POLYETHYLENE | Pipeline Coatings

Summary

In this episode of 'Bite-Sized Corrosion,' Vanessa and Neil delve into the complexities of pipeline coatings, focusing on polyethylene coatings. They discuss the benefits and challenges of these coatings, including their toughness, chemical resistance, and the difficulty of adhesion. The conversation explores various types of polyethylene coatings, such as single-layer, two-layer, and 3-layer polyethylene (3LPE) systems, and touches on issues like cathodic shielding and AC interference. The episode aims to guide new engineers on selecting appropriate coatings for pipeline projects, considering factors like environment, service life, and cost.

Takeaways

• 🌟 The session is part of a series discussing pipeline coatings, starting with polyethylene coatings.
• 🎨 Vanessa Silly Fisher and Neil Webb are the hosts of the series, aiming to shed light on the complexities of pipeline coatings.
• 🔍 Vanessa shares a personal anecdote about the challenges of identifying coatings in the field, highlighting the importance of understanding different types of coatings.
• 🛠️ Polyethylene coatings are prevalent due to their toughness, high electrical resistance, and good chemical resistance, making them suitable for pipelines.
• 📦 The black color of polyethylene coatings is due to carbon black pigment, which is a significant component of the material.
• 🧲 One of the main challenges with polyethylene is its poor adhesion to pipes, as it doesn't stick to other materials easily.
• 🔄 The industry has developed solutions like 'Yellow Jacket' coatings, which use a bitumen-based adhesive to improve adhesion between the polyethylene and the steel pipe.
• 📚 The 3-layer polyethylene (3LPE) system combines the corrosion resistance of epoxy with the electrical and mechanical properties of polyethylene, offering a robust coating solution.
• 🛡️ Proper surface preparation is critical for the application of coatings like fusion-bonded epoxy (FBE), which includes cleaning and a phosphoric acid-based wash as a pre-treatment.
• 🔩 Field joints, where pipes are joined together, require special attention with coatings to ensure they are protected to the same standard as the rest of the pipeline.
• 🌐 AC interference is a concern for polyethylene coatings due to their high electrical resistance, which can lead to inductive and capacitive interference issues.
• 🔄 The balance between the electrical insulation properties of the coating and the environmental conditions it will encounter is crucial for effective pipeline protection.

Q & A

What is the main topic of the 'bite-sized corrosion' series for 2022?

The main topic of the 'bite-sized corrosion' series for 2022 is pipeline coatings, specifically focusing on polyethylene coatings in the first session.

Why is knowledge of the specific coating applied to a pipeline important?

Knowledge of the specific coating applied to a pipeline is important because it affects pipe laying logistics, backfilling, long-term performance, cathodic protection, and AC mitigation.

What is Vanessa Silly Fisher's initial experience with pipeline coatings?

Vanessa Silly Fisher's initial experience with pipeline coatings was overwhelming. She was on-site to investigate a corrosion problem that turned out to be a coating issue and found the experience challenging due to her lack of knowledge at the time.

What is the typical color of polyethylene coatings and why?

Polyethylene coatings are typically black due to the significant pigment content of carbon black in the material.

Why are polyethylene coatings widely used for pipelines?

Polyethylene coatings are widely used for pipelines because they are tough, have high electrical resistance, excellent chemical resistance, and are not easily damaged.

What is one of the main challenges with applying polyethylene coatings to pipes?

One of the main challenges with applying polyethylene coatings to pipes is adhesion. Polyethylene is very inert and does not stick to anything else easily, making it difficult to get the coating to adhere to the pipe.

What is the purpose of the 'Yellow Jacket' coating in pipeline applications?

The 'Yellow Jacket' coating is a polyethylene external extrusion or shrink sleeve that is applied over a layer of bitumen-based adhesive. It provides chemical adhesion between the steel and the polyethylene and offers good chemical and corrosion resistance.

What does 3LPE stand for and what does it combine in terms of pipeline coating properties?

