Mae falf wirio codi yn cyfeirio at y falf sy'n agor ac yn cau'r disg yn awtomatig yn dibynnu ar lif y cyfrwng ei hun i atal ôl-lifiad canolig, a elwir hefyd yn falf wirio, falf unffordd, falf gwrthlif, a falf pwysedd cefn. Mae falf wirio yn falf awtomatig. Ei brif swyddogaeth yw atal ôl-lif canolig, pwmp gwrthdroi a modur gyrru, a rhyddhau cyfrwng cynhwysydd. Gellir defnyddio falfiau gwirio hefyd mewn piblinellau i gyflenwi systemau ategol lle gall pwysau godi uwchlaw pwysedd system. Gellir rhannu falfiau gwirio yn falfiau gwirio swing (cylchdroi yn ôl canol disgyrchiant) a falfiau gwirio lifft (symud ar hyd yr echelin).
Data technegol
| PN(MPa)Pwysau enwol | 1.6 | 2.5 | 4.0 | |
| (MPa)Pwysau prawf | Prawf cryfder cragen | 2.4 | 3.75 | 6.0 |
| Prawf sêl (Hylif) | 1.76 | 2.75 | 4.4 | |
| Prawf sêl (Nwy) | 0.5 ~ 0.7 | |||
| Cyfrwng addas | dŵr, stêm, olew | PAsidau niter | Rolew | |
| Tymheredd addas | ≤425 | ≤100 | ≤550 | |
Mesurydd y prif rannau
| Nac ydw. | Enw rhan | Deunydd | |
| ASTM | GB | ||
| 1 | Corff falf | WCB, WC1, WC6, WC9, C5 CF8,CF8M,CF8C,CF3,CF3M | WCB, WC1, WC6, WC9, C5 CF8, CF8M, CF8C, CF3, CF3M |
| 2 | Disg falf | WCB, WC1, WC6, WC9, C5 CF8, CF8M, CF8C, CF3, CF3M | WCB, WC1, WC6, WC9, C5 CF8, CF8M, CF8C, CF3, CF3M |
| 3 | Bolltau gre | A193-B7,A320-B8,A193-B8M | 35CrMoA,25Cr2MoV,0CM8Ni9,0Cr17Ni12Mo2 |
| 4 | Cnau hecs | A194-2H,A194-8,A194-8M | 45,35CrMoA,25Cr2MoV, 0Cr18Ni9,0Cr17Ni12Mo2 |
| 5 | Gasged | Graffit hyblyg + dur di-staen | Graffit hyblyg + dur di-staen |
| 6 | boned falf | A105, F11, F22, F5, F9 F304, F316, F321, F304L, F316L | 25,1Cr18Ni9Ni,0Cr18Ni12Mo2Ti 20Cr1Mo1V,25Cr2MoV |
Prif dimensiynau
| PN(MPa) | DN(mm) | L | H | D | Ch1 | D2 | D6 | b | dd | f2 | Z-ød |
| 1.6 | 15 | 130 | 77 | 95 | 65 | 45 | - | 14 | 2 | - | 4-14 |
| 20 | 150 | 77 | 105 | 75 | 55 | - | 14 | 2 | - | 4-14 | |
| 25 | 160 | 80 | 115 | 85 | 65 | - | 16 | 2 | - | 4-14 | |
| 32 | 180 | 85 | 135 | 100 | 78 | - | 16 | 2 | - | 4-18 | |
| 40 | 200 | 95 | 145 | 110 | 85 | - | 16 | 3 | - | 4-18 | |
| 50 | 230 | 105 | 160 | 125 | 100 | - | 16 | 3 | - | 4-18 | |
| 65 | 290 | 120 | 180 | 145 | 120 | - | 18 | 3 | - | 4-18 | |
| 80 | 310 | 130 | 195 | 160 | 135 | - | 20 | 3 | - | 8-18 | |
| 100 | 350 | 140 | 215 | 180 | 155 | - | 20 | 3 | - | 8-18 | |
| 125 | 400 | 155 | 245 | 210 | 185 | - | 22 | 3 | - | 8-18 | |
| 150 | 480 | 180 | 280 | 240 | 210 | - | 24 | 3 | - | 8-23 | |
| 200 | 600 | 245 | 335 | 295 | 265 | - | 26 | 3 | - | 12-23 | |
| 2.5 | 15 | 130 | 100 | 95 | 65 | 45 | - | 16 | 2 | - | 4-14 |
| 20 | 150 | 105 | 105 | 75 | 55 | - | 16 | 2 | - | 4-14 | |
| 25 | 160 | 120 | 115 | 85 | 65 | - | 16 | 2 | - | 4-14 | |
| 32 | 180 | 130 | 135 | 100 | 78 | - | 18 | 2 | - | 4-18 | |
| 40 | 200 | 135 | 145 | 110 | 85 | - | 18 | 3 | - | 4-18 | |
| 50 | 230 | 149 | 160 | 125 | 100 | - | 20 | 3 | - | 4-18 | |
| 80 | 310 | 169 | 195 | 160 | 135 | - | 22 | 3 | - | 8-18 | |
| 100 | 350 | 194 | 230 | 190 | 160 | - | 24 | 3 | - | 8-23 | |
| 150 | 480 | 255 | 300 | 250 | 218 | - | 30 | 3 | - | 8-25 | |
| 200 | 600 | 305 | 360 | 310 | 278 | - | 34 | 3 | - | 12-25 | |
| 4.0 | 15 | 130 | 100 | 95 | 65 | 45 | 40 | 16 | 2 | 4 | 4-14 |
| 20 | 150 | 105 | 105 | 75 | 55 | 51 | 16 | 2 | 4 | 4-14 | |
| 25 | 160 | 120 | 115 | 85 | 65 | 58 | 16 | 2 | 4 | 4-14 | |
| 32 | 180 | 130 | 135 | 100 | 78 | 66 | 18 | 2 | 4 | 4-18 | |
| 40 | 200 | 135 | 145 | 110 | 85 | 76 | 18 | 3 | 4 | 4-18 | |
| 50 | 230 | 149 | 160 | 125 | 100 | 88 | 20 | 3 | 4 | 4-18 | |
| 80 | 310 | 169 | 195 | 160 | 135 | 121 | 22 | 3 | 4 | 8-18 | |
| 100 | 350 | 194 | 230 | 190 | 160 | 150 | 24 | 3 | 4.5 | 8-23 | |
| 150 | 480 | 255 | 300 | 250 | 218 | 204 | 30 | 3 | 4.5 | 8-25 | |
| 200 | 600 | 305 | 375 | 320 | 282 | 260 | 38 | 3 | 4.5 | 12-30 |















