LET-LOK® FITTINGS INSTALLATION INSTRUCTIONS
LET-LOK
®
fittings are supplied, assembled
and finger tight. Disassembly before use can
allow the entry of dirt or other particles.
Insert the tubing into the
LET-LOK
Check that the tube rests firmly on the
fitting shoulder and that the nut is finger
tight. At this point it is recommended that
a scribe mark be drawn on the hex of the
nut extending onto the fitting body. This
mark will serve as an indicator for the
starting point and proper pull-up.
®
fitting.
REASSEMBLY INSTRUCTIONS
LET-LOK® connections may be
disconnected and remade repeatedly,
without the loss of the leaktight seal.
1. Before disconnecting, mark the
position of the nut in relation to the
fitting body.
2.To reassemble, use a wrench to
tighten the nut to the original position.
3.Tighten slightly with a wrench until a
slight rise in torque is felt.
TUBE CUTTING
Two differnet methods can be used
to cut tubes
1. Tube Cutter
2. Hacksaw
TUBE CUTTER
To attain a leak free connection, the tubing
must be cut squarely. A good quality tube
cutter with an appropriate blade for tubing
material is recommended. Do not try to
reduce the time of cutting by taking deep
cuts with each turn of the cutter. This will
work harden the tube.
The end of the tube must be deburred to
avoid damage to the fitting and to ensure
that the tube reaches the bottom of the
fitting.
INSPECTION GAUGE
Use: This is a “No-Go” gauge and
should be used as follows:
1. Make up the fitting according to the
following instructions:
1/4 inch (6mm), 3/8 inch, 1/2 inch
(12mm) make up 1-1/4 turns from the
finger tight position.
2. Check gap between nut and body,
using the appropriate sized gauge.
If the gauge slides easily into the gap,
tighten the nut further until gauge
cannot enter the gap.
Gauge enters
gap...No good,
tighten further
CONNECTORS
Tighten the nut.
1-1/4 turns of the nut are required
for 1/4” (6 mm) and higher (see Fig. A).
3/4 turn of the nut is required for 3/16”
(4 mm) and lower (see Fig. B).
Figure A
Figure B
HACKSAW CUTTING
In order to cut the tube with a hacksaw
and get square ends, the tube must be
cut with guide blocks.
This method of cutting necessitates
deburring of the tube ends.
Warning
Do not hold the tube in a vise in the place
where it will be inserted into the fitting (the
vise will leave a mark on the tube that may
cause leaks, and might cause ovality).
TUBE HANDLING
Scratches on the tube might cause leaks.
It is, therefore, important to handle the
tube carefully to reduce the risk of leaks.
SOME PRECAUTIONS TO BE
TAKEN
1.Tubes must not be dragged on the floor.
2.Tubes must not be dragged out of
a tubing rack, especially in cases of large
O.D. tubes.
COPPER TUBING
If using copper tubing from a roll, hold the
end of the tube and roll the roll outwards,
allowing the tubing to lie on a flat surface.
Gauge does
not enter gap...
Good
For Gauge Ordering Information:
see page 91.
HAM-LET ADVANCED CONTROL TECHNOLOGY
9
LET-LOK® FITTINGS INSTALLATION INSTRUCTIONS
PHYSICAL DIFFERENCES AND MARKINGS
LET-LOK
Tee & Elbow (see Fig. 1)
Body marked: MM
Straight Connectors: (see Fig. 2)
LET-LOK 316 6M SD8
CONNECTORS
Fig. 1
Back side
(1)
Tube O.D.
LET-LOK
Tee & Elbow: (See Fig. 3)
Straight Fittings: (see Fig. 4)
Body: Shoulder marked:
LET-LOK 316 AV2
®
METRIC FITTINGS:
MM
Fig. 1
Front side
(2)
Material Batch
®
INCH FITTINGS:
(2)
Body: Stepped shoulder
Marked: LET-LOK
Nut: (see Figs.1 & 2) Stepped shoulder
Marked: LET-LOK
®
316 AV1
®
316 6M
LET-LOK
(2)
(1)
SD8
®
316 AV1
(2)
Stepped Shoulder
Fig. 2
Stepped Shoulder
Nut: (See Fig. 3 & 4): Shoulder marked
LET-LOK 316 1/2
(1)
BU2
(2)
TUBING DATA FOR LET-LOK
®
FITTINGS
In order to assure maximum fitting
reliability and performance, great care
should be given when selecting the tubing
for each application.
TUBE SELECTION
Four variables must be considered when
ordering tube for use with LET-LOK
®
fittings:
1. Material
2. Tube wall thickness
3. Tube surface finish
4. Tube hardness
Tubing should comply with standard
ASTM A213 or ASTM A269, be seamless,
and fully annealed.
The tube must be free of scratches and
suitable for bending and flaring.
TUBE O.D. TOLERANCES
1/16” - 1/8”
2mm - 3 mm
3/16” - 1 1/4”
4mm - 25 mm
1/2” - 2”
1
38mm - 50 mm
±
±
±
0.003”
0.076 mm
0.005”
0.127 mm
0.006”
0.152 mm
LET-LOK® 316 1/2 BU2
LET-LOK 316 AV2
Fig. 3
Back side
(1)
Tube O.D.
(2)
Material Batch
Fig. 3
Front side
Fig. 4
HIGH SAFETY
In applications where severe conditions and high pressure exist, we recommend the following installation procedures:
1. Check that the nut is finger tight.
2. Insert the tube (up to the shoulder).
3. Rotate the nut with a wrench until the tube does not rotate freely.
4. Mark the position of the nut.
5. Rotate the nut 1-1/4 turns.
This method ensures that even if the tube O.D. is at the minimum tolerance,
the ferrules will be in contact with the tube for the full 1-
1/4 rotation.
The ovality of twice the O.D. tolerance
is not suitable for LET-LOK
®
fittings.
The tube must be reasonably round.
The ends of the tube must be free of
burrs.
Tubing hardness: The hardness of the
tube must be lower than the hardness of
the fitting material.
The hardness must not exceed Rockwell
90 HRB (200HV).
10
COMPRESSION TUBE FITTINGS
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