tiu chun vit nam tcvn 4513 : 1988

8. Kt n|c p lc v b cha n|c 8.1. Kt n|c p lc phi bo m cha |c mt khi l|ng n|c d tr iu chnh

ch n|c khng iu ha v cp n|c cha chy. Cn phi c ng phn phi ring m bo l|ng n|c cha chy nguyn vn v khng s dng n|c vo cc mc ch khc. Ch thch:

l. Tr|ng hp bn trong mi cn h ca nh cao tng c b cha n|c d tr ring th khng cn phi t kt n|c p lc chung trn mi.

2. Trong mi tr|ng hp, dung tch kt n|c p lc khng |c v|t qu t 20 n 25m3. Nu v|t qu quy nh trn phi chia nh mi kt phc v cho mt khu vc cp n|c nht nh.

8.2. Dung tch iu ha ca kt n|c p lc hoc kt n|c kh nn ca my bm n|c sinh hot v sn xut cn xc nh theo cng thc :

hQW b.4

(8)

Trong :

W - Dung tch iu ha ca kt n|c (m3); Qb- cng sut nh mc ca mt my bm hay my bm c cng sut ln nht trong nhm my bm cng tc cng m (m3/h);

n - S ln m my bm nhiu nht trong mt gi. Tr s n ly nh| sau:

- My bm kt h : n= t 2 n 4;

- My bm vi kt kh nn : n = t 6 n l0;

Gi tr ln dng cho my bm c cng sut nh n l0 KW.

8.3. Kt n|c p lc v b cha n|c c my bm tng p dng cha chy phi d tr mt l|ng n|c nh| sau:

a) i vi cng trnh cng nghip: l|ng n|c d tr cha chy tnh vi thi gian dp tt m chy dng hng cha chy bn trong v thit b phun n|c t ng l l0 pht u khi xy ra chy.

b) i vi cng trnh dn dng th n|c d tr phi bo m cung cp n|c cha chy bn trong thi gian l l0 pht, ng thi vn phi m bo l|ng n|c dng cho sinh hot ln nht. Ch thch: Tr|ng hp my bm cha chy iu khin t ng th l|ng n|c d tr cha chy c th gim xung l thi gian cha chy lin tc c th tnh l 5 pht.

8.4. Dung tch ton phn ca kt n|c kh nn cn xc nh theo cng thc :

DE 1WVK (9)

Dung tch ton phn kt n|c p lc c my bm cha chy t ng tnh theo cng thc :

VA = E (w + wl) (10) Trong :

REERectangle