TCVN 5067 : 1995

Cht lng khng kh - Phng php khi lng xc nh hm lng biair quality - Weighing method for determination of dust content1. Phm vi p dng Tiu chun ny trnh by phng php xc nh hm lng tng phn (30 pht) v trung bnh ngy m (24h) ca bi trong khng kh bn ngoi phm vi cc x nghip, cng nghip vi kch thc ht t 1 n 100 m. 2. Nguyn l ca phng php Phng php ny da trn vic cn lng bi thu c trn ci lc, sau khi lc mt th tch khng kh xc nh. Kt qu hm lng bi trong khng kh c biu th bng mg/m3. 3. Dng c 3.1. Dng c ly mu u ly mu Lu lng k hoc ng h o lu lng c sai s khngln hn 5%; My ht khng kh; ng h bm giy; Panh gp bng kim loi khng r, u bng nha hoc bt nha khng c rng hoc mu. 3.2. Ci lc bi Ci lc bi lm bng vt liu c sc cn nh, hiu sut lc cao. Din tch lm vic ca ci lc phi m bo sao cho lu lng khng kh i qua trn mt n v din tch khng vt qu lu lng cho php, c hng sn xut quy nh cho tng loi vt liu lm ci lc; Ci lc c ng trong bao kp lm bng giy can k thut. Bao trong cha ci lc c nh s v sy, cn cng ci lc, bao ngoi bo v, c cng s th t vi bao trong; 3.3. Dng c x l mu; T sy c kh nng khng ch nhit vi chnh xc khng vt qu 2OC; Cn phn tch c chnh xc 0,1 mg; m k o m khng kh; Nhit k o nhit khng kh; Hp bo qun mu. 4. Ly mu 4.1. Yu cu chung Mu khng kh c ly cao 1,5m cch mt t im ly mu c b tr ni trng, thong gi t mi pha, m bo i din cho khu vc quan tm; s lng im o, phn b cc im trong

khu vc o cng nh chng trnh o c xc nh theo nhng yu cu c th; Th tch khng kh cn ly cho mt mu phi m bo sao cho lng bi thu c trn ci lc khng nh hn 10 mg; 4.2. Chun b ly mu Trc khi ly mu ci lc c x l, cn theo iu 4 ca tiu chun ny; Dng c ly mu c lp rp theo trnh t: u ly mu - lu lng k - my ht; Dng panh gp ci lc lp vo u ly mu, h thng u ly mu - lu lng k phi m bo kn; Ghi a im, thi gian ly mu, s hiu ci lc vo s ring. 4.3. Ly mu: Bt my, ng thi xc nh thi im bt u ly mu; C 3 pht ghi gi tr lu lng 1 ln - vi mu 30 pht; C 1 gi ghi gi tr lu lng 1 ln - vi mu 24 gi; Sau thi gian ly mu cn thit, tt my Dng panh gp ci lc vo bao, vo hp bo qun. 5. X l mu 5.1. Ci lc, trong bao kp c sy nhit 60OC trong thi gian 4 gi; 5.2. Sau khi sy, cc bao ng ci lc c t trong mi trng cn 24 gi trc khi cn; 5.3. Mi trng cn lmi trng c nhit 25 2OC m khng kh 60 5%; 5.4. Tin hnh cn ci lc cng vi bao trong. Vic cn ci lc trc v sau khi ly mu phi c thc hin trong nhng iu kin nh nhau, trn cng mt cn phn tch, bi cng mt k thut vin; 5.5. Ghi kt qu cn trc v sau khi ly mu ln bao ngoi ca ci lc (m1 v m2); 5.6. Mi loi ci lc v mi l ci lc cn ly mt s mu trng (ci lc i chng). 6. Tnh kt qu 6.1. Xc nh th tch khng kh i qua ci lc Th tch khng kh i qua ci lc, lt, c xc nh bng cng thc sau: t N V = L i N i=1 Trong : t - thi gian ly mu, pht; N - s ln c gi tr lu lng L; Li - gi tr lu lng thi im i, lt/ pht. Th tch khng kh (VO), lt, qua ci lc c quy v iu kin tiu chun (P = 102 kPa, T = 298K) c tnh theo cng thc sau:Vo =

Trong : V - th tch khng kh i qua ci lc; P - p sut trung bnh ca khng kh ti ni ly mu, kPa;

( 273 + t ).10 2

298 .V.P

T - nhit trung bnh ca khng kh trong thi gian ly mu, OC. 6.2. Xc nh hm lng bi trong khng kh Hm lng bi mt ln (C30min) v hm lng bi trung bnh mt ngy m (C24h), mg/m3 ca khng kh c tnh bng cng thc sau: 1000 .( m 2 m1 b ) C 30 min.C 24 h = Vo Trong : m1 - khi lng ban u ca ci lc; m2 - khi lng ca ci lc sau khi lc mu; b - gi tr trung bnh cng ca hiu khi lng ca nhng ci lc i chng c cn cng thi im vi ci lc ly mu, mg; Ch thch: 1 - to mi trng cn c m thp, n nh, nn s dng t cch ly, kn, c hai ca nh c gng tay cao su; 2 - Cn c t trong t cch li cng vi vt liu ht m (silicagen); 3 - Ci lc c t vo t ng kn; 4 - Cc thao tc khi cn c thc hin qua gng tay cao su.