McElroy Discussion Forums

McElroy Fusion Discussion
It is currently October 27th, 2020, 6:59 pm

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 8 posts ] 
Author Message
 Post subject: system drag
PostPosted: January 30th, 2013, 1:44 pm 
Offline
New Member

Joined: October 14th, 2009, 1:31 pm
Posts: 10
what is the default or minimum drag pressure on the McElroy hydraulic fusion machines?


Top
 Profile  
 
 Post subject: Re: system drag
PostPosted: January 30th, 2013, 6:04 pm 
Offline
New Member

Joined: August 5th, 2010, 10:09 am
Posts: 16
I was told 30psi is what it takes to overcome the drag created by the seals of the cylinders. Somebody may correct me if I'm wrong but, that's what I remember


Top
 Profile  
 
 Post subject: Re: system drag
PostPosted: January 31st, 2013, 9:40 am 
Offline
New Member

Joined: October 14th, 2009, 1:31 pm
Posts: 10
hmm... :lol: 3 different cylinder choices...HF-MF-LF..cannot be 30psi for all.

Make me believe...any takers? :mrgreen:


Top
 Profile  
 
 Post subject: Re: system drag
PostPosted: January 31st, 2013, 11:11 am 
Drag will vary based on many possible factors. Here are a few.

Age and wear on machine

alignment of pipe stand

Cylinder selection. Different cylinders require different pressures to do the same amount of work. For example, a 28 low force (yellow cylinders) will generally have a drag value around 70.

We teach to measure drag. There is not a drag value that will work in all situations.

Here is how to do it:
Drag pressure is the minimum measured gauge pressure required to move the carriage with the pipe loaded.
With pipe installed in the machine, move the carriage so that the pipe ends are about 2” apart.
Shift selector valve to the Heating position and set the pressure as low as possible.
Move the carriage valve to the left.
If the carriage is not moving, increase the pressure on the heating pressure reducing valve until the carriage starts moving.
Back the pressure off until the carriage is barely moving. This is the drag pressure.

This is an animation that shows the process.
http://www.mcelroy.com/fusion/animations/drag.htm


Top
  
 
 Post subject: Re: system drag
PostPosted: January 31st, 2013, 8:06 pm 
Offline
New Member

Joined: October 14th, 2009, 1:31 pm
Posts: 10
then what does a 28 HF " generally " have for a drag value?

why do dataloggers default to 30psi regardless of machine selected?

:idea: last one :wink:
3 new 412 machines 1 ea flavor, HF MF LF no pipe in carriage, what would the "general " drag value be for each?

someone in engineering must have this already.


Top
 Profile  
 
 Post subject: Re: system drag
PostPosted: February 1st, 2013, 2:26 pm 
Offline
Senior Member

Joined: June 17th, 2007, 12:23 am
Posts: 125
Location: Brisbane, Australia
It sounds like you’re a very well trained operator of fusion equipment. The best way to answer this is there will be that there is no number that will fit all units. There would be no number that will aways work with even the same unit over its life. The fact of the matter is that this is a number that has too many variables that control it. the ambient temptaure, how it is being used, age of the machine, past maintenance preformed along with many other items where one alone may not make a measured difference but when combined make almost impossible to have a “one size fits all” drag number. The 30 PSI found on the DLs is nothing more than a sound baseline that if it were left at 0 then there would be lots of people using 0 as drag and this could be a concern. I would agree that reading drag pressures on every weld is to be part of a proper welding procedure and Josh has provided the link above on how this is to be done on McElroy equipment. I would also suggest that you confirm the procedure you are using noting that the IFP has in fact a spread where 74PSI is just the number that falls in the middle. If you were to change this by a few PSI this would affect the gauge pressure more than a drag pressure of a few PSIs. but if Josh sees this in a different light then,,,,,,,


Top
 Profile  
 
 Post subject: Re: system drag
PostPosted: February 1st, 2013, 2:27 pm 
Offline
Senior Member

Joined: June 17th, 2007, 12:23 am
Posts: 125
Location: Brisbane, Australia
,,, IFP was to read 75PSI. :mrgreen: fat fingers and all


Top
 Profile  
 
 Post subject: Re: system drag
PostPosted: February 1st, 2013, 3:21 pm 
Well put Dave.

Here are the answers to the questions.


then what does a 28 HF " generally " have for a drag value?
Usually 25 or so. The pr valve won't go any lower.

why do dataloggers default to 30psi regardless of machine selected?
It is a feature designed to speed up the data entry process. Many machines will move a single piece of pipe with only 30 psi applied. Dave is correct that if we defaulted to zero, many people would just use that.


last one
3 new 412 machines 1 ea flavor, HF MF LF no pipe in carriage, what would the "general " drag value be for each?
someone in engineering must have this already.

We actually don't. We have a drag pressure maximum as that would indicate that there is an issue with the carriage. Here is what we have for our QA people to check in our Quality Assurance Final Checklist for the T412:

The drag pressure is within tolerance [HF] [50 PSI max] [MF] [50 PSI max] [LF] [100 PSI max]

To me, this question is similar to what is the mortgage rate? A quick google search tells me that the prime is 3.25. Does that number tell me what my mortgage rate would be if I run out and buy a house? Not so much. One should always check with their lender. But if I were told my rate would be 8% I would suspect there was an issue.


Top
  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 8 posts ] 

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group