1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Pump Tube Removal and NRV Rework

Discussion in 'Fettlers Master Class' started by exeter_yak, Oct 5, 2007.

  1. exeter_yak

    exeter_yak United States Subscriber

    Offline
    Joined:
    Mar 3, 2006
    Messages:
    429
    Location:
    Ayer, Massachusetts
    Greetings,

    I've just completed this tutorial for Doc Mark and sent it along, so thought maybe others could benefit as well.

    A Campingo 2 burner stove was disassembled expressly to obtain photos of the process, and then re-assembled. Following is the document. Copies in pdf are available if you PM me with an email address. You will need ability to receive 1 meg files to your email account.

    Pump Tube Removal and NRV Rework - Doug Weise 9/29/07

    Preliminary Notes:

    1. This document shows my procedure for removing a stuck NRV without damage. My normal removal method is to clamp a T-bar type NRV removal tool to a workbench using a piece of softwood over the T handle. This allows use of both hands on the stove tank and gives maximum torque transfer. I push the tank towards the socket tool, and I can feel when the tool is perfectly aligned. With this method you could effectively twist the heads off the NRVs. At the least sign of trouble with stuck NRVs however, I use the following procedure because it is easy, I prefer to get a first hand review of all the pump system components and prefer that they are clean and in perfect operational order like when the stove was new.

    2. The keys to successful pump tube removal and reinstallation are cleaning and inspection.

    3. I used a damp rag on the Campingo used as a demo for this procedure. The rear outlet fitting on the tank that feeds the fuel tubes to the burners is silver brazed so the rag is not really necessary to keep it from melting, and the tank halves may be silver brazed as well, so the rag mostly serves as an insulating handle and keeps you from getting burned. On a typical Swedish model stove with pot legs or pot leg sockets, the damp rag will also prevent solder melting on those connections and any others that are soldered with lead tin solder. I don't fill my stoves with water.

    4. I left the rear cover on the NRV to demonstrate the damage that will occur, but you should remove it (with a screwdriver that fits the slot in it perfectly in order to get effective torque without damage). Remove the NRV cover as soon as the pump tube has been removed and has cooled which saves the NRV spring from heat damage. I am set up to make the springs, and have documented how others can make them in another procedure.

    5. I highly recommend the TS 4000 torch by Bernzomatic. The object of the soldering game is to get the heat into the part, do the work, and get out. A miniature torch is an aggravation and can't keep up with heat being conducted away from the place where you are trying to melt solder. This work requires free hands at different stages of the work, so having a torch that goes out as soon as you take your finger off the trigger and lights as soon as you pull the trigger is extremely effective. It is also effective for plumbing work. Any torch will work.

    6. Some people don't have a small portable vise like the one shown. There are some nice ones on ebay offered by seller 800watt and others. These are China made and have a V groove on the horizontal, and on the vertical. These vises are indispensable and work for holding a pump shaft, holding the pump leather back nut, holding the NRV head, and a lot of other jobs for stove work and other applications. The 2 inch vise is $19.99 and the 3 inch is $24.99 starting bid. The 3 inch is shown below. It is money well spent in my opinion, and a US made version would be well over $100.

    3inchvise.jpg

    Pump Tube Removal and NRV Rework - Doug Weise 9/29/07

    The subject tank is from an Optimus Campingo 2 burner stove. At the least, the area around the pump tube should be cleaned to avoid ingress of contaminates into the solder joint. The tank should be drained of fuel and cleaned with soap and water. One half of the subject tank has been cleaned to demonstrate citric acid cleaning. A paste was made with a small amount of water with a 1/2 teaspoon of citric acid crystals and 1/8 teaspoon of powder type wallpaper paste. The paste was applied for an hour and then rinsed with dish soap and water, and mildly scrubbed with dish soap and an old toothbrush.
    P9240032B.jpg

