×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

"Hydraulically actuated mechanical tensioners"

"Hydraulically actuated mechanical tensioners"

"Hydraulically actuated mechanical tensioners"

(OP)
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!

RE: "Hydraulically actuated mechanical tensioners"

Quote:

(our questions) were we met with blank expressions, and mummbled choruses of, "we will get back to you after consulting the design boys"

That would've been my first clue to (1) show them the door and stop wasting my time, and (2) were I sufficiently interested, to speak directly with the design engineers.

As a rule, I refuse to spend more than 5-10 minutes with sales guys unless they provide a direct contact to their engineers.

Time spent with non-technical sales folks is generally a waste.

--------------------
Bring back the HP-15
www.hp15c.org
--------------------

RE: "Hydraulically actuated mechanical tensioners"

(OP)
So true, and usualy I would, but this is being marketed by a reputable manufacturer, we were promissed all the answers to our questions by the time the stuff arrived, I guess I was over anctious to try out some new technology, uh, guess i wont be that rash again.
The thing that worries me most in this though is the fact that a reputable manufacturer is making such claims! is it an act of desperation to break into a market that they dont really know, or are they really convinced they have an answer? even though it is wrong?
I see now that two other companies usualy associated with tensioning work have fallen to the big corporate take over, quite frankly all I can see is our options are getting smaller, because I cant see how two companies that were locked in competition over thirty years can all of a sudden start working together? and which product do we buy? which will remain on the market?? Hydratight Sweeney, or Hedley Purvis?? from what I can see now, where I had three choices to chose my tensioning requirements from, I now have none, Ive had dealings with the company responsible for buying out these two stalwarts in the tensioning business, with hydraulic cylinders and pumps, and again, I wouldnt trust these people as far as i could spit them, again the engineers are at the mercy of the salesman!

RE: "Hydraulically actuated mechanical tensioners"

We have several of these folk’s tensioners,  some were demonstrated by John Biach himself and have never had the problems you mention.  Biach was the first I ever saw and used.      

http://www.biach.com/Home/home.html

RE: "Hydraulically actuated mechanical tensioners"

(OP)
unclesyd, those are not the ones I am fuming about, I know of the biach product, never used it so cant comment on it, the ones I am talking about are the Hytorc answer to normal hydraulic bolt tensioning, I dont have a weblink for you to look at, basically ive trashed all the information i ever got from that company in frustration.
but thanks for the comment and the link, its good reference for future work.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources