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November 17, 2021

Understanding Induction Bending and its Applications



All right.

So welcome everyone to this fifth

Livestream of

My name is Luuk Hennen.

I'm the founder of  EngineeringTrainer,

and today I will have a conversation

with Sondre Luca Helgesen,

who's the CEO and founder

of Stressman Engineering

and with Øyvind Storehaug, who is the

business development manager of NIRAS.

A world leader in the production

 of Induction Bends.

We'll be covering the topic of induction

bending, what it is, how it compares to

welded bands and how they can be applied.

And I think the topics that we will

address during this conversation will both

be interesting from a piping design

point of view, but also especially

from a pipe stress point of view.

Before I move to the speakers, let me,

first of all, welcome all of you who are

watching this stream to the session.

It's a delight having you and I actually

want to invite everyone who's watching

this to participate in the chat.

So as a first invitation, I invite you

to let us know what your location is.

That's always a good ice

breaker and good fun.

Let us know where you're from

and from where you are viewing.

Obviously, I want to invite you all

to connect with me with Sondre,

with Øyvind on LinkedIn,

just to connect or to start a conversation

and to consider subscribing

to the YouTube channel.

If this type of content

is relevant for you.

Having said this, Sondre, Øyvind,

welcome on board.

We are honored to have you, of course.

How are you both doing?

Doing great.

I'm doing fine, thank you.

All right.

So we just organized the whole setup and

I'm really happy with it and that you

could both join us from the

location of Stressman, Norway.

Before we move to the slides,

just a quick brief introduction.

Like Øyvind,

you've been involved with Induction

Bending for quite a while at NIRAS.

Since how long have you

been working at NIRAS?

I've been working for ten years,

but I've been working with Induction

Bending since 1983, so I've been into the

business for almost 38 years.

So a lot of experience with piping.

All right.

That's amazing.

And I'm happy that you could join us

for this conversation.

Sondre and I,

we are connecting on a regular basis

and discussing loads and loads of topics.

So it's nice too,

now that we're doing this live stream

about the Induction Bending that you were

able to join us,

I actually think that's great.

We see all kinds of messages coming in.

So people, Martin watching

from Netherlands, Tara from Singapore,

Alma from the Philippines, we got London,

we got England, we got Spain.

All right.

That's amazing.


Thank you, Kokan.

So, as I mentioned, it's a delight

having you all on board for this stream.

And I do invite you to share your

thoughts, ask questions in the chat.

It will really make this session a lot

of fun if you participate actively.

Having said this,

we will now switch to the slides

that will guide our conversation.

All right.


So here we got the slides Sondre!

Take it away.

Thank you.

I'm going to do that.

So as you already introduced me.

I'm the CEO of Stressman

Engineering. And at Stressman we like to say

"Relax, let us handle your stress."

So I've been doing this

for about ten years.

I'm not as old as 

Mr. Øyvind here.

So I was one year old when he started

working with Induction Bends.

But we have known each other.

We have known each other

for quite a long while, actually.

In Stressman

we've done so far about 370 projects.

It's within all fields,

all kinds of different industries,

oil and gas, maritime,

land-based also in the energy sector.

And it's basically numerical analyzes.

Give us a problem.

We'll solve it with the laws

of physics and computational power.


I don't talk too much about

exactly what you're doing today.

Today we're going to talk more about

Induction Bending,

which is a very interesting topic that

there is a lot of, call it urban

myths about it because it's

a topic that's kind of easy to understand.

But at the same time, it's

encouraging a lot of questions to it.

For the past, I would guess like 15 years

we've been working together because we've

been doing the calculations and Øyvind

has been Bending the pipes, not himself.

But he got up at which is a small town

like 40 minutes away

from here, quite close.

So we are from the same

district of Norway called Telmark,

and there is a lot of industry here.

So it's actually

an interesting place to be.

So I don't know if you want to say a few

words about NIRAS just very briefly.


NIRAS was established in 1955.

So we have a long time in the business.

Almost all the people coming

from a machine dealer called Bombak,

starting with the Induction

Bending machines in 1983.