    You can sand a tank after cleaning if a fine enough grit sandpaper is used. In this example, 600 grit wet or dry sandpaper was used to remove remaining corrosion, with water and a drop of dish soap, and was followed by 1000 grit wet or dry sandpaper also used wet to remove the 600 grit scratch marks.
    P9240033B.jpg

    To remove the pump tube you will need a damp rag to be used as a heat sink to safeguard other solder joints. The removal is much easier with a puller tool, which uses a pump lid silver brazed to a shaft, with a handle that is heat proof, such as phenolic or wood. I make mine with phenolic rod. Phenolic handles can be purchased from McMaster Carr Supply or Lee Valley Tools, and a 1/4 -20 bolt can be used to thread into them with a tank lid brazed onto the head end of the bolt. An old modified screwdriver handle and shaft can also be used. I use a Bernzomatic TS4000 torch with Mapp gas because it is instant on and instant off, but any torch will work.
    P9240034B.jpg

    The method requires that you heat around the pump tube, set down the torch and with one hand holding the damp rag to steady the tank, the other hand is used to wiggle the puller and pump tube while pulling the tube out of the tank. The easiest wiggle direction will become evident, but in this case it is in the direction that is perpendicular to the length of the tank. Once the solder on the tube is clear of the tank there is no hurry to extract it before the solder solidifies so you can carefully continue the extraction.
    P9240035B.jpg

    After cooling, it is advisable to clean the pump tube. Brass cleaner or 220 to 600 grit wet or dry sandpaper work well. Again, the cleaning is done to prevent contamination of solder when you re-assemble. It is best to remove the back part of the NRV at this time with a screwdriver while securely holding the tube, or you can engage the NRV body from inside the tube with an NRV socket tool. If the back part will not come free then it can be removed later, possibly at the expense of the spring being annealed and made un-useable. I left the back NRV cap installed for demonstration purposes. You will need some pliers to pull out the rear cap of the pump tube in this step. Hold the tube with a damp rag or a small vise and heat the cap end, then remove cap/NRV assembly and allow to cool.
    P9240036B.jpg

    P9240038B.jpg

    You should now be able to remove the back portion of the NRV using a NRV socket tool and screwdriver. Apply heat if needed for a second try at removal. Next, the rear pump tube cap can be held in pliers and a modest attempt at removal of the NRV body from the cap can be performed with a NRV socket tool. If it does not budge, heat the cap while it is in the pliers and try again. The object is to remove it without making a lot of plier tooth marks on the cap, let the heat do the work.
    P9240040b.jpg

    The pump bucket and spring can be pushed out of the NRV back section with a small drill, piece of stiff wire, or an unbent portion of a small size paper clip. You can see that the spring has been wasted, and close inspection will show that it is softened and useless as a spring. Remove what is left of the seal in the NRV bucket with an X Acto knife or similar.
    P9240039b.jpg

    Cleaning of the pump tube rear cap can be done with a small smooth file. I prefer a type with no cutting teeth on the edge, but careful use of any type file will work. Remove the extra solder in the joint area, then clean the balance with the file, and/or 220 or 400 grit wet or dry sandpaper. Twisting the cap on the sandpaper works well for both flat sides of the cap. Carefully clean debris out of the groove around the lip designed to enhance the lead seal using the tip of the Xacto knife or similar tool. The inside of the tube should be cleaned starting with Xacto knife and then sandpaper. Restrict the knife and sandpaper work to just the end of the tube so as not to affect where the pump cup operates which can be seen if you inspect the inside.
    P9240042b.jpg

    I prefer to also clean all parts shown in a citric acid dip for a couple of hours. This bath is a 1/4 teaspoon of citric acid in 100 ml of hot water. Any container of glass or plastic will work, as will other cleaning methods.
    P9240044b.jpg

    For re-assembly you will need a good spring, a new lead seal, and a new nitrile rubber disk. I make springs using .016 dia. brass spring wire, and this is described in another how to document. The lead seal can be purchased or made from lead sheet of .040 thickness which is available from McMaster Carr in the US in a 6inch x 6inch (or larger) sheet. I punch nitrile disks from 70 durometer sheet also available from McMaster.
    PA010004B.jpg

