标准阀杆
STANDARD STEM

无泄漏动负载　　　　　　　　　　　动负载
LIVE-LOADING WITH LEAK-OFF 　　　LIVE-LOADING

Velan根据下列试验结果开发自己的阀杆密封：
The Velan stem seal evolved from these test findings:

• 通过大量的实验室测试，确保泄漏小于所宣布的万分之一。
  Ensures leakage of less than 100 ppm as demonstrated through extensive laboratory testing.
• 大负载。
  密封安装是在很高的压缩负载下进行，这样填料就会形成一块低多孔性和渗透性的材料（对于石墨压力达4,000 psi）。
  Large loads.
  Sealing is achieved when compression load is high and packing forms a mass of low porosity and permeability (4,000 psi for graphite).
• 在活动部件之间的间隙很小。
  Small clearances between vital parts.
• 高精度的阀杆和填料腔。
  阀杆和填料腔的平直度、圆度和高光洁度是最基本的特征。
  Precision stem and packing chambers.
  Straightness, roundness and fine finish of stem and packing chamber wall are essential.
• 又短又窄的填料腔改善了密封性能。
  在一个填料腔内，最多只放置六个密封环，无论在填料腔内的什么地方，宽度都只有1/4英寸。
  Short and narrow packing chambers improve sealing.
  Maximum six rings in a single set chamber and wherever possible, only 1/4" wide.
• 阀杆和填料腔壁。
  精确的圆度、平直度和阀杆上6 RMS以上的超级表面光洁度，以及填料腔上63 RMS的表面光洁度。
  Stem and packing chamber walls.
  Close roundness, straightness and superior surface finish of 6 RMS or better for the stem and 63 RMS for the packing chamber.

动负载选项
LIVE-LOADING OPTIONS

• 动负载。两套Belleville弹簧对填料保持3500-4000 psi的永久性压力。动负载延长了低辐射寿命，特别适用于压力/温度瞬时变化幅度大或频繁开关的场合。
  Live-loading. Two sets of Belleville springs maintain a permanent packing stress of 3500–4000 psi. Live-loading extends low emission service life especially in service with large pressure/ temperature transients or frequent cycling.
• 无泄漏。对于关键场合，一个套环和双填料可以提供无泄漏连接。无泄漏能够从低部填料上收集泄漏介质。
  Leak-off. For critical service a lantern ring and double packing can be provided with a leak-off connection. The leak-off is provided to allow collection of leakage from the lower packing set.
• 在填料腔内，石墨密封环都分别经过3500-4000 psi压力的压缩，PTFE密封环都分别经过2000 psi压力的压缩，以保证所有密封环具有相同的压力分布和有效性。
  Rings individually compressed in packing chamber to 3500 –4000 psi for graphite and 2,000 psi PTFE to ensure equal stress distribution and effectiveness of all rings.
• 在阀门动负载方面，Velan具有丰富的经验。1972年，在AECL工程中，Velan在研究核应用过程中如何防止泄露课题时首次提出动负载概念。如今，Velan为核应用和非核应用领域提供动负载阀门已有30多年的历史。
  Velan has extensive experience in valve liveloading. The original live-loading concept was developed by Velan in 1972 in a research project for AECL to eliminate leakage in Nuclear service. Velan has been supplying live loaded valves for Nuclear and non-Nuclear service for more than 30 years.