What is a Bilge Pump? | How does a Bilge Pump work?

The pumps are most famous all over the world. Different types of pumps are using in different houses, industries, and many other applications. There are numerous types of pumps, and the bilge pump is one of them. The bilge pumps are mainly used to eliminate the bilge water.  This article mainly explains different aspects of the bilge pump.

What is a Bilge Pump?

A type of water pump that uses to eliminate the bilge water is known as a bilge pump. Due to the potential for fuel in bilge water, electric bilge pumps are manufactured so that the pump can’t produce a spark, and the risk of the fire can be eliminated. An electric bilge pump also has a float switch that turns the pump on when the bilge fills according to the organized level.

Bilge pump system on ship

Generally, bilge pumps used on ships are located below sea level—this assists in building up additional suction pressure. Nowadays, centrifugal bilge pumps are the most common because these pumps deliver consistent flow and take low time for pumping.  But these pumps don’t have the self-priming capability. While the piston bilge pump has the self-priming capability, but its use is reduced day by day.

It is generally recommended to use a backup pump (secondary pump) with a bilge pump because it may damage at any time. The primary pump is usually placed at the bottom point in the bilge and the secondary pump a little higher. It means the secondary pump turns on only in the situation when the primary pump has been failed or overloaded. This setup of the primary and secondary pumps in the bilge prevents the secondary pump from debris in the bilge that could easily block the primary pump.

The bilge pump can be made of bronze or wood. Bronze seems to be the best appropriate material according to ancient texts, as it lasts a long time and is easy to transport. Wood is easier to build, repair, and assemble but not as durable as bronze. Therefore, bronze is a preferred material for the construction of the bilge pump. These types of pumps have a very simple structure and consist of a piston, a cylinder, and several valves.

Working of Bilge Pump

A bilge pump has two types that centrifugal and reciprocating bilge pumps. Here we will discuss the working of the centrifugal bilge pump.

The bilge pump has a runner, volute casing/diffuser, and runner blades. This runner is linked with a motor via a shaft.

Bilge Pump Working

During the working of the bilge pump, as the runner starts rotating, the bilge water begins to enter into the runner’s eye. After passing through the eye, the water strikes with the blades of the runner. As the water hits the blades, the blades increase the water speed by converting its kinetic energy into speed.

As the water discharges from the runner, it enters into the diffuser area. The diffuser increases the pressure of the bilge water by converting its speed into pressure energy. As the pressure rises according to the requirements, the bilge water discharges from the discharge valve.

Types of Bilge Pumps

The bilge pumps have multiple types because all the boats don’t have the same and capacity. The most common types of bilge pumps are given below:

  1. Centrifugal pump
  2. Flexible impeller pump
  3. Reciprocating pump
  4. Diaphragm pump
  5. Automatic bilge pump

1) Centrifugal Bilge Pump

Nowadays, centrifugal pump is the most common type of bilge pump. These pumps use a centrifugal force for pumping the water. A centrifugal pump has a diffuser or volute casing, an impeller, and impeller blades. It uses impeller blades to convert the kinetic energy of the water into speed. The diffuser uses for transforming the impeller’s bilge water speed into the pressure.

Centrifugal Pumps

These pumps have low costs, the capability to handle small debris, simple design, and high capacity. These pumps have the capability to deliver a consistent flow of water. Due to these reasons, centrifugal bilge pumps are replacing reciprocating bilge pumps. But the main problem with centrifugal bilge pumps is that they don’t have the self-priming capability. 

Advantages and Disadvantages of Centrifugal Bilge Pump

It has high capacity than a reciprocating pump.They have priming problems.
Low price.It can’t pump to debris and solids.
These pumps have simple design.They use rotation instead of suction to move water.
They are affordableIt can’t transfer high vicious fluids.
These have easy maintenance.Impeller damage problems.

The centrifugal bilge pumps have the following different types:

I) Radial Flow Pump

In the radial flow pumps, the water enters axially into the eye of the impeller while exit the impeller in the radial direction. These pumps provide a pulsation-free flow rate.

II) Axial Flow Pump

In the case of the axial flow pump, the bilge water enters radially into the impeller’s eye while discharging the impeller in an axial direction.

2) Reciprocating Bilge Pump

It is another famous type of bilge pump. These pumps use a plunger or piston for the pumping of water. These are the most reliable and efficient pumps. The main advantage of a reciprocating bilge pump is that it has a self-priming capability. This pump uses a piston for pumping purposes. As the piston moves downward, it sucks the water inside the pump chamber, and when it moves upward, it increases the water pressure inside the chamber.

reciprocating bilge pump

The major disadvantage of these pumps is that they can’t deliver a continuous flow of water, and also, these are less efficient than centrifugal pumps.

