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发表于 2010-7-10 17:18
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本帖最后由 jack_lai 于 2010-7-10 18:52 编辑
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足球看完了来看看题目。4 s1 w! p- d/ i" x# i7 O
( P9 D' I. `( W: tThe length of the heat trace is 22 meters. The size of the heat trace is 5/16 inch (WATTS/ m SUPPLIIED is 43.7)2 @6 |: H9 V5 @- G% ?4 j- c6 {7 y
The drawing is shown as figure 1. (All data is from the memory. They are not the same as the real drawing, but a little bit different)
}" \( r: v! w3 ?6 n: M" qWe can see it is not easy to install the 22 meters heat trace according as figure 18 S* {0 L6 o4 x6 J7 z
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4 b% t$ p5 l+ p4 }7 IAs a normal question we just discuss:
- `. P# ?5 y- r- B1 |! M2 }& u$ pHow do you run these 9.4 meters heat trace (size 5/16 inch) on the 3 inches 1.4 meters pipe ?
0 N1 K- n0 B G! d+ y% NI call this is JACK LAI Spiral Method 螺旋法
3 E2 i: f- g6 n# d/ g' gThe outside circumference of the 3 inch pipe is more than 10 inches. See figure 2.
6 Z* d$ p0 a/ n3 A! f# oThere are 10 positions to plac the heat trace. They are 0.1,2,3,,,,,9. The distance between each position--heat trace is about one inch. 6 z$ T4 _4 E- \4 k. y& r
Because the pipe is horizontal, position 0 can not be placed. See figure 2
9 N1 G. k, p6 T4 l4 vBecause the maximum bend radius of the heat trace is 2 inches( see note 1), position 5 can not be placed. See figure 2. Then the route of the heat trace can be like figure 3
. A0 x' H2 D, p3 a( H& z. Y9 V' QThe total heat trace that can be installed here is about
* c0 e7 x+ E# ^' p! w8 \1.4 * 6 + 1 * 2 = 8.6 + 2 =10.8 Meters7 ~) T: ~2 s: k6 M2 y. d
So, the 9.4 meters heat trace can be installed along the 3 inched 1.4 meters pipe without a problem. " t3 t9 k9 T* P4 o0 F8 a
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Note :2 b. v3 y+ ]* _5 f4 }( m/ L& A
1. The minimum bend radius:
# n: O/ F i* V+ f. ?+ KBecause the heat trace size here is 5/16, 6 times the outside diameter of the heat trace is; f# [+ V. T; a2 g
5/16 *6 = 30/16 almost = 2 inches9 J& i' N, h2 H9 Z5 w9 }
So the maximum bend radius is 2 inches.# w+ @% d) V2 x: b6 {7 J% }; `4 ~
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For 3 inch pip: If heat trace size is 5/16 inch, and no RTD, the box position is close to the end of pipe. 1 meter long pipe! a7 X8 P6 n2 B9 P, i
if the pipe is horizontal, The length of heat trace can be installed is about" r; s2 I2 J3 G; q5 |
1 * 9 = 9 meters. x; A7 m5 w9 G* e1 o+ `" U& s
If the pipe is vertical, The length of heat trace can be installed is about
7 d/ l- ^2 x9 U' \+ l" h# X) I1 * 10 = 10 meters. : |# R0 _9 f: E
For 2 inch pipe: If heat trace size is 5/16 inch, and no RTD, the box position is close to the end of pipe. 1 meter long pipe
* |& `; V& f6 E3 Yif the pipe is horizontal , The length of heat trace can be installed is about& T! L) y; A" b% l+ _4 m6 L7 n
1 * 4 = 4 meters
9 |" x# c' t2 Z+ g9 c. ^; ~3 dIf the pipe is vertical, The length of heat trace can be installed is about! z2 f" w0 ]% t1 o: \. w& y
1 * 5 = 5 meters. |
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