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  • well stem / merchant couplings?

    I am in the process of putting together a material list and plans to build a water well rig. One grey area for me is how to couple the drill stem which in my case will be 2" black pipe from Home depot or my local wholesale plumbing supply. I have read that for better strength I should use merchant couplings? Are these straight threads with zero taper? Does this mean the pipe has to be threaded to match or can you use straight coupling with standard threads. I'm guessing not? If not how does one go about cutting those treads? I do have a ridgid manual die set that I think I can get one for 2 inch but... do they make different dies say one for NPT and one for straight? Thanks
    Rick

  • #2
    Re: well stem / merchant couplings?

    I see some good imfo here but still don't know what I'm looking at for sure. Seems like I would want drive couplings? But again the pipe needs to be cut to match??? The well rig will be driven by a high torque hydraulic motor so lots of torque not much downward force like with a driven well. Thanks
    Rick
    http://www.anvilintl.com/ProductSear...roductId=10499

    Comment


    • #3
      Re: well stem / merchant couplings?

      NO expert here,

      the merchant couplings I have used are steel and most of the other are cast,

      on all my windmill drop pipe and any other well drop pipe most all in our area, has used the merchant couplings, and the pipe is standard pipe with tapered threads,

      IN pressure situations the merchant couplings most likely will not seal up as fast or good,

      many times the merchant couplings wil come on one end of a full length of pipe, as a thread protector,

      but electrical conduit at one time and some may still come with straight threads, but most I am aware of is now tapered threads on the end of the pipe even tho most of the fittings are straight,

      and I do think they make a straight thread dies, (I know my 141 threader is said to be able to cut both tapered as well as straight), and this page says they have the straight dies if one would want it,

      I personally do not think you will have any problems with the merchant couplings and the tapered pipe threads, (as far as the straight couplings and the tapered pipe),

      I do not know how much drilling or depth your considering but most commercial drill stem/pipe uses a entirely different type of tapered thread system, even on small water wells rigs,


      my guess is your building some thing on a king-sized "Deep rock rig" probably something like one of the Hydraulic driven units one can get plans off of Ebay for?

      GOOD luck with the project,
      Attached Files
      Push sticks/blocks Save Fingers
      ~~~~~~~~~~~~~~~~~~~
      "The true measure of a man is how he treats someone who can do him absolutely no good."
      attributed to Samuel Johnson
      ~~~~~~~~~~~~~~~~~~~
      PUBLIC NOTICE: Due to recent budget cuts, the rising cost of electricity, gas, and oil...plus the current state of the economy............the light at the end of the tunnel, has been turned off.

      Comment


      • #4
        Re: well stem / merchant couplings?

        Originally posted by BHD View Post
        NO expert here,

        the merchant couplings I have used are steel and most of the other are cast,

        on all my windmill drop pipe and any other well drop pipe most all in our area, has used the merchant couplings, and the pipe is standard pipe with tapered threads,

        IN pressure situations the merchant couplings most likely will not seal up as fast or good,

        many times the merchant couplings wil come on one end of a full length of pipe, as a thread protector,

        but electrical conduit at one time and some may still come with straight threads, but most I am aware of is now tapered threads on the end of the pipe even tho most of the fittings are straight,

        and I do think they make a straight thread dies, (I know my 141 threader is said to be able to cut both tapered as well as straight), and this page says they have the straight dies if one would want it,

        I personally do not think you will have any problems with the merchant couplings and the tapered pipe threads, (as far as the straight couplings and the tapered pipe),

        I do not know how much drilling or depth your considering but most commercial drill stem/pipe uses a entirely different type of tapered thread system, even on small water wells rigs,


        my guess is your building some thing on a king-sized "Deep rock rig" probably something like one of the Hydraulic driven units one can get plans off of Ebay for?

        GOOD luck with the project,
        So just so I am understanding this.. the couplings they have at say Home Depot are NOT merchant couplings?

        Do you have a link for where you got your couplings? I do not want my entire project subject to crap from China!

        Yea I am building a small DIY rig however it will be driven by a 70 hp tratcor with a hydraulic drive so I do need to get the appropriate drill stem. I do not want to get down 80 feet and twist off a coupling!!

        Thanks!
        Rick

        Comment


        • #5
          Re: well stem / merchant couplings?

          Like this??
          http://cgi.ebay.com/2IN-BLACK-MERCHA...item439d68821a

          Comment


          • #6
            Re: well stem / merchant couplings?

