London Engineering Group Report of the subcommittee
On
Barge Mounted Power Plants
October 2003
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Contents
1. Introduction
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2. Transportation to site of operation
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3. Types of Operating Environment
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Floating static Floating Special Mooring Grounded Moved about barges
4. Land based Auxiliary Equipment Cabling up
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Fire Protection Fuel Supplies Warehouse and Stores 5. Location Considerations
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Remoteness Inaccessible 6. Types of Power Generation Plant
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Diesel Engines Gas Turbines Steam turbines 7. Contamination
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Fuel Quality Water Quality Air Quality 8. Impact of wave motion and environmental conditions
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9. Maintenance
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10. PML Considerations
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Diesel Sets Waste Heat Boilers Construction Other major non PML losses 11. Consequences of a major failure
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12. Underwriting considerations
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1. Introduction This committee was formed to look at the unique characteristics of Barge Mounted Power Plants, and the implications to machinery Breakdown and Machinery Loss of Profits Insurance.
Power barges have unique characteristics, when compared to other forms of Power generation, in that the construction of the plant is undertaken in a completely different environment to one in which the plant will operate.
Barges will be manufactured within a shipyard and then fitted out with generating equipment before being transported t o the location where they are to operate
This has implications for the ability to maintain and repair such plants and can pose unique problems when major work is to be undertaken.
The composition and operating conditions will vary considerably from barge to barge
Power barges offer a quick and economic solution to building Power plants in remote parts of the world. All-weather accessibility is a problem and consequently entails considerable extra expense in transporting components to site as well as skilled construction labour which need to be housed and the availability of construction equipment .
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2. Transportation to Site of Operation Transportation of the barge to the site of operation can be by wet tow, when the barge is floating freely and is pulled by a larger vessel or tug boat, or conveyed on/in a specially constructed Ocean going ship Two Frame 6B power barges leaving for Nigeria
Excessive movement during a rough sea crossing can cause derangement of components and unbalancing of rotor parts if not properly secured. Possible displacement of fluids.
Five barges onboard conveying ship
Contamination can occur due to the ingress of salt water and the atmosphere having a high saline content.
Heavy lift ship ballasted for power barge loadout
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3. Types of Operating Environment Floating Static Where there is to the long-term demand for a constant power supply, the barge will be permanently located at one site. Barges can be permanently moored alongside wharfs, jetties, quays, and while still being a floating vessel will not move from this location. Such barges are therefore exposed to wave movement and potentially impact from other vessels.
Mooring arrangement
Floating Special Mooring In some instances special moorings have been created where the floating barge is protected from passing traffic. The site is dredged to create a mooring off a river. Another example of a special mooring is where a permanent “wet berth” is created with a lock gate enabling the power barge to be floated into the mooring and then the water level maintained to protect t he barge form fluctuations in river level. This also provides protection from impact from other vessels. Grounded To achieve a more stable operating environment and eliminate perils of sea or water, a dock is excavated, the barge is floated in and then sealed off f rom the water course, water is pumped out and the dock is filled to create a permanent land based generating station. For all intents and purposes this is now a land based station, Special considerations still apply as the means by which the barge was transported, could not be utilised in the event that spares or replacement parts needed to be delivered. Moved about Barges Barges can provide the temporary power supply when land based generating plants undergo major overall for maintenance. Barges used in these circumstances are then moved from site to site to cover for stations which are out of commission. In some instances barges are used to supply power where short term power is needed to overcome temporary shortages. In these circumstances the facility will have a power purchase agreement probably of less than ten years duration. Barge owners sometimes rely on the threat of moving their barges to another country as a means of extracting payments from customers who are reluctant to pay.