So today we have a five Induction Bending

machine and we are Bending at 20-inch and

we can handle wall thickness of

up to 100 millimeters.

We are much into high pressure,

high temperature area for replication.

Quite big pipes as well.


As you always say, it's not about size,

because most of the pipes that are high

pressure, high temperature

is not 30 inches 40 inches.

But it's a lot of, like,

six-inch piping, eight-inch, ten-inch.

And so on.

I think about 90% of the pipe is

from nine or eight inches and down.

So the big volume is below 20.

That is a big number.

And as you say, it can bend up

to 100 millimeter wall thickness.

That's about four inches.

But our last machine

was going to OD 125 millimeters.

So there is a big volume for us

for high pressure, high-temperature piping. And we are much into super duplex, duplex and all these materials. 

That is our speciality.

All right.


And these are some of the companies

who actually use Induction Bending or

Induction Bends in their facilities,

in the process plans, in their

subsea applications.

A lot of people I meet at least never used

Induction events in their designs before.

So it's just to show that there is a lot

of end users who have induction

bends in their systems.

We are a supplier.

But the first Induction

Bending machine also designed and built in 1964 so

of course, a lot of Induction Bending

pipes around in the world, but still

the big volume is waving stand available.

We're looking very much to come into the

sector, both top side and subsea.

What would you say

before we dive into the technicalities

of Induction Bending, et cetera, what

would you say is the market share?

Is there, like, an estimate

you could make? The market share between

Induction Bends and Standard Bends?


like welded bends

I'm not sure.

But I think maybe 0.1% of the Induction pipe.

And the rest is standard welded elbows,

almost 200 year standardized

way to make pipelines.

We have a big market if you could get

a bigger share of the market that people

are going away from welding and elbow.

All right.




But, for example, subsea applications

that we see here in Norway, they are

quite good at using Induction Bends.


And of course, the Norwegian Equinor our

supplier is very happy

to use super duplex.

We are very happy

for every super duplex coming up.

Of course, we have many club pipes

and carbon steal and whatever.

But we are very happy for our project, for subsea pipelines and

of course, high pressure, high

temperature to avoid welding.

All right.



This talk today is more about

understanding Induction Bending.

What is Induction Bending?

How do we apply it in the design and how

do we do the calculations of it?

That's what we're going

to talk about here today.

What this Induction Bending? It is going to be

just a very quick crash course

into Induction Bending.

Basically, it's not going

to be all the details.

This is a speciality in itself.

How you actually do the work

that you are so good at.

As you can see in this picture here,

there is the heat affected zone

that's being heated up to around 150 could it be for super duplex

and 900 degrees for carbon steel?

So we have a very good control over

temperature and the trenching.

So we are almost doing the heat treatment

for super duplex when we are doing it in the bending machine.

What I really enjoy about this picture

is really also it's very local heating.

At least that's what it

seems from this image.

Interesting. What people are

saying is with regards to ovality.

A lot of people are concerned about

ovality that when you bend the pipe,

it's not going to be a circle anymore.

It's going to be more like an ellipse

for example.

This is very local heating.

Very local and the thinner the heating zone is, the more cold circle

material we have on both sides.

And that keeps the shape around.


very often, almost for every project

for a subsea we have to do pigging

and it could be 97% of the nominal ID.

So it could be very tight

to the original pipe.

So I think sometimes the pipe could be

 more out of roundness 

than we could make into the pipe.

All right.

So basically what is happening is

that a part of the pipe is being heated up

and then you have an arm that's

not shown so well in this picture.

But there's an arm that is bending

the pipe, and then you have cooling

or crunching, as you said over here.

And that was a very brief

introduction to it.

As you also mentioned,

sometimes if you have very big wall

thickness or big wall thickness, you

need to do post-heat treatments on it.

And again tempering for carbon and carbon steel.

So we have the metallurgists,

we have the Induction by the machine and we have

the heat treatment furniture

to give us the right quality.

So here we could

do the heat treatment in the Induction

Bending machine itself,

up to 25 millimeters for super duplex.

So then we could avoid the possible heat treatment after bending. 

