Velan的阀杆密封是根据下列试验结果设计出来：
THE VELAN STEM SEAL EVOLVED FROM THESE TEST FINDINGS:

• 大负载。
  当压缩负载（对于石墨为4,000 psi）很大，并且填充物形成少孔性和低渗透性紧密纤维时，就能形成密封。
  Large loads.
  Sealing is achieved when compression load is high and packing forms a mass of close fibers of low porosity and permeability (4,000 psi for graphite).
• 又短又窄的填料腔改善密封性能。
  Short and narrow packing chambers improve sealing.
• 关键部件之间的间隙小。
  Small clearances between vital parts.
• 精密加工的阀杆和填料腔。
  阀杆和填料腔壁的平直度、圆度和表面光洁度是最基本的要求。
  Precision stem and packing chambers.
  Straightness, roundness and fine finish of stem and packing chamber wall are essential.
• 又短又窄的填料腔。
  在一套填料腔内，最多可达六个密封环，腔内宽度均不超过4.76-6.35 mm。
  Short and narrow packing chamber.
  Maximum six rings in a single set chamber, and, wherever possible, only 3/16 – 1/4” (4.76–6.35 mm) wide.
• 石墨密封环经过3500 - 4000 psi压力的预压缩，Teflon密封环经过1800 - 2000 psi压力的预压缩，以确保所有的密封环具有相等的应力分配和效率。
  Rings precompressed to 3500 – 4000 psi for graphite and to 1800 – 2000 psi for Teflon to ensure equal stress distribution and effectiveness of all rings.
• 阀杆和填料腔壁。精确的圆度和平直度，高级8-16 RMS或镜面表面光洁度。
  Stem and packing chamber walls. Close roundness, straightness and superior 8–16 RMS or burnished surface finish.
• 动负载（备选项）。两套Belleville弹簧保持永久性的3500-4000 psi填料应力。
  Live-loading (optional). Two sets of Belleville springs maintain a permanent packing stress of 3500–4000 psi.