安全阀冷热态整定压力偏差致因研究

Research on the Cause of Setting Pressure Deviation in Cold and Hot Test of Pressure Relief Valve

同一安全阀的整定压力试验结果会随着校验介质的不同而产生差异,造成这一现象的原因长期困扰着安全阀行业。本文建立了一种密封面孔隙内介质吸附的多尺度模型,指出狭缝内不同介质的吸附作用不同是冷热态整定压力偏差的主要成因。针对校验介质分别为压缩空气和饱和水蒸气的情况,利用经典密度泛函理论研究计算了不同介质在密封面的吸附作用。研究发现在密封面纳米尺度的楔形狭缝内,饱和蒸汽对壁面吸附力总要高于压缩空气,造成蒸汽安全阀的整定压力小于通过压缩空气所获得的整定压力,计算结果得到了试验验证。

The set pressure of pressure relief valves(PRVs)varies with the type of the sealed medium,which has been puzzling the sector of the pressure relief valves for many years.A multiscale model was set up to describe the pores on the sealing surface,and it was pointed out that different adsorption effect of different medium in the slits is the major cause for set pressure deviation in cold and hot state.The adsorption effect of two different types of medium gases(i.e.,saturated steam and air)on the sealing surface was evaluated using the classical density functional theory(DFT).Through the research it was found that the adsorption force of saturated steam in the slit was always higher than that of compressed air,resulting in the set pressure of steam safety valve being less than that obtained by the compressed air,and the calculation results were verified experimentally.