    Check to ensure that the lead seal will fit in it's appropriate recess in the cap with the NRV body also installed. When satisfied that it will assemble properly, remove the items from the cap.
    PA010005B.jpg

    I use liquid rosin flux and electronics solder of either .032, or .040 inch diameter. In this tutorial, .032 inch diameter is being used. The small size allows great control. Install the pump tube rear cap in the pump tube after making one last inspection. Make sure there are no fibers or crud in or near the solder joint area. Fixture the tube at a slight angle above horizontal. Vertical may allow solder to drip down the inside, horizontal may allow the cap to fall out when solder is molten. Use a toothpick or the back of a cotton swab stick to apply rosin to the joint. I applied 3 drops at the top and watched it wick all around.
    PA010006B.jpg

    Apply heat with the torch at intervals. Remember to pull heat off, and test with the solder at the top. No melt ? Continue the heating intervals. With practice you will know by the smoke, or by the silvering of any residual original solder that melts and silvers when your heat level is right. Don't over heat, that is why you are using intervals. Apply solder when it melts to the top at 10 o'clock, and 2 o'clock positions. It will wick down the tube joint. If there is a drip at the bottom, use the cotton swab with some rosin flux on it and carefully wipe whilst it is molten. Be careful as you can pull the cap out, so wipe with the grain of the crack.
    PA010007B.jpg

    Clean up with denatured alcohol, then file or use wet or dry sandpaper such as 400 grit to clean the soldered area. Install the assembled NRV into the tube (with the lead seal washer). Clean the outboard end of the tube (threaded end) and you can suck on it and hold vacuum as a leak test, or you can put a balloon on the NRV end and do a bubble test to check for leakage. Properly cleaned parts usually make for trouble free soldering. Clean the hole in the tank and the pump tube, then install the tube. Fixture or position the tank, again so that you are working mostly in the horizontal plane. Previous solder on the tube is a guide for tube placement.
    PA010008B.jpg

    Use a damp rag as a heat sink, and apply a few drops of rosin flux, watching it wick around the joint. Use the same heating method as before, apply from at least 2 angles for uniformity, and watch for re-melt, and/or use the solder to test if up to temp. Apply solder at the crack, again at 10 o'clock, and 2 o'clock positions, and possibly a little at 12 o'clock. Wipe excess carefully with rosin soaked swab when molten as needed. When cool, clean with alcohol, sand with 600 or 1000 grit wet or dry as needed. You can leak test by corking the outlet, installing the tank lid and pumping up. It is ready for polish when you are satisfied with the seal.
    PA010009B.jpg

    Re-assembly and polishing completed.
    PA010010B.jpg

    Regards,
    Doug
     
  2. shagratork

    shagratork United Kingdom Moderator Subscriber

    Offline
    Joined:
    Aug 9, 2005
    Messages:
    7,979
    Location:
    Durham City, England
    Well, bugger me with a raggy tramline!!!
    Brilliant! :D
     
  3. kerophile

    kerophile United Kingdom Subscriber

    Online
    Joined:
    Sep 23, 2004
    Messages:
    8,663
    Location:
    Far North of Scotland
    Hi Doug. Wonderful tutorial!
    A real Masterclass.
    Best Regards,
    George.
     
  4. spudz Ireland

    Offline
    Joined:
    Aug 31, 2005
    Messages:
    2,576
    Couldn't have put it better meself.

    Mr. Yak sir, I raise my hat to you.
     
  5. Doc Mark

    Doc Mark United States Subscriber

    Offline
    Joined:
    Dec 12, 2004
    Messages:
    14,891
    Hey, Guys,

    SEE??!!! I TOLD you it was a fine bit of instructions, didn't I??!! :D :D :D :D Doug has really offered all of us something of great value, with this simply outstanding tutorial!! Thanks, again, Mr. Yak!!! Take care, and God Bless!

