LPG Piping
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Transcript of LPG Piping
LPG Training Course – Korea May 2007LLOYD’S REGISTER EMEA
LPG Gas Carriers
Cargo Piping
Robbie SillarsLead Specialist – Refrigeration
London Design Support Services
Busan Korea - May 2007
LPG Training Course – Korea 2007LLOYD’S REGISTER EMEA
Piping Functions – Cargo operations
• Cargo tank inerting
• Line inerting
• Loading
• Venting
• Reliquefaction
• Heating
LPG Training Course – Korea 2007LLOYD’S REGISTER EMEA
Piping Functions – ancillary systems
• Initial loading
• Tank drying (low dew point air)
• Inerting and gassing up
• Changing cargo or gas freeing
• Stripping and puddle heating
• Inerting and gas freeing
• Other systems
• Emergency discharge
• Hold drainage
• Methanol
LPG Training Course – Korea 2007LLOYD’S REGISTER EMEA
Typical Layout of an LPG Tanker
Cargo Machinery Room
Water Ballast Tanks Cofferdam
Ballast Pump RoomGas Dangerous area
Gas Safe Area
ForePeak
Engineroom
Cargo Pump
LPG Training Course – Korea 2007LLOYD’S REGISTER EMEA
Typical Layout of an Oil Tanker
Water Ballast Tanks CofferdamPump Room
Gas Dangerous areaGas Safe
Area
Cargo TanksForePeak
EngineRoom
LPG Training Course – Korea 2007LLOYD’S REGISTER EMEA
Oil Tanker Pumping Arrangements
Pump room Cargo tanks
Manifold
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Mast Riser
Cargo Pumps
Cargo Heater
Booster Pumps
Relief Valves
Manifold
Sea Water
Cargo Tank
Dome
Gas Carrier Pumping Arrangements
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Reliquefaction Plant - Simple System
ExpansionDevice
Vapour
Liquid Gas Return Oil-lessCompressors
CargoCondenser
LiquidSump
CargoTank
Sparge Pipe
Intercooler
Single stageconnections
Seawater
KO Pot
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Deck Tanks
• Dependant on proposed cargoes to be carried
• Reduced time alongside at terminal
• Sufficient liquid to ‘gas up’ and cool down one system
• Size depending on cargoes
• Standard arrangement - 1 large and 1 small deck tank
• Ammonia main reason – Propane butane compatible
LPG Training Course – Korea 2007LLOYD’S REGISTER EMEA
LPG Cargo Piping System – Piping requirements
• Material as per Tables 6.1 & 6.4 of the IGC Code
• Stainless steel
• Thin wall – large sizes schedule 10
• ‘L’ Grades (low low-carbon) to allow welding
• Design pressure – IGC Code 10 bar (Boosters more)
• Design Temperature – LPG warmer than minus 55 deg C
• Class II system
• Guidance notes available
LPG Training Course – Korea 2007LLOYD’S REGISTER EMEA
LPG Cargo Pipe Fittings
• Type testing not required due to design temperature
• Isolation arrangements
• Removable spool pieces
• ‘Block and bleed’
• Seut valves
• Bellows pieces (EJMA)
• Ball and Butterfly valves
• Remote control valves – closing time critical
LPG Training Course – Korea 2007LLOYD’S REGISTER EMEA
Hold Drainage Arrangements
Hold void space Ballast tanks
Duct keel / Pipe tunnel
Wateroverboard
Cargo tank(Type A tank)
Machinery space
Cargoto tank
Ballast wateroverboard
Dome
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Why Use Inert Gas?
Gas Free
Inert
Cargo
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Inert Gas Non-return Devices
Oil tanker Gas Carrier
Deck water seal
+N.R. Valve
Two N.R. valvesbleed valve between valves
(no liquid, no ice)(Back flow from hold
spaces only)
LPG Training Course – Korea 2007LLOYD’S REGISTER EMEA
Filling Limits Requirements
• IGC Code filling limit states a limit of 98% at the reference temperature
• Type ‘C’ tanks may be loaded to a level higher than their relief valve set pressure, but never greater than 98%
• SIGTTO document covers how to calculate ‘highest voyage temperature’
• Dispensation of 98.5% now common on Type A LPG carriers
• Dispensation to be acceptable to the administration
• SIGTTO overfill protection guidelines to be followed
LPG Training Course – Korea 2007LLOYD’S REGISTER EMEA
Filling Limits - Type C
• The difference for Type ‘C’ tanks is that the relative density can now be taken at the highest temperature the cargo will reach at design conditions, IGC Code paragraph 15.1.5
• This can only be applied where the venting system has been approved and shown to be suitable for two phase flow.
• Savings are not so great for low pressure tanks where the loading and reference temperatures are close.
• High level alarms are still to be fitted for 98%
LPG Training Course – Korea 2007LLOYD’S REGISTER EMEA
Pressure Relief Arrangements
• The setting of the second pressure relief valve can be at 5%
above MARVS.
• Reduces the amount of cargo vented during short periods
of pressure rise (not fire condition)
• Relief valve vent exit is to be 6 m above the deck storage
tanks and the cargo liquid lines.
• Low melting point materials (< 925C) such as aluminium and
neoprene could be accepted for use as internal parts of relief
valves.
LPG Training Course – Korea 2007LLOYD’S REGISTER EMEA
Pressure Relief Arrangements
• The setting of the second pressure relief valve can be at 5%
above MARVS.
• Reduces the amount of cargo vented during short periods
of pressure rise (not fire condition)
• Low melting point materials, less than 925OC such as
aluminium and neoprene can be accepted for use as internal
parts of relief valves. Neoprene diaphragms being common.
• Relief valve vent exit is to be 6 m above the deck storage
tanks and the cargo liquid lines.
LPG Training Course – Korea 2007LLOYD’S REGISTER EMEA
Relief Valve Pressure Drop Calculations
• Pressure drop calculation s need to be undertaken and
submitted for approval
• Inlet pressure drop, from tank to relief valve, to be < 3%
• Outlet pressure drop is dependant on type of relief valve
fitted.
• For Type A tanks with pilot operated relief valve <
50%
• For Type C tanks with coiled spring < 10%
• Vent mast to be fitted with grill but not flame arrester
CHANGE TITLE IN SLIDE MASTERLLOYD’S REGISTER (amend as req.)
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Services are provided by members of the Lloyd’s Register Group Lloyd’s Register, Lloyd’s Register EMEA and Lloyd’s Register Asia are exempt charities under the UK Charities Act 1993.
For more information please contact:
Robbie SillarsLead Specialist - RefrigerationEngineering SystemsLondon Design Support ServicesLloyd’s Register EMEADirect Tel No. +44 (0) 20 7423 1921Direct Fax No. +44 (0) 20 7423 1824Email [email protected]