Theoretically dropping high pressure across two valves is better than one valve. However, in practice, two valves will not usually control well together unless the process can operate with a very low proportional band with a slow response time. A better alternative is to use a valve with internal multiple pressure drops. THINKTANK™ manufacture multi-hole and labyrinth trim for such condition. This design reduces cavitation, excessive leakage, hazardous noise, vibration, and mechanical failures.
Before choosing series valves or multi-stage trim, document the required sizing process data, evaluate energy dissipation, and check both cavitation risk and noise-control options. The arrangement must be reviewed as a system rather than assumed from pressure drop alone.
