Proceedings Of The Marine

FAL 2012

Proceedings magazine is a communication tool for the Coast Guard's Marine Safety & Security Council. Each quarterly magazine focuses on a specific theme of interest to the marine industry.

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A % & Engineering nswers 1. Note: The purpose of attaching a gauge manifold set to a refrigeration unit is either to check the low- and high-side system pressures or to assist in SHUIRUPLQJ D SDUWLFXODU VHUYLFH SURFHGXUH ,I WKH SXUSRVH LV WR FKHFN WKH UHIULJHUDWLRQ XQLW·V V\VWHP SUHVVXUH WKH JDXJH PDQLIROG VHW YDOYHV DUH WR be closed, and the refrigeration unit's low- and high-side service valves must be in the mid position. This is accomplished by cracking the service valves off their back-seats by turning in clockwise approximately ¼ to ½ a turn of the stem. A. RSHQ WKH GLVFKDUJH VHUYLFH YDOYH VHUYLFH SRUW E\ FORVLQJ WKH VHUYLFH valve FRQWLQXH WR EDFN VHDW WKH GLV- FKDUJH VHUYLFH YDOYH E\ WXUQLQJ LW clockwise RSHQ WKH GLVFKDUJH YDOYH VHUYLFH SRUW E\ FORVLQJ WKH VHUYLFH YDOYH DSSUR[LPDWHO\ õ WR ô D WXUQ D. RSHQ RQO\ WKH YDOYH FRQQHFWHG WR the discharge service fitting on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õ WR ô D WXUQ IURP WKH EDFN VHDWHG SRVLWLRQ SODFHV WKH GLVFKDUJH VHUYLFH YDOYH LQ WKH PLG SRVLWLRQ DOVR FDOOHG WKH JDXJH SRVLWLRQ 7KLV LV WKH UHTXLUHG SRVLWLRQ IRU FKHFNLQJ RU PRQLWRULQJ V\VWHP SUHVVXUH ,QFRUUHFW $QVZHU 6LQFH ERWK JDXJH PDQLIROG YDOYHV DUH FORVHG DQG LW LV GHVLUHG WR FKHFN RU PRQLWRU ERWK WKH ORZ DQG KLJK VLGH V\VWHP SUHVVXUHV LW ZLOO EH QHFHV- VDU\ WR HQVXUH WKDW WKH ORZ VLGH VHUYLFH YDOYH LV LQ WKH JDXJH SRVLWLRQ 2. Note: Another name for a slip ring induction motor is a wound rotor induction motor. Discrete multispeed operation of a wound rotor motor can hypothetically be achieved by changing the number of poles, which at constant frequency changes the speed of rotation of the rotating magnetic ÀHOG DVVRFLDWHG ZLWK WKH VWDWRU 'LVFUHWH PXOWLVSHHG RSHUDWLRQ FDQ DOVR EH DFKLHYHG E\ LQVHUWLQJ GLVFUHWH DPRXQWV RI UHVLVWDQFH LQWR WKH ZRXQG URWRU circuit, which changes the torque-speed characteristics of the motor. A. DGMXVWLQJ JRYHUQRU OLQNDJH % & FKDQJLQJ WKH QXPEHU RI SKDVHV WR the motor inserting resistance into the stator FLUFXLW D. inserting resistance into the rotor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slowly. During the entire ignition/combustion event, the cylinder pressure is held essentially constant, as fuel continues to be injected and burned. ,Q WKH WKHRUHWLFDO 2WWR F\FOH LJQLWLRQ LV DFKLHYHG E\ PHDQV RI D VSDUN 7KH IXHO XWLOL]HG KDV D UHODWLYHO\ KLJK YRODWLOLW\ DQG EXUQV LQVWDQWO\ UHVXOWLQJ in a rapid build up in cylinder pressure. During the extremely brief ignition/combustion event, the cylinder volume is essentially constant. ,Q DQ DFWXDO GLHVHO HQJLQH WKH F\FOH EHKDYLRU WDNHV RQ FKDUDFWHULVWLFV RI ERWK WKH 'LHVHO DQG 2WWR F\FOHV 6LQFH WKH GLHVHO IXHO KDV D PRGHUDWHO\ ORZ volatility, a fair amount of diesel fuel accumulates in the cylinder before ignition actually begins. This results in a rapid pressure rise at constant volume. As the piston descends downward on the power stroke, fuel continues to be injected and continues to burn moderately slowly. This results in combustion ending on a constant pressure basis. A. EHJLQV RQ D FRQVWDQW YROXPH EDVLV &RUUHFW $QVZHU ,Q WKH SUDFWLFDO GLHVHO HQJLQH FRPEXVWLRQ EHJLQV RQ D FRQVWDQW YROXPH EDVLV DV H[SODLQHG DERYH % EHJLQV RQ D FRQVWDQW SUHVVXUH EDVLV D. EHJLQV DQG HQGV RQ D FRQVWDQW YRO- XPH EDVLV 88 Proceedings ,QFRUUHFW $QVZHU ,Q WKH SUDFWLFDO GLHVHO HQJLQH FRPEXVWLRQ EHJLQV RQ D FRQVWDQW YROXPH EDVLV QRW RQ D FRQVWDQW SUHVVXUH EDVLV DV H[SODLQHG DERYH & HQGV RQ D FRQVWDQW YROXPH EDVLV ,QFRUUHFW $QVZHU ,Q WKH SUDFWLFDO GLHVHO HQJLQH FRPEXVWLRQ HQGV RQ D FRQVWDQW SUHVVXUH EDVLV QRW RQ D FRQVWDQW YROXPH EDVLV DV H[SODLQHG DERYH ,QFRUUHFW $QVZHU ,Q WKH SUDFWLFDO GLHVHO HQJLQH FRPEXVWLRQ EHJLQV RQ D FRQVWDQW YROXPH EDVLV EXW HQGV RQ D FRQVWDQW SUHVVXUH EDVLV DV H[SODLQHG DERYH Fall 2012 www.uscg.mil/proceedings

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