Use of Dresser Couplings

[eml]

I work in a refinery ~ 50 years old and the original owner used many Dresser couplings mostly near the piping connection to an atm storage tank however we have also seen them used on underground piping near valve pits. My guess (or hope) is that they were popular to use for misalignment not that they were looked at as a inexpensive alternative to minor expansion joints. Does anyone have a historical perspective on why they were so popular?

 

[rconner]

You could probably get better answers from the company you name, that may have a history going back a hundred years or so, or maybe also numerous other companies such as Rockwell/Smith-Blair, Romac, Ford, JCM, Victaulic/Brico etc. or many other international folks that I believe may presently also market couplings very similar in principal to those made by Dresser for much of the last century. I guess they might say that unlike welded joints the couplings can of course basically be assembled rather quickly with simple small wrenches, in virtually any weather or conditions, and of course maybe also without as much need for welding equipment or expertise etc. Also unlike welded joints, the couplings are capable of providing some significant level of deflection, or corrections to alignment etc. (in the case of imperfect surveying or construction etc.), and even after assembly due to settlement or seismic etc., essentially without bending or imparting bending stress or heat to pipes/linings/coatings etc. It is even possible some serviceable joints might perhaps be made with lesser specific control of radial alignment between pipe ends than is necessary for the best quality welds. I even suspect well-assembled coupling joints might even allow some level of axial movement, or rebating axial movement, between pipe ends, though I would think this could be some limited (in magnitude/cycles etc.) due to the still rather labor intensive and labor-reliant as well as highly confined nature of the stuffing-box seal and pipe end surface conditions etc., again without stressing the pipes.

Some of these same features that make the couplings desirable might arguably also be detriments in some applications, particularly when the joining concepts and limitations are not well understood. For example, such stuffing-box couplings in and of themselves, unlike a weld, are not restrained joints, and if the pipes are subjected to forces attempting to overdeflect or pull the joints apart, there is nothing in the coupling itself that will prevent this (supplementary restraint can however be provided with rods/harnesses etc.)
Likewise, the couplings normally employ some sort of rubber or elastomeric seal with perhaps far different properties (including heat, hydrocarbon from inside or ouside the joint, or other resistances etc.?) than the normal steel of some process piping etc. Again, if not well understood, and particularly when not judiciously chosen and assembled properly for the exposures, this can eventually result in problems.
Finally, although not requiring a skilled welder the bolting of the couplings is however some labor-intensive and reliant, and may in larger sizes require proper lubrication and several even, circumnavigations of tightening around the joints to appropriate torque levels. If this sometimes hard work, particularly in larger pipe sizes that have a great many bolts, is not completed with adequate knowledge and diligence, problems(leaks) can also result. Of course, however, there can be various problems with fused or welded joints as well!
Maybe this brief discussion will at least provoke more detailed and/or learned responses.

 

[oldestguy]

Are these used on pvc pipe, say for local shared well water distribution? Probably 1-1/4" to 2" size?

there is a job near here where it appears the line is leaking and some form of non-threaded or non glued joint was used.

comments?

 

[dicksewerrat]

Almost every plumber and excavating contractor has used a Dresser coupling. /they are very forgiving on alignment and connecting dissimilar materials,( pvc to G.I.)

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[oldestguy]

In backfilling a trench, have you seen a case where the joint opened up due to backfill dragging the pipe? the leaking line is just recently installed and it didn't have a pressure test.

I've seen gas pipes open up, but partly due to cold weather shrinkage and partly due to some digging damage to an existing gas line. But these were steel. I understand plastic has a much higher temp coef. of linear change. I'd guess the grip of the coupling is pretty slight also.
Comments?

 

[rconner]

There could be many reasons for a "stuffing-box" coupling leak; however, I would think any such couplings and particularly with short laying length (at least when used unrestrained or without restraint features) might be especially problematic in plastic pipe systems. If/when a pipeline is installed in warm conditions (sunlight), then backfilled and/or charged with cold water for a cooler environment, there is considerable tendency for axial shrinkage that might not be resisted entirely by any earth backfill. The axial shrinkage can be on the order of 15-20 times that observed in common metal pipe. If plastic pipes are installed by pulling into place, there can be even greater (compound) tendency toward axial shrinkage, due to a sort of "recoil" or memory behavior. You may wish to obtain the applicable coefficients and make some assumptions in your specific conditions, to guesstimate effects.

Then again, I guess there is also the chance of a piece of pipe being inadvertently hooked by a backhoe, or snagged by a moving trenchbox, in process of installation!

 

[mizzoueng]

Dresser couplings were and still are used for misalignment in long underground runs.

They are also used to get small bends in underground piping without actually having to calculate and order an elbow. Dressers can give you up to 3-5 degrees of flex (can't remember exactly, check their website) which over long distances can be a lot of movement.

The most common used coupling is the Style 38, but check their catalog and if you can check the existing coupling for the style.

Remember these are not "expansion" joints. They will give you no linear expansion, but you may be able to get about 2" of total compression. This compression will limit your angular deflection though. Most of these couplings are held into place by a backing ring and a gasket. You can get ones that require a welded clip ring like those commonly found on DI pipe.

There is the chance that the pipe will pull out. It really doesn't take much, you are just overcoming the friction of the backing ring and the gasket. A backhoe or a good 6" ground compaction can pull the pipe.

If you need an actual linear expansion joint, Dresser makes one, I think its the Style 68.

 

[crjones]

They were also very popular in plant air compressors. They used to come with only a solid sealing ring or you could sacrifice some sealing and have a gripper inserted. They were used for minor mis-alignments of piping. Some applications needed a restraining strap to stop pipe separation.