Abstract: This paper deals with research of low noise relief valve Type YF-L20H-YI(A). It describes noise sources that old YF relief valve has and the means of decreasing its noise.This paper gives structural principle of low noise relief valve Type YF-L20H-YI(A) and its computer aided design. Using the program that determines frequency characters from block-diagram directly, the dynamic analyses were carried out on computer. The experiments and manufacture of new valves were in progress. In this paper, sound power level, sound pressure level and other important quality indexes of new low noise valve are announced. The noise level of low noise valve Type YF-L20H-YI (A) comes up to. Existing international advanced standards which the same-type-products have.

Key words: 低噪声, 机辅分析, 结构图, 稳定裕度, 溢流阀