But the bigger question

is why Induction Bending?

If you see, for example, this FPS over here,

the process facilities here are huge.

So there's so much piping.

And as you said earlier,

most of this is not Induction Bends.

It's standard bends

that are welded into place.

So by switching to Induction Bends,

how do you say it? It would be optimized

with regards to cost delivery time?

Also, it could have

an impact on the weights.

It helps on the pressure drops.

It makes your systems more

energy optimized.

And also it will help on the erosion.

So Sondre, costs would mostly be affected because you

simply reduce the number of welds, right?


That's the main thing,

as you can see in the next picture here,

this is what we call

a flow loop or a spool.

In this case,

as you can see here,

this is what they call the nearest loop or

the nearest spool I mean and it is a

one piece that's bent all in one process.

While the original would

look something like this.

If you're only going to have 90 degrees

and 45 degrees bends,

it's going to look like this.

And here we got 1 2 3 4 5 6 7 8 welds.

While this one, you don't have any welds

between point A and B on the loop.


And then if you compare the two floor

loops together or two spools together,

they're almost the same.

A lot of people are saying that this 3D

bend radius is taking more space

than one and a half D bend radius.

So yeah, it takes a little bit more space,

but not too much space either.

Just a cost comparison between

the two different spools here is that,

as Øyvind was saying,

there is a lot of things going into this.

So if you buy

piping from one vendor with the same batch

number or heat number,

and let's say you make ten spools.

For a six-inch pipe schedule extra extra

strong, you can save up to 66% in cost.

If it's a small pipe, a two-inch

then it's 61%.

For example, another thing that is very nice

 is that when you're designing

you can start to use your imagination

because the Bending machine

can bend in all directions.

It's not like you need to do one by one

bend or something like that,

you can bend in all directions.

So by looking on this spool here,

if it was standard bend, you will

have 1 2 3 4 5 6 7 8 9 10 11 12  welds.

On a regular piping system.

This one, I don't know how much time

you use to bend the pipe like this.

I could take about 20 minutes for every

bend, but you don't have to cut the part.

You don't have to order the bends.

You don't have to have the lineup bending,

welding, welding complication.

And you save a lot of documentations.

But another issue is that we always

can give your attention before the bend.

So you can get to the welding area, away from the interzone.

Just from my understanding,

just to be absolutely clear,

this obviously is a little bit of a dummy

question, but we see the bands

here and different colors.

But this was like

a straight piece of piping.

And now we see these bands

because those were heated.

That's what colorized.

What changes the color, right?


In the beginning, it was

a long pipe with this color.

And then when it's getting

bent with induction heat.

Inside, we use the gas

to reduce the oxide.

So we don't have the same side.

So this is a bend.

We don't have any welds at all.

Typical seal we have the heating zone

have been attached to the pipe.


We got a few questions, and I think

some of these are nice to just

ask immediately.

So is there a minimum bend radius, Øyvind?


So the minimum physical bending

radius for machines is 65 millimeters.

But very often you have a specification

who limits the wall thinning in the outer

wall of the pipe to be example

12.5% on the middle dimension.

So that is normally what we have to follow

to give our customer

within this publication.

But we can talk a little bit later about this.

People are a little bit

scared about the thinning of the pipes.

That is our limit.

So that's the reason, we are saving what increased the radius 

because we ask people to use

the same batch and line pipe for 

both the straight section 

as the bend sections.

You don't have to waste

money to buy more expensive

line pipe for the bend section.

The limit is a little bit more what

the customer has

for requirements to the whole thing.

All right.

So that's interesting.

Thanks for answering.

We already have a few questions

that jump straight in.

Like what about the sieves and

stress analysis. We'll get there.

I'll reserve those questions for now

for those who ask them,

and I'm confident that they will

be answered a little bit later on.


Sondre, feel free to continue.


So also the next picture here.

It's just a different way of reading it.

For example, instead of going, we are going all this

from a simple pipe from A to B.

So in this case, it's one,

two, three bends in between here.

We got six welds on it.

So one way of doing this

could be taking one long

line pipe and bend it with two bends.

