Safety Alerts 2

Pipelines

• 1,000 mm buried HP pipeline. Pressure lowered for maintenance and ground excavated. Excavation had damaged thickness by 75%. On pressure restoration, pipeline exploded. 250-450m high flame

• Ineffective anti-corrosion coating + poor cathodic protection of gas pipeline. Exploded

• 20-year-old gas pipeline leak was clamped. On pressurization, the pipeline burst around clamp point, weakened by clamping action

• Gasoline pipeline. Poor route marking. Pipeline routed around an oak tree. Bent section got punctured by excavator while installing an adjacent water pipeline. Released gasoline ignited by water pipeline welding

• Condensate leak between Gas and NGL plants. Line ownership issues delayed isolation. Fire. 3 Crude units + 2 reformers damaged

• For pig trap installation on an export gas pipeline, a cold cut was made on the pipeline. HC leaked and fire. Platform destroyed

• Crude Oil leaked from 2 pipelines, followed by fire and explosion. Massive spill into the sea. Cause?: Improper injection of desulfurizer, an oxidizing agent after a tanker unloaded oil

• European Gas Pipeline Incident Data Group: External interference (35%), corrosion 14%, construction defects 16% and ground movements 13%. Read their ‘Gas Pipelines Incidents Report’

• Wrong pipeline: A contractor instead of cutting an emptied propylene pipeline, mistakenly cut a butene pipeline. The high pressure butene ignited and damaged an ethylene pipe and other pipelines nearby. Fire and explosions 

Pig Launchers/ Receivers

• Pig got stuck in receiver neck. On opening door to pull it out, residual pressure behind the pig blew it. Add a 2” pressure equalization line with Normally Open (NO) valve connecting inlet to door end

• A pipeline dewatering pig got stuck. Air pressure applied to move it cannoned off the pig

• Offshore pipeline dewatered to shore using spheres. A steep rise near landfall stopped the spheres. Offshore gas pressure was increased to move the spheres. The spheres moved but a sudden pressure surge caused the onshore T joint between the Slug Catcher and Sphere Receiver to burst, due to water hammer, releasing water and hydrocarbon

• Pig Launcher interlock sequence was defeated by electrically operated inlet/outlet valves. Manual valves had interlocks. Check

Separators/ Vessels

• Hydrotest: Cold water used ruptured a column. Water was too cold in winter. Hydrotest water should be above 16°C or 10°C above metal impact test temperature. Some avoid SA 515 Gr 70 to avoid brittle failure and go for SA 516

• Pyrophoric Fire: Column collapsed after internals caught fire on opening and admitting air. Wet spent metallic parts with water on opening a vessel in H2S service

• NGL Drier: Spent Mol Sieve was raked down to a truck, kept wet with fire hose to avoid pyrophoric fire. Workers who climbed into the truck to level the sieves were overcome by H2S desorbed on wetting. P&ID Caution Box: “On wetting, Mol Sieve may release H2S. Care and precautions required”

• Exercise caution while opening vessels with Iron Sulphide (H2S presence), Pyrophoric Polymers and Metal Packing (Structured Packing is susceptible). Self-heating may be slow but will eventually catch fire. Fill vessels with water and drain. Keep them wet once open to air. Large surface area of packing is hard to clean of combustible material even with washout or steam-out. Avoid hot work above or below packing. See DOE’s “Primer on Spontaneous Heating and Pyrophoricity”

• Sodium hydrosulphite becomes pyrophoric when wet. Pyrophoric: Catalysts, deposits like coke, adsorbents and filter elements. Butadiene compounds

• Hydrocarbon or chemicals adsorbed in desiccant beds or trapped in sands and sludge can get released, harm or explode while cleaning vessels. Ventilate before entry and while inside. Monitor HC continuously. P&ID Caution Box: “Hydrocarbon/ chemicals adsorbed in desiccants/ sand/ sludge may ignite/ asphyxiate. Care required”

• Static Electricity: Generated during vacuum-emptying adsorbent beds ignited the released HC. Use: Good Earthing, low conductivity hoses and avoid air ingress

• Static Electricity: While water jetting out a gel to clean Test Sep Turbine Meter Filter. Avoid non-antistatic hoses in HC facilities. Earth while working on components like filters

• Passing Valve: Column top blew off as steam leak thru a corroded valve caused a chemical reaction. Use DBB (Double Block and Bleed) or Spec Blind or RSP (Removable Spool Piece)

• Isolation: Reactor was taken out for maintenance with valve isolation only without  isolation blinds, as no manual entry or welding was planned. Flammable vapor leaked into the reactor via the closed valves and the resultant HC:air mixture ignited by a high-speed abrasive wheel used cut thru a piping attached to the reactor. WWW

• Isolation: HC from a column leaked into stripping steam line and reached a Steam Drum. Blind flange ‘harmless’ steam lines when they are connected to process units. WWW

• HP/LP/Atmospheric Sep under purging. Atmospheric Sep outlet was closed and didn’t have an inlet valve or PSV. Ruptured under purge gas pressure

• Faulty level instruments: Column overfilled and spewed out HC liquid and gas via vent. Explosion/Fire. LTs of LC and LAHH/LALL should track each other and give discrepancy alarm

• Faulty level instruments: Gas blowby from HP Sep to LP Sep, whose relief valve was sized for fire only. LTs of LC and LAHH/LALL should track each other and give discrepancy alarm. Size PSVs for gas blowby, if applicable

• Vacuum column: Bottoms operate hot in corrosive, dirty and sour service. Prone to internal erosion/corrosion. Leak caught fire. Skirt was not fire-proofed. Column fell and destroyed the VDU. Selection of right metallurgy and regular inspection for thinning is key

• Chloride Stress Corrosion Cracking: Happens at ~ 50°C in SS 304/316 vessel/ pipe. Adhesive warning tape had 4% Cl in its glue and caused cracks below it. Caution: Stickers, glues or marker pen inks will have Cl