Steam hammering Vs Water Hammering

What is Steam hammering?

It happens when there is direct contact of steam with liquid, as hot steam comes in contact with cooler condensate or liquid, creating a low-pressure zone. The liquid then rushes in to fill the low-pressure zone creating a pressure spike. As the steam flow increases, steam carries the water with it a lot of momentum is created and hammers the line loops with tremendous forces causing a lot of stress.

Effects of steam hammering

• Cause valve failure.
• Break pipe welds and rupture piping.
• Failure in heat exchange or tubes.
• Crack steam trap and pressure gauges.

How to prevent Steam hammering?

• Have a checklist for the start and shutdown of various steam systems onboard.
• Correct usage of the warm-up valve.
• Drain the steam line and make it free of condensate
• check and repair insulation to reduce  heat wastage and accumulation of condensate
• Gradual opening and closing of the valve.
• Ensure steam traps are working satisfactorily.

What is water hammering?

Water hammering is the sudden pressure surge caused by rapid change in the velocity in the pipeline, which sounds like being pounded with a hammer

It is caused when a fluid in motion is forced to change direction or stop abruptly. When a pump is suddenly stopped, or when an open valve is closed suddenly.

How to prevent Water hammering?

• Reduce operating pressure.
• Open and close the valve slowly.
• Installing pressure reducer.
• Good pipeline control (start-up and shut-down procedure).

What does CCA and Ah in battery mean

Cold-cranking amps (CCA)

It is a battery rating system that defines the battery's ability to start an engine in cold conditions.

What does a 400 CCA battery mean?

It means a battery rated 400 cca will give 400 amps of power for 30 seconds at 0 deg cel maintaining a voltage of 1.2v per cell or 7.2v for a 12v battery

And  battery rated 200 CCA will give 200 amps of power for 30 sec at 0 deg celsius, maintaining a voltage of 1.2v per cell

How much CCA do I need?

The thumb rule is one amp per cubic inch of engine displacement.

Why do batteries deteriorate at cold temp?

At cold temperatures, the reaction in the battery slows down impacting its ability to start the I.C. engine.

LO viscosity increase at lower temp making it harder to pump oil and start the engine. This makes a situation where your battery has to work harder to start the engine.

It is always better to have a higher CCA-rating battery for marine applications.

Ah rating?

Ah typically measures batteries' total energy-storing capacity.

A 100 Ah battery is capable to deliver10 amp for 10 hrs before the voltage drops to a standard value of 1.67 volts per cell or 10.02 volts for a 12v battery.

Similarly, 50Ah would supply 5 amps for 10 hrs

Ah = Amps x hours

Amps hour(Ah)= Current(I) x Discharge time (T)

CCA VS Ah

CCA is the ability of the battery to deliver a burst of power over a short time like a sprinter

Application- ➡Starting lifeboat engine, Emergency generator, etc.

Ah is the ability to deliver power over a length of time like a marathon runner. 

Application➡GMDSS battery, general service battery, etc (deep cycle application)

Difference between purifiers and clarifier

What are centrifuges?

A centrifuge is a device that uses centrifugal force to separate component parts of a fluid. This is achieved by rotating the fluid at high speed within a container, thereby separating fluids of different densities (e.g. cream from milk) or liquids from solids.

• It works by causing denser substances and particles to move outward in the radial direction.
• At the same time, objects that are less dense are displaced and move to the center.
• In ships, we use two types of centrifuges ie. purifier and clarifiers 

Definition

• Purifier is a type of centrifugal separator that we can use to separate two liquids with different densities 
• Clarifier is a type of centrifugal separator that we can use to separate solid impurities from fuel.

The main difference between the two

Purifier

1. In a purifier there exists an inference or a line separation between the oil and water, this is achieved using a dam ring. the position and the diameter of the dam ring plays a major role in the creation and maintenance of interface line
2. Purifier needs to be filled completely with sealing water for the generation of a seal that prevents the oil to leave from the water outlet
3.  The conical disc has feed holes/distribution holes to help with the interface
4. It has two outlets clean oil outlet and water outlet
5. Generally used for lubricating oil

If the interface is broken or misplaced water can go into the clean oil outlet or oil can enter the water outlet, hence disturbing the purification process 

Clarifier

1. In a clarifier, there is no interface between oil and water, this is achieved by using a sealing ring, which seals the water outlet. this allows the water and impurities to stay within the bowl and is discharged when the bowl disludges
2. The clarifier doesn’t need to be filled up with sealing water.
3. The conical discs in a clarifier usually don’t have feed holes in them but if they do, then a disc without any holes is fitted at the bottom of the stack.
4. It has only one outlet clean oil outlet
5. Generally used for fuel oil depending on fuel density and design