The Proceedings of the Marine Safety and Security Council is a principal outreach and communication tool for the Coast Guard's Marine Safety & Security Council. The quarterly magazine focuses on a specific theme for each edition that relates to the m
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A. mechanical pushrods.
Incorrect Answer: Medium and high speed diesels engines equipped with the conventional over- head valve arrangement utilize mechanical pushrods. The pushrod, along with the camshaft lobe, cam follower, and rocker arm are the means by which valve is opened. The valve is closed by spring force.
B. compressed air pressure &RUUHFW; $QVZHU ([KDXVW YDOYHV RQ PRGHUQ ODUJH VORZ VSHHG XQLÁRZ VFDYHQJHG PDLQ SUR- SXOVLRQ GLHVHO HQJLQHV DUH ÀWWHG ZLWK H[KDXVW YDOYH DFWXDWRUV XWLOL]LQJ ÁXLG SRZHU IRU YDOYH operation. The valves are opened under hydraulic pressure and are closed with compressed air pressure. The air actuator is sometimes called an air spring, since it performs the same function as conventional valve springs (valve closure) using compressed air.
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Incorrect Answer: Exhaust gas is not a suitable media for exhaust valve operation. Exhaust gas is not high enough in pressure to close the exhaust valve.
2. Note: Controllers that feature proportional action exhibit a unique behavior. The set point value, as the name implies, is the setting of the controlled process that the controller is designed to maintain. Ideally, the set point value and the actual measured value are identical. As with all process control action types, with load or demand changes the measured value will differ from the set point value. This difference is called deviation (or error), which causes a corrective response. As the controller reacts to the deviation, the controlled variable will stabilize at a value proportional to the load or demand, and it will be different from the set point value. This difference is called offset. The new point at which the controlled variable stabilizes is called the control point.
A. offset B.
deviation ' ORDG SRLQW
Incorrect Answer: Offset is the difference between the set point value and the control point value. Incorrect Answer: Deviation is the difference between the set point value and the measured value.
C. control point Correct Answer: The value at which the controlled variable stabilizes is called the control point. It will vary with the load or demand.
,QFRUUHFW $QVZHU /RDG SRLQW LV D ÀFWLWLRXV WHUP 7KH SRLQW DW ZKLFK WKH FRQWUROOHG YDULDEOH ZLOO VWDELOL]H IRU a given load is called the control point, not the load point.
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pump. See solution below. Solution: The potential energy gained by the liquid is equal to the weight of the liquid pumped, multiplied by the height it is to be discharged, multiplied by the pump capacity.
Expressed mathematically: (8.58 lb/min) (100 gal/min) (15 ft) = 12,870 foot-pounds 8VLQJ WKH FRQYHUVLRQ IDFWRU RI WKH SXPS ZRXOG EH
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A. air ejector inter-condenser &RUUHFW; $QVZHU &RQGHQVDWH; GLVFKDUJHG E\ WKH PDLQ FRQGHQVDWH SXPS ÀUVW SDVVHV WKURXJK WKH tubes of the air ejector inter-condenser. The condensate passing through the inter-condenser tubes condenses the steam/gas mixture discharged to the inter-condenser shell E\ WKH ÀUVW VWDJH air ejector unit. The resultant condensate drops to the bottom of the inter-condenser shell, and drains back to the main condenser via a U-shaped loop seal.
B. main condenser hotwell C. air ejector after-condenser
Incorrect Answer: The main condensate pump takes suction from the main condenser hot-well.
Incorrect Answer: Upon exiting the air ejector inter-condenser tubes, condensate from the main FRQGHQVDWH SXPS WKHQ ÁRZV WKURXJK WKH WXEHV RI WKH DLU HMHFWRU DIWHU FRQGHQVHU 7KH FRQGHQVDWH passing through the after-condenser tubes condenses the steam/gas mixture discharged to the after-condenser shell by the second stage air ejector unit. The resultant condensate drops to the bottom of the after-condenser shell, and drains back to the atmospheric drain tank.
D. DC heater vent condenser
Incorrect Answer: Condensate discharged by the main condensate pump must pass through the air ejector condenser unit and gland exhaust condenser before entering the DC heater vent condenser.
88 Proceedings Winter 2011-2012 www.uscg.mil/proceedings
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