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4. Land based Auxiliary Equipment Cabling up The power barge usually has a generator step up transformer and switching substation mounted on the barge. An overhead line usually makes the connection to the host system. This provides a flexible interconnect allowing the barge to move with changes in tide or river level without a significant impact on the reliability of the connection. A cable connection, particularly at higher voltages is less reliable where the barge moves causing Land Based Main transformers the cable to flex. The cable design has to ensure that bends are not less than the minimum recommended. The cable is protected from direct sunlight in high ambient temperature locations and is properly clamped t o secure the cable in the event of short circuit to earth, A short circuit to earth results in high forces trying to force the cables apart. This can result in the cable lashing about and causing damage to equipment and injuries to personnel. Fire Protection The power barge may be moored in a place where the land based local fire fighting capability is not great or if adequate will have difficulty reaching the barge. The barge usually has its own fire fighting capability in the form of diesel and electric motor driven firewater pumps. In some instances either or both of the pumps are inadequate to supply sufficient water. In some cases the only large capacity pump is electric and depends on the barge to supply the electric power. Shore based fire fighting equipment should be capable of operating independently of the power barge. If the power barge fuel supply is from fuel barge moored close to the power barge, this adds another fire hazard. A major fire on the fuel barge may spread to the power barge or cause heat damage to expose equipment Fuel Supplies Barges are typically fuelled with natural gas or liquid fuels and in some cases both. Where barges move with changes in tides or river levels the fuel connection to the barge has to be flexible. The flexible connection needs to be well designed and maintained to prevent failure of the connection. Oil spills are likely to have a significant environmental impact with significant clean-up costs. Barges fuelled with naphtha or gas condensates pose a higher fire risk than those fuelled with distillate oil because these fuels are very volatile at relatively low temperatures and have a low self ignition temperature. Because of the fire hazards associated with most fuels strict no smoking policies should be in place with prominent notices posted around the facility 6
Warehouse and Stores Warehouse facilities for spare parts storage can be severely limited when the major stores area is on the barge itself. This can result in inadequate spare parts holdings with the possibility of increased exposure to business interruption claims in the event of a plant failure.
5. Location Considerations Remoteness Power barges are an attractive solution to the provision of power to remote locations, providing of course that they have access to the sea. Power barges being constructed away from the location where they will operate has the advantage that components do not have to be transported across hostile and difficult terrain. Labour costs are minimised as skilled staff do not have to be transported to and accommodated in remote locations avoiding the extra infrastructure costs and allowances.
Five operational power barges
Inaccessible Whilst the barge has been sited at a location with navigational access to the sea, the location may be inaccessible or not easily accessible over land. This becomes a major consideration when maintenance or repairs are undertaken. It may not be possible for large cranes that would be required for lifting machinery to access the site. Weight limits on roads and bridges, or height of tunnels may prevent Large replacement components being transported to the site by road or rail. Where it is not economically or physically possible to supply cranage and parts by waterway, the option is to remove the barge to a dry dock or quayside, where the work can be undertaken.
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6. Types of Power Generation Plant Diesel Engines Operating in isolation or in association with waste heat boilers and steam turbines, appear to be the most common method of generation employed on barges. The size of the diesel Engine should not be underestimated and equally the craneage needed for lifting the block. Marine Diesels are robust and have a proven track record for operating in a 1.5 MW Waukesha reciprocating engine generator marine environment. They are not. immune to catastrophic failure An obstruction can however cause destruction of the destruction of cylinders and crankshaft Gas Turbines Becoming more common, operating with waste heat boilers and steam turbines. More susceptible to damage from environmental perils Steam turbines Not very often seen and then usually second hand, possibly previously in military use
7. Contamination Fuel Quality Contamination – Fuel may be conveyed by sea, potential contamination from tanks of conveying vessel not being cleaned properly. Poor checking of quality when fuel delivered, due to lack of facilities at site to analyse if fuel meets design specifications, could lead to contaminated fuel being used. Large sums of money transfer at this point and the possibility of incorrect fuel being supplied for fraudulent purposes has to be considered. When in close proximity to the sea, there can be exposure to salt water and air with high saline content, which can cause contamination to fuel oil if t here is inadequate protection. Water Quality For barges with a steam cycle, make-up water quality is important. The demineralised water storage tanks can become contaminated with salt water and if undetected cause rapid corrosion damage to the steam generator. If this water is used for NOx control on a gas turbine the introduction of sodium and potassium will cause rapid corrosion of the hot gas path components.
