09.02.07
Reconditioning of cylinder liners
After extended use, cylinder liners of both 4-stroke, and 2-stroke engines will show signs of wear and tear. This wear is not evenly distributed. Most of the wear occurs between the reversal points of the upper and lower piston rings. Often we find scuffing marks where the upper piston ring changes direction. Also most cylinder liners, especially those of 4-stroke engines, will become slightly oval over time.
Another effect of this wear is increased lubricating oil consumption. When a cylinder liner comes out of the factory, it will have a slight cross-hatch pattern honed into it’s surface. This increased roughness helps the liner surface to retain the lubricating oil needed to provide an evenly distributed oil film between the piston ring reversal points. If the surface becomes too smooth due to wear and/or glazing of the surface, the piston rings will easier break the oil film, causing even more wear. Also any excess oil will no longer be retained by the liner surface, and burn off in stead, causing increased lubricating oil consumption.
If the total amount of wear is still within the rejection criteria as given by the manufacturer, the liners can be reconditioned. When we get them in our workshop, we will first clean and measure them. All measurements go into special protocol sheets. The next step is using a honing machine to make the cylinder bore round again, with a slightly bigger diameter, and restore the surface roughness needed to retain sufficient lube oil. Our honing machine can handle cylinder liners up to a diameter of 1 meter. The machine is made by the Swedish company Chris Marine. Here is a brief description of one of their typical honing machines: honing-machine.pdf
The pictures show a liner of a MAN B&W K80MC (this is a marine 2-stroke engine with a cylinder bore of 800mm). The first as we receive it in our workshop, the second with the liner in the honing pit with the honing machine inserted.
Finally the cylinder liner is measured again. Sometimes the landing surfaces between liner and cylinder cover, or liner and engine frame need to be skimmed on the lathe, to ensure the correct flatness of the sealing surfaces. Diameters, surface roughness, and other critical dimensions are recorded, and if everything is within the right tolerances, the liner is packed and shipped back on board again.
If necessary we can also transport our honing machine on board, and perform the honing in-situ, while the liner is still in the engine.
Why China is trying to colonise Africa
Interesting article by David Blair in the Telegraph of August 31.
No one alive at the close of the 19th century could have missed the “scramble for Africa”. A motley collection of robber barons, imperialist ideologues, explorers, rogues and adventurers - the likes of Cecil Rhodes and the appalling Leopold II, King of the Belgians - carved up the continent in the name of five European powers.
Today, few appear to have noticed that a second “scramble for Africa” is under way. This time, only one giant country is involved, but its ambitions are every bit as momentous as those of Rhodes and company. With every day that passes, China’s economic tentacles extend deeper into Africa. While Europe sought direct political control, China is acquiring a vast and informal economic empire.
Reliable information on Beijing’s African adventure is hard to come by. But we do know that trade between China and the world’s poorest continent totalled about £30 billion last year - a sixfold increase since 2000.
China now buys about one third of its oil from Africa, mainly from Angola, where an £800 million deal to develop a new field was signed last May, and from Sudan, where Beijing built a 900-mile pipeline and invested at least £8 billion. China is spending another £1.2 billion on a new offshore oilfield in Nigeria.
Meanwhile, Beijing has acquired mines in Zambia, textile factories in Lesotho, railways in Uganda, timber in the Central African Republic and retail developments in almost every capital.
The reasoning behind China’s new focus on Africa is simple. If its economic boom is to be sustained, Beijing must find more raw materials and new markets for manufactured goods. Chinese oil consumption is forecast to grow by at least 10 per cent every year for the foreseeable future. At this level of demand, its domestic reserves will vanish within 20 years.
Hence the quest for overseas oil. Yet Beijing’s options are limited. America and the Western powers have already snapped up the world’s largest oil reserves. Saudi Arabia and Iraq - with 45 per cent of the world’s oil between them - are in effect closed to China.
So the less developed tracts of Africa are an obvious target. Sudan’s six billion barrels of proven reserves - with more still to be discovered - have become of vital strategic significance to China.
These facts are of deep concern to many Africans. Their governments may welcome Chinese investment, but Africa’s independent voices do not share this enthusiasm. The consequences of China’s new role there have already been catastrophic.
Thanks to Beijing’s interest in Sudan’s oil, President Omar al-Bashir’s regime in Khartoum has received a windfall. Ten years ago, Sudan’s oil revenues were negligible; last year, Chinese investment ensured that they totalled at least £3 billion.
Without this ready cash, Mr Bashir could never have sustained the war in Darfur, where four years of fighting have claimed about 300,000 lives, either from violence, starvation or disease. The military machine that has laid waste to vast tracts of land, forcing hundreds of thousands to flee their homes, was, in effect, bankrolled by Beijing. Moreover, China has sold weapons directly to Sudan, notably Fantan ground attack aircraft.
Elsewhere, China provides a convenient alternative for African leaders spurned by the West for their human rights abuses. Devoid of aid and foreign investment, President Robert Mugabe’s regime in Zimbabwe would be entirely isolated but for China’s backing. Beijing has given Mugabe civilian and military aircraft, and its experts helped design a new mansion for the old dictator, in the style of a Chinese pagoda.
Yesterday, the Chinese government assured Lord Malloch-Brown, the Foreign Office minister responsible for Africa and Asia, that any future aid for Zimbabwe would be purely humanitarian. Whether China will keep this promise is another matter: Mugabe’s Zanu-PF has received Chinese money for at least 30 years; Zanu-PF’s national headquarters in Harare - found, aptly enough, on Rotten Row - was built by China.
The harsh truth is that Beijing has become the ally of choice for Africa’s worst rulers. While China likes to portray itself as a benign force in Africa, free of the historical baggage carried by the former colonial powers, Beijing’s conduct is already resented.
During last year’s presidential election in Zambia, the leading opposition candidate, Michael Sata, campaigned on an explicitly anti-Chinese ticket. Beijing’s investment was, Mr Sata argued, almost entirely worthless for Zambia.
Yes, China had reopened some copper mines, but the workers were being exploited and all health and safety regulations ignored. An industrial accident at one Chinese-run mine claimed 46 lives in 2005. Later, workers rioted over low wages and poor conditions. Meanwhile, local companies were being driven out of business by cheap imports.
While Mr Sata lost the election overall, he won huge majorities in all the areas of Zambia affected by Chinese investment. His defeat prompted a day of anti-Chinese riots in the capital, Lusaka. Every Chinese-owned shop in the city was barricaded to avoid being looted. Meanwhile, shops owned by whites or Asians carried on trading without incident.
Even inside Mugabe’s crumbling domain, it has not gone unnoticed that all three MA-60 aircraft supplied by China to Air Zimbabwe have a terrifying history of engine fires and emergency landings.
While Americans and Europeans have only just encountered shoddy Chinese consumer goods, ordinary Zimbabweans talk of “zing zong” products - by which they mean exports from China which have a tendency to break in your hands.
Like all empires, China’s economic domain in Africa is stirring deep resentment. The wonder is that it has happened so quickly, and where the scramble will end.