First, let's take a closer look at the components of the FK medium-pressure compression fitting. A typical unassembled FK fitting consists of the following components:
Installation Preparation: Tube Preparation
1. Tube Cutting
Before installing the fitting, the tube must be properly cut and deburred. Since FK fittings are designed for use with thick-wall tubing, a hacksaw or powered tube cutter is recommended for cutting the tube.
2. Deburring
After cutting the tube, deburring can be performed using a chamfering tool or a facing machine. Make sure that the deburred tube can be fully inserted into the fitting body and rotate freely without any obstruction. The chamfered section must not extend into the sealing area of the front ferrule.
Standard Installation Instructions: 1/4 in. to 3/4 in. or 6 mm to 12 mm
The following installation procedure applies to FK medium-pressure compression fittings in sizes ranging from 1/4 in. to 3/4 in. or 6 mm to 12 mm.
Step 1
Thread the pre-assembly module (nut, ferrules, and plastic mandrel) into the fitting body until finger-tight.
For applications with temperatures exceeding 400°F (204°C), it is recommended to apply Silver Goop™ high-temperature thread lubricant to the fitting nut threads.
Step 2
Remove the plastic mandrel.
Step 3
Insert the tube into the fitting.
Step 4
Ensure that the tube is firmly seated against the shoulder of the fitting body.(A depth marking tool can be used to provide a visual reference.)
Step 5
For fittings 1/4 in. through 9/16 in. or 6 mm through 12 mm, secure the fitting body and tighten the nut to the specified torque. Alternatively, mark the nut, secure the fitting body, and tighten the nut one full turn.
For 3/4 in. fittings, mark the nut, secure the fitting body, and tighten the nut one full turn.
Step 6
Use the medium-pressure gap inspection gauge to ensure that the fitting is properly tightened.
Special Installation Instructions: 1/2 in., 3/4 in. and 1 in.
1/2 in. and 3/4 in. FK medium-pressure compression fittings can be installed using an MHSU Hydraulic Pre-Assembly Tool.
1 in. FK medium-pressure compression fittings must be installed using an MHSU Hydraulic Pre-Assembly Tool.
Reassembly of FK Fittings
FK medium-pressure compression fittings can be disassembled and reassembled multiple times.
Reassembly Step 1
Insert the tube with the pre-assembled ferrules into the fitting until the front ferrule is firmly seated against the fitting body. Tighten the nut finger-tight.
Reassembly Step 2
Secure the fitting body and tighten the nut to the specified torque shown in the table.
Alternatively, rotate the nut to its previously tightened position. At this point, you will feel a significant increase in resistance. Tighten the nut slightly further using a wrench.
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