14. Sea Valves
About the sea valves, please refer to INTERNATIONAL CONVENTION ON LOAD LINES, Regulation 22.
Here in this chapter the inspection of the water suction and discharge valves (hereinafter called "sea valves") during a docking survey is described.
If a sea valve and the distance piece are holed, water enters into the hull
and may cause a major casualty such as sinking of the ship; therefore, the inspections should be
14-1-1 Hull
"Sea inlets and overboard discharges below the waterline are to be examined and valves and cocks together with their fastenings to the hull are to be dismantled and examined. Dismantling may be dispensed
with at the discretion of the Surveyor, provided they were dismantled and examined at the last Docking Survey."
14-1-2 Machinary
"All openings to the sea including sanitary and overboard discharges in the machinery spaces and pump room with valves and cocks are to be examined internally and externally. The fastening of valves and cocks to the hull are also to be examined."
14-2 Position of valve
The weather deck discharge pipes are fitted above load water line without any valves but most of discharge and inlet pipes are in stalled below the load water line directly to shell plate through the distance piece or the sea chest.
Fig.14-5 Valve fitted directly to shell plate
Fig.14-6 Valve fitted to the sea chest
Photo. 14-3 Storm valve
Two storm valves are fitted because the open end of the pipe in the accommodation ie. drain hole of bath tub, located more than 0.1L, above LWL but less than 0.2L
Here in this chapter the inspection of the water suction and discharge valves (hereinafter called "sea valves") during a docking survey is described.
If a sea valve and the distance piece are holed, water enters into the hull
and may cause a major casualty such as sinking of the ship; therefore, the inspections should be
14-1-1 Hull
"Sea inlets and overboard discharges below the waterline are to be examined and valves and cocks together with their fastenings to the hull are to be dismantled and examined. Dismantling may be dispensed
with at the discretion of the Surveyor, provided they were dismantled and examined at the last Docking Survey."
14-1-2 Machinary
"All openings to the sea including sanitary and overboard discharges in the machinery spaces and pump room with valves and cocks are to be examined internally and externally. The fastening of valves and cocks to the hull are also to be examined."
14-2 Position of valve
The weather deck discharge pipes are fitted above load water line without any valves but most of discharge and inlet pipes are in stalled below the load water line directly to shell plate through the distance piece or the sea chest.
Fig.14-5 Valve fitted directly to shell plate
Fig.14-6 Valve fitted to the sea chest
Photo. 14-3 Storm valve
Two storm valves are fitted because the open end of the pipe in the accommodation ie. drain hole of bath tub, located more than 0.1L, above LWL but less than 0.2L
Photo.14-4 Overhauled sea valve at the sea chest
14-3 Kinds and Construction of Sea Valve There are many kinds of valves in the engine room. The biggest valves are in the cargo pump room in ULCC (Ultra Large Crude oil Carrier). Generally valves are in charge of Machinery crew but depends on the
practice of the ship-owners valves in the cargo oil pump in tanker are in charge of deck crew.
14-3-1 Kinds of Valves
(1) Flow direction
Depends on the liquid flow direction there are 3 kinds of valves such as
vertical, horizontal and angle as shown below.
| Vertical | Horizontal | Angle |
Photo.14-5 kinds of valve (1) from the catalogue of Niikura Kogyo Co.Ltd.
(2) Construction
There are four types of valves depends on the construction.
(2) Construction
There are four types of valves depends on the construction.
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| Storm valve | Angle valve | Sluice valve | Butterfly valve |
1) Storm valve
Fig. 14-3 is a sketch of the construction. If sludge accumulates in the pipe, the valve plate automatically opens with the weight of sludges and discharges them. After discharging, the counterweight fitted to one side of the valve plate closes the valve, It prevents the sea water from outside come into the hull.
Fig.14-7 Mechanism of storm valve
2) Angle valve and Globe valve
The stem ascends or descends when the handle is rotated. When the valve disc at the end of the stem descends and comes in contact with the metal latch in the dis shaped valve seat, the suction/discharge stops.
Fig.14-8 Mechanism of angle valve
3) Sluice valve
The valve body is wedge?shaped; when the handle is rotated, the valve body descends because of the threads cut into the stem and the valve plate stops the flow of fluid. In ships where the engine room is amidships and a shaft tunnel is provided, the construction of this valve is analogous
to a watertight door installed at the aft end of the engine room.
Fig.14-9 Mechanism of sluice valve
4) Butterfly valve
When the spindle is rotated, the valve body rotates by 90 degrees and stops the flow of fluid.
Fig. 14-3 is a sketch of the construction. If sludge accumulates in the pipe, the valve plate automatically opens with the weight of sludges and discharges them. After discharging, the counterweight fitted to one side of the valve plate closes the valve, It prevents the sea water from outside come into the hull.
Fig.14-7 Mechanism of storm valve
2) Angle valve and Globe valve
The stem ascends or descends when the handle is rotated. When the valve disc at the end of the stem descends and comes in contact with the metal latch in the dis shaped valve seat, the suction/discharge stops.
Fig.14-8 Mechanism of angle valve
3) Sluice valve
The valve body is wedge?shaped; when the handle is rotated, the valve body descends because of the threads cut into the stem and the valve plate stops the flow of fluid. In ships where the engine room is amidships and a shaft tunnel is provided, the construction of this valve is analogous
to a watertight door installed at the aft end of the engine room.
