Wet Steam Accumulator: Design, Requirements, Operation and Advantages

In this article, I will explain the design, requirements, operations and advantages of wet steam accumulators.


Wet steam accumulators are mostly used in small boilers to supply steam to the plant processes when the demand is higher than the boiler can provide.


They store steam in form of saturated water and when there is a pressure decrease in the steam line due to heavy processes that require more steam, this saturated water will turn into steam and be supplied to the plant processes to keep the processes going on smoothly.


I will discuss the operation of the steam accumulator in another section (end of this article).


For now, you should know that wet steam accumulators are a modern invention that decreased the size of boilers, enhanced efficiency, and prolonged their lives.


A boiler that has a steam accumulator is likely to have a prolonged life because it can meet the demand of the plant processes without any issues.


When you compare a boiler with no accumulator, it’s likely to have a short life because the demand for steam tends to be higher than the boiler can provide.


This wears out the boiler and within a concise period, the boiler won’t be used.


Wet steam accumulators are needed to ensure that the steam provided to the processes is steam of high pressure, the required quality and with enough thermal energy.


Low-pressure steam tends to be dirty, decreases the process times of the machine and the thermal energy is deficient to sustain some of the processes.


With that much said, let me share what you should know about wet steam accumulators.


Design of wet steam accumulators

A cylindrical pressure vessel is used to store water that is converted into steam when needed during a spike in demand.


A distribution manifold fitted with a series of injectors that is connected to the pressure vessel from the boiler charges the steam accumulator.


The ball float type is used to monitor the level of water in the pressure vessel. It’s also usually fitted with an integral thermostatic which is responsible for stopping or allowing the steam in the pressure vessel.


A steam distribution line is necessary for the supply of steam into the pressure vessels and for supplying steam to plant processes when the demand is high.


A stop valve is mounted on the pressure vessel to control the flow of steam to the processes when the demand is high. This also ensures that the wet steam accumulator is not entirely discharged during the peaks.


A non-return valve is installed on the connection between the accumulator and the boiler. It’s used to prevent the backflow of steam into the boiler in case the boiler is shut down or it stops working for any other reasons.


The steam is supposed to be fed into the steam accumulator from the boiler, it’s a one-way thing and it should remain that way.


The surplussing valve is another mounting that is installed between the accumulator and boiler to control the flow of steam flowing into the accumulator.


It ensures that a considerable amount of steam is charged into the accumulator according to the amount of steam discharged during the peaks.


The pressure gauge is another important mounting on the steam accumulator that is used to show the pressure of the steam.


It shows the minimum pressure of the plant steam, the maximum pressure of the boiler and the pressure inside the pressure vessel of the accumulator.


This pressure gauge is able to show these readings due to the pressure differential between the discharge outlet of the accumulator and the charge inlet.


The safety valve is necessary to be installed on the wet steam accumulator to ensure the safety of the pressure vessels and the operators.


If by accident the steam from the boiler is charged in the steam accumulator without any control, there is a possibility that the pressure vessel isn’t going to handle all the steam from the boiler and this will lead to an explosion.


And that is why the safety valve is a design factor that an accumulator should not miss.


An air vent is needed to remove any air inside the accumulator. The air inside the accumulator will destroy the working pressure of the accumulator.


Vacuum breaker as the name suggests it’s needed to eliminate the vacuum in the accumulator.


Vacuum in the accumulator can be a result of the condensed steam which leaves a room. It will be the work of the vacuum breaker to eliminate this vacuum.


You have to know vacuum in the accumulator will result in air leakages in the accumulator which is a bad thing for steam generation in the accumulator.


Drain c*ck is also mounted on the steam accumulator to drain any unwanted contaminants from the accumulator and give room for inspection whenever there is a problem.


Requirements of a wet steam accumulator

For the wet steam accumulator to work perfectly these are the requirements it should fulfil;


1. Enough water should be supplied.

Enough water should be supplied to the wet steam accumulator to ensure that there are no shortages of steam during higher demands.


If the pressure in the steam line drops because the processes need more steam than the boiler can provide, the wet steam accumulator should ensure that it provides a load that can compensate for the loss in the steam line.


For this to happen effectively, the wet steam accumulator should have enough water to ensure that it meets the demand required by the processes that are taking place.


