Commissioning and Startup Training Curriculum

Mod 10 - Startup Sequences

Module from the Commissioning and Startup Training Curriculum curriculum.

Module 10 — Startup Sequences · Learning Objectives · 1. Execute cold startup of a unit from fully blocked-in condition. · 2. Execute hot restart following a trip or short shutdown. · 3. Manage transition from circulation to feed-in safely. · 4. Control severity ramp to avoid thermal runaways and catalyst damage. · 5. Troubleshoot common startup problems across units. · Cold Startup — Generic Sequence

Step	Action
1	PSSR complete; permit issued
2	Utilities confirmed (IA, N2, CW, steam, fuel gas, flare)
3	Reactor / column inert <1% O2
4	Pressure up with recycle/N2 per rate
5	Circulate clean oil via pumps; warm up to feed temp
6	Raise reactor inlet to threshold temp
7	Introduce feed at reduced rate (50% typical)
8	Slowly raise WABT per licensor curve
9	Bring product side to spec; place draws in service
10	Ramp to 100% rate over defined shift sequence
Hot Restart After Trip
Trigger	Immediate Action
Reactor trip (EPRV / EDV)	Reactor depressured to flare; maintain recycle H2
Heater trip	Hold feed circulation on cold-only path until heater relight
Compressor trip	Depressure or hold per PSM procedure
Utility loss	ESD logic per hazard matrix; save catalyst by maintaining H2
Restart window	Hot restart allowed if <4 hr; cold sequence if longer
Transition: Circulation → Feed-In
Item	Action
Rate	Start ~50% design
Slop handling	Off-spec product to slop tank until on-spec
Delta-T limit	Per licensor, usually <50 °F/hr on reactor
H2S / H2 make-up	Maintain H2 partial pressure per design
Column temps	Stabilize reflux before pulling side draws
Catalyst hot spot	Watch bed T-profile for runaway
Recycle gas purity	Verify before increasing severity
Common Startup Problems
Symptom	Likely Cause
Heater tube overheat	Low flow with high firing
Reactor runaway	Exotherm in bed
Compressor surge	Low flow / high MW
Flare smoking	Incomplete combustion
Pump cavitation	Low NPSHa
Column flooding	Heat/reflux imbalance
Sour water foul	Inert / wet system
Common PSSR Findings
Area	Common Finding
Procedures	Draft versions used — require approved revision
Training	Operator training records missing per task
MOC	Field change not recorded
Relief	Nameplate set pressure differs from design
Car-seal	Car-seals missing on critical isolations
Signage	LEL zone markings incomplete
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Source: Commissioning_and_Startup_Training_Curriculum_v1.xlsx · Sheet: Mod 10 - Startup Sequences

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