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- Hi, I'm Stan Riddle with VibrAlign.
Today, we're going to talk about thermal growth,
specifically as it relates
to aligning and leveling machinery.
When I started in maintenance work some 34 years ago,
thermal growth was one of those cryptic things
that you heard engineers talking about.
And it was really math heavy and took a lot of calculations.
At the end of the day, thermal growth
is a pretty straight forward thing.
As machines get hotter, they get bigger.
They grow because of expansion.
That expansion is measurable
and it's pretty easy to calculate.
We're going to go over some different methods to do that.
There are some just purely mathematical calculations.
We have an app to calculate thermal growth
that works really well.
But, I just want to talk about some
of the basics to start with.
As an example, let's just say we have a pump,
and it's pumping a 250 degree liquid.
We need to calculate its thermal growth.
So there's only three things you really need to know.
How big it is.
How hot it is.
Or how hot it's going to get from cold to hot,
its differential temperature.
And the material it's made out of.
So we're going to show you a couple
of examples on where you can find those things
and how to calculate it.
So, we can take, for example, a pump.
It's pumping a 250 degree liquid.
We need to know number one, what is the heighth
of the pump from the bottom of the foot
to about the center line of the shaft?
So that is its heighth or its length vertically.
The second thing that we need
to know is, what is its differential temperature?
And that is the temperature between
what it's at when it's at its running speed,
and what temperature it would be when it is shut down.
So, let's say it's pumping a 250 degree liquid when it's hot
but the room's only 80 degrees when it's cold.
That gives us the differential temperature.
And lastly, we've got to know this little number called
the coefficient of linear thermal expansion.
That can be calculated many different ways
based on the materials.
But in essence, a good rule of thumb
for industrial equipment is cast iron or carbon steel.
Those numbers are fairly close to each other
and we'll show you here that the coefficient
of linear thermal expansion for cast iron is about 0.000006.
For carbon steel it's about 0.0000058.
So those numbers are really close.
So close that I'm not as concerned when we get down
to six decimal places.
I just want to get a good estimation
of what the thermal growth calculates out to be.
So back to our pump example,
if it is, let's just say 12 inches tall from the bottom
of the foot to the center line of the shaft,
that gives us the length.
If it is running 250 degrees when it's hot
and 80 degrees when it's not hot,
that's a difference of 170 degrees.
And lastly, it's cast iron, so we know the coefficient.
And so here is an easy example,
I've heard people for years call this TLC,
temperature times length times the coefficient.
So, if we add those three things together
or multiply them together,
it gives us our thermal growth calculation.
But here's where you have to be a careful.
The entire pump may not heat up to 250 degrees.
It may be 230 at the split line
of the shaft. It may be only be 100 degrees
down at the bottom of the foot.
And somewhere in between those two, it's going
to be some temperature in between those two.
So, it's best if you take a few averages
of temperature from the split line all the way
to the bottom of the foot
and get an average growth.
So, let's show you how to do that.
So, in our discussion we talked about these two items.
We have an electric motor, coupled,
driving an end suction pump.
I'm not an artist but that's my example.
So, here's the things we talked about.
We said we need to know TLC.
"T" is the temperature and
that's the differential temperature, a delta "T".
We also need to know the length
and we need to know the coefficient
of linear thermal expansion.
So in this case, we probably have,
in most cases this would be cast iron,
and if it's a good quality pump it's cast iron as well.
I need to know the distance from the, roughly the split line
to the bottom of the machine feet.
We're going to say that's 12 inches.
So we know our length is 12.
Our temperature is, it's an 80 degree room
when this pump's not running.
250 degrees when it's up and at its operating temperature.
So, that is a differential of 170 degrees.
If I know the cast iron and its coefficient is .000006
and that's roughed around,
depending on type of cast iron
it could be a little more, could be a little less.
Carbon steel is about the same.
At that many decimal places,
we're not going to be as concerned about complete accuracy.
So, I will say "T" temperature, 170 degrees
times "L" the length, 12 inches
times the coefficient .000006.
And if I add all this together, multiply this together,
it's going to give me the answer
of calculated thermal growth of this motor.
But there's some caveats we have
to pay particular attention to.
I might want to take an average temperature
right here at the center of the split line.
And maybe another one halfway down.
I may even want to take that on both bearings
so I can get an average of growth.