Advantages and Disadvantages of Reciprocating Pump

These pumps have self-priming capability.They have low power than centrifugal pumps.
A reciprocating pump can pump high viscosity fluids.It can’t transfer debris.
There is no need for initial priming.Less efficient
It has the capacity to remove all the bilge water.It delivers a pulsating flow of water.

The reciprocating pumps further divide into the following major types:

I) Single Acting Bilge Pump

The piston of the single-acting bilge pump uses only one end for suction and compression. It means, in the first stroke, the piston sucks the water in the pump, while in the second stroke, the piston pressurizes the water and increases its pressure.

II) Double Acting Bilge Pump

In this type of pump, both ends of the piston are used for suction and compression. One end of the piston uses for suction, while the other end uses for pressurizing the water. In this pump, the suction and compression process complete in just one stroke of the piston.

III) Single Stage Pump

This reciprocating bilge pump uses one cylinder and a piston to increase the pressure of the water. It is less efficient than a multistage pump.

IV) Multistage Pump

This pump uses more than one cylinder for pressurizing the water. And each cylinder has a piston.

3) Diaphragm Pump

A diaphragm pump is the most efficient pump. It uses one or more diaphragms for increasing the bilge water pressure. But diaphragm pumps have low efficiency than centrifugal pumps. These are the best choice for large ships, but these are best for small and medium-size ships. Like reciprocating pumps, these pumps also have self-priming capability and can also run dry.

Diaphragm pumps

Advantages and Disadvantages of Diaphragm Pump

It has a self-priming capability.Less efficient.
It can handle high viscosity fluids.You can’t pump debris.
Can operate manually.Provide pulsative flow.

The diaphragm pumps also have the following major types:

I) Single Diaphragm Pump

It uses a single diaphragm or membrane for pulling and pushing the water.

II) Double-Diaphragm Pump

It uses two diaphragms that are positioned parallel to each in two different cylinders. These two diaphragms are connected with the help of a connecting rod. 

III) Manual Diaphragm Pump

These pumps are operated manually. There is no need for an electric motor or electric power for the operation of these pumps. The manual diaphragm pumps have a significant advantage in that they can be operated if there is no electricity.

4) Flexible Impeller Bilge Pump 

The looking of these pumps is very similar to centrifugal pumps, but their working is very different. A flexible impeller pump is a type of positive displacement pump, but it uses a flexible impeller made of rubber.

flexible impeller pumps

These pumps also have a self-priming capacity, but they are less efficient than centrifugal pumps. These have the capability to transfer the debris and solids. Compared to other types of positive displacement pumps, the flexible impeller pump can’t run in dry conditions.

Advantages and Disadvantages of Flexible Impeller Pumps

Self-priming capability.Less efficient.
It has low price thanThe rubber of the impeller wears down.
These have flexible impellers.This can’t be used for high-pressure applications.

5) Automatic Bilge Pump

The body of the automatic bilge pump is made of corrosion-resistant thermoplastic. This is an electrically operated pump. An electric motor uses to supply the power to this pump. During the pumping process, the electric switch observes the bilge water level so that you can complete your other activities at the same time.

The automatic bilge pump switches off automatically when the water is discharged. It has the capability to clean the surface of the water without supervision. Usually, these pumps use to drain flooded basements, window shafts, flat roofs, plunge pools, and spas without supervision.

Components of Bilge Pump

The bilge pump has the following components:

  1. Casing
  2. Runner
  3. Runner Blades
  4. Diffuser
1) Casing

It provides protection to the pump internal parts. It acts as a safety guard. If any heavyweight falls on the pump body, it prevents the internal parts from any type of damage.

2) Runner

It is a rotating component of the pump. The runner gets power by an electric motor through a power shaft. It has one or more blades.

3) Runner Blades

These blades are located on the pump runner. They convert the kinetic energy of the water into speed. 

4) Diffuser

This component of the boat bilge pump uses to convert the speed of the liquid into pressure.

How to arrange Priming of Centrifugal Bilge Pump?

Centrifugal bilge pumps have no self-priming capability, requiring extra placement to remove air from the suction line. If the water level that is to be transferred is more than that of the pump, the air in the suction line may be removed easily by opening the air cock installed in the suction connection of the pump. This allows the water to flow automatically because of gravity.

bilge pump priming arrangement

If your pump is below sea level and you want to use the pressurized sea water, you can prime the pump by opening the air cock and the seawater cock at the same time.