So you get from A to B.

Of course, there could be

some limitations on this.

Maybe you need to have a bit more

flexibility due to stress, for example.

But there is a lot of

ways you can route it and you're

not tied up with the conventional

bends and fittings.

That is normal.

Get creative. Could be very hard

to make the spool without any weld.

Then you can cut it in the middle

of the stripe section.

And maybe you can ask for get a little

more over length in this

section so you can

get one weld compared to six.

So anyway, you will save time and save

money and make a more safer system if

you need to have one weld for adjustment.


If you want this kind of routing,

you could bend these bends as well.

Yeah, from the other pipe.

With regards to weight, for example,

you can optimize your routing basically

to save weight on a project

you can easily get from A to B,

in many cases.

Pressure drops.

This is

something that the end user is

typically very worried about.

So if you have a lot of pressure drop

in a process plant, for example,

or anywhere, basically,

you need some energy to pump it along.

For example, if you have a 1D bend rate,

this is this bend that you see here going

to a 3D bend,

you get a reduction of the pressure drop

through the bend with a ratio of 48%.

So if you go from 1.5D to 3D

times the radius, we still drop.

Maybe not as much as 48, but at least it's

22% and over 20 years, maybe 30 years.

That could be a lot of money in the end.

And also that's energy saving.

And that's what we need

to do in the future.

We define ways to save

energy to get a cleaner future.

So this is also, that's a fair point.

And then similar

to the pressure drop

it's the erosion that can occur if you

have particles, for example,

in your flow that might erode your pipe

on the inside, then increasing the radius

will decrease the erosion rates.

That's another good thing

to use Induction Bends.

Because if I remember correctly,

Sondre, you once stated that

the angles that you can

basically make are completely free.


You can do, like, 72 degree bend.

If you would want to.

Yes, you can have a 1.5 degree bend or 3 degrees bend.

It would make the design

process a lot more creative.

I would love to do that.

I think some one said they have, like,

88 deg or 87 degrees angle instead of a 90

degree because they were going

to be used as sloped system.

For example,

but back to the design of the pipeline.

So it's the point A and B,

they're important.

So maybe if you have the role that you

want to have 90 degrees and it's here

to hit the endpoints,

maybe we have to bend 92 degrees.

It doesn't matter so much

if the issue is 88 deg or 92,

the most important is that the end

point of the pipe is going

to be in the right position.

Yeah, but we can be bending in 0.5 degrees

accuracy, so that's no

problem with the induction bending.

Then you have spring back on.

Okay, thanks.

So this brings us into the last

part of this session is okay.

This is how you can use it in design.

And if you're going to use induction bends

in your design,

there's always going to be a lot of questions

 popping up with regards

to how can I calculate those?

Today's session is based on B31.3. But

first, let's take a look

at the wall thinning effects.

So as you can see here,

actually, I don't know if you can see it

very well, but we got chopped up

Induction Bends in our office,

of course. It's actually

been several times to

Singapore, its been traveling the world, this chopped up bend.

I didn't mean to skip the slide.

I'm sorry about that.

There we go.

So as you can see here,

the inside is getting thicker

and the outside is getting thinner.

The neutral line, as you like

to call it, it stays the same

and the metal doesn't

disappear or add to it.

So it's going to be the same amount

of metal around this cross-section here,

which is good, because then the sectional

modulus is going to be about the same.

And then I took this picture.

I went into Photoshop and I colored it so

that it was easier to see the thinning

effect that you can see here.

And then we had a thickening

effect over here.

We can calculate that very accurately.

It's not a problem to anticipate

what it's going to be.

If you know the wall thickness before

bending, we can find out what is going

to be after bending with a very

high accuracy. And how to do that?

And also, this is a white paper that's

available on our website as

its made together with NIRAS.

It's free of charge, just download it.

You don't even need to register at all.

I'll make sure to put the link

to that white paper in the notes

of this video on the YouTube.

Yeah, that'd be good.

So basically what I like about this, you

managed to simplify formulas quite a lot.

So to find out,

either you can define a wall thinning or

thickening in percentage or basically

calculate the new thickness if you

have the original wall thickness here.

