Probabilistic Design and Safety-Constrained Optimization of a Firewater-Powered Portable Valve Actuation System

Almost every hazardous facility owns a pressurized, regularly inspected source of hydraulic power: its firewater system. This study asks whether a portable water-hydraulic operator driven through a fire hose can stroke seized or stiff valves without overloading the stem or taking the water that firefighting needs, and which design and operating rules make that likely. A Monte Carlo model with an explicit hydraulic circuit, motor leakage, a relief valve and the surge on stall is evaluated on 200,000 draws; every added mechanism can be switched off, recovering the earlier first-order model exactly. Under assumed input distributions a baseline tool (200 cc, 250:1, 60 gpm) completes the stroke in 75% of the draws but without exceeding the allowable stem torque in only 63%, because a median surge of 45 psi accompanies the stall; a stroke needs about 1,600 L of water. A hose-side accumulator and a relief chart set from the stem strength reduce the over-torque probability to 1% (motor speed at most 3,000 rpm) at a cost of 3 to 9 percentage points of safe strokes, of which a slow creep flow at the start and end of travel recovers 4 to 6. The surge model reproduces classical water-hammer results. The optimum holds out of sample but not under a stem 30% weaker than its data sheet (14% over-torque), and the 2 firefighting reserve is protected only if the spare flow of the source is known. The results are simulation outputs under assumed priors, not measurements.