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    Default Help with epoxy concerns about temperature.

    Hello members. This is my first post but I'll keep the introduction to a minimum due to time constraints. My name is Phil, I am a job-shop machinist and millwright with W. R. Martin in Louisville, Kentucky.

    We have a particular project at one of our customers in which a horizontal machined surface on the base of a large industrial machine has placed upon it a machined plate which then has a bearing housing placed upon it and then they are held tightly together with bolts.

    The customer does not keep these bolts tight. Protocol is to hy-torque the bolts after every 12 hours--this is never done and frankly I don't blame them because it is a pain to do--however failing to do so allows them to loosen and then debris is introduced between the machine base and the plates the bearing housings sit upon and it now looks like an ant farm. We are in one of those situations in which what is truly best for the customer would be to build-up the surface with weld and then bring in our portable mill and machine it but they do not want the downtime or the cost.

    They were going to set the shaft and bearings on Friday, however we were able to get them to concede to letting the project go until this coming Wednesday. I inform you of this because it may be of importance to the situation.

    We've decided that anything is better than what the customer has currently, and have arrived at the decision to use a self-leveling epoxy, which is what brings me here asking for your guidance.

    My concern is the temperature. It is currently 28* and expected to be 20* by midnight, with a high of 36* tomorrow (Thursday).

    We will be using Kaufman SurePoxy 117: http://www.kaufmanproducts.net/pdf_f...Poxy%20117.pdf

    We'll have the area we are working with tented and run heaters, however the machine weighs in around a million pounds, so I have doubts that our tent and a salamander is going to provide any appreciable change in temperature, and the plate and the what used to be machined surface will be warmed with torches to both clean and warm them.

    Friday will provide us with an estimated high of 43*.

    If we pour this epoxy tomorrow with these temperatures, will there be a considerable difference as if it were poured Friday?

    It is a horizontal surface, the epoxy will be poured roughly at least an 1/8" - 1/4", and the pieces are all hy-torqued tightly together.

    There is at least one known upside to this situation, whereas the pot-life sure is a lot longer in the cold.

    Yes, I understand that I could call the manufacturer, however it is 1030p and frankly I trust the wisdom of these members.

    Thanks a lot and have a fun rest of your day,

    Phil T. Brun

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    Quote Originally Posted by Farmer Phil View Post
    My concern is the temperature. It is currently 28* and expected to be 20* by midnight, with a high of 36* tomorrow (Thursday).
    According to the boatbuilding guys, not a chance. You might pm Trboatworks here for a better rundown.

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    If there's any geometric relationship between these two elements that has to be met, there's a good chance that simply adding epoxy to the interface does nothing. I'd expect both surfaces to be worn, one concave and one convex (or variations of that).

    So leveling one side (with a mechanically weak material), then reattaching the other to it sounds iffy, unless there' no need to be at right angles, or whatever it was designed to be.

    I'd look at why the fasteners loosen, why they don't retighten them, and whether changes can be made to improve the structure. It just sounds like a kludge fix, even if it's the best that can be done right now.

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    Quote Originally Posted by Milland View Post
    If there's any geometric relationship between these two elements that has to be met, there's a good chance that simply adding epoxy to the interface does nothing. I'd expect both surfaces to be worn, one concave and one convex (or variations of that).

    So leveling one side (with a mechanically weak material), then reattaching the other to it sounds iffy, unless there' no need to be at right angles, or whatever it was designed to be.

    I'd look at why the fasteners loosen, why they don't retighten them, and whether changes can be made to improve the structure. It just sounds like a kludge fix, even if it's the best that can be done right now.
    A new plate has been made and the bearing housing is flat, so only the machine has a worn surface.

    In regards to why the bolts loosen, the machine beats itself to death, bolts becoming loose is just part of the process which is why retorquing is protocol after 12 hours. Why they do not do it? Cannot answer that. I think it is because it is easier not to for the guys having to do it.

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    +1 to Milland. A properly designed bolted joint really shouldn't loosen -- especially every 12 hours. I'm struggling to think of any bit of machinery where "re-torque the bolts every 12 hours" is a sign of proper engineering.

    Sounds like the bolt size and/or tensile strength of the bolt and compressive strength of the mating faces really isn't up to the job?