Sorry to interrupt.

Time is flying.

Obviously, maybe let's not go

into the details of the actual formulas.

If people want to look into them,

they can download the white paper.

But let's discuss the numbers

and the conclusions.

You just take a look at the white paper

and you will have a better

understanding of the thinning effect.

I think what is more important is

the wall thickness calculation.

To calculate how much wall thickness do

you need to keep the pressure inside


I'm guessing that a lot of people

following this broadcast are 

pipe stress engnieers that are

very familiar with this formula here,

which is the wall thickness formula from 

B31.3, which is pressure times

the outer diameter divided by two

times the allowable stress,

multiply the two factors there

divided by "I" see that here.

It's an "I" here and mark it in orange.

And then "I" depends on if Intrados

 or the Extrados.

These are two formulas for it.

And this is just an example.

It's an extreme example because

it's easier to show by numbers.

It tested it out in several sizes as well.

But if you have a 1D bend,

this is typically the numbers

you're going to get in B31.3,

independent of the size as well.

So if you have B31.3,

you get a factor on the intrados

of 1.5, meaning that actually your

intrados needs to be thicker.

It should be thicker.

It shouldn't be the same

size as the pipe here.

If you have the same wall thickness as

the pipe and that pipe size is just by 9%

utilized, for example,

it's going to fail inside of here.

So you need to have athicker wall

on the inside and on the extrados,

which is outside here, you can

have a smaller wall thickness.

And the reason for that,

if you look at this image here,

you can see that if you do an area

calculation like we do for nozzles

in pressure vessel calculations,

and we assume that all the pressure inside

of this neutral line goes towards

the intrados,

and then all the pressure on the outside

of this neutral line goes to the extrados,

 you can see that the areas compared

becomes bigger on this

side than this side.

And basically, this is more

explained also in the white paper

with an example, this exact example.

So when we did that simple calculation,


what is the pressure force due to this

area we got here with the pressure divide

that by the area of the extrados,

you get a factor 0.83.

So we got exactly the same as B 31.3

by hand calculation, we get 1.48

by hand, while B31.3

get 1.5, its about the same.

And then with the FEA that we can see

on the screen right now,

this number rounds up to 1.48,

which is the red area on the intrados here.

And then we got the 0.83,

which is identical to the extrados here

of B31.3 and our own hand formulas.

It gives us a value that runs

up to 0.83 as well.

So this is confirmed by FEA.

It's also confirmed by burst testing.

Basically, if I understand correctly,

sorry for jumping in.

So the idea of like you bend the pipe,

you have a thicker intrados

and a thinning on the extrados.

That isn't too surprising.

It's even part of the equations

that are in the B31.3 codes.


what I'm taking away here. That the concept

of that being a bad thing

is not necessarily so.

I mean, it's even accepted in the codes,

as I now understand exactly.

So as you say, the wall 

thinning on the extrados

isn't as badly as it sounds like.

If you calculate the percentage

of reduction of wall thickness and compare

it with the allowed thinning effect,

it's not as bad as just taking the percentage 

of wall thickness comparing it

to the straight pipe.


Probably going to get a few

questions about that.

So I'm going to save a little bit

more of the explanation for later.

All right.

And also the same thing is that we get

an increase in wall thickness

on the intrados,

which is also beneficial with regards

to how the stresses are

distributed in a pipe end.


this is just for the pressure calculation.

But then you want to insert your bends

into a system into a piping model.

And if you're using Caesar II, 

Triflex, Autopipe,

many other softwares out there,

they all do the same with regards to the

stress intensification factors.

In this case, it's based on B31.3.

Now B31.3 has  a link

to that chapter about stress investigation

factors, and it refers to B31 J.

But for the bends,

the formulas are the same.

So if you see this orange line going here,

that in plain bending stress intensification factor

based on the bending radius divided by the

outer diameter of the pipe.

So meaning that this is a one and a half D bend.

This is a standard bend. Over here

we got the 2D bend.

You can see that the stress intensification is getting lower and lower.