3LPE stands for 3-Layer Polyethylene. It combines the corrosion-resistant characteristics of epoxy with the electrical resistance, chemical resistance, water impermeability, and mechanical toughness of polyethylene.

What is the significance of the epoxy layer in a 3LPE system?

The epoxy layer in a 3LPE system is significant because it provides a corrosion-resistant interface between the steel and the polyethylene. It is essential for the system's effectiveness and must be equivalent to a standalone epoxy system.

How does AC interference impact polyethylene coatings?

AC interference impacts polyethylene coatings because of the high electrical resistance of polyethylene, which provides insulation between the pipe and its environment. This insulation can lead to inductive and capacitive interference, causing high voltages on the pipe due to its insulation from the earth.

What are some alternative polyethylene coating systems mentioned in the script?

Some alternative polyethylene coating systems mentioned in the script include cold-applied and hot-applied tapes, and heat shrink sleeves, which are based on polyethylene and are used for field joints and mainline wrapping.

Outlines

00:00

🌟 Introduction to Pipeline Coatings Series

The script introduces a six-session series on pipeline coatings, starting with a focus on polyethylene coatings. Vanessa Silly Fisher and Neil Webb are the hosts. Vanessa shares a personal anecdote about her early days in the industry, highlighting the complexity of understanding pipeline coatings. The importance of knowing the type of coating applied to a pipe is emphasized, as it affects various aspects of pipeline logistics and performance. The series aims to address questions engineers should ask when selecting a coating for a pipeline project.

05:01

🔍 Understanding Polyethylene Coatings

This paragraph delves into the specifics of polyethylene coatings, their benefits such as toughness, electrical resistance, and chemical resistance, and their widespread use in the industry. Challenges with polyethylene, such as its inability to adhere to surfaces, are discussed. The paragraph explains how sintered polyethylene coatings are applied using a mechanical interlocking method but lack inherent corrosion inhibition. It also touches on the development of 'Yellow Jacket' coatings, which combine polyethylene with a bitumen-based adhesive to improve adhesion and corrosion resistance.

10:02

🛠️ The Evolution of 3-Layer Polyethylene (3LPE) Coating

The paragraph discusses the development of 3LPE coatings, which combine the corrosion-resistant properties of epoxy with the electrical resistance and mechanical toughness of polyethylene. It explains the process of applying 3LPE, involving a hot melt adhesive layer and extrusion over a pipe. Early issues with the bonding of the epoxy layer to the steel are mentioned, along with improvements over time. The importance of proper surface preparation for coating application is emphasized, including the use of phosphoric acid-based washes and the phasing out of chromate treatments due to environmental concerns.

15:03

💰 Cost Implications and Field Joint Protection

This section examines the financial considerations of using 3LPE coatings, noting that while the coating itself is more expensive, it can lead to cost savings in pipe laying operations due to reduced backfilling material requirements. The importance of protecting field joints with additional coatings is highlighted, ensuring they meet the same standards as factory-coated pipes. The paragraph also introduces the topic of AC interference and its impact on polyethylene coatings, setting the stage for further discussion in future sessions.

20:03

⚠️ Addressing AC Interference and Coating Selection

The final paragraph addresses the challenge of AC interference, which can cause high voltages on pipes due to the high electrical resistance of polyethylene coatings. The need for a temporary earth connection during pipeline construction to prevent shock is mentioned. The paragraph concludes with a metallurgical perspective on balancing the electrical insulation properties of the pipeline against the environmental factors it will encounter, suggesting that the choice of coating may depend on the presence of AC interference and the need for electrical insulation.

🔄 Other Polyethylene Coating Systems

The script concludes with a brief overview of other polyethylene-based coating systems, such as tapes and heat shrink sleeves, which are used for field joints and mainline wrapping. These systems are highlighted for their ease of application and versatility in providing additional protection to bare pipes. The discussion sets the stage for more detailed exploration of tapes in upcoming sessions.

