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Subject: butterfly valves - dead-end services Many/Most bidirectional high-performance butterfly valves can act for dead-end service, if you mean end-of-pipe service.Простите, но я никак не могу понять, что такое dead-end services? Помогите, пожалуйста! Контекст(простите, если много, и вообще, простите, если что-то не так оформила):
Many/Most bidirectional high-performance butterfly valves can act for dead-end service, if you mean end-of-pipe service. However, they are frequently de-rated because if they are installed with the shaft upstream, the pressure tends to unload the seat retainer. Options are offered for a bolted seat retainer, but quite franlkly the easiest and most reliable way to install one is with a flange bolted to the seat-retainer side of the valve. The flange gives the seat retainer the support needed so that the valve is rated for full pressure in either direction. That being said, the preferred direction is still with the seat Upstream of the shaft, if for no other reason than to take the pressure off the packing while the valve is closed.
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