That's quite normal because the longer

and smoother transition you got,

the less stress concentration

you'll have in that area.

What is interesting here?

This was based on a shell study,

meaning that you have equal wall

thickness all around the FEA model.

Then we get approximately the same

numbers up to three times

 the diameter and bending

radius, and then it drops down.

But what we can see, which is very nice is

that B31.3 is always giving a higher

number or the same number

as what we get from FEA.

The same goes for other plain bending.

As you can see, this line is from B31.3.

This line is from our FEA.

As long as our FEA is lower than what

B31.3 is telling us,

we're going to be on a safe side.

And then another interesting study was with

the FEA of what we call solid elements or

3D elements, where we included

the thinning and the thickening effects.

We could see that this is still the B31.3

SIF as well as this one.

So this is the in plane,

and this blue line is the in plane when we

include thinning and thickening effects.

So you can see that we are always below

B31.3, or we are equal to it.

The same goes for the outer plane.

This is the outer plane B31.3.

This is the outer plane FEA.

So as you can see it is still below,

in every case, we went up to

three and a half times the diameter

in the bending radius in this study.

So what's the conclusion here, is that as

long as you're using the SIFs from B31.3

or B31.J, you're going

to be on the safe side.

Also, with regards to the

wall thickness calculation use those

calculations and you're going

to be on the safe side.

All right.

And then this is just an example

from subsea manifold, that we did a few years back.

As you can see, there is

a lot of bends in there.

Every single bend in this

model are induction bends.

And these are six-inch pipes

schedule xxs or estra extra strong.

And the two-inch are also two inches.

schedule 160,

same as the three inches schedule 160.

So quite significant thickness.


So it's quite significant

wall thickness on this one.

So in this case, also, you can see

that these bends here are not 90 degrees,

for example. These are bends to what suits

the system the best. And what we did here,

when you're going to code check it,

you don't need to do any hand calculations

with regards to stress intensification

factors, not with regards

to pressure containment.

If you use a B31.3, of course,

that's an important thing.

So if it's different codes

and regulations, it might be

different ways of looking at it.

But from a B31.3 perspective,

that's no problem.

All right.

That's interesting.

Validation of what we are

doing is very important.

So this is a pipe that was

bent and bursted.

This is a six inch pipe, six inch pipe.

Scheduled 120.

That is a duplex to make it easier to burst

about 14 mm of wall thickness.

Burst pressure was around 1300 bars.

So it's a safe as well.

When you start bursting these pipes, before they bent it,

all the wall thickness

was measured along the mother pipe

or the line pipe here, they bent it.

Then we could confirm the formulas

that we are using as well

as we got an accurate,

this is our 3D model.

It's not so interesting to watch because

it looks like a perfect pipe,

but it's actually not.

So we modelled

all the different wall thickness

that was measured throughout here.

Yes, a perfect representation as possible.

Nothing is perfect, but as possible.

We got the material models,

but the material properties from someone

who was testing the base material.

Also the bend material.

And we could model

that into our calculation.


it bursted over here.

As you can see in our analysis,

also indicated that it was going to burst

the plastic strain in the pipe.

And we got approximately the same range

of pressure as well where

it was supposed to burst.

And this confirmed our numerical model.

And what is interesting here is that the area

here, it was thicker than what was only extrados over here.

The extrados was thinner

than the burst area.

So you mean the plain pipe section

on the right image was thicker?


So it was thicker and it confirms also

when we talked about B31.3, chapter two,

about wall thickness calculation confirms

that as well that we can have

a thinner wall on the extrados.

And we need to have a thicker

wall on the intrados.


And this is just a cross-section

of the pipe itself where we

have made like an automized

model or a parameterized model

in SolidWorks where

if you need to do a local FEA like you do

sometimes for subsea piping,

you need to go in there,

do very local FEA,

 or something called hydrogen induced stress tracking.

Then we need to see the exact

stresses at different locations.


All right.



I would like to just about to point

that out that as I mentioned,

time is always flying on these sessions.

Last time Sondre and I went on for 2 hours

straight, but we'll make

sure to avoid that this time.

