A valve is a mechanical device used in opening /closing, regulating the flow of fluid, and directs the flow. Valves are the lifeline of any system whether starting air, lubrication, sea water line, etc. These require extensive maintenance and caution because if the valves have a small amount of fault, it can be drastic for the whole operation and could take significant time for normalizing it.
Following are some valves used onboard in various systems:-
OPERATION- This gate v/v also called as sluice v/v has a barrier or gate-like structure which is attached at the end of the spindle. As we rotate the handwheel whether manually or by automation, it transfers the energy to the spindle, and thus the gate lifts or sits down.
NOTE- This v/v can’t regulate the direction of flow of fluid rather it can only be used for the starting /closing of the flow of fluid.
There are two types of gate v/v- stem rising and stem non-rising.
As in stem rising, the spindle will also move up and down therefore, it’s not recommended to use it because of space constraints on board whereas, stem non-raising is used.
APPLICATION- All lines onboard where simple opening/closing of fluid required without regulating the direction of flow.
OPERATION- Earlier days this v/v shaped like a “globe”, hence it was named as globe v/v but now its shape is different from the earlier one. This is used for regulating fluid flow. Unlike in gate v/v, which has a gate or barrier, globe v/v has a plug; with the help of the clearance between the plug and v/v seat, the flow is regulated. It is to be noted that this can be used in a partial open position which is not possible in gate v/v.
There are two types of globe v/v-
1. SDNR globe v/v
Screw down non-return globe valves also known as SDNR globe valves are used to prevent reverse flow when in the open position and for providing a leak-tight shut off with the capability of being used partially open to regulate flow.
2. SDR globe v/v
Screw down return globe v/v also called SDR globe valves are simple globe v/v which are not leak-tight.
3. Angle type globe v/v
Angle type globe v/v is very much necessary in shipping because of a number of bend pipes in ships, for such type of pipes we use angle type globe v/v.
APPLICATION- Used in bilge suction lines and systems where regulation of flow is necessary.
As we can see in the above diagram, there is a flap or plate-like thing which we call a disc in this which is used to regulate the flow of fluid. We can use either handwheel, lever, or by automation (in the figure, it’s by lever) to control the v/v; as the lever is connected to the spindle and subsequently to the disc, the disc is finally controlled similar to the globe v/v.
- Cooling water, air, gases, fire protection, etc.
- Slurry and similar services.
- Vacuum service.
- High-pressure and high-temperature water and steam services.
- Compressed Air or Gas applications.
If you want to know about solenoid valves, click here.
Authored By:- Cdt. Suraj Mohanty, TMI