Keywords

💡Polyethylene coatings

Polyethylene coatings are a type of protective layer applied to pipelines, known for their toughness, high electrical resistance, and chemical resistance. They are a significant topic in the video as they form a large percentage of pipeline coatings due to their durability and resistance to damage. The script discusses various methods of applying polyethylene coatings and the challenges associated with them, such as adhesion and under film corrosion.

💡Pipeline corrosion

Pipeline corrosion is the degradation of the pipe material due to chemical reactions, primarily an issue the video aims to address through proper coating selection and application. The script mentions a personal anecdote about investigating a corrosion problem that turned out to be a coating issue, highlighting the importance of understanding and managing corrosion in pipeline maintenance.

💡Coating adhesion

Coating adhesion refers to the bond or connection between the coating material and the surface of the pipe. It is crucial for preventing corrosion under the coating. The script discusses the challenges of getting polyethylene to adhere to pipes due to its inert nature and the industry's solutions to improve adhesion, such as mechanical interlocking and adhesives.

💡Fusion bonded epoxy (FBE)

Fusion bonded epoxy is a type of coating applied to the surface of steel pipes to protect them from corrosion. The script describes the process of applying FBE, which involves cleaning and pre-treating the pipe surface before the epoxy is bonded. FBE is used as an intermediate layer in 3-layer polyethylene (3LPE) coatings to enhance corrosion protection.

💡3-layer polyethylene (3LPE)

3LPE is a composite coating system consisting of an epoxy layer, an adhesive layer, and an outer polyethylene layer. The script explains that this system combines the corrosion resistance of epoxy with the mechanical and electrical properties of polyethylene, making it a desirable coating for pipelines. It also discusses the evolution and improvements in 3LPE technology over time.

💡Cathodic protection

Cathodic protection is a technique used to control the corrosion of a metal surface by making it act as a cathode of an electrochemical cell. The script touches on how the electrical shielding properties of polyethylene coatings can affect cathodic protection, particularly in cases of coating damage that may lead to under film corrosion.

💡AC interference

AC interference, also known as alternating current interference, refers to the unwanted electrical currents from external AC power sources that can affect the pipeline. The script discusses how the high electrical resistance of polyethylene coatings can insulate the pipe from the earth, potentially leading to higher induced voltages on the pipe due to inductive and capacitive interference.

💡Surface preparation

Surface preparation is the process of cleaning and pre-treating the surface of the pipe before applying a coating. The script mentions that this step is critical for achieving good adhesion of coatings like FBE and has been improved over the years to ensure a clean, angular mechanical profile free of dust and contaminants.

💡Field joint coating

Field joint coating refers to the application of protective coatings on the joints of a pipeline that are welded together on-site. The script describes how these joints are coated with fusion bonded epoxy or other materials and then overwrapped to ensure they have the same level of protection as the factory-coated pipe.

💡Bitumen-based adhesive

Bitumen-based adhesive is a mixture of bitumen and polymers used to provide chemical adhesion between the steel pipe and the polyethylene coating. The script mentions 'Yellow Jacket' coatings, which use this adhesive layer to improve the bond between the pipe and the polyethylene, enhancing the coating's performance against corrosion.

💡Environmental impact

The script briefly touches on the environmental impact of coating materials, particularly the use of chromate treatment, which has been criticized by environmental groups due to its harmful effects. The industry has had to find alternatives to chromate pre-treatment, which had excellent corrosion resistance properties, to mitigate its environmental impact.

Highlights

Introduction to a six-session series on pipeline coatings with Vanessa Silly Fisher and Neil Webb.

Discussion on the importance of understanding different pipeline coatings and their impact on logistics, performance, and protection.

Vanessa shares her initial experience with pipeline coatings and the challenges faced in identifying the type of coating.

Overview of polyethylene coatings, their benefits, and common use in the industry due to their durability and chemical resistance.

