Safety Alerts 2

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 using spheres. A steep rise near shore stopped the spheres. Offshore gas pressure was increased to move the spheres. The spheres moved but the sudden pressure surge - water hammer - broke a T joint between a Slug Catcher and Sphere Receiver. Water and HC release

• After a hydro test, a foam pig was launched with air to displace the water. It got stuck. Pig Receiver was opened to propel the pig to a front end loader. As the air pressure was raised, the pig was ejected and the force flipped the front end loader

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

• Intelligent Pig: Data collected by a pig was not adequate. A second launch was planned and the pig launcher was left under 120 bar pressure for a month. Door Viton O-ring absorbed the HP ethylene gas. Destructive decomposition damages. During the second launch, the O-ring failed and ethylene was released. BP

• Corrosion over decades increased the gap between Pig Launcher flanges from less than 0.2mm to around 4mm. O-ring failure and gas release. BP

Separators/ Vessels

• Hydrotest: Cold water used in winter ruptured a column. 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

• Hydrotest: Vessels and supporting structures not designed for water load have collapsed. So also columns with weak/ corroded skirts and LPG spheres with supports corroded under insulation

• Hydrotest: Poor quality plate. Vessel failed under hydrotest

• Pyrophoric: Exercise caution while opening vessels with pyrophoric materials - catalysts, coke, adsorbents, filter elements, Butadiene compounds, polymers and metal packing (structured packing is susceptible) - with Iron Sulfide (H2S presence). Sodium hydrosulfite becomes pyrophoric when wet. Pyrophoric materials slowly self-heat and eventually catch fire. Fill vessels with water and drain. Keep pyrophoric materials wet once open to air. Large surface area of packing makes it hard to clean off combustible material even with washout or steam-out. Avoid hot work above or below packing. See DOE’s “Primer on Spontaneous Heating and Pyrophoricity”

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

• Pyrophoric: Evaporator bottom with titanium random packing. Air admitted during start-up + highly reactive titanium. Fire and rupture. BP

• Leaks allowed water to enter a column. Resulting internal corrosion removed iron from column walls and formed Iron Sulfide (pyrophoric) from H2S present in the process. When manways were opened for maintenance and to remove solvent and hydrocarbons, air entered, starting a pyrophoric fire. Tower collapsed. Site had a prior incident but the crew were not aware of alternative procedure to remove solvent and hydrocarbon. CSB

• 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. Add P&ID

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

• Propane Dryer: Purged with N2 and tests done for H2S and H2. Slight N2 purge was maintained to avoid air entry and prevent pyrophoric fires. On removing a valve from a piping skid, trapped H2S was pushed out by N2 purge into worker’s face. Fatality. PPE is a must in a H2S areas. BP