{"id":76446,"date":"2020-03-16T00:00:00","date_gmt":"2020-03-16T00:00:00","guid":{"rendered":"https:\/\/discover.restek.com\/?p=76446"},"modified":"2025-12-26T19:47:16","modified_gmt":"2025-12-26T19:47:16","slug":"over-tightening-your-fittings-has-consequences","status":"publish","type":"post","link":"https:\/\/discover.restek.com\/de\/blogs-ja\/gnbl5523\/over-tightening-your-fittings-has-consequences","title":{"rendered":"Over tightening your fittings has consequences."},"content":{"rendered":"\n

If you use the correct fittings and seals in the gas chromatography system, and follow some simple steps, there is absolutely no need to over tighten any fitting to achieve a leak free seal.<\/p>\n\n\n\n

For almost all fittings that use seals in a GC system, whether they are ferrules, septa or o-rings, the tightening process should be the same:<\/p>\n\n\n\n

    \n
  1. Make sure the place where you are applying the fitting is cooled down and the gas flow is turned off<\/li>\n\n\n\n
  2. Select the correct size fitting and seal for the application<\/li>\n\n\n\n
  3. Correctly fit the fitting and seal together according to the manufacturer\u2019s guidelines<\/li>\n\n\n\n
  4. Finger-tighten the fitting on to the receiving part<\/li>\n\n\n\n
  5. Using the appropriate tool (wrench or fingers) tighten the fitting and extra\u00a0\u00bc turn<\/u><\/strong>.<\/li>\n\n\n\n
  6. Establish a gas flow and pressurize the section of the GC system.<\/li>\n\n\n\n
  7. Use a Restek electronic leak detector (28500) to check for leaks around the fitting<\/li>\n\n\n\n
  8. If you do detect a leak further tighten the fitting in\u00a01\/8 turn<\/u><\/strong>\u00a0increments until the leak ceases.<\/li>\n<\/ol>\n\n\n\n

    Note: If you continue to notice a leak and you have done one complete revolution<\/u> of the fitting STOP<\/strong>.  There is something wrong.  Rather than damaging the fitting, or the receiving part, remove the fitting, get a new one and a new seal and start again.<\/em><\/p>\n\n\n\n

    \u00a0Common fittings and seal, and the consequences of over tightening<\/strong><\/p>\n\n\n\n

    Septa<\/em><\/p>\n\n\n\n

    This is the easiest seal to get leak free.  You should not need a wrench; minimal finger tightening is usually sufficient.  If you over tighten you compress the septum.  This puts the septum under stress, and so when the septum is penetrated by a needle it is more easily ripped apart leading to coring and leaks.  Coring can result in particles of septum in the liner which can adversely affect chromatography results.<\/p>\n\n\n\n

    You should leak check with and electronic leak detector around the septum fitting every day.  It is one of the hardest working seals, and the easiest and cheapest to change.<\/p>\n\n\n\n

    Reducing Nut<\/em><\/p>\n\n\n\n

    This is the fitting at the bottom of the inlet where the column nut attaches.  Over tightening this nut can damage the threads on both the nut and the inlet fitting.  We have also seen the inlet bent by over tightening to such an extent that liners could not fit down inside.<\/p>\n\n\n\n

    For GCs like Agilent, Thermo Trace 1300\/1310 and Perkin Elmer 590\/690 the simple way to avoid over tightening, or the use of excessive force, is to use a dual vespel ring inlet seal.  The dual vespel ring allows for a soft but effective seal, and enables you to follow the tightening procedure above.<\/p>\n\n\n