    As for the epoxy -- don't know that particular one. However, I'd think you'd need to blanket the entire machine near that joint with surface mount resistance heaters set to maybe as much as 180F and get at least room temperature in the joint. The salamander heater is likely going to have moisture condensing everywhere. And I can't imagine someone playing a torch over the metal for a day or so the best epoxies like to cure -- without introducing hot spots and stress.

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    Quote Originally Posted by Farmer Phil View Post
    A new plate has been made and the bearing housing is flat, so only the machine has a worn surface.

    In regards to why the bolts loosen, the machine beats itself to death, bolts becoming loose is just part of the process which is why retorquing is protocol after 12 hours. Why they do not do it? Cannot answer that. I think it is because it is easier not to for the guys having to do it.
    It sounds like they can't tighten the bolts enough, therefore they never reach the tensile stress that allows them to clamp correctly. Or, as noted above, that the joint is underdesigned and may require "magic" to fix.

    If the bolts are large in diameter but short, they may never stretch correctly to give a reliable clamp load. Sometimes collars can be added to allow use of a longer bolt. If the bolts can't be tightened due to access and available tools, then bite the bullet and get the right powered wrenches or gear multipliers in place to apply the correct torque.

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    I am aware (very much so) of customer confidentiality concerns but we need a better description of the application. If you can's show pix then at least what is this machine and what does it do? There might be a half dozen guys here who have solved the same problem but no one can tell from your description.

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    This fastener concept was used for the main connections on the vertical mole we used to drill the visitors shaft at Hoover. Extreme vibration. We drilled about 600 ft and only had to "retighten" once. I realize it isn't exactly what you have ask about but your problem sounds expensive and repetitive. Is there a way that this concept could be adapted for use on the equipment mounts. I believe you could achieve better control of the clamping force and, if necessary, the time required to "tighten" could be reduced to where it could actually occur.

    SES' Hydraulic Bolt Tensioning Tool - YouTube

    Thank you,
    Mr.Smith

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    Or look into using Superbolts (which are frequently actually nuts):

    Superbolt™ Multi-Jackbolt Tensioners - YouTube

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    Quote Originally Posted by Farmer Phil View Post
    Hello members. This is my first post but I'll keep the introduction to a minimum due to time constraints. My name is Phil, I am a job-shop machinist and millwright with W. R. Martin in Louisville, Kentucky.

    We have a particular project at one of our customers in which a horizontal machined surface on the base of a large industrial machine has placed upon it a machined plate which then has a bearing housing placed upon it and then they are held tightly together with bolts.

    The customer does not keep these bolts tight. Protocol is to hy-torque the bolts after every 12 hours--this is never done and frankly I don't blame them because it is a pain to do--however failing to do so allows them to loosen and then debris is introduced between the machine base and the plates the bearing housings sit upon and it now looks like an ant farm. We are in one of those situations in which what is truly best for the customer would be to build-up the surface with weld and then bring in our portable mill and machine it but they do not want the downtime or the cost.

    They were going to set the shaft and bearings on Friday, however we were able to get them to concede to letting the project go until this coming Wednesday. I inform you of this because it may be of importance to the situation.

    We've decided that anything is better than what the customer has currently, and have arrived at the decision to use a self-leveling epoxy, which is what brings me here asking for your guidance.

    My concern is the temperature. It is currently 28* and expected to be 20* by midnight, with a high of 36* tomorrow (Thursday).

    We will be using Kaufman SurePoxy 117: http://www.kaufmanproducts.net/pdf_f...Poxy%20117.pdf

    We'll have the area we are working with tented and run heaters, however the machine weighs in around a million pounds, so I have doubts that our tent and a salamander is going to provide any appreciable change in temperature, and the plate and the what used to be machined surface will be warmed with torches to both clean and warm them.

    Friday will provide us with an estimated high of 43*.

    If we pour this epoxy tomorrow with these temperatures, will there be a considerable difference as if it were poured Friday?

    It is a horizontal surface, the epoxy will be poured roughly at least an 1/8" - 1/4", and the pieces are all hy-torqued tightly together.

    There is at least one known upside to this situation, whereas the pot-life sure is a lot longer in the cold.

    Yes, I understand that I could call the manufacturer, however it is 1030p and frankly I trust the wisdom of these members.