Challenges with polyethylene coatings, particularly the difficulty in achieving adhesion to the pipe surface.

Explanation of the process of applying sintered polyethylene coatings using a fluidized bed for mechanical adhesion.

The limitations of polyethylene in terms of under film creep resistance and corrosion inhibition when damaged.

Introduction of 'Yellow Jacket' coatings, a two-layer system combining polyethylene with a bitumen-based adhesive for improved adhesion and corrosion resistance.

Description of 3LP or 3-layer polyethylene (3LPE) system, integrating epoxy for corrosion resistance with polyethylene's mechanical and electrical properties.

Historical issues with 3LPE and the evolution of the epoxy layer to ensure effective bonding and corrosion protection.

The necessity of proper surface preparation for effective coating application, including the use of phosphoric acid-based washes.

Economic considerations of coating selection, including the cost savings associated with polyethylene coatings during pipe laying.

Addressing field joint coatings and the importance of protecting bare steel during pipeline construction.

The impact of AC interference on polyethylene coatings and the need for balancing electrical insulation with susceptibility to interference.

Discussion on alternative polyethylene systems, such as tapes and heat shrink sleeves, for field applications and mainline wrapping.

The importance of considering the environment and specific project requirements when selecting pipeline coatings.

Conclusion and anticipation of further discussions on pipeline coating selection criteria in the final session of the series.