    Every Good Wish,
    Doc
     
  6. sefaudi

    sefaudi Turkey Subscriber

    Offline
    Joined:
    Oct 19, 2004
    Messages:
    621
    Location:
    Turkiye
    .


    Ahhhh you, great fettler, good man Doug. That's a wonderful tutorial. Many many thanks.
    And your nice brass springs 8)

    Sefa...
     
  7. Diesel

    Offline
    Joined:
    Aug 14, 2007
    Messages:
    284
    Excellent A fine piece of work like I have never seen. Thanks.
     
  8. Handi-Albert

    Offline
    Joined:
    Jul 25, 2004
    Messages:
    415
    Nice work and a lot of detail there.
     
  9. Bart Netherlands

    Offline
    Joined:
    Mar 18, 2010
    Messages:
    61
    Location:
    the Netherlands
    oh im already happy i became a member of this site
    i didnt know you could take the NRV apart and fix it.
    i'm going to try that.
    the NRV is the only thing not working in my
    1/4 litre optimus

    Bart
     
  10. Big BTU

    Big BTU United States Subscriber

    Offline
    Joined:
    Jan 21, 2010
    Messages:
    868
    Location:
    Hawaii
    Wow Fantastic tutorial.

    Many thanks!
     
  11. Jan-Willem Netherlands

    Offline
    Joined:
    May 7, 2006
    Messages:
    152
    Thank you very much!
    I just fixed my radius 20 stove, after I completely destroyed the nrv while trying to remove it.
    the next time when one is stuck i'll do this without hesitation... With this guide is not at all as difficult as I imagined it would be.
    Jan-Willem
     
  12. Doc Mark

    Doc Mark United States Subscriber

    Offline
    Joined:
    Dec 12, 2004
    Messages:
    14,891
    Hello, Jan-Willem,

    This is good news, indeed, and I really appreciate reading your thoughts on this job. One day, I'll get to it, too, until then, it's nice to read about the experiences of other Stovies. Take care, and God Bless!

    Every Good Wish,
    Doc
     
  13. colemanblues

    Offline
    Joined:
    Jul 7, 2011
    Messages:
    31
    Thank you for the class. I am new to collecting coleman, and learning tricks,etc. Need to learn all I can about working on coleman. But I need a CV tool,and a few others. So if you could tell me where I may find them, I would appreaciate it.

    Thanks Again,
    colemanblues
     
  14. snwcmpr United States

    Offline
    Joined:
    Nov 16, 2011
    Messages:
    6,306
    Location:
    USA
    Great to re-read this thread.
    Ken in NC
     
  15. snwcmpr United States

    Offline
    Joined:
    Nov 16, 2011
    Messages:
    6,306
    Location:
    USA
    Re-reading this again. A Campingo 1 I am still working on.
     
  16. threedots New Zealand

    Offline
    Joined:
    Sep 2, 2006
    Messages:
    630
    Location:
    Kapiti, New Zealand
    Thanks Doug for your very informative topic.
    I remember reading it some time ago and I was impressed with the quality of your work and the detail that you provided.

    Those Campingo's are a problem with the original NRV being hard to remove. The NRV tends to lock in over time.

    I have repaired 8 of them(1's and 2's) and all had a stubborn NRV.
    Luckily I have not had the pleasure of having to remove the pump tube from any of them but I have come close to having to on a couple of them.

    Why the lead washer was not installed when they were originally assembled still mystifies me.
    I guess Optimus thought having a lead washer was an unnecessary part in the assembly process but servicing them later was made more difficult. John
     
  17. snwcmpr United States

    Offline
    Joined:
    Nov 16, 2011
    Messages:
    6,306
    Location:
    USA
    Thanks to the instructions I got it apart and the real problem was that solder had gotten onto the NRVs threads.
    I couldn't break it using an easy out until I applied heat.
    Now all back together.
     

Share This Page