gas pipeline; and In-line inspection thickness. This method is safe for the outside temporarily before installation, resistance to cavitation, erosion, and superior fl exibility; and a top PE or PP
 Using in-line monitoring or exami- Inline inspection involves smart inspector, but it involves digging to get an internal coating provides the neces- slip. These coatings ensure superior layer for high-temperature and mois-
nation tools to inspect the pipe and pigs, or sensing devices placed inside access to the top surface of the pipe. It sary temporary corrosion protection(5). adhesion to steel surfaces even in hostile ture-resistant applications. For higher
to mark the spots of metal wall loss, gas pipelines at special entry points. may also fail to detect the onset of cor- environments, and can withstand heat temperatures and offshore applications,
pitting corrosion and rust formation. These get carried by the gas fl ow along rosion at an early stage. Surface preparation of up to 110°C. PP is more appropriate. The high-den-
a certain length of the pipe. If the pig- The longevity of internal coating sity PE top layer provides toughness
Gas quality control ging of the pipes at the time of initial Combination techniques of gas pipes depends on the quality of FBE is available as a powder coat- as well as reduced permeability for
Risk of internal corrosion of the construction is not planned, it can Some companies offer a combi- surface preparation. Steps involved in ing. It is charged electrostatically, to oxygen and moisture.
gas pipe is minimized by reducing the require costly modifi cation at a later nation of an ultrasonic system and an surface preparation include: chemical enable it to attract and adhere to the
contaminants in the gas entering the stage. electrical resistance device. Others (phosphoric acid) cleaning; thermal heated surface of the grounded metallic Coextruded three-layer tapes
inlet of the pipeline. Efforts are made to use an instrument transducer, which is cleaning; internal grit blasting (which pipe. The pipe is heated and maintained Three-layer tapes contain a stabi-
enforce strict quality control standards. Certain sensors are able to measure mounted permanently on the pipeline also reduces risk of stress corrosion at 240°C, using induction heating lized carrier fi lm of PE, covered with
Gas samples are analysed on fi xed properties of pipeline contents indirectly along with a handheld device carried by cracking); and surface curing. elements, ensuring that the powder has an adhesive of a butyl-rubber material
intervals, and solids and liquids taken from the outside. Acoustic emission the inspector for recording the changes enough time to melt, spread and cross- on the top and bottom of the layers.
from the inside of pipelines are also techniques, for example, can measure a in wall thickness based on transducer During these steps, the removal of link on the surface. Adhesive layers, used in between the lay-
checked for corrosive substances such pipeline’s wall thickness from the out- indication. This system can be ope- mill scale and other deposits from the ers of three-layer coextruded tapes with
as sulphur compounds and bacteria. side. rated by maintenance technicians inside surface is ensured. The most common gas pipeline carrier fi lms, provide seamless adhe-
checking the cathodic protection (CP) coating systems are: Single FBE layer; sion without any clearly marked inter-
Monitoring natural gas pipelines Intrusive techniques system, thus saving on the manpower Selection of coating material Dual FBE layer; and Three-layer sys- face between the adhesive layer and the
is both complicated as well as expen- Intrusive techniques include corro- required(4). Factors to be considered during tem (FBE with polyolefins or butyl intermediate carrier fi lm. These tapes
sive, because the pipelines are spread sion coupons along the length of pipe- the design and selection of coatings rubber). are wrapped in spirals inside and out-
out through large areas. Sampling and line; and probes that measure electrical We need to progress toward real- include(5): side the pipe, forming a homogeneous
investigation, as well as manual inspec- resistance. time monitoring, which is comprised of  Mechanical properties of the coat- FBE in single layer is coated with seamless sleeve coating on the metal
tion, costs billions of dollars per year. permanently installed probes collecting ing; a thickness of 400-700 microns. The substrate. The layer of butyl rubber will
The coupon is comprised of a strip signals from continuously, and data-  Susceptibility to damage during application is solvent-free. It has inherent self-amalgamate in the interface area,
Moisture in the gas, and its ingress of metallic substance having the same logging devices that highlight changes pipe handling for installation and chemical resistance, but cathodic dis- producing an impermeable sealed pipe.
at pipe joints, greatly infl uences the composition as the pipeline material. in wall thickness and the rate of metal repair; bonding can occur in rare cases. FBE
onset of corrosion. It dissolves sulphur After its initial weight is recorded, the loss(3, 4).  Soil chemistry; is also highly compatible with cathodic Some limitations of coating materials
compounds and chlorine compounds. If weight loss is monitored at a pre-  Compatibility for in-situ joint coat- protection, and has low permeability Normally, a PE top layer restricts
corrosion begins, on average pipeline determined interval by removing it and Protective coatings ing; for oxygen. the application to temperatures between
thickness is reduced by almost 2 mils accurately weighing it. Weight loss Along with cathodic protection, an  Pipeline operating conditions, such -20°C and 80°C. On the other hand,
annually, but in many cases, corrosion points to the onset of corrosion and its anti-corrosion coating provides the best as fl ow velocity, pressure changes, Dual-layer FBE is comprised of the PP top layer makes it suitable for
occurs much more rapidly. Moisture progression. However, examination is practical preventive measure against temperature; a bottom anti-corrosion layer of FBE temperatures of up to 105°C. Specially
can accumulate at bends, pipe joints an important limitation in diffi cult ter- explosions and corrosion damage. Both  Compatibility with the cathodic with strong adhesion, with a top layer formulated, high-temperature single
and low-lying zones, where corrosion rains, as corrosion often occurs in spots internal and external coatings work in protection selected for the pipeline. designed and formulated with fi ll- and dual-layer FBE can be used up to

188 Chemical Weekly December 12, 2023 Chemical Weekly December 12, 2023 189

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