Valtek Severe Service Equipment

Valtek Severe Service EquipmentMegaStream TrimIntroductionMegaStream valve trim effectively reduces control valvenoise in a range of gas applications. MegaStream trim isavailable in two styles (Figure 25): a very economical,interchangeable one- or two-stage design for noisereduction up to 15 dBA, and a highly effective multistagedesign for noise reduction approaching 30 dBA(Figure 26).MegaStream trim eliminates the problem of controlvalve noise by dealing effectively with gaseous pressurereduction, and by controlling turbulence carried into thedownstream piping. The pressure drop in MegaStreamtrim is distributed so that it occurs not only at thethrottling point between the plug and seat, but also atFigure 27: Staged Pressure ReductionThrough MegaStream Attenuatoreach stage, from the inside of the attenuator to theoutside (Figure 27). This pressure drop occurs largelyas a result of the sudden expansions and contractionsthat take place as the flow passes through theMegaStream trim. Each stage is designed to take asmall pressure drop, avoiding the high velocities presentin single-throttling-point trims. This gradual pressurereduction is achieved by designing sufficient stages tokeep the velocity low.Figure 25: One and Two-stageMegaStream Attenuators30Attenuation (dBA)2520151057-STAGE6-STAGE5-STAGE4-STAGE3-STAGE2-STAGE1-STAGE01 2 4 6 8 10 20 40 60 80 100P 1 / P 2Figure 26: Noise Reduction VersusNumber of MegaStream StagesFigure 28: MegaStream Trim Restructuringof Noise Generating TurbulenceA basic principle of MegaStream noise control valvesis the restructuring of noise generating turbulence.This principle is illustrated in this polariscope display(Figure 28) of MegaStream trim with birefringent fluid.Note the turbulence generated in the fluid as it passesthrough the seat and how this turbulence decreasesas the flow continues through each successive stage.Flowserve Corporation, Valtek Control Products, Tel. USA 801 489 861119