Sealing Performance: The Primary Criterion
Whether a valve can seal perfectly tight directly impacts system safety. Testing typically involves simulating 1.5 times the working pressure to observe for internal leakage and external seepage. Valves equipped with metal sealing rings are permitted to exhibit trace leakage (not exceeding 3 drops per minute), whereas soft-seated valves must achieve zero leakage to be deemed qualified. Under high-temperature operating conditions, the sealing effectiveness following thermal expansion must also be tested; certain specialized valves are required to maintain excellent sealing integrity even in environments reaching 400°C.
Flow Characteristics Determine Control Precision
The relationship curve between valve opening and flow rate directly influences the effectiveness of flow regulation. During testing, flow rate values must be recorded at various opening positions as the valve transitions from fully closed to fully open:
Quick-opening valves: Allow 50% of the total flow to pass within the first 10% of valve opening.
Linear valves: Exhibit a flow rate that is directly proportional to the valve opening.
Equal-percentage valves: Are better suited for fine-tuning and precise regulation.
In chemical manufacturing processes, a deviation exceeding 5% in the flow characteristic curve can potentially compromise product quality.
Durability Testing Simulates Real-World Conditions
A valve is considered reliable only if its performance variation remains within 10% after undergoing 5,000 cycles of repeated opening and closing. Durability testing simulates the following conditions:
Opening and closing under pressure (simulating the water hammer effect).
Erosion by particulate media (simulated via sand-injection testing).
Extreme temperature cycling (ranging from -196°C to 350°C).