McElroy Discussion Forums

Hi,

We are using PE Heat Fusion procedures that are somewhat similar to the following procedures:

http://www.performancepipe.com/en-us/Do ... edures.pdf

I'd be grateful if someone could help me with the following questions:

a) Regarding all procedures, how much variation from the stated values might be allowed? E.g. during socket fusion of 1-1/4" dia pipe/fitting, if heating is performed for 32 s instead of 24-29 s, would it be allowed? What about 40 s? Is there a general rule to determine the amount of variation permissible?

b) Regarding butt fusion, it is stated that heating should be done until the stated time elapses OR melt bead of certain size has formed. If we were to focus on size of melt bead, wouldn't the stated time be insignificant? Again, how much variation from stated time might be allowed - e.g. if recommended heating time for 2" pipe is 16-19 s, but the specified melt bead size is obtained at 45 s would it still be acceptable?

c) Regarding saddle fusion, what is the difference between utility cloth, emery cloth, garnet cloth and sandpaper? Can sandpaper be used for roughening pipe surface prior to performing saddle fusion?

d) Regarding socket fusion, is there supposed to be a gap between the pipe end (including internal melt bead) and the middle portion of socket? In link #1, pg. 5 (below), there seems to be a significant gap. However, in link #2, pg. 26 (below), the gap appears to be very narrow. The picture in first link, however, is not very clear. I was wondering whether there is any specification regarding this gap in the relevant standard(s)? If there is no such specification, how would you know whether the gap is there because of the design of the socket or because depth gauge was not used?

Link #1: http://www.performancepipe.com/en-us/Do ... edures.pdf

Link #2: http://www.performancepipe.com/en-us/Do ... edures.pdf

e) Is mechanical testing (bend-back test etc.) of PE heat fusion joints necessary for personnel qualification as well or only for procedure qualification?

Hello,

I hope to help with some of your questions. Remember that there are many different fusion standards but when using one in particular, like this PLEXCO bulletin pertaining to 2406 gas pipe that you have listed, the steps must be followed precisely to conform to those parameters.

a) For socket fusion, the times listed in this bulletin have been tested and found to be optimal by PLEXCO. It is generally not recommended to go outside of those times. There is a range to allow for adjustments to be made, if needed, but try not to exceed those time.

b) According to this PLEXCO bulletin, you adhere to the time recommended and it is your final bead size after the fusion that is measured. This is not always the case but that is what this bulletin calls out.

c) Utility cloth is the only one recommended by this bulletin. Usually, you will find that saddle fittings come with a 50-60 grit utility cloth in each package. You would not want to use sandpaper as the particles will transfer to the pipe and fitting much easier, due to the design of sandpaper, and this can create a potential for contamination.

d) The two pieces of pipe should not touch one another within the fitting and it is acceptable for there to be a gap between the two pieces of pipe as they come together inside the fitting. If there is a large gap between the pipe ends within the fitting, there could be a stab depth issue. Here are some other tips for identify if the fusion is done correctly: The melt pattern for socket fusion is primarily inspected on the outside of the pipe. First, on the exterior of the pipe, look for a complete impression of the rounding clamp in the melt surface. There should be no gaps, voids, or un-bonded areas between the pipe and fitting. On the interior of the pipe, there should be no excess material inside the fitting, as this would be an indication of over melt.

e) Destructive testing, such as bend back tests, can be done in the field to assist in the qualification process but this does not have to be done. The governing body responsible for the qualifications can determine what testing needs to be done. It is generally recommended that operators need to go through a course with a testing procedure and destructively testing the operator's fusions is an option method, as well. There are other ways to destructively test fusions in addition to the bend back test, such as the Guided Side Ben Tester and the In-Field Tensile Tester. Here is a link to learn more about these options:

http://www.mcelroy.com/en/fusion/testingtools.htm

I hope this has been helpful. There is a lot to cover with these different procedures and because there are many written procedures available, I chose to refer to only the one you referenced for these questions. If you are interested in any other standards or any additional information, just let us know.

Sincerely,
Chris Passmore

Dear Chris,

Thanks a lot for the advice. I would like to meet you some day and learn more from you, but acquiring the necessary approvals from my company would take a long time. Until then, I guess the only option is to ask online.

Can you please also clarify the following:

Strictly adhering to heating / fusion times: Does this apply to all 3 procedures (socket, butt and saddle)?
Also, one important thing I would like to know is that as per PLEXCO's procedures (as well as various other procedures I have studied), there is something stated to the effect that those heating / fusion times and possibly some other parameters as well are "guidelines only, exact time depends upon environmental conditions and condition of fusion equipment". In some procedures, there is only a single value for heating / fusion time instead of a range (and the statement above is also mentioned). Considering this, how would you determine the timing on the basis of environmental conditions?

Utility cloth: I am not very clear about what utility cloth means. Is it the same as emery / garnet cloth? Moreover, what does "sandpaper" mean? Does it have a paper-back instead of cloth-back?

Sorry for the delay on replying to your question. This post didn't show up for me and I just happened to open it to look at it.

Generally speaking, yes you should strictly adhere to the heating and fusing times for all fusion types. More specifically, when performing socket fusion to ASTM F2620 and many other standards you will have a heat time range that you will need to be inside of (somewhere in between the minimum and the maximum values), and a specific cool time that serves as a minimum. For butt fusion and saddle fusion you will have various times to heat but you will also be looking for minimum bead size requirements. The bead size is very important. For butt fusion you will have minimum heat times to reach and for saddle fusion you will have maximum heat times only on live mains (to keep from blowing out a pressurized main).

To say all of this another way, it is important to understand what the desired result is and things that can cause problems if you heat too short or too long. We want a properly bonded fusion where the polymer chains are connected throughout the fusion zone so we want to heat long enough to ensure the material is molten. On the other hand, we do not want to heat so long that we blow out a live main doing saddle fusion or restrict the inside of a socket fusion with too much melt. So the various standards give guidelines on times that are as specific or as general as they need to be. If the standard defines a minimum time, then you want to heat or cool at least that amount. If the standard has a maximum time then you want to be sure you do not heat over the maximum. If there is no maximum time then you are generally safe to heat until you know you have proper bead size and cool until you know you've achieved an adequately solid fusion joint.

Emery cloth and utility cloth appear to be very similar if not the same thing. The main difference between them and more common sand paper is the material used as the abrasive and the quality it is applied to the backing. While sandpaper is mostly backed with paper it can be backed by cloth as well. In general, emery / utility cloth is more consistent and has less trouble with the abrasive falling off as you use it.

I hope this helps. Thanks.