And if that average growth isn't 170 degrees,
but maybe I add these three together
and I add these three together and I divide the answer
by three, that gives me an average.
Maybe it's only 140 degrees.
So that may be the real thermal growth number I need
to contend with.
And again, if I say 140 times 12 inches times .00006
gives me the answer.
I'm sorry, I'm going to have to do the math on this.
Are you okay with that?
- [man] um-hum
- 140 times 12 inches times .00006 equals, hang on,
140 times 12 times .000006 tells me that
this is going to grow by about 10 thousandths of an inch.
From cold to hot.
But now my motor may have some thermal growth as well.
It may be, 80 degrees when it's cold
and 130 when it's hot.
So, now I've got to calculate a second temperature change.
Maybe it's the same heighth times .000006,
sorry I'm missing a decimal place there,
or roughly one third of this.
If this grows 10 this maybe this grows three.
So, what I'd have to do is actually
get the differential between these two
and calculate thermal growth of the pump
for seven thousandths of an inch.
And what that means is this,
I'm going to set my motor, when it's cold,
I'm going to flip this page. Is that okay?
- [man] um hum
- So when I set up on my laser,
and I would do this on the laser screen,
I'm going to say my motor is going to be here
plus seven mills or seven thousandths of an inch.
So, when my alignment is cold,
it's going to be something like this.
My pump is actually going to be sitting a little lower.
Because, it's going
to grow seven thousandths more than this grows.
So, when we get up to temperature
both these shafts will be collinear
or in the same straight line.
There are a couple of things I recommend
that are really important about thermal growth.
Number one, it is an engineering calculation.
And while it's pretty straight forward,
mechanics typically should not have
to calculate thermal growth.
They should either one,
get it from their engineering department.
Two, get it from the machinery manufacturer
because they should have more depth
into calculating thermal growth.
So don't just go a little wild with it.
But I want you to have a good understanding
as maintenance mechanics,
you need to understand something about thermal growth.
So, if someone tells you,
this little 40 horsepower machine
is going to grow a hundred thousandths of an inch,
you can almost assure it's not going to happen
because it doesn't grow that much.
So you need to have some understanding of the calculations.
I would get it from the manufacturer or
from your engineering department.
We also have a free app called Therm Align
that you can download to your smart phone or
tablet device, where you punch in these
same types of things.
The center heighth,
the temperature and the coefficient.
It will even allow you to put in up to 4 averages
and it calculates thermal growth very well,
using the same math that we used in our demonstration.
Lastly, if you really need to get alignment on the spot,
you need to know not only thermal growth,
but dynamic changes in machinery.
Not only does temperature move machinery around,
but pressures and thermal changes in piping do as well.
So, I would recommend if you really need
to get it on the money, check with us at VibrAlign.
We have an OL2R, Offline to Running program
that works with our NXA professional
which actually measures the dynamic
and thermal changes in movement from machinery from cold
to hot or from hot to cold.
So I want to thank you for joining us today
with this webinar on thermal growth from VibrAlign.
We appreciate your input and your patience with watching us.
Hopefully, this has been beneficial.
But stick around, we're going
to have a question/answer session.
We'll do this as long as we can until the clock runs out.
So give us a couple of minutes and we'll be right back
with you to try our best to answer your questions.
Thanks.
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- I think anybody who has pumps or fans, any kind
of equipment that's mounted up
to a motor, should take this class.
- You can always read the instructions
and go through step by step,
but stuff always comes up.
Especially working on old equipment.
It's always good to talk to somebody who's been doing it
for 30 years.
- What intrigued me about the class is all the precision,
alignment, vibration, analysis everything the class offered.
- Most the classes we've been to
that you just sit there all day in class
with a book and a PowerPoint.
- A lot of other classes I had, they kind
of just read the book to you.
- I think we spent at least 80 percent hands-on.
Probably more, which made it a whole lot better.
- Our RPM class is really good for anybody in the industry.
We're teaching some old skills and some new skills.
(high energy rock music)
- Number one thing is the instruction that you're getting.
The knowledge that they have.
Hands-on knowledge not book knowledge,
but hands-on experience knowledge,
where they can, in layman's terms tell you
what they're talking about by giving you a past experience.
- You know, we have brand new technicians,
straight out of tech school.
We have engineers with 2 or 3 decades
or more of experience.
We've had maintenance managers,
supervisors, everybody benefits from that.
- This, I'm able to ask question after question.
