79
1) Threads should be processed by the threading machine.
2) Use marnen as stuffing material and remove those outside of the threads after pipes
have been installed.
3) Threads should be clean and at least 90% threads should be intact. Exposed threads at
the connection joint after installation should be 2-3 without any exposed stuffing.
Galvanized pipes should be protected and local damage should take anti-corrosion
treatment.
(2)Welding
1) See the table below for types and sizes of grooves for welding which should be proc-
essed by the facing machine.
Table 5.5.1 Types and Sizes of Grooves for Welding
Item
Thickness
Type
Groove
Remarks
T(mm)
Clearance Shoulder
Angle
（º）
C(mm) P(mm)
1
1～3
I-shaped
0.1～1.5
— —
Misalign-
ment for
the inner
wall
should
be≤0.1T
and≤2mm,
and
should be
≤3mm for
the
external
wall.
3～6
Double
Welding
1～2.5
2
6～9
V-shaped
0～2.0 0～2.0 65～75
9～26 0～3.0 0～3.0 55～65
3 2～30
T-shaped
0～2.0
— —
2) When pipes with the same diameter and thickness are butt connected, their inner walls
should be aligned within a deviation of 1/1000. Length of the groove for welding can’t
be larger than 10mm.
3) The groove for welding should be as far as away from the unit and should not be parallel
with the center line of the equipment interface. The welding seam should keep a dis-
tance of at least 50mm with the hanger and bracket.
4) Welding should be done by the qualified welder. In welding, there should be a wind,
rain, or snow guard. The environmental temperature for welding can’t be lower than
-20℃. A 250mm groove for welding should be preheated to 100℃.
A Series Modular-type Air-cooled (Heat Pump) Chiller
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