| 摘要 |
The present invention relates to an on-off valve provided with sealing means for the control stem. The sealing means comprise a plurality of sealing rings of expanded graphite and a gland device for placing said rings in compression. The sealing means further comprise a further active element arranged on the bottom wall, provided with an expansion room wherein the fluid pressure causes a thrust action towards said sealing ring. Said sealing means distribute the strain state of the compressed rings in an optimum manner.
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