Transcripts

well good afternoon everyone and

welcome to bite-sized corrosion

in fact i say welcome back it's really

wonderful that you've joined us again

today

and we're really really excited to kick

off 2022

with a six session series where neil and

i will be discussing pipeline coatings

for those of you who don't know me my

name is vanessa silly fisher

and as i've already indicated i'm joined

today by neil webb

today we'll start the series by

discussing polyethylene coatings and

we'll try and answer the question

how many layers

just remembering and looking at that

picture of the truckload of pipes

it reminds me just how challenging it

can be to try and figure out what a

pipeline coating is

in fact i'm quite ashamed actually

embarrassed when i remember when i

really started out in the industry many

years ago now

i went to site to investigate a

corrosion problem

which

turned out to be a coating problem and i

was very green

and in some ways actually i found the

whole experience quite overwhelming i

was trying to take in as much

information as i could

what could have caused this problem what

were the conditions

frantically scribbling notes everywhere

and on my return to the office neil i

don't know if you remember you asked me

this clanger question

so vanessa what was the coating

my word

silence

i realized that i had no idea

so i sheepishly think i said

black

and i wondered then like many do how on

earth

can you tell the difference between

these pipeline coatings

that is a challenging

question what

is the coating

and

there are many different coatings

available for pipelines

and

having knowledge of which coating is

actually applied to the pipe is really

important

because it affects the

pipe laying

logistics it affects the

back filling it affects the long term

performance it affects the cathodic

protection it affects the ac mitigation

and so

the

selection of a coating for a particular

pipeline

in terms of its environment and its

service life and so on

is very very important and actually the

last session of this series is going to

be devoted to

some of the

questions that we should be asking

ourselves as engineers when you're faced

with a pipeline project and that is

which coating should i be using which

ones are suitable because not all

coatings are suitable for all conditions

so let's change this up a little bit and

let's start thinking as a new engineer

where do we even start

it's a good place to start is black

the

pipeline that you see in this photograph

is in fact a polyethylene coated pipe

the pipe sections themselves were coated

in the factory with polyethylene and

generally polyethylene is black

due to the fact that it has a

significant pigment content of carbon

black

in the

makeup of the material

and polyethylene coatings in general are

excellent

for

pipeline service because they're tough

they have high electrical resistance

they have very very good chemical

resistance

and they don't get damaged very easily

and so

for that reason polyethylene coatings

form a large percentage of the coatings

that are applied to pipelines you make

them sound as though they're almost

perfect and

we know that's not the case let's have a

look at some of the challenges

associated with the polyethylene

coatings neil if you think about

polyethylene polyethylene is the

material that is generally used for

plastic bags you'll see on the recycling

labels either

number two or number three i remember

correctly which is low density and high

density polyethylene

and

have you ever tried to fix something

made out of polyethylene when i mean fix

it have you tried to glue it back

together yeah nothing sticks to it but

like absolutely plastic wrap in the

kitchen

yeah so if nothing sticks to

polyethylene conversely polyethylene

doesn't stick to anything else

and so

when you put polyethylene onto a pipe

you are immediately faced with a

challenge

that how on earth do you get the

polyethylene to stick to the pipe

and adhesion is one of the paramount

characteristics

that is important for a pipeline coating

and that is good adhesion

because we don't want corrosion to occur

underneath the coating and that brings

us to the the second

limitation of polyethylene because

polyethylene is so inert it doesn't have

particularly good under film creep

resistance or inhibition of corrosion if

and when the pipeline coating is damaged

in this photograph we see a very good

example

of a large diameter pipeline that is

coated with sintered polyethylene in

this situation

the

pipe is blast cleaned to provide a rough

