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Bi 3.2 SONG CHN RC
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BI 3.2 SONG CHN RC123Phn loi song chn rcMt s kiu song chn rcNhim
v v cu to ca SCR4Cc dng bi tp
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3.2.1 Cu to v nhim v ca SCR Song chn rc c chc nng chn gi nhng rc
bn th (giy, nylon, c, rc.), nhm m bo cho my bm, cc cng trnh v thit
b x l nc thi hot ng n nh.Nhim v:
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Cu to
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Thanh chn rc c th dng loi tit din trn d = 8:10 mm, ch nht s x b
= 10 x 40 v 8 x 60 mm, bu dc
Hnh 3.1 Cc kch thc v hnh dng ca thanh chn rc Cu to
- 3.2.2 Phn loi song chn rcTh ln(30-200mm)Loi nh
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Lng rc c gi li ph thuc vo khe h gia cc thanh chn. Ty theo mc rc
trong nc thi, ngi ta nh cc khe h ca song chn rc, nu rng qu th s
khng ngn rc hiu qu, nu hp qu th cn tr dng chy.Bng 3.1 Ch s thit k
thanh chn3.2.2 Phn loi song chn rc
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Mt s lu khi thit k SCRKhng ch tc dng chy nc thi qua song chn t
0,5 1,0 m/s.Nu lng rc W > 0,1 m3/ngy th c th ly rc bng tay.Nu
lng rc W 0,1 m3/ngy th c th ly rc bng c gii.Tn tht ct nc khi i qua
song chn rc c th xc nh theo:
S l b dy thanh chnb khong cch h gia 2 thanh chnhv l ct nc dng
chy on gn n SCR, hv = V2/2g l gc nghing ca thanh chn so vi chiu dng
chy.Khng ch tc dng chy nc thi qua song chn t 0,5 1,0 m/s.Nu lng rc
W > 0,1 m3/ngy th c th ly rc bng tay.Nu lng rc W 0,1 m3/ngy th c
th ly rc bng c gii.Tn tht ct nc khi i qua song chn rc c th xc nh
theo:
S l b dy thanh chnb khong cch h gia 2 thanh chnhv l ct nc dng
chy on gn n SCR, hv = V2/2g l gc nghing ca thanh chn so vi chiu dng
chy.Khng ch tc dng chy nc thi qua song chn t 0,5 1,0 m/s.Nu lng rc
W > 0,1 m3/ngy th c th ly rc bng tay.Nu lng rc W 0,1 m3/ngy th c
th ly rc bng c gii.Tn tht ct nc khi i qua song chn rc c th xc nh
theo:
S l b dy thanh chnb khong cch h gia 2 thanh chnhv l ct nc dng
chy on gn n SCR, hv = V2/2g l gc nghing ca thanh chn so vi chiu dng
chy.
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B l h s hnh dng ca thanh chn, ly theo bng sau:
Bng 3.2 H s hnh dng thanh chn rc
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3.2.3 Mt s kiu song chn rc3.2.3.1 Song chn rc co bng tay Dng ph
bin cc cng trnh u mi ca trm bm nc thiThanh chn rc thng khng nh hn
10 mm theo chiu dy v 50 mm theo chiu su.Vn tc dng chy ch gii hn
trong khong 0,4 m/s 0,8 m/s l tt nht.
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3.2.3.2 Song chn rc c b phn ly rc bng c gii a. Kiu vn hnh bng
xch quay B phn co rc vn hnh bng xch quay theo mt u dn, rc c cun
theo chiu i xung ca dy xch v a ln mt mng lc .u im: Ly rc tng i trit
nht l cc loi rc mm nh giy, vi nylon.Nhc im: Thnh thong b kt do cc
loi rc cng gy ra, ng thi gp kh khn khi chnh sa bnh xch v cn thit
phi tho nc khi lng knh.
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3.2.3.2 Song chn rc c b phn ly rc bng c gii b. Kiu bn co trt
(Theo Franklin Miller) B phn co rc di chuyn theo mt gi , ln n u gi
rc s t ri xung v a i ni khc. nghing ca gi c th iu chnh ty theo tnh
trng rc thi.u im: Hu ht cc b phn ly rc u nm trn mc nc, c th d dng
lm sch v qun l m khng cn phi tho sch nc trong lng knh.Nhc im: B phn
co rc ch hot ng trn mt chiu gi thay v lin tc nh loi xch quay.
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3.2.3.2 Song chn rc c b phn ly rc bng c gii c. Kiu ti quay (Theo
Dresser Industries) B phn co rc c gi trn gi nh vo trng lng ca dy
xch.u im: B phn u bnh rng c kh khng b ngp chm trong nc thi Nhc im:
Chim nhiu khng gian lp t
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3.2.3.2 Song chn rc c b phn ly rc bng c gii d. Kiu ly rc bng u
cp B phn co rc i ln xung trn mt gi trc qua s chuyn ng ca h thng dy
cp v u trng quay. B phn co i xung bng trng lng bn thn v nng ln bng
cp quay.u im: B phn co rc t trng lng bn thn n m nhn mt phn vic vn
hnh c hc khi ri vo vng nc thi Nhc im: Kh nng co rc b gii hn, qun l
hi phc tp, cun cp hay b vng do cht thi rn v b phn thng hm c hc thng
b trc trt.
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3.2.4 Cc dng bi tpBi tp 1: nh hnh kch thc lin quan n vic thit k
mt knh dn trc khi i n mt b phn song chn rc co tay vi cc thng s tnh
ton sau:+ Lu lng thit k ln nht Q = 1 m3/s+ Vn tc dng chy i qua SCR
V = 0,5 m/s+ Khong cch cc thanh chn rc b = 50 mm+ Chiu rng ca 1
thanh chn s = 5 mm+ Chiu su dng chy trong knh ly rc H = 1mTnh h s
hu dng ca SCR v s lng rc qua SCR mi ngy, gi thit SCR c kh nng gi 20
m3 rc/ 106 m3 nc thi.
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3.2.4 Cc dng bi tpBi tp 2: Mt song co rc dng thanh ng vi khong h
l b = 25 mm lc rc t nc thi n mt nh my x l qua mt ng dn hnh trn. Cho
bit:+ ng knh ng dn D = 1,25 m+ H s nhm ng ng n = 0,013+ dc ng ng S
= 0,00064+ Vn tc trung bnh dng nc Vavg = 0,8 Vmax + Kch thc thanh
chn s = 10 mm (dy), b rng song chn 1,5 mYu cu xc nh: 1. Vn tc trung
bnh dng chy trong ng2. S thanh chn cho b phn song co rc theo cc s
liu trn.3. Tn tht ct nc qua song chn ng vi Vavg
