Inadvertent Valve Operation (IVO)

InadvertentValveOperationAnalyzer is a screening tool that diagnoses the credible consequence of a valve being operated outside its intended state — either spuriously opened or closed, or stuck on demand. It implements the scenario taxonomy of API 521 §4.4.13 (inadvertent opening / closing) and NORSOK P-002 §5.5, and ranks severity against the API 521 §5.4.2 accumulation limits.

The analyser is deliberately conservative: it produces frequency-tagged, severity-classified IVO scenarios and remediation recommendations (HIPPS / SIL, double block-and-bleed, CSO / CSC, key-locked, dual check valves, partial-stroke testing). It does not size relief loads — feed the resulting scenario into runRelief or LOPA for that.

Theory

The valve role and the failure mode together determine the credible consequence:

Role × Mode Consequence Severity driver
BLOCK / CONTROL spurious close Blocked outlet Overpressure factor $p_1 / p_d$
BYPASS spurious open into LP segment Overpressure of LP side $p_1 / p_{d,2}$
PSV_ISOLATION closed Loss of relief path SAFETY_CRITICAL
ESD / BLOWDOWN stuck open Failure to isolate / depressure on demand SAFETY_CRITICAL
CHECK stuck open Reverse flow MAJOR

Severity is classified against the API 521 §5.4.2 accumulation limits:

\[\text{severity} = \begin{cases} \text{SAFETY\_CRITICAL} & p_1 / p_d > 1.21 \\ \text{MAJOR} & p_1 / p_d > 1.10 \\ \text{MINOR} & p_1 / p_d > 1.00 \\ \text{NONE} & \text{otherwise} \end{cases}\]

where 1.10 is the maximum accumulation for a single-jeopardy non-fire scenario and 1.21 is the fire / multiple-jeopardy limit.

Default initiating-event frequencies (OREDA / IOGP Report 434-9 screening values):

Both defaults can be overridden via setFrequencyPerYear().

Quick example

SystemInterface fluid = new SystemSrkEos(298.15, 150.0);
fluid.addComponent("methane", 1.0);
fluid.setMixingRule("classic");

Stream feed = new Stream("feed", fluid);
feed.setFlowRate(1000.0, "kg/hr");
feed.setPressure(150.0, "bara");
feed.setTemperature(25.0, "C");
feed.run();

ThrottlingValve xv = new ThrottlingValve("XV-100", feed);
xv.setOutletPressure(50.0);
xv.run();

// Convenience method on ThrottlingValve
InadvertentValveOperationResult result = xv.analyseInadvertentOperation(
    InadvertentValveOperationResult.ValveRole.BLOCK,
    InadvertentValveOperationResult.IvoMode.SPURIOUS_CLOSE,
    100.0);   // downstream design pressure [bara]

System.out.println(result.toJson());

Typical output:

{
  "valveName": "XV-100",
  "role": "BLOCK",
  "mode": "SPURIOUS_CLOSE",
  "severity": "SAFETY_CRITICAL",
  "frequencyPerYear": 0.1,
  "upstreamPressureBara": 150.0,
  "downstreamPressureBara": 50.0,
  "designPressureBara": 100.0,
  "overpressureFactor": 1.5,
  "blockedOutlet": true,
  "reverseFlowRisk": false,
  "lossOfReliefPath": false,
  "failureToIsolateOnDemand": false,
  "description": "Spurious closure of a block / control valve isolates ...",
  "recommendations": [
    "Verify PSV / HIPPS sized for blocked-outlet scenario per API 521 §4.4.13",
    "..."
  ]
}

API surface

Method Purpose
ThrottlingValve.analyseInadvertentOperation(role, mode, designPressureBara) Convenience wrapper
new InadvertentValveOperationAnalyzer(valve).analyze() Run full analysis
setRole(ValveRole) BLOCK / CONTROL / BYPASS / CHECK / PSV_ISOLATION / ESD / BLOWDOWN
setMode(IvoMode) SPURIOUS_OPEN / SPURIOUS_CLOSE / STUCK_OPEN / STUCK_CLOSED / PARTIAL_STROKE
setDesignPressure(p, "bara") Upstream segment design pressure (severity reference)
setDownstreamDesignPressure(p, "bara") LP-side design pressure (for spurious-open / bypass)
setUpstreamPressure(p, "bara") Override the upstream pressure (what-if)
setFrequencyPerYear(double) Override the default initiating-event frequency

Result fields

InadvertentValveOperationResult exposes:

// 1. PSV isolation valve closed → loss of relief path
v.analyseInadvertentOperation(ValveRole.PSV_ISOLATION, IvoMode.SPURIOUS_CLOSE, 100.0);
// severity = SAFETY_CRITICAL, lossOfReliefPath = true

// 2. ESD stuck open → failure to isolate on demand
v.analyseInadvertentOperation(ValveRole.ESD, IvoMode.STUCK_OPEN, 100.0);
// severity = SAFETY_CRITICAL, failureToIsolateOnDemand = true

// 3. Check valve stuck open → reverse flow risk
v.analyseInadvertentOperation(ValveRole.CHECK, IvoMode.STUCK_OPEN, 100.0);
// severity = MAJOR, reverseFlowRisk = true

// 4. Bypass spurious open into LP segment
new InadvertentValveOperationAnalyzer(v)
    .setRole(ValveRole.BYPASS)
    .setMode(IvoMode.SPURIOUS_OPEN)
    .setDesignPressure(150.0, "bara")
    .setDownstreamDesignPressure(50.0, "bara")
    .analyze();
// severity = SAFETY_CRITICAL, overpressureFactor = 3.0

Python (Jupyter) usage

IvoAnalyzer = ns.JClass(
    "neqsim.process.equipment.valve.InadvertentValveOperationAnalyzer")
IvoResult = ns.JClass(
    "neqsim.process.equipment.valve.InadvertentValveOperationResult")

result = valve.analyseInadvertentOperation(
    IvoResult.ValveRole.BLOCK,
    IvoResult.IvoMode.SPURIOUS_CLOSE,
    100.0)
print(result.toJson())

When to use it