Shortage of water in the accumulator will result in low steam production which will eventually result in poor production, long process time and decreased efficiency of the boiler.


Water should be enough it should not be completely full (between 50% and 90%).


2. Sufficient evaporation capacity.

This is another requirement that wet steam accumulators should fulfil. Sufficient evaporation capacity is necessary to ensure that there is higher production of steam from the accumulator.


You must remember that the steam accumulator’s water is stored in its saturation form.


So, this means it has to be evaporated for it to turn to steam before it’s provided to the plant processes that need more steam.


For the evaporation capacity to be higher, there has to be a large pressure difference between the fully charged accumulator and when it’s discharged.


3. Appropriate design pressure.

The design pressure of the accumulator should be designed in a way that favours high steam production.


This means that the design pressure of the accumulator should be higher than the downstream.


For this to be achieved the wet steam accumulator should be well-built, right mountings, good controls and fittings


Operation of a wet steam accumulator

The pressure vessels are filled with water that is in its saturated form to make it easier and fast for it to be converted into steam.


When there is a peak of demand for steam there will be a pressure drop in the steam line (in such a way that the plant processes utilize more steam than the boiler can provide) the water will turn into steam and be supplied to the plant processes to ensure there is a continuous flow of high-pressure steam.


The steam from the accumulator can be produced by either heating the water indirectly via a heat exchanger, hot gasses from the furnace or by reducing the pressure of water stored and this ends up changing a portion of water into steam.


After the steam accumulator has supplied enough steam to terminate the high demand, the pressure in the steam line will go back to normal, the accumulator will stop supplying steam to the plant process and it will recharge from the boiler.


Advantages of using wet steam accumulators in boilers

1. No downtime.

As you now know that wet steam accumulators feed steam to the plant processes when the demand is high.


This clearly tells that when the plant processes are going on there is no time a downtime will be experienced.


If by any chance there is a problem for a short duration and the boiler can’t meet the demands then the steam accumulator will be there to solve that problem until the boiler issues are fixed.


2. Save money and space.

With the introduction of wet steam accumulators, which makes the boiler to be more efficient; there is no need for more giant boilers that cost so much.


One can just purchase a small boiler and install a steam accumulator to enhance its productivity.


Buying a small boiler doesn’t cost much compared to when one will buy a huge boiler to ensure the needs of the processes in that industry are met.


The other thing is that a small boiler needs a small space to be installed which also ends up saving so much money for the ground needed to house the boiler.


3. Reduced boiler maintenance.

Using steam accumulators ensures that the boiler is not overloaded. This leaves the boiler in great working conditions for a long period.


If the boiler works perfectly the maintenance needed will be very minimal.


This is a good thing for any power production process since one doesn’t have to spend so much on maintaining the boiler for smooth operations.


Without the steam accumulator, the boiler is likely to struggle to meet the demands of the plant processes especially if the boiler is not big enough.


This will end up causing complications to the boiler because of the overloading issues and maintenance will be increased.


4. Prolong the life of the boiler.

With the steam accumulator in use in a boiler, the workload of the boiler will be reduced, there will be minimal maintenance and this will end up prolonging the life of the boiler.


5. Increases thermal efficiency of the boiler

High-pressure steam tends to be the perfect one for large plant processes because of the energy it provides.


When there is a peak in demand (more steam is needed than the boiler can provide) the pressure of the steam is likely to reduce significantly.


If it reduces, the thermal energy of the pressure is also going to drop and eventually the energy will drop.


This will drag behind the plant processes if the boiler can’t meet the demands in the spur of the moment.


With the wet steam accumulator installed, these demands are likely to be met immediately when they happen. This ends up ensuring that the pressure of the steam remains high.


If the pressure of the steam is higher all the time, then this means the thermal efficiency of the boiler is going to be higher too.


And it will increase the overall efficiency of the boiler.


Final thoughts


This is what I can share about wet steam accumulators. You have to know that there is a dry steam accumulator too that you should check out to know which you should go for.


Maybe, I research and come up with that article too.


There is still more to be learned when it comes to steam accumulator calculations and how much they contribute to the overall efficiency of the boiler.


But for now, I hope you have got much from the short summary that I have shared about the wet steam accumulators.


Thanks for reading the article, if you have any questions or there is a point that you need me to clarify don’t be afraid to leave your comment.


See you in my next article.


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