I was just talking to Stan about a really unique
problem I'm having and he's actually helped out a lot.
- It's time well spent, you're going to learn a lot
and it's going to be fun.
It's not a boring class.
- It's a good class. I think any mechanic and any
industrial site, power plant, refinery, water treatment,
whatever it is, it's all the same.
It's definitely not going to hurt.
- Awesome class, I got to tell you straight up.
Some of the best training I've ever been,
if not the best.
(high energy rock music)
- So we have a few questions here
through the magic of smart devices.
We'll try to get to at least a few
of these before our time runs out.
And, again, in case I forget it,
keep sending those questions in.
Those that we can't answer online,
we will try to reach you by email
and answer any questions you have.
The first one says, "You said use the .00006 number,
or whatever, for the thermal expansion number.
Where did that come from?"
That's a good question.
Coefficients of linear thermal expansion
is just physics numbers.
And it's just based
on as molecules heat up,
they get further and further apart.
So the cast iron gets bigger.
That's where it comes from.
The numbers I got where from the machinery's handbook.
Which is a big green book that been around forever,
with a lot of math stuff in it
for maintenance and engineering.
You can find these numbers online.
Just type in linear thermal expansion for cast iron
or carbon steel. Or, whatever.
But, a good question. Thank you.
Let me try another one here.
Here's a good one.
Says, "I have a chilled water pump that gets pretty cold.
Does thermal growth formulas work the same way for that?"
Good question. Yes, it does, just in reverse.
So, if I have a pump that's getting cooler
as it heat, as it gets it to its temperature,
it actually shrinks. So, instead of setting the motor high,
you may have to set it a few thousandths low.
That's a good question.
Something I don't think about very often.
But, yeah, thermal growth works going colder
the same way it does going hotter.
Let me try another one here.
Here, here we go.
"I'm curious, just how picky should we be
about thermal growth? We've never had any problems
on our compressors and they get pretty warm."
It's a good question. I'm not sure I know how
to answer that.
If you're not having any vibration problems,
you're not having any excessive wear problems,
you're not blowing seals on your compressors
then, honestly I wouldn't be too terribly concerned
about it.
Flexible couplings take up a little misalignment.
You always have an alignment tolerance,
plus or minus two or four six thousandths,
whatever, depending on its speed.
So, it may be, and what I've found just in reality,
a lot of times is,
even though the compressor heats up a little bit,
the motor heats up a little bit, too.
And sometimes they grow almost the same amount relative
to each other.
So, it may not be an issue for you.
Again, I would check with my engineering
or maintenance department
and just find out if you think that's something you need.
Let's try to get a least one more before we run out
of time here.
Here we go.
Says, "We always set our motors five high as long
as I've been working here.
That's what my boss told me to do.
But, we also lose a lot of couplings.
Do you think five high might be wrong?"
I assume five you mean five mills
or five thousandths of an inch.
Honestly, I can't answer that with out more information.
I can tell you that back in the stone age
when I started in maintenance,
they told us, you know thermal growth's five thousandths.
Well, where does that come from?
And nobody could answer it.
I'm not saying that your boss or whoever gave you
that number is right or wrong,
but you might want to look into it a little more.
Again, I mentioned the Therm Align app
that we have at VibrAlign, it's free.
You might want to download it and just try it out.
Do the math, take some temperature measurements
with a little heat gun, a little laser gun
and find out if that machine is really heating up as much
or as little as you think.
Certainly, make sure you
have the right coupling application,
that the alignments good, things like that.
But, if you're losing a lot of couplings,
I think it was couplings,
yeah, if you're losing a lot
of couplings then I would be investigating why
that happens.
Could be alignment, could be thermal growth,
could be the wrong design
or too much horsepower or something.
But I'd look into that and make sure.
Just from a time stand point
that's all we can probably answer online
during the course of the video.
But, again, please send your questions to us.
We'll try to get back to you as promptly as we can
and answer your questions if we can.
We've got a good pool
of resources here at VibrAlign we can turn to.
And lastly, I want to thank you all for tuning in,
thank you for your time and your patience with us.
Hopefully, this has been some benefit.
You've learned a little more about thermal growth.
And as always, if we can help feel free
to contact us at VibrAlign.
Give us a call or shoot us an email.
We'll be glad to help in any way we can.
Again, I'm Stan Riddle with VibrALign
and thanks again for tuning in.
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