Fig.14-9 Mechanism of sluice valve
4) Butterfly valve
When the spindle is rotated, the valve body rotates by 90 degrees and stops the flow of fluid.
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Fig.14-10 Mechanism of butterfly valve
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14-4 Damages of valves and distance piece14-4-1 Storm valve
In aged ships storm valve should be completely opened up and inspected.
If the cover protruding from the valve body, it should be removed and completely opened up.
(1) Blockage
When the valve is opened up, you might sometimes find toothbrushes or combs etc. came down from the washing basin which block the flow in the valve. In such cases, the valve plate will not operate, and the valve will not function as a non-return valve.
(2) Corrosion
If the casing or the valve plate is excessively corroded, there might be corroded hole and if the arm to the hinge is also corroded and worn out, the valve plate should be renewed.
Fig.14-11 corroded valve plate
In the above figure ,(1) original valve plate, (2) gasket, counterweight missing and broken hinge
(3) Wear of gasket
The gasket of the valve plate and the gasket fitted to the cover might be worn out and thickness reduced. If the cover is worn out, naturally water will leak.
(4) Wear or missing hinge pin
The hinge pin might be too much corroded or missing. If the hinge pin is missing, the valve plate works loose.
(5) Missing counterweight
Sometimes the lead counterweight fitted to the valve plate is lost . In such a case, the valve will remain open permanently and will not function as a non- return valve.
(6) Defective spindle and handle
In the screw-down type stop valve, sometimes the spindle and the handle are broken.
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14-4 Damages of valves and distance piece14-4-1 Storm valve
In aged ships storm valve should be completely opened up and inspected.
If the cover protruding from the valve body, it should be removed and completely opened up.
(1) Blockage
When the valve is opened up, you might sometimes find toothbrushes or combs etc. came down from the washing basin which block the flow in the valve. In such cases, the valve plate will not operate, and the valve will not function as a non-return valve.
(2) Corrosion
If the casing or the valve plate is excessively corroded, there might be corroded hole and if the arm to the hinge is also corroded and worn out, the valve plate should be renewed.
Fig.14-11 corroded valve plate
In the above figure ,(1) original valve plate, (2) gasket, counterweight missing and broken hinge
(3) Wear of gasket
The gasket of the valve plate and the gasket fitted to the cover might be worn out and thickness reduced. If the cover is worn out, naturally water will leak.
(4) Wear or missing hinge pin
The hinge pin might be too much corroded or missing. If the hinge pin is missing, the valve plate works loose.
(5) Missing counterweight
Sometimes the lead counterweight fitted to the valve plate is lost . In such a case, the valve will remain open permanently and will not function as a non- return valve.
(6) Defective spindle and handle
In the screw-down type stop valve, sometimes the spindle and the handle are broken.
 | Fig.14-12 Broken handle |
14-4-2
(1) Corrosion and cracks
A major problem in valves is a corrosion of the valve body. In old ships, openings appear suddenly because of corrosion, water floods into the engine room and in bad case the ship sinks.
Examine the thickness of body by hammering; if it feels thiner, open the valve completely and inspect thoroughly the internals . If a rubber lining has been provided, corrosion will be small; however, if the rubber lining has partly peeled off, concentrated local corrosion occurs.
Even if other area is is satisactory, holes might develop at the peeled off spots.
In angle valves and globe valves, corrosion in valve body, valve stem and valve seat can be carefully examined, in addition to corrosion in the
casing, sometimes, cracks are also detected in the casing.
In Sluice valve, the grooved disk guide is provided on both sides of the casing. It prevents horizontzl movement of the valve disk. When this guide is heavily corroded valve disk do not move smoothly.
(2) Valve connection bolts or studs
Bolts or studs used for securing the valve to the sea chest do not have any problems when they are made of stainless steel. But if they are made of mild steel they rapidly corrode because they are immersed in bilge.
If the base of the valve is, corrosion progresses rapidly. In some cases, bolts head is disappeared.
Fig.14-13 Valve connecting bolt
(3) Damage and wear to the valve seat
When the valve seat is damaged and the contact between sest snd valve disk is defective, watertightness will not be maintained even if the valve is closed. If such defect is found , it should be taken to the machine shop
and repaired to obtain the proper seating.
(4) Leakage from gland
When the gasket through which the valve stem passes is deteriorted,
the tightness is not kept. The basket is the important parts.
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| Photo.14-5 Corroded valve disk | Fig.14-14 Defective valve disk |
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| Fig.14-15 Defective valve seat | Fig.14-16 Defective valve disk |
14-5 Distance Piece
Generally valves are not directly fitted to the shell plating, but short piece of pipe which is called distance piece, is used between valve and shell plate. If a hole is made in this distance piece due to corrosion or crack,sea water runs into the engine room.
We have to carefully examine the condition of distance piece. If corrosion is suspected, the plate thickness should be measured.
Not only corrosion sometimes crack appeas at the bracket end.
If the paint in the distance piece is partly dirty, there is a possibility of hole or crack.
The scupper pipe on the exposed deck is the same as the distance.
piece.
Check point of distance piece is as shown in the following figures.
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| Fig.14-17 Corrosion of distance piece (1) |
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| Fig.14-18 Corrosion of distance piece (2) |
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| Fig.14-19 Corrosion of distance piece (3) |
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| Fig.14-19 Corrosion and crack in distance piece |
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