Bilge Injection Valve
Both these types of emergencies (fire and flooding) involve the use/role of sea water. If there is a fire, sea water is the biggest resource of water available in the sea. Similarly if it involves flooding of the engine room, cargo spaces or any other place on the ship for that matter; you would again require pumping the sea water out of the ship. In both these cases you require pumps.
We have studied a lot about sea water pumps, marine bilge pumps and piping arrangement on ships including various types of valves. Now in this article we will study about another important valve which is used to take suction from the bilges in case of serious flooding and this is known as the emergency bilge injection valve. I suggest that you take a close look at the diagram below before actually going through the text, so that you can correlate the two and absorb it properly.
So as you must have noticed, there are two valves in close proximity namely main injection valve and bilge injection valve. Both of them have their own independent controls. The diameter of the bilge injection valve is kept nearly 66% of the main valve diameter which draws water directly from the sea through the grid. This is a legal requirement that the diameter of this injection valve is at least 2/3 times the main suction, though it can be more also.
Hence the injection valve is an arrangement where the main sea chest can be bypassed in case of emergency so that instead of the sea, water gets drawn from within the ship itself.
There is a strainer attached to the bilge injection valve and the pump used for this valve is normally the largest sea water pump (or pumps) available in the engine room. Hence this valve is used to suck sea water from one of the lowest points in the engine room which you can also see from the sketch. This basically means that when you need to remove a lot of water from the ship, you simply need to open this valve and run the big pump/s.
If the junior engineers are reading this, they must always remember that opening up of the bilge injection valve always needs to be done with approval/permission from the chief engineer of the vessel.