Method and apparatus to assemble a high purity liquid distribution system

A joint used in a liquid distribution system and connected to a tube, the tube being fabricated from plastic material, the joint comprising:

• a sleeve fabricated from the plastic material, the sleeve defining a sealing length and an overall length, the sealing length defined by an enlarged portion and cylindrical portion, the overall length defined by the enlarged portion, the cylindrical portion and a distal end portion, an outer diameter of the enlarged portion being greater than an outer diameter of the cylindrical portion, the enlarged portion having a conical straight surface which is at an oblique angle to a central axis of the sleeve;
• a fitting having threads and a recess for engaging a protrusion of the distal end portion and an inner surface, the tube being disposable between the inner surface of the fitting and the enlarged and cylindrical portions of the sleeve;
• and
• a union nut having a pressing surface having a conical straight configuration and threads which engage the threads of the fitting, the pressing surface having a length which is shorter than a length of the conical straight surface of the sleeve and the length of the pressing surface entirely seated below an apex of the conical straight surface of the sleeve, the pressing surface is at an oblique angle to a central axis of the union nut prior to engagement of the union nut to the fitting, the central axis of the union nut coaxially aligned with the central axis of the sleeve when the union nut is engaged to the fitting, the pressing surface evenly presses on the conical straight surface of the sleeve when the union nut is fully tightened on the fitting to make the joint liquid tight;
• wherein the pressing surface is monolithically formed with the union nut and remains at the same oblique angle when the union nut is engaged and disengaged to the fitting.