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Air Quality High salt content in the air can clog air filters as well as causing accelerated corrosion to compressors.
8. Impact of Wave Motion and Environmental Conditions Not considered a problem during normal operation and with the anticipated sea conditions. The mooring of the barge should act as a stabilizing factor to reduce the impact of wave movement. Extreme sea conditions could cause derangement or misalignment to occur. The atmosphere will have a high saline and moisture content, which can cause corrosion problems. Air purification will need to be capable of dealing with this to filter out excessive saline and moisture. Cooling water and feed water may well be drawn from the sea and purified through a desalination plant on board. This must be capable of taking out the salt content and coping with other pollutants which might be discharged into the sea. The feed water is far more vulnerable to fluctuating quality than land based sites.
9. Maintenance Static risks should be no more hazardous than a conventional power plant, subject to the ability to transport adequate spares to site and the competence of the maintenance staff. Maintenance standards are however sometimes less than those for similar land based plant, because barge operators tend to have less resources and the more remote locations are easily forgotten. Barges which are moved from site to site, pose an enhanced risk, as there is a tendency for maintenance to be neglected as responsibility moves from one location to another.
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10.PML Considerations Diesel Sets Overspeeding or obstruction can cause destruction of cylinders and crankshaft. The cost to repair damage could exceed 50% of the unit value. . Series loss through fuel contamination. If all units on a barge are being f ed the same fuel, any impurities in the fuel quality will equally cause damage to all of the sets. Waste Heat Boilers, Distortion through dry firing. Steam / Gas Turbines, 100% damage due to overspeeding / first stage blade failure. Construction Compact nature of the barge may increase repair costs
Other major non PML losses Corrosion caused by poor feedwater quality Fuel contamination Corrosion of hot gas path components from Contaminated NOx control water Winding failures due to salt water ingress on direct air cooled stators
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11. Consequences of a Major Failure Unlike other power stations, power barges are not built or assembled at the location where they operate. If major damage occurs, it may not be possible to get a Jib crane either to the location or the location may prevent the crane from operating alongside the barge. This could be either due to the barge being moored away from the land or the ground not being solid enough to support the weight of the crane and the Engine it is lif ting. The implications of not being able to repair on site and the barge being taken to manufacturer/dry dock are that: 1. There is a loss of production for all units on the barge, not just the one that is damaged, while the barge is away for repair. 2. The Barge is at risk during the Journey to dry dock, and if sinks there the Loss of profit could be attributed to the original cause, till replaced and full production resumes, with a replacement barge, subject to application of the indemnity period. 3. There is an increased risk of damage to machines during the transit. Exposure to a salt air and derangement due to rough weather could pose an increased breakdown risk when the barge resumes operation. 4. There can be seasonal considerations, e.g. hurricane season, which would prevent the barge from being moved at certain times of the year, resulting in a prolonged interruption period. 5. Significantly increased repair costs. 6. Prolonged Interruption period and increased costs due to re-cabling between ship and Shore
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12. Underwriting Considerations Confirmation is needed that the largest generator set can be replaced at the location of operation and that the barge is static and will not be moved to any other locations To avoid losses from perils of the sea and prolonged business interruption, from an event occurring while the barge is removed for repairs, An Exclusion needs to be applied for any loss or damage or consequential loss while the barge is away from the location irrespective of the reason for removal being due to an insured event or otherwise Series Loss clause would protect from common fault claims and could assist fuel contamination, but would have no effect if the damage was caused simultaneously . Warranties to ensure that units are serviced in accordance with OEM’s recommendations would document an obligation for the Insured to ensure that machinery is properly maintained. Suitable equipment depreciation clauses can be considered A suitable fuel quality clause would be appropriate. Cover would normally be subject to a satisfactory survey or subject to the recommendations from a survey being carried out.
LEG Subcommittee Steven Norcliffe – Munich re Simon Wilcock – Swiss Re Andrew Bowles – Zurich London
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