We got a ton of interesting questions that really

tune into this story.

And I would love to discuss

those with both of you.

First of all, thanks

for asking the questions.

We had a question about siefs.

I feel that that is covered.

If not, Tony, feel free

to provide a follow up question.

An interesting question.

Let me just see, a question from Shazada.

Thanks Shazada, for asking.

In addition to wall thinning,

there is a loss of yield strength

of material in induction bends.

Is there some range for this

strength reduction?

Can you maybe comment on this?

So what about material properties

and laws of yield strength?

So when we receive the modified pipe

from the Mills, we have to do test of the

pipe and see everything in the pipe.

We then have discussed with the metallurgs by the clients,

and then we try to achieve better quality

section than in the modified.

So it's very important for us to get

the modified from good deals that we can

trust the values in the test circuit.

So almost all quotes we could

give you at least the same quote.

What approach is used? Is it like all like

post-process annealing, heat treatment?


We have very often three different

certifications coming from our clients.

So that is a challenge to try to find

out what they are asking for.

And then they have to start

analyzing what they are asking for.

And we have to do a qualification test.

So when you're doing the bending,

we have to do a hardness and corrosion test

and all this after bending. And then we

have to get this approved

from the client before we start bending.

We have

over 30 years experience

with this and we have done

over 1000 qualification tests.

We know a lot of information from different

mills, different heat numbers,

qualities and all that.

So very often we can pull out almost

the same heat number from the same mill

from before and see what

the results we get.

But very often the specification

pressures to do another qualification test

if we have it from ten times before.

I think we are one of the biggest

companies Norway doing most mechanical

testing, so we have a very good

data bank.

All right.

Thanks for sharing and commenting.

I would just like to point out a comment

that Ian made, which I think

is a fairly good point.

The bend extrados should be expected

to be stronger than

the straight pipe, he writes.

Since the shape approaches a sphere,

the hoop stress in a true sphere

is half of that of a cylinder.

So that's a nice comment

in relation to the pressure tests

that were shown previously, I think. Let me just drop another question

that I saw passing by which I think is

an interesting topic for discussion, ovalization.


Shazada, thanks for asking this question,

she writes for induction bend ovality

at the welding and within

the bend can be an issue.

Please highlight this

in your discussion as well.

What is your take on ovalization?

Is there a difference in ovalization

compared to typical welded

bends in the piping system?

We have this discussion with our

clients because we never are

doing the bending in the tangent.

So very often the shape of the ends where

they are doing the welding

is light modified.

But if we have to do a

separate additional post and heat

treatment, it could maybe change

a little bit in the shape.

And then today we are doing

straightening and roding by different

metals that it could be bending

and machining it is very tight to tolerance,

but for some bigger 20-inch pipelines

very often are doing

hard forming of the ends

to be within the tolerance.


When we are not doing any post 

bending heat treatment

We are not going to do any process

to the end, but still we have to try

to serve the customer with

the end preparation,

and we're doing the bevelling.

And in the same time we're

doing the bevelling.

We are very often doing the machining

to the inside and outside.

But this is quite a very critical

operation to reach the tight tolerance.

Specially if you're doing a glass pipe and you

have maybe a three millimeter

pipe and a little bit ovality at the end then you

don't have the machine to make sure.

So that's always a challenge,

but it's a very good question and we have

to have focus on it from the beginning.

All right.

Thanks for detailing that.

Another question from Ian,

which maybe Sondre you can share your

thoughts about this, do you make any

distinction or did you make any

distinction in the analysis that you

did between seam-welded and seamless

base pipes?

I now understand this

question a little bit better.

So if you do like induction bending,

do you make a distinction between

seam-welded and seamless base pipe?

What is your comment?

I'm just thinking here. Seam welded, do you

have anything to add on the

fabrication method there?

Do you see any how

do you make it?

So when we receive

the RFQ and we make a quotation,

we make all the induction bending

procedures, end procedure. And there very often is

seamless or what kind of pipe it is.

So then we have to discuss

if it could be single.

Mind weld area.

If we have to cut the weld in the neutral

So we don't have to cut it in