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The weld used in joining a tube to a socket weld tube fitting is like any other type of “tee” weld. The root (i.e., the point of intersection of the outside of the tube and annular end area of the fitting) must be included in the weld zone.

Careful welding procedures are normally followed to assure that this root area is included in the weld. If penetration is not achieved, the joint will have two builtin stress risers which may greatly reduce the strength of the weld. Upon application of an extreme load, these stress risers could result in cracks which could propagate out through the weld or tube depending upon the direction of the greatest load.

Often to achieve full root penetration in TIG welding of stainless steels, a fusion pass will be made first, followed by an final pass utilizing a filler rod to achieve the desired fillet size.

NOTE:
  • Other drop sizes available upon request.
  • Dimensions for reference only, subject to change.
    • Unit of Measure

    Connection Type

    		 N/A Socket x MNPT

    Tube O.D.

    		 N/A 3/8 in

    Male Pipe

    		 N/A 1/4

    E Small Bore

    		 N/A .28 in

    B

    		 N/A .34 in

    D

    		 N/A 1.34 in

    J

    		 N/A .53 in

    R

    		 N/A .56 in

    W HEX

    		 N/A 11/16 in

    X Dia.

    		 N/A .63 in

    Work. Press.

    		 N/A 7500 psi

    Features

    		 N/A HCT offers these advantages:

  • Raw materials for manufacture must meet code requirements. This can be verified through documentation so that the customer is certain that what is ordered is received.
  • HCT provides a record of chemical analysis with the raw material. Thus, in areas requiring welding, the correct welding technique is applied.
  • HCT relieves the user of Parker instrumentation tube fittings of any doubts. It acts as an assurance for today and for tomorrow.

    The material used in Parker Hannifin instrumentation fitting components is 316 stainless steel as specified and referenced in Section III of the ASME Boiler and Pressure Vessel code.
    •

    Assembly

    		 N/A The codes applicable to the welding of socket weld fittings require that the tube be inserted into the socket until bottomed against the stop. The tube is then to be backed out approximately 1/16 of an inch and then welded.

    If the tube is not backed out, but welded when against a flat bottom stop, the contraction of the weld fillet and fitting socket can combine to produce a static stress on the weld. During thermal transients, the fitting and the portion of the tube within the fitting may experience a differential rate of heating or cooling, again adding to the stress level in the weld.

    Tacking

    		 N/A If the weld joint is to be “tacked” before welding, it is recommended that the “tack” weld build-up be held to a minimum.

    Excessive build-up on the “tack” may cause an interrupted final bead and a stress riser or lack of complete fusion.

    Backing Gas

    		 N/A Backing gas is an inert (no active properties) gas used to flood the interior of the fittings and tube system during welding. It serves the same purpose internally as the shielding gas used in TIG or MIG welding. By reducing the interior oxygen level to as low as practicable, it also serves to control the combustion of contaminates that could affect weld quality.

    When a backing gas is not used and nearly 100% weld penetration is achieved, blisters will tend to form on the internal tube wall. This will result in scale which may later break loose. Therefore, in 0.050 wall or thinner tube or where the wall thickness is such that the selected weld process may burn through, the use of a backing gas is required.

    In most cases the backing gas will be argon or helium connected to the system through a control regulator. Flow rates, while small, should be high enough to purge the system. Welds should be made in downstream sequence from the gas connection.

    Note that the entire system should be purged to insure that there are no openings that will allow air to be drawn into the system.

    The use of backing gas, while often not mandatory, will give a better weld joint. This is because the effects of contaminate combustion by-products are eliminated and because the welds are made and cooled under a shielded atmosphere, thus eliminating internal scaling or blistering.

    Welding Methods Arc Polarity

    		 N/A When welding Weld-lok® fittings, best results will be obtained by the following arc polarities:
    TIG – Direct Current, straight polarity
    MIG – Direct Current, reverse polarity
    STICK - Polarity dependent on rod used.