Update time:2025.08.27 Views:193
In our daily work, we often receive inquiries from customers regarding the testing standards and methods applied to the valves we were produced,here we ZhengFeng valve provide the offcial answer;
|
Standard |
Grade of leakage |
testing medium |
Maximum allowable leakage |
decision method |
|
API 598 |
Metal seated | Liquid |
No visible water droplets (visual inspection) |
Qualitative determination: No water droplets form at the outlet end within ≥1 minute |
| Gas |
No continuous bubbles (single bubbles are allowed to occur intermittently) |
Qualitative determination: No continuous bubble flow within ≥1 minute (observe by immersing the outlet in water) |
||
| soft seat seal | Liquid / Gas | Zero leakage |
There are no droplets or bubbles at all |
|
|
ANSI/FCI 70-2 |
Class II |
Liquid / Gas |
≤ 0.5% Rated flow of the valve |
QL≤0.005×Qrated |
|
Class III |
Liquid / Gas |
≤ 0.1% Rated flow of the valve |
QL≤0.001×Qrated |
|
|
Class IV |
Liquid / Gas |
≤ 0.1% Rated flow of the valve |
QL=0.0004×ΔP×D (ml/min) |
|
|
Class VI |
Gas |
Bubble counting method （DN≤50：≤6 bubbles/min） |
（ΔP=differential presasure/kPa, D=diameter of seat/mm） |
|
|
ISO 5208 |
Class B |
Liquid |
≤ 0.1 × DN (ml/min) |
QL≤0.1×DN (example : size DN100≤10 ml/min) |
| Class C |
Liquid |
≤ 0.3 × DN (ml/min) |
QL≤0.3×DN |
|
| Class D |
Gas |
≤ 0.3 × DN (ml/min) or ≤ 3 × DN (bubbles/min) |
QL≤0.3×DN (ml/min) |
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