zepp
Industrial
- Mar 8, 2004
- 12
I dont know if any of you guys have come accross this new "revolution in bolting" as it is being marketed,
Basically after one application, I can confidently state that we will never be taken in by such a sales pitch again.
basicaly the claims made that
(1) 50% tool coverage was gone: this turned out to be true, 100% coverage is required, and has to be left in place!
(2) dedicated hydraulic tensioners is gone:how true, god forbid should you ever require to unfasten again!
(3) Manual nut turning and seeting is gone: untrue, you still have to manualy apply this method, and if the threads stick or sieze, god help you, because you can only remove them by cutting the bolt!
(4) Transfer bolt relaxation is gone: an unproven factor that the manufacturer has been unwilling to supply data for!
(5) Measuring bolt elongation is gone: not true, after we finaly got this unit together, we realised that we had no idea what load we had just put into the bolts, so we ended up with an educated guess, and fingers crossed!
Never have i worked with such uncertanties before, and all of these come to light after purchasing the equipment from the manufacturer,
As oposed to the normal bolt tensioning methods in which we had a good idea of where we were, we were convinced by the salesman that this new so called revolution would actualy give us 100% accuracy, and like the ever hopeful fool, I bit the bullet, it was only when applying these over expensive NUTS! that we began to run into problems and suspect that the manufacturer simply had no idea of what he was marketing, when we asked about the effects of lubrication on the "tensioning nut" in relation to the torque we should apply, were we met with blank expressions, and mummbled choruses of, "we will get back to you after consulting the design boys"
We also had problems in running these nuts down on the threads of the studs, when asked about the thread tolerance, we were advised that it was standard, with no further assistance, after six of the twenty four units siezed onto the stud bolt before actualy seating, the response was "well thats never happened before! perhaps you should consult with the manufacturer of the stud bolts"
In the end we decided to carry out our own tests, and i recomend that anyone using this system does exactly the same, as it will prevent future heart ache.
we ran one unit up as supplied on two pieces of machined plate, we also ran one up with a splashing of 32 grade oil, and then we ran one up with molycote smeared onto the surfaces, I dont think I have to say that we had three different extensions of the same bolt, and the other thing we found out was that although it says no need to worry about clearence heights, you had better check all the same, the size of the tensioning unit that is left in place is not all that you need to worry about, the size of the hydraulic wrench required to drive it is the main concern! luckily with our tests, we had already determined that with using molycote, we could get away with a smaller wrench.
Unfortunately, the other thing we found out was that after relaxation had taken place (which is claimed not to happen) we could not use the same wrench to remove the units, we had to go up two sizes, so as you can guess, where the interference was too much, the hot spanner was used and we cut the units off, and resoted to normal tensioners.
A cautionary word of warning when trying new technology, make sure you have seen it work before you buy it!
Basically after one application, I can confidently state that we will never be taken in by such a sales pitch again.
basicaly the claims made that
(1) 50% tool coverage was gone: this turned out to be true, 100% coverage is required, and has to be left in place!
(2) dedicated hydraulic tensioners is gone:how true, god forbid should you ever require to unfasten again!
(3) Manual nut turning and seeting is gone: untrue, you still have to manualy apply this method, and if the threads stick or sieze, god help you, because you can only remove them by cutting the bolt!
(4) Transfer bolt relaxation is gone: an unproven factor that the manufacturer has been unwilling to supply data for!
(5) Measuring bolt elongation is gone: not true, after we finaly got this unit together, we realised that we had no idea what load we had just put into the bolts, so we ended up with an educated guess, and fingers crossed!
Never have i worked with such uncertanties before, and all of these come to light after purchasing the equipment from the manufacturer,
As oposed to the normal bolt tensioning methods in which we had a good idea of where we were, we were convinced by the salesman that this new so called revolution would actualy give us 100% accuracy, and like the ever hopeful fool, I bit the bullet, it was only when applying these over expensive NUTS! that we began to run into problems and suspect that the manufacturer simply had no idea of what he was marketing, when we asked about the effects of lubrication on the "tensioning nut" in relation to the torque we should apply, were we met with blank expressions, and mummbled choruses of, "we will get back to you after consulting the design boys"
We also had problems in running these nuts down on the threads of the studs, when asked about the thread tolerance, we were advised that it was standard, with no further assistance, after six of the twenty four units siezed onto the stud bolt before actualy seating, the response was "well thats never happened before! perhaps you should consult with the manufacturer of the stud bolts"
In the end we decided to carry out our own tests, and i recomend that anyone using this system does exactly the same, as it will prevent future heart ache.
we ran one unit up as supplied on two pieces of machined plate, we also ran one up with a splashing of 32 grade oil, and then we ran one up with molycote smeared onto the surfaces, I dont think I have to say that we had three different extensions of the same bolt, and the other thing we found out was that although it says no need to worry about clearence heights, you had better check all the same, the size of the tensioning unit that is left in place is not all that you need to worry about, the size of the hydraulic wrench required to drive it is the main concern! luckily with our tests, we had already determined that with using molycote, we could get away with a smaller wrench.
Unfortunately, the other thing we found out was that after relaxation had taken place (which is claimed not to happen) we could not use the same wrench to remove the units, we had to go up two sizes, so as you can guess, where the interference was too much, the hot spanner was used and we cut the units off, and resoted to normal tensioners.
A cautionary word of warning when trying new technology, make sure you have seen it work before you buy it!