    Thanks a lot and have a fun rest of your day,

    Phil T. Brun
    Given your epoxy datasheet specifies temperatures 60-95 F, I'd say that product may not perform as expected and the manufacturer would likely agree.
    Epoxies don't set up well when cold and if temperatures are cold for too long, the components separate and prevent proper reaction- this is an issue in gluing wood, maybe less so in metal.
    I use WEST epoxy for gluing wood and routinely test. Below 10 C (about 50F) full strength and hardness takes 4-6 x longer to achieve and are slightly less at 10 days than a joint glued at 20* C (68F)
    If you can get temperatures up into the recommended range by supplementary heating and keep them there until full cure is achieved, the properties should be as described. Metal has a lot of thermal inertia so it may not be easy.
    Maybe a moisture cure polyurethane product?

    WRT the bolts that require retorquing- are they slackening by unwinding or stretching?

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    How long are the bolts?, it may be possible to fit 2-3x longer bolts with a spacer to allow the bolts to stretch more before achieving full torque and make unscrewing less likely. Kind of like cylinder head bolts on an engine.

    With regard to the epoxy it sounds like you'll need to apply some gentle heat from a hot air gun or high wattage halogen work lights to keep it warm. Some epoxies are actually much stronger when cured at warmer temps ~60 deg C.

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    Quote Originally Posted by Milland View Post
    Or look into using Superbolts (which are frequently actually nuts):

    Superbolt™ Multi-Jackbolt Tensioners - YouTube
    We've actually purchase these earlier this week to install!

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    Guys, thank you very much for taking a moment to reply.

    I'm in one of those situations where I'm confident that something is not going to go wrong with the epoxy, but had a small bit of hope in my gut heart that one of you would say, "by all means I do it all the time..."

    Being that warmer is better, I'm at least going to try to hold this off until tomorrow.

    In regards to the bolted joint and it's design, I understand that it typically should not need to tightened after once set, however that is not the case.

    This author has to run out to get to the stress inducing job site. An update will be provided if you desire.

    Thanks again and have a fun day!

    Phil

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    I don’t try for epoxy cures below 50^0 F for generic pot mix resins.
    Epoxies are one of those things where chemists can design in all sorts of cure parameters- a call to a supply house might land you in a better fit to your application.
    Even at reasonable but lowish temperatures the cure stages extend way out.
    The resin might be sort of playdough hard for two or three days and still have no real strength after a week.

    But epoxy!?
    Why?
    Are you just looking for a gap filler to keep debris out?
    Generic pure epoxy resin is quite brittle.
    If I am understanding your approach it seems to be the epoxy gasket will get shattered in short time and be of no use.
    Aren’t there much better gap filling compounds?

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    general advice regarding epoxies, broadly speaking they require heat to cure, room temperature cure stuff has catalysts in it that help the reaction to start and since it is exothermic it may provide enough heat by curing to finish the reaction, but these catalysts take up space in the glue, so the performance of the room temperature cure product is already compromised when compared to oven cured stuff, and if you do decide to use that product, give the manufacturer a call and ask if it will actually start to react at temperatures that low, and it will take a lot of time for the reaction to finish before the machine would be ready to do work again, if you start to use it before it cures, it will most likely damage the matrix of the epoxy and it will have no structural strength at all - be totally useless

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    Quote Originally Posted by Trboatworks View Post
    Aren’t there much better gap filling compounds?
    If there are, I'm at the right place to find out.

    We know how to repair correctly. This is a moment where a gun is to your head and just right solution but wrong time.

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    Quote Originally Posted by Farmer Phil View Post
    A new plate has been made and the bearing housing is flat, so only the machine has a worn surface.

    In regards to why the bolts loosen, the machine beats itself to death, bolts becoming loose is just part of the process which is why retorquing is protocol after 12 hours. Why they do not do it? Cannot answer that. I think it is because it is easier not to for the guys having to do it.
    There are many examples of high vibration machinery since the dawn of the wheel.

    Looks at a forge hammer or a air jack hammer.

    they use extra long bolts with very heavy springs.

    Also look into using longer bolts, with hardened spacers for more
    bolt stretch.

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    Quote Originally Posted by digger doug View Post
    Also look into using longer bolts, with hardened spacers for more
    bolt stretch.
    Very valid points are made and I cannot take a stance against any of them.

    Once we are able to have a somewhat flat surface then we can/will address the bolting.

    I think maybe we don't do anything at the moment to address the surface, bolt it down, let it run and deal with the bearings until it is warm enough and we can have seven days time for this stuff to work.

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    What is the machine in question ?

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    It is a shredder.


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