Module 6 : Bilge Pumping System

Question 1

Bilge Pumping System : Purpose

Answer 1

The purpose of a bilge pumping system is to remove water that has accumulated in the various spaces in a vessel like machinery spaces and cargo holds. They are also used to remove water from spaces that have flooded due to an accident or to maintain the vessel’s stability

Question 2

Bilge subsystems

Answer 2

1. Bilge Main
2. Direct Bilge
3. Emergency Bilge System
   These systems work together to ensure that machinery spaces have at least 3 different methods of being drained
   Bonus: bilge ejection

Question 3

Bilge pumping system rules

Answer 3

Set out by SOLAS and TC Marine Machinery Regulations.
- Some are vessel specific but there are some commonalities across the board

Question 4

Bilge Piping

Answer 4

• 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
• Piping must be independent from other systems on board.

Question 5

Bilge Suction lines : double buttoms

Answer 5

• 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)

Question 6

Bilge system : valves

Answer 6

SDNR valves must be fitted at all sea suctions, valve manifolds, bilge main suctions, and overboard
- Legible name plates must be fitted to each valve.

Question 7

Bilge Systems : Cargo Holds

Answer 7

The piping, valves, strainers and mud boxes will be protected against damage

Question 8

Bilge pumps

Answer 8

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)

Question 9

Bilge systems in machinery spaces

Answer 9

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

Question 10

Stipulation for electrical propulsion

Answer 10

If the main propulsion system is electrical, a means must be provided to prevent accumulation of bilge water under the generators and motors

Question 11

Bilge Main

Answer 11

• 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

Question 12

Direct Bilge

Answer 12

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

Question 13

Bilge suction : placement

Answer 13

• Placed at the lowest point in the machinery spaces where water will normally accumulate
• 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, one port and one starboard. 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)

Question 14

Mud Box

Answer 14

Between the bilge well and the valve, a mud box will be fitted.
- Fabricated from steel
- Has a removeable cover fitted with a gasket
- 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 pipe.
- 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.

Question 15

Straight tailpipe

Answer 15

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

Question 16

Direct bilge suction line strainer

Answer 16

Fitted around the bottom of the suction pipe for direct bilge systems, a strum box will be fitted. Also called a rose box, it is a perforated metal box fitted around the pipe that prevents debris from chocking the suction pipe. The size of the perforations follow the same guidelines as the mud box.

Question 17

Bilge Ejection Valve

Answer 17

Every machinery space must be fitted with an emergency bilge suction pipe connected to the main engine cooling water pump. This pipe is fitted with a valve and the suction must descend down into the bilge at a suitable drainage location. The valve must be a SDNR type and the hand wheel must extend a minimum of 460 mm above the deck plates. The valve wheel must be tagged “For emergency use only”.
- When opened, any accumulated bilge water will be pumped overboard via the main engine cooling water pump and systems. However, this is only to be used as a last resort as any debris in the water will clog up the cooling passages in the main engine cooling system
- Note : if there are more than two cooling water pumps, then only 1 is required to be fitted with the pipe. As well, if the cooling pump is not suitable (or not fitted) then the emergency bilge suction arrangement must be fitted to the largest independent powered pump in the space.
Used as a last resort when all other means of removing water aren’t capable of keeping up with the flooding.

Question 18

Emergency Bilge Suction

Answer 18

Set up such that a space can be pumped out in an emergency without using the regular system or machinery. These are governed by a separate set of rules:
- Must have at least 1 power pump available for use in all of the flooding conditions that the vessel is designed to withstand. The pump is either a) submersible having power and controls above the freeboard deck or b) power source will be designed to that at least 1 pump in an undamaged compartment is operable
- Pumps are powered from the emergency generator but in some cases the pump may be driven by a hydraulic motor, with the power pack for this system located above the freeboard deck
- Often acts as an emergency fire pump as well. Lines will pass from a manifold fitted to the suction side of the pump to specific locations in the machinery spaces (as set out in the regulations). A manifold on the discharge side passes water overboard or to the fire main.
- Controls for the pump must be clearly identified and valves must be capable of being operated from a location above the freeboard deck. The pump control station is centrally located and must be clearly identified