IT IS THE ALLAH WHO SUBJECTED THE SEA TO YOU.THAT SHIP MAY SAIL THROUGH IT BY HIS COMMAND ,THAT

YE MAY SEEK OF HIS BOUNTY,AND THAT YE MAY BE GRATEFUL

(Al-Quran)

Marine Engineering

Valves and cocks

Valves

• There are three types of valve mainly– Globe valve– Gate valve– Butterfly valve

Globe Valve

– Typical Globe Valves– Angle Globe Valves– SDNR and screw both are include in the

above categories.

Globe valve (Screw down nonreturn valve(SDNR)

• It a type of nonreturn valve • It is used where fluid allowed to move in

one direction only• Several turns will open or shut the valve• Usually used in air, lub, fuel oil line

Globe valve

• Screw lift valve• Several turns will open or shut the valve• Used in • Ballast and De-ballast lines

Gate Valve

– Flanged End Butterfly Valves– Wafer Butterfly Valves

Gate valve

• Several turns will open or shut the valve• Throttling of valve is possible• Used in sea and fresh water circuit

Gate Valve

– Rising Stem Gate Valves – Wedge type– Rising Stem Gate Valves – Double Disk type– Non Rising Stem Gate Valves – Wedge type– Non Rising Stem Gate Valves – Double Disk

type

Butterfly valve

• Half turns will open the valve-(viceversa)• Used also in sea and fresh water circuit

Various type

• Also ball and wedge type of valve are also used in marine practice.

Maintenance of valve

• If the seat and valve degree is damage• Used the fine grinding paste with oil• Spring is also corroded in nonreturn type

Safety valve

• Safety valve is used where the pressure exceed it mawp then it lift and relief the pressure and then close at working pressure

Relief valve

• Relief valve is used in various line eg oil and pneumatic hydarulic

• At the preset pressure it lift and and close immediately

Author Introduction ZEESHAN AHMED, Marine Engineer. After doing FSc(pre-engineering) from PAF(fazaia) intermediate college Lahore cantt. I joined Pakistan Marine Academy and choose Marine engineering branch. Two years of training at academy (practical + theoretical) we learned a lot of thing like CNC (computerize numeric code), trained on various models (like control valve, solenoid valve, flow meter, refrigeration system, CPP

propeller, Main engine model (TWO stroke), Boiler model (water tube) ……………………………….. in GEK (general engineering knowledge) lab, Mechanical and physics lab, Engineering workshop. ETC . After two years, we joined PNSC workshop for the training of ONE year Industrial training. That was also the golden time where we learnt a lot of things at different shops as well as onboard (repairing and watch keeping). I learn many thing on tanker E.g. MT Johar (learn how to dismantle turbine rotor from casing and what are the precautionary measurement while working on turbine, learn how to change the diaphragm(stationary blade) Plate type heat exchanger gasket change, shell and tube Cooler Anode replacement and (Cont.)

Introduction (cont.)cleaning of SALT WATER tubes etc.) , MT Swat (major thing which I learn in Swat is how to dismantle head of main unit and copper gasket replacement with a minor facing defect which is found during overhauling which is filled and faced by Belzona) , MT Lahore(About the DEAD MAN ALARM, Alpha lubricator for Cylinder Main Engine Unit, Pump operation and watch keeping), MT Quetta(Auto load sharing of Generator Set, MT Karachi (Dry washing of the main engine turbocharger with granules, water washing of IG Fan of Inert Gas system, sludge removal of from purifier(centrifuge) etc., . One thing I want to added is that the trend in ship building is more toward based on electronic and electrical application. So a marine engineer must strong in automation, instrumentation and control system. PLC (programmable and logic control) and SCADA (supervisory central access and data acquisition) are the upcoming technology that are using on modern ship. The latest engine of MAN B&W is based on Camless technology. Chain is removed ; fuel pump and exhaust valve actuation is control by hydraulic servo(lub) oil which is driven by Axial piston pump mounted on the Fly wheel.

Regards,Z.A.

Author contact information• zeetec4@yahoo/gmail/hotmail.com

Social networking sites.• Facebook: mariner46

Website: zeetec4.googlepages.com

Zeeshan Ahmed 46th Batch PMAammariner46@yahoo.comzeetec4@yahoo.com

Any question and suggestion are welcome