            IT is basically my understanding that any straight threaded coupling is basically called a merchant couplings, (I live in a very rural area, and yes we have a good hardware store/wholesale pluming supply), (but to what most on here have access to, would most likely die with laughter on what they carry), but what they carry are the steel merchant couplings and a cast tapered coupler, I am sure other kinds are made but like I the locations I have dealt with most all the steel couplers that are smooth (I have come across very few that are with tapered threads), most all are straight thought threaded, and called merchant couplings,

            the tapered threads will make a difference on how the threads seal, I doubt if there is much difference on strength,

            as far as twisting off, I would guess a lot would depend on the actual power that was rotating the string of pipe, and if there was any give in the system to absorb shock loads, and how fatigued the pipe is, (I would think the failure point would be on the pipe and where the treads end, or where the coupler stops).

            using a heaver schedule of pipe would give some extra protection, I think I would consider it any way,

            look up "CA-21 1 1/2" drill pipe"
            It is my under standing that one can buy the threaded parts to weld on to your own pipe, by some companies.

            these are a few sites I have looked at a few times.

            http://www.drillingfab.com/

            http://www.drill2water.com/drillpipe.html

            but unless you a have number of holes to drill I do not know if one can justify the cost for just a few holes,

            personally I would worry less about the coupling than the end of the pipe where it is threaded, in the first page you listed, beside of the construction of the coupler, I really do not see one is heaver, as the size is the same OD. the drive coupler does weigh more but is longer as well, (from your first link),

            when I started to figure up the costs, and figured If I was to build a rig of some kind I was leaning more to a Cable Tool Rig,
            Push sticks/blocks Save Fingers
            ~~~~~~~~~~~~~~~~~~~
            "The true measure of a man is how he treats someone who can do him absolutely no good."
            attributed to Samuel Johnson
            ~~~~~~~~~~~~~~~~~~~
            PUBLIC NOTICE: Due to recent budget cuts, the rising cost of electricity, gas, and oil...plus the current state of the economy............the light at the end of the tunnel, has been turned off.

            Comment


            • #7
              Re: well stem / merchant couplings?

              I know what you mean about the rural hardware. Rubber boots by the cash register in the spring shot gun shells in the fall. Wood floors that creak but just about anything you might need is in there. nails by the pound too!

              Okay I guess I sort of know what you mean on those couplings. They tend to be a bit longer and smooth. Yes I have seen those weld on ends but good God that gets into some real money. Guess I will have a go at it with the merchant unions and try to be cool on the stem as I go. I suppose I could just weld the next section of pipe on as I go but at some point that would turn out to be a bad idea.
              Thanks
              Rick

              Comment


              • #8
                Re: well stem / merchant couplings?

                Merchant couplings are the throw away couplings which are included with a 21' stick of pipe. They are illegal to use as a coupling in plumbing but have a standard thread like in plumbing. It sounds like what you really need is a drive coupling which is a different thread and is made for driven wells. I have a bunch of 1" stuff sitting in my building in Utah that came with a small DIY well digger I bought years ago and it definitely is a different thread.

                Mark
                "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

                I never lost a cent on the jobs I didn't get!

                Comment


                • #9
                  Re: well stem / merchant couplings?

                  Originally posted by ToUtahNow View Post
                  Merchant couplings are the throw away couplings which are included with a 21' stick of pipe. They are illegal to use as a coupling in plumbing but have a standard thread like in plumbing. It sounds like what you really need is a drive coupling which is a different thread and is made for driven wells. I have a bunch of 1" stuff sitting in my building in Utah that came with a small DIY well digger I bought years ago and it definitely is a different thread.

                  Mark
                  Okay a drive coupling yea for like a well point. I had a guy who owns a well rig company tell me to use merchant couplings. I get the feeling there's a lot of slang in this field ripe for miss-communication. All I know is the China couplings at HD stink. I found out the hard way not to use those in a driven well. I think the idea with the drive couplings is the ends of the pipe butt so the pipe takes the brunt of the hammering not the threads. So perhaps that is what I want in this case as well and as mentioned earlier steel not forged. Or break out 2 grand plus for real drill stem. All this saving me money is really adding up!
                  Thanks for the input
                  Rick

                  Comment


                  • #10
                    Re: well stem / merchant couplings?

                    $28.. made in USA... Steel... gotta be better than the crap at HD. Might be I will sacrifice a nipple and one of these couplings with my rig and see what gives first.

                    http://www1.mscdirect.com/CGI/NNSRIT...MT4NO=80340432

                    Comment


                    • #11
                      Re: well stem / merchant couplings?

                      This may save you a few dollars.

                      http://doitbest.com/Well+pump+suppli...sku-484938.dib

                      It looks like they may be standard pipe threads.

                      Mark
                      "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

                      I never lost a cent on the jobs I didn't get!

                      Comment


                      • #12
                        Re: well stem / merchant couplings?

                        How much experience do you have in water well?
                        Buy cheap, buy twice.

                        Comment


                        • #13
                          Re: well stem / merchant couplings?

                          The well "rigs" they use for drilling here run about $500,000 new.

                          J.C.

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