surface which gives you mechanical

adhesion

and then the heated the pipe is heated

and the pipe is dipped into a fluidized

bed of polyethylene powder

the powder then sticks to the pipe

surface it fuses and forms a coating

which is a couple of millimeters thick

and you land up with this centered

polyethylene coating which is then

secured to the pipe purely by mechanical

interlocking

between the polyethylene and the rough

surface of the pipe

one of the challenges that i see with

that is that

although it's holding onto the pipe

it doesn't have any corrosion inhibition

in and of itself

that is correct because as i said the

polyethylene itself is very inert and it

doesn't interact

with the the moisture and oxygen there's

no

what i like to call glue factor

there's no glue factor nothing that

makes it stick

to the underlying steel it's just this

mechanical interlocking and i'm not

saying

that it doesn't work it does work

but it does have its own shortcomings

and in order to address

those shortcomings the industry

has had a number of developments

and one of the first ones that came

along was well if we've got

polyethylene which has got good

electrical and mechanical properties

uh

how can we get it to stick to the pipe

and

one of the first

options

then was

this material

which a lot of our international viewers

will recognize

and they've probably heard of the term

yellow jacket

coatings and

it is a trade name i granted but it is a

polyethylene external either extrusion

or shrink sleeve that is put over a

layer of

bitumen

based adhesive a mixture of bitumen and

polymers very much like we use in many

other products for the pipeline industry

and it is used between the steel and the

polyethylene

because it is one of the few things that

does provide you a with some adhesion

some chemical adhesion and also it

provides you with

good chemical resistance or corrosion

resistance on the layer underneath the

polyethylene up against the steel itself

so effectively you've described

something now that is two layers and i

suppose we could term a two-layer

polyethylene well you're absolutely spot

on the money there because you will find

two layer polyethylene

described in the literature and in the

standards

as one of the material systems that is

available for pipeline coatings

now the product that i and probably many

of our listeners i'm really familiar

with

is 3lp or 3-layer polyethylene and i

don't recall that having any bitumen

anything in it so let's have a look and

see what's in 3lpe

well the 3lpe system is the next step if

you want to call it that we know that

epoxy

is

one of the real workhorses of the

corrosion engineer and the corrosion

protection fraternity

and

epoxy coated pipelines have been used

extensively

overseas in particular we had them in

south africa for a while

but epoxy coatings also have some

shortcomings we're going to talk about

epoxies on their own tomorrow taking the

good corrosion resistant

characteristics of the epoxy

and combining that with the electrical

resistance and the chemical resistance

and

water impermeability and mechanical

toughness

of polyethylene

has brought about the development of the

three layer polyethylene or three lpe as

it's known or trilaminate is another

phrase that is often used and in this

photograph you can see

that we have an fbe coded pipe and

this pipe is rotating in a an

application plant

and the white layer that you see over

there is only a hot melt adhesive a bit

like the glue gun that you use

around the the diy fraternity

and then the

polyethylene the black layer at the back

is also then extruded over the top as

the pipe spirals and you get this

thick polyethylene layer with an

intermediate layer of adhesive and the

underlying epoxy and that then gives you

your three layer polyethylene system

which has both the corrosion protection

and the mechanical properties and the

electrical properties that are desirable

for a pipeline so in other words we now

have the perfect coating

maybe not

well i wish

so the three layer polyethylene

comprises this layer of epoxy

in between the steel

and the polyethylene on the outside but

it had some issues when it first was

produced because initially the

industries thought that it was only

necessary to put a smidgen of epoxy

onto the steel in order to provide an

interface between the steel and the

polyethylene

and over the years it was discovered

that this led to this bonding

between the the system and the steel

and

the systems over the years have

gradually been improved and it is now

pretty much accepted that

[Music]

