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缸體執(zhí)行機構
Cylinder Actuators
空氣或燃氣缸體執(zhí)行機構包括單動或雙動，由機械彈簧或氣動力實現(xiàn)故障開啟或關閉等各種類型?？諝飧左w執(zhí)行機構的局限性在于機械彈簧的局限性和要求推力不超過75,000磅?？諝飧左w執(zhí)行機構所采用的機械彈簧可以達到20,000磅的推力，及大14英寸的沖程限制，主要取決于所需要的輸出推力。
Air or gas cylinder actuators include single or double acting, fail open or closed by mechanical spring or pneumatic force. They can be manufactured to accommodate any length stroke. The limitations of air cylinder actuators are mechanical spring limits and thrust requirements in excess of 75,000 Ibs. Mechanical springs used with air cylinders can be sized for up to 20,000 Ibs. of thrust and have a stroke limit of about 14" max. depending on thrust output required.
對于有些無法采用機械彈簧的應用場合，可以配置氣動彈簧，以儲備足夠?qū)崿F(xiàn)故障**功能的氣源壓力。大于25,000磅的推力要求可以通過配置標準鏜孔的缸體執(zhí)行機構來實現(xiàn)，在此假定現(xiàn)場氣源壓力小為80 PSIG。在25,000磅至75,000磅之間的推理要求可以通過對現(xiàn)場氣源進行增壓或加強，使其具有更高的工作壓力來滿足缸體執(zhí)行機構的要求，并儲存在當?shù)氐母邏簹夤迌?nèi)。
In applications where mechanical springs can not be used, a pneumatic spring provided with stored air pressure is capable of providing a fail safe mode. Thrust requirements up to 25,000 Ibs. can be accommodated with standard bore size cylinders assuming minimum 80 PSIG field air supply. Thrust requirements between 25,000 Ibs. and 75,000 Ibs. can be accommodated by boosting or intensifying field air pressure to a higher working pressure for the cylinder and stored locally in a high pressure air tank.
對于超過75,000磅的推力要求，液動系統(tǒng)會更加適合，也更加經(jīng)濟。缸體執(zhí)行機構可以配置針對緊急狀態(tài)下的手動過載裝置，閥門驅(qū)動，故障**功能和其它附件。
Hydraulic systems are better suited and more economical for thrust requirements over 75,000 Ibs. Cylinder actuators can be provided with manual overrides for emergency valve actuation, fail safe mode and other accessories.
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隔膜執(zhí)行機構
Diaphragm Actuators
隔膜執(zhí)行機構適用于：雙動(氣壓開啟或關閉)，直接作用(氣壓關閉，機械彈簧開啟)或反向作用(機械彈簧關閉，氣壓開啟)。
Diaphragm actuators available are: double acting (air pressure required open or close), direct acting (air pressure required to close, mechanical spring to open) or reverse acting (mechanical spring to close, air pressure required to open).
這是一種很簡單也很經(jīng)濟的執(zhí)行機構，但是應用的局限性也比較大。種局限在于沖程，對于大多數(shù)制造商來說，4英寸就是大的沖程。這種局限性使得隔膜執(zhí)行機構只能適用于通徑DN100以下的閘閥和更小通徑的截止閥。*二種局限性在于輸出推力，這是無法為我們的不平衡旋塞截止閥選擇這種執(zhí)行機構的主要原因。大多數(shù)制造商可以提供面積達到200平方英寸的隔膜，但是，可用于執(zhí)行機構的大氣源壓力卻在遞減。大多數(shù)主要制造商提供的大面積隔膜的大氣源壓力小于45 PSIG，因此限制了推力的輸出。作為選配件，可提供手動過載手輪。
This very simple and very economical actuator has application limitations. The first limitation is stroke; a 4" stroke is the longest available from most manufacturers. This limits adaptable valve size to gate valves 4" and smaller and globe valves in smaller sizes. The second limitation is output thrust, this is the major constraint in selecting this type of actuator for use with our unbalanced plug globe valves. Most manufacturers can provide diaphragm areas up to 200 square inches, however, maximum air pressure allowed for actuation decreases. Maximum air pressures are as low as 45 PSIG for large area diaphragms available from most major manufacturers thus limiting thrust output. Manual override handwheels are available as an option.
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