Every loading condition on a ship or workboat starts with one question: is the vessel stable enough to sail? The fastest first answer is the transverse metacentric height, GM. This post sets out the hydrostatic fundamentals behind it, shows how free surface in slack tanks erodes it, explains how the inclining experiment fixes the lightship KG, and works through a loading condition for a small cargo vessel. It ends with the first checks against the IMO 2008 Intact Stability Code. It is a screening method, not a substitute for a full stability booklet. It also sits alongside our wider overview of marine engineering and naval architecture . Fundamentals: KB, BM, KM, KG and GM A floating vessel is in equilibrium when weight equals buoyancy and both act along the same vertical line. Buoyancy is the resultant of hydrostatic pressure on the hull, a topic we cover in pressure and fluid statics . When the vessel heels through a small angle, the underwater shape changes, and the centre of buo...
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Boiler Safety and Test
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Boiler Hydro Test
Boiler hydro test is used to ensure all the welding joints, pipe bents and all headers are water leak proof.
It is done at pressure of 1.5 times of design pressure.
E.g.: If design pressure of boiler is 50 bar, then the hydraulic test pressure will be 75 bar.
Pre-Checklist Hydro Test
Following are the pre-checklist for the hydro test of Boiler:
All erection work should be completed.
Confirm that no foreign material left in the boiler.
Confirm the drum manhole is closed with proper gasket.
Confirm all the drain system ready for operation.
All safety valve should be gagged.
The range of the pressure should be 2 times of the maximum test pressure but not less than test pressure.
The pressure gage should be pre-calibrated before test.
The test pump should have capacity of more than test pressure.
Minimum quantity of demineralized water should be available equivalent to the boiler capacity.
Ensure condensate and Feedwater chemistry parameters to strictly adhere to the required standard.
PH value should be in range of 8 - 9.
The water temperature should not less than 21.1 ℃.
Isolate all pressure and temperature gages except some pressure gages for hydraulic pressure measurements.
Start the boiler filling with the filling pump through the drain header (or filling time).
Close all vents sequentially after water coming from the vents.
Start the hydro test pump ensure all vents closed and rise pressure gradually to the design pressure and then the pressure to be raised up to the test pressure. E.g.: Design pressure = 200 bar, Test pressure = 300 bar).
Hold the pressure raising at 50 bar and 100 bar to check any valve passing and inspect leakage in pressure parts.
Once the pressure reached to the test pressure stop pressurizing and observe pressure drop if the pressure drop is very less then the test is successful.
If any defect is found, type of defect should be solved.
If the pressure is holding better then the pressurizes at 50 bar by opening top vents.
After this, checking team is ready is to inspect inside boiler physically.
After safety test, documents to be prepared and signed with the concerned authorities.
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