Water Hammer Characteristic of the Pipeline in Ship Pitch Balance System

In ship pitch balance system, serious flow impact and water hammer occur because of the turning on and off of valve during the procedure of water-shift. Flow area of the ball valve used most on ship was derived, and mathematical models of pressure lost before and after valve were formulated. Besides, considering the fact of water-shift balance system, an AMESim model was established based on improved traditional throttle model. And the validity of AMESim model was ascertained by comparing simulation results of stable pressure before and after valve with calculated values from mathematical models. Then, with the AMESim model, impact characteristics of water-shift pipeline were investigated when adopting various valve switch rules, length of pipelines before and after valve and using an accumulator in system. From that, methods to reduce pipeline impact were proposed, which make good references for noise control of ship pitch balance system.

VII. An account of a bitumen lake or plain in the island of Trinidad

A most remarkable production of nature in the island of Trinidad, is a bituminous lake, or rather plain, known by the name of Tar Lake; by the French called La Bray, from the resemblance to, and answering the intention of, ship pitch. It lies in the leeward side of the island, about half-way from the Bocas to the south end, where the Mangrove swamps are interrupted by the sand-banks and hills; and on a point of land which extends into the sea about two miles, exactly opposite to the high mountains of Paria, on the north side of the Gulf.