the

epoxy

inner layer has to be the equivalent

of a standalone epoxy system if it's

going to work

underneath the polyethylene because even

though polyethylene has a very low

water vapor transmission rate it does

still allow water vapor through and if

the epoxy layer underneath is not

man enough for the job

we land up with with this bondment of

polyethylene of the 3lp system

and effectively a loose bonded sleeve

now it's still

pretty tight around the pipe but there

may well be water underneath it it's not

a problem

unless

there is a defect in the coating

mechanical damage in other words or a

failed field joint or something like

that that allows electrolyte to be

transferred between the space underneath

the coating

and the external environment

and when that happens then you get under

film corrosion underneath the

polyethylene cathodic protection can't

do anything about it because of the

electrical

shielding properties of the polyethylene

and in fact we have this situation that

is known as cathodic shielding in that

situation but cathodic shielding and

cathodic disbondement really i think are

a subject or on their own that will have

to talk about it

on another day

in terms of getting your pipe ready for

your fbe you're gonna have to have

really critical

surface preparation cleaning

pre-treatment

has that been improved over the years or

are we still using kind of

the old original standards

i think there's not really a lot wrong

with the old the old standards except

perhaps that they were not

stringent enough

so

you have to have a typically a

sa3

surface preparation grade you have to

have

a good mechanical profile

in other words angular not rounded it

has to be clean and it has to be

particularly free of dust

and that is possibly one of the most

critical aspects and in order to achieve

that a lot of the pipelines now use a

phosphoric acid-based wash

as a pre-treatment for the application

of

fusion bonded epoxy

and there has also been other chemical

treatment

notably chromate treatment

which has been given the black flag

by the environmental

lobby

and

it's unfortunate because a chromate

treated pipe or chromate pre-treated

pipe actually has absolutely

outstanding

corrosion resistance properties

with with a fusion bonded epoxy coating

on it

and

the industry really has to jump through

hoops

in order to compensate for the lack of

that chromate sadly that's often the

case but all of those

improvements surely have pushed up the

price

of 3lpe comparatively to the other

coatings

for sure but we need to remember that

the

cost of the coating itself standalone

has applied in the factory is not the

only consideration when looking at the

overall financial system of costing of a

project if you have a polyethylene

coated pipe

you

have significant advantages

in terms of the

cost of pipe laying

and in this particular project

the selection of the polyethylene

coating which you can see on the pipe

that is strung on the left hand side of

the trench allow the trenching and back

filling operations to be substantially

less expensive

than if you had a different coating

which required a higher grade

of backfilling materials like for

example sand padding

and bedding and so on don't get me wrong

this pile of rocks in the front is not

suitable and that represents an area

where there would have to be some due

care taken but the bulk of that trench

was cut out of the soil

and pipe was just laid in the native

soil put back in without any

restrictions and that is a huge cost

saving and that in fact

was what drove the selection of this

particular project

because the pipe laying was that much

less expensive

given the material that was applied

through the pipeline in the factory

the other concern that engineers we

shouldn't

lose sight of is

the bare bits of steel that still need

to be joined together when we get our

field joint coating yeah well we saw

that

end of a pipe a few slides back and

here's one of those pipes that's now

being welded together

and you can see the epoxy toe sticking

out from underneath polyethylene

and this particular joint has now been

coated with a fusion bonded epoxy it

could have been a liquid epoxy and then

this in turn will get over wrapped

with a further either polyethylene or

perhaps a bbc or a shrink sleeve or

in the form of either an extrusion or a

tape to provide the additional

mechanical and electrical protection so

that the field joints are protected to

the same standard

as majority of the line pipe

that is factory coated

and here's an example of the interface

between the

line pipe of the the factory coated pipe

coming in from outside

through the wall of a valve chamber and

then the pipe in the chamber epoxy

coated and the interface in this case

has been protected with an adhesive tape

and we're going to be talking about

tapes in some detail

in one of the later programs

neil another consideration that we are

now needing to take into account with

our coatings is

what i always talk about as the new pink

on the block which is ac interference

let's just chat quickly about

what impact ac interference has

on the polyethylene coatings

well the advantage of the polyethylene

coatings is their extremely high

electrical resistance

and

this then provides the

insulation

between

the pipe and its environment the soil

the challenge of course is that

electrical interference or ac

interference

is not

necessarily conductive in other words it

doesn't have to travel through the

coating you get what we call inductive

interference

as well as capacitive interference

which

actually cause very high voltages on the

pipe

irrespective

of the presence or in fact in many cases

because of the presence of this

insulating layer because it means that

the pipe is insulated from earth and the

induced voltage is then able to be

present in the pipeline

instead of discharging through the

coating because of the coatings high

electrical resistance

and in this picture we can actually this

is taken during pipeline construction

phase when the pipes are above ground

you can see the proximity of those

overhead power lines and in order to

prevent the operators from being shocked

whilst working with the pipes above

ground because they've obviously got to

weld them into a long string pick them

up put them in the trench and so on

these pipes are being erst with a

temporary earth connection

in order to discharge in this case any

capacitive

interference

and so being a metallurgist i'm allowed

to say it

all metallogists

have

two hands

on the one hand you have a pipeline with

a good electrical characteristic and

insulation which reduces

the cost of cathodic protection

on the other hand you have a highly

insulated pipeline which is susceptible

to ac interference

so the challenge then is to balance

the

pipeline

and its coaching and the characteristics

of the coaching

against

the environment that the coating is

going to see

so you may well

find that

a coating of

lower resistance may be preferable

in an area where you have got a lot of

ac interference in an area with highest

dc straight currents you may want to

have a pipeline with good electrical

insulation characteristics and that is

going to be one of the subjects that we

address in some detail

in the last session of the series when

there's no ways that we will be able to

cover the full suite of

pipeline coating selection in a 20

minute presentation

but we can certainly

give you all some pointers

on what to consider and what questions

to ask

in terms of selecting coatings for a

particular

project neil are there other

polyethylene systems other than the the

fusion bonded

polyethylene the scented polyethylene

and the two and three lps

most of the other systems are based on

tapes

and so there's a range of polyethylene

based tapes that are available cold

applied and hot applied significantly

used for field joints but also for

mainline wrapping if you have a

situation where you get bare pipe

delivered to a site and you need to give

it some additional protection it's quite

easy

to apply a tape you don't need fancy

equipment

in order to

achieve that and we'll we'll be talking

about tapes in some detail later on and

then for fuel joints in particular which

is another coarser on its own

there are heat shrink sleeves available

which are wrap around

all based on polyethylene because you

can get polyethylene to shrink

when you heat it

those would be the two primary

systems

that that are available

great neil thank you and i hope that

that everybody who's been joining us

today has

found some of your own questions have

been clarified

when we've discussed the polyethylene

coatings