How to Prime the Bilge Pump

The priming problems mainly occur in the centrifugal bilge pumps. If you are also using the centrifugal pump and don’t know how to prime to your pump, then follow the below-given steps to prime the bilge pump:

  1. First of all, you need to close the outlet valve and open the inlet valve of your pump before starting the pump operation.
  2. Now, turn on the priming unit to the suction line
  3. Turn on the electric motor
  4. And also, monitor the priming process (this process will begin when you turn on the pump).
  5. After the completion of the priming process, open the outlet valve gradually.
  6. Regulate the water flow rate through the inlet valve.
  7. Fix the required output flow via adjusting the outlet valve.
  8. After the completion of the pumping process, firstly turn off the electric motor and then shut off the inlet and outlet valves.

Why do You Need a Marine Bilge Pump?

You should use the marine bilge pump due to the following reasons:

  1. Prevent Flooding
  2. Bilge Pump prevents the ship from sinking
  3. It’s a Legal Requirement
1) Prevent Flooding

Washing, drainage, and leakage of the liquids end up in the ship’s bilge wells. If your boat bilge pump is not activated, your ship’s bilge wells will ultimately overflow, and bilge’s liquid will start entering into the engine area. This may create many problems.  

If oily water increases, it can penetrate and damage the engine. Even if the compartment gets into the water, it may heavily disturb the balance of the boat.

This is the reason due to that you should use a bilge pump in your boat.

Maximum ship bilge pumps have an automatic float switch. This switch starts the pump when the water level goes more than a specific level. So, because of this switch, you don’t need to check the bilge water level manually.

2) Save the Ship from Sinking

In addition to routine cleaning of the bilge hole, bilge pumps may also save lives in emergency situations.

If the ship has a small hole and is filled with water, the bilge pump can discharge water faster than the incoming water into the hole (depending on the size of the hole and the GPM of the pump).

By removing water from the bilge hole, you can quickly repair the wells or perform emergency docking.

 Note: Do not rely on the bilge pumps to float. If the boat has holes, also fix them as soon as possible.

It is highly recommended to install an emergency bilge pump with the stated maximum capacity. Ballast water pumps and fire pumps can also use to pump water in an emergency.

3) Legal Requirement

The installation of a bilge pump with a boat is also a legal requirement. According to law, your ship must have a bilge pump.

The maritime law strictly forces the shipowner to install a good bilge pumps system in his ship so that he can ensure the safety of the ship’s passengers.

If your ship is big, you must have many bilge pumps into your ship. The number of bilge pumps varies according to the ship size and number of passengers.

Bilge Pump Regular Maintenance for Ships

To make sure the proper working of your bilge pumps, you need to perform the below-given maintenances:

Daily Inspections

  • In the daily inspection, you need to inspect the pump
  • You must regularly inspect the temperature of the bearing.

Weekly Inspections

  • Inspect the vibration of your pump. If it is vibrating heavily, it may have a problem due to the damage of any part. In such a situation, immediately find the reason for vibration and fix it. 
  • Inspect discharge pressure
  • Check the reading of the power output

Monthly Inspections

  • Inspect foundation bolts
  • Grease coupling
  • Inspect the alignment of the coupling

Semi-Annual Checks

  • Operate emergency bilge pump (if standing by)
  • Inspect coupling alignment
  • Check the pitting or grooves

Bilge Pump General Maintenance

In the general maintenance of your bilge pump, you need to follow the below-given steps for proper maintenance of your pump.

1) Clean the bilge:

Contaminated bilge water is particularly destructive for the small boat bilge pump. Contamination may clog the pump filters and prevent water from entering. So, maintain your pump by cleaning it regularly and ensuring no contaminated water in the boat bilge.

2) Clean the filters:

The pump filters can clog due to debris or dirt. If there is any debris or dirt, clean immediately. If you have a mud box or drag box, it’s also important to check from time to time.

3) Check the Automatic Switches:

The last thing that you need to regularly maintain is the automatic switches. On small boats, mishaps can cause water to rise into the boat’s wiring. On ships, even a single switch failure leads to oily water getting into the dry compartment.

If you want to prevent this incident, you need to regularly inspect and maintain the circuit breaker. In addition, if you have installed bilge alarms, test them as well.

FAQ Section

Who invented the Patent Ship Pump?

 George Dodgson invented the patent ship pump.

What are the types of Bilge Pump?

The bilge pumps the following major types:

  1. Reciprocating pump
  2. Centrifugal pump
  3. Diaphragm pump
  4. Flexible impeller pump
  5. Automatic pump

See also:

1) What are the different types of Pumps?

2) What are the types of positive displacement pumps?

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