Rupture Disk Dynamic Behavior

This document explains the rupture disk implementation in NeqSim, demonstrating the key difference between rupture disks and pressure safety valves (PSVs).

What is a Rupture Disk?

A rupture disk (also called a bursting disc) is a non-reclosing pressure relief device that:

• Bursts at a specific set pressure
• Opens rapidly and remains fully open
• Cannot reseat - it’s a one-time use device
• Must be physically replaced after activation

This is fundamentally different from a safety valve which:

• Opens at set pressure
• Closes again when pressure drops to blowdown/reseat pressure
• Can cycle multiple times
• Uses hysteresis to prevent chattering

Applications

Rupture disks are typically used for:

1. Primary relief for rapid pressure rise scenarios (runaway reactions)
2. Backup protection in series with safety valves
3. Corrosive/fouling services where PSVs would fail
4. Emergency relief where instant full opening is required
5. Low maintenance applications

Implementation

RuptureDisk Class

RuptureDisk disk = new RuptureDisk("RD-001", inletStream);
disk.setBurstPressure(55.0);  // bara - disk ruptures at this pressure
disk.setFullOpenPressure(57.75);  // bara - fully open (typically 5% above burst)
disk.setOutletPressure(1.0, "bara");
disk.setCv(150.0);
disk.setCalculateSteadyState(false);

Key Parameters

Parameter	Description	Typical Value
Burst Pressure	Pressure at which disk ruptures	Set by design
Full Open Pressure	Pressure for 100% opening	105-110% of burst
Cv	Flow coefficient	Sized for relief scenario

Automatic Behavior in runTransient()

The rupture disk automatically:

1. Monitors inlet pressure each time step
2. Ruptures when pressure ≥ burst pressure
3. Remains fully open regardless of subsequent pressure changes
4. Tracks state with hasRuptured() flag

Comparison: Rupture Disk vs Safety Valve

Safety Valve (PSV) with Hysteresis

Pressure rises → Opens at 55 bara → Relieves pressure
Pressure drops → Stays open until 51.15 bara (blowdown)
Pressure below blowdown → Closes → Can reopen if needed

Rupture Disk

Pressure rises → Bursts at 55 bara → Relieves pressure
Pressure drops → STAYS 100% OPEN
Pressure at any level → STAYS 100% OPEN (one-time device)

Example: Blocked Outlet Scenario

// Setup separator with gas splitter
Separator separator = new Separator("HP Separator", feedStream);
Splitter gasSplitter = new Splitter("Gas Splitter", separator.getGasOutStream(), 2);

// Normal operation path
ThrottlingValve pcv = new ThrottlingValve("PCV-001", gasSplitter.getSplitStream(0));
pcv.setPercentValveOpening(50.0);

// Emergency relief path
RuptureDisk disk = new RuptureDisk("RD-001", gasSplitter.getSplitStream(1));
disk.setBurstPressure(55.0);
disk.setFullOpenPressure(57.75);

// Dynamic simulation
UUID id = UUID.randomUUID();
for (int i = 0; i < numSteps; i++) {
    double time = i * dt;
    
    // Simulate PCV blockage at t=50s
    if (time >= 50.0 && time < 51.0) {
        pcv.setPercentValveOpening(1.0);
    }
    
    // Simulate PCV recovery at t=200s
    if (time >= 200.0 && time < 201.0) {
        pcv.setPercentValveOpening(50.0);
    }
    
    // Run transient - disk bursts automatically
    separator.runTransient(dt, id);
    gasSplitter.runTransient(dt, id);
    pcv.runTransient(dt, id);
    disk.runTransient(dt, id);  // Automatic rupture control
}

Test Results

From RuptureDiskDynamicTest:

Behavior Sequence

Time:   0-120s: Normal operation, disk closed, pressure below 55 bara
Time:   ~130s: Disk ruptures at 55 bara
Time: 140-200s: Pressure controlled at ~53 bara, disk 100% open
Time: 200-300s: PCV reopens, pressure drops to 30 bara
              → Disk STILL 100% open!

Key Observations

| Metric | Value | |——–|——-| | Burst pressure | 55.0 bara | | Max pressure | 55.35 bara | | Max relief flow | 5950 kg/hr | | Final pressure | 30.5 bara | | Final disk opening | 100% |

Critical Behavior: Disk remained fully open even though pressure dropped 24.5 bara below the burst pressure!

Disk Reset (Simulation Only)

For simulation purposes, you can reset a ruptured disk:

disk.reset();  // Simulates disk replacement
// Disk is now unruptured and closed
// In reality, you would physically replace the disk

Best Practices

1. Sizing: Size rupture disks for full relief capacity - they open instantly
2. Series Protection: Often used upstream of PSVs to protect them from corrosion
3. Burst Tolerance: Account for manufacturing tolerance (typically ±5%)
4. Rapid Opening: Full open pressure is typically 5% above burst (vs 10% for PSV)
5. One-Time Use: Plan for system shutdown and disk replacement after rupture
6. Testing: Use reset() method in simulations to test multiple scenarios

When to Use Rupture Disk vs PSV

Use Rupture Disk When:

• ✅ Pressure rise is extremely rapid
• ✅ Medium is highly corrosive or fouling
• ✅ Instant full area opening is required
• ✅ Low maintenance is critical
• ✅ Operating as backup to PSV

Use Safety Valve When:

• ✅ Pressure relief is cyclic
• ✅ Need reseating capability
• ✅ Clean, non-fouling service
• ✅ Controlled gradual opening preferred
• ✅ Want to avoid system shutdown

See Also

• Rupture disk class: RuptureDisk.java
• Test implementation: RuptureDiskDynamicTest.java
• PSV comparison: psv_dynamic_sizing_example.md
• ASME Section VIII - Pressure Relief Devices
• API 520 Part 1 - Sizing and Selection