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DQC116
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dixonvalve.comGeneral Product Information
Installation of Tapered Thread Connections (NPTF)
Be Safe When Installing Quick Couplings!
All quick disconnect couplings should be viewed as potential hazards that can cause property damage, personal injury or
even death if used or installed improperly!
Couplings should be installed in a location that will allow easy operation of the coupling and accessibility for all necessary
installation tools. Care should be given to consider operator safety, especially if spillage upon disconnection could result in fluid
ignition or skin and eye irritation.
Only apply wrenches to the hex or machined wrench flats that are provided for assembly purposes, nowhere else. Never clamp
on the sleeve of the coupler or the nose of the nipple, this will cause distortion and/or damage.
Finally, always test quick coupling installations before putting into operation by pressurizing the unit to 150% of the working
pressure in an enclosed/protective environment.
The seal for NPTF threads is created by the metal-to-metal contact between the roots and crests of the male and female threads.
Too much PTFE tape, or pairing liquid sealant with PTFE tape may cause distortion, poor thread engagement, or cracking of the
coupling during assembly.
The total number of tapered threads engaged should be between 3½ to 6. Any number of threads outside this range may
indicate either under or over tightening of the joint or out of tolerance threads. After assembly of a NPTF thread connection,
always proof-test the connection before operating the system. If the joint proves to be inadequately tightened during
proof-pressure testing, tighten it further in 1/8 turn increments until a reliable seal is attained (do not exceed 3 T.F.F.T!)
Apply 1½ to 2 wraps of PTFE tape,
starting one or two threads from the
lead edge, in a clockwise direction.
For 316 stainless steel, be sure to
use stainless grade tape.
Check threads to make sure there
is no obvious damage on either
half and that tape is properly
installed. Align male and female
threaded connections and carefully
begin threading the two halves
together.
Finger tighten the connection and
create a reference mark on the
hex of the hose end/adapter and
the coupling. This mark will help
identify the number of revolutions
during the next step in the
procedure.
With even and smooth force
applied, wrench tighten according
to the 'Turns From Finger Tight'
(T.F.F.T.) values listed below.
DO NOT OVERTIGHTEN!
1
2
3
4
SAE Size
NPTF Thread Size
T.F.F.T
-4
-6
-8
-12
-16
1/4" - 18
3/8" - 18
1/2" - 14
3/4" - 14
1" - 11 1/2
2
2
2
1.5
1.5