Målesystem for hydrauliske stempelakkumulatorer

Abstract

This report is based on the challenges FMC Technologies has due to measuring the amount of hydraulic oil inside a piston accumulator tank on the bottom of the sea. It is favorably to know at any given time how much hydraulic oil is left in the tank; in time some of the oil will be lost to the environment due to its function. There are several hydraulic accumulator tanks attached to a subsea Xmas tree, each operating on different system but perform the same main function, which is to send hydraulic oil to an actuator. The actuator uses the hydraulic oil as energy to open and close valves. Today FMC Technologies does not have any satisfying solution regarding this problem; rather they use prior experience of how long it takes before an accumulator tank needs to be refilled. In collaboration with FMC Technologies a solution to the problem has been developed for measuring the remaining hydraulic oil inside the tank, where a measuring system were put on the top of the accumulator tank protected by a housing. The critical issue for the system is an expected lifetime of 25 years. Several solution regarding a measuring system where proposed. A scoreboard criterion where used to distinguish out the best solution according to the requirements given by FMC Technologies. A detailed concept regarding the best solution where developed, which consist of a time-offlight laser placed inside a housing which is attached to the top of the accumulator tank. The housing must be able to withstand water pressure down to 2750m (275 Bar). The bottom of the housing must be able to withstand internal pressure from the accumulator tank which is 345 Bar. The bottom of the housing also is a second barrier against the water pressure. Hydraulic Accumulator Measuring Unit. The report is a document which follows the process from a problem given by FMC Technologies to a concept idea which is generated step by step through this document.