Mechanical fastening method for valve plug with carbide tip

A method of forming a valve plug assembly for use in a control valve, the control valve having a rigid valve stem, a flow passage, and a valve seat disposed in the flow passage, the method comprising:

• providing a plug base defining a longitudinal axis and having a first end and a second end;
• arranging the first end of the plug base for attachment to the valve stem of the control valve such that the plug base moves in conjunction with the valve stem;
• providing the second end of the plug base with a bore extending along the longitudinal axis, the bore including a first portion extending into the plug base a first distance and a second portion extending into the plug base a second distance less than the first distance;
• providing the first portion of the bore with a first diameter and the second portion of the bore with a second diameter greater than the first diameter;
• providing the second portion of the bore extending from the second end of the plug base with a first shaped seat;
• providing a spacer having a through bore, a first end, and a second end, the spacer sized for insertion in the second portion of the bore of the plug base, and the first end of the spacer having a shaped portion to cooperate with the first shaped seat, and providing the second end of the spacer with a second shaped seat;
• providing a plug tip having a through bore, an inner portion defining a first end having a conical shape arranged to engage the second shaped seat, and a second end shaped to engage the valve seat of the valve;
• providing a cap screw sized for insertion through the plug tip and the through bore of the spacer, and arranging the cap screw for threaded engagement with the first portion of the bore of the plug base, the cap screw thereby mechanically securing the plug tip to the plug base.

A valve plug assembly for use in a control valve having a valve stem, a flow passage, and a valve seat disposed in the flow passage, the valve plug assembly comprising:

• a plug base defining a longitudinal axis and having a first end and a second end;
• the first end of the plug base arranged for direct attachment to the valve stem of the control valve;
• the second end of the plug base having a bore extending along the longitudinal axis, the bore including a first portion extending into the plug base a first distance and a second portion extending into the plug base a second distance less than the first distance, an inner end of the second portion of the bore terminating in a first shaped seat;
• a spacer having a through bore, a first end, and a second end, the spacer sized for insertion in the second portion of the bore of the plug base, the first end of the spacer having a shaped end to cooperate with the first shaped seat, the second end of the spacer having a second shaped seat;
• a plug tip having a through bore, an inner first end, and a second end, the first end being shaped and arranged to engage the second shaped seat, and the second end shaped to engage the valve seat of the valve;
• and
• a cap screw sized for insertion through the plug tip and the through bore of the spacer, the cap screw arranged for engagement with the first portion of the bore of the plug base, the cap screw securing the plug tip to the plug base.