Update time:2025.08.27 Views:71
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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