Module 6 : Bilge Pumping System Flashcards
Bilge Pumping System : Purpose
The purpose of a bilge pumping system is to remove water that has accumulated in the various spaces in a vessel. They are also used to remove water from spaces that have flooded due to an accident or to maintain the vessel’s stability
Bilge subsystems
- Bilge Main
- Direct Bilge
- Emergency Bilge System
These systems work together to ensure that machinery spaces have at least 3 different methods of being drained
Bilge pumping system rules
Set out by SOLAS and TC Marine Machinery Regulations.
- Some are vessel specific but there are some commonalities across the board
Bilge Piping
- Made of steel
- Must be separate from ballast and sea water suction lines
- Will be fitted in readily removable lengths
- Connected with flanged joints
- Secured to prevent chafing and bending
- Provisions for expansion and vibration will also be fitted
Bilge Suction lines : double buttoms
- Bilge suction lines may not pass through double bottom tanks unless alternate routing is impractical.
- If they pass through double bottoms, pipes must be of extra heavy thickness.
- May not pass through deep tanks but if they must, then they must be of extra heavy thickness and fitted in one length (welded or heavy flanged)
Bilge system : valves
SDNR valves must be fitted at all sea suctions, valve manifolds, and bilge main suctions.
- Legible name plates must be fitted to each valve.
Bilge Systems : Cargo Holds
The piping, valves, strainers and mud boxes will be protected against damage
Bilge pumps
Normally centrifugal and fitted with a self-priming device. In some cases, dedicated pumps are fitted but in most cases, the pumps will share many duties (bilge, ballast, general services)
Bilge systems in machinery spaces
Must be set up so that any water can be pumped out through at least 2 bilge suction lines when the ship is on even keel or heeled over at 5 deg.
- One line will be from bilge main and the other will be a direct bilge suction leading from a separate pump that may be used independently of the bilge main system
Stipulation for electrical propulsion
If the main propulsion system is electrical, a means must be provided to prevent accumulation of bilge water under the generators and motors
Bilge Main
- A common line that travels down the length of the vessel
- Set up so that it can draw from every machinery space, cargo hold, or similar compartment
- The exception is for spaces located far forward or aft in a vessel (chain locker, steering gear compartment). In this case, small individual pumps may be used to draw directly from the space
- Centrifugal pumps are commonly used
- At least 3 power pumps must be connected to the bilge main system
Direct Bilge
A direct bilge line is one that is fitted from the suction manifold of the pump to a location in the machinery or cargo spaces
Bilge suction : placement
- Placed at the lowest point in the machinery spaces
- If the vessel has a double bottom in the machinery space and no provision is made at the ship side for bilges, then bilge wells will be fitted. A bilge well is a recess constructed into the double bottom with a capacity of at least 150L. Bilge wells will be placed in areas where bilge water will accumulate and must be easily accessible for cleaning
- In double bottoms, one branch suction (from bilge main) and one direct suction will be fitted to each side of the space.
- In single bottom, one branch suction and one direct suction will be fitted as close to the center line as practical.
- A bilge main suction pipe will be fitted to the farthest aft point of the shaft tunnel (where one is fitted)
Mud Box
Between the bilge well and the valve, a mud box will be fitted.
- Fabricated from steel
- Has a removeable cover
- Contains a perforated plate that acts as a strainer to trap debris that may clog the piping, valves, or pump.
- The holes in the perforated plate may not be larger than 10 mm and the total area of the perforations must be at least twice the area of the suction pupe.
- Designed to be cleaned without having to break (disconnect) the bilge main
- Must be easily accessible above both the machinery space and shaft tunnel deck plates. If this is not practical, then they must be clearly identified and made readily accessible.
Straight tailpipe
A straight tailpipe descends down into the bilge well and ends a sufficient distance from the bottom of the well. This is done to ensure free suction and to facilitate cleaning