Basic Boiler Steam Cycle Drawing w/ Explanation

After the novel yesterday, anything less should be easy yeah?  Figured this post we could write a little but include a very simple one line drawing of a basic steam cycle in the life of a water molecule in a boiler system.

For whatever reason, Paint, yes MS Paint, used to be basic, rudimentary, and kind of intimidating. You felt like you couldn’t really do anything, like Notepad (which I use every day now lol,) and whatever you could draw, looked like crap a few clicks later.

Paint is perfect for engineering drawing though. Basic shapes, straight line tools. I’m sure there are way better but for throwing together basic stuff for a knucklehead audience, it’s perfect.

The refrigeration cycle drawing is up, but that is it. We should do more posts with drawings and schematics and we will. It helps with the explanation, they are fun to make, and a person can visually comprehend what is going on as they read.

Basic Steam Cycle of a Boiler Drawing

basic boiler steam cycle drawing

There you go. Got it?  Good.

Brief Explanation

drawing of the first steam engine

Drawing of the first steam engine.

This explanation of the basic steam cycle should be easily understandable for most. Use the yellow numbers with the explanations, follow along with your finger.  Seriously put your finger on your monitor (call the IT department later to clean your monitor screen,) and trace it as you read.

How a boiler uses the basic steam cycle will make sense to even the most mechanically challenged people. If you have ever wondered how a big building heats itself – this is how.  Or how steam is used in the Navy by channeling and directing it down machined nozzles to turn massive turbines which turn the propeller (or screw)? This is how.

A boiler steam cycle is so simple and it is the same steam cycle that we use in other applications, just like this one, to get work done. The steam engine has been voted on of the most influential inventions ever. Why?

Because of the simplicity and efficiency. Once a person can harness this power, any work is possible. Huge cruise liners, nuclear submarines, buildings, heating, sterilization, water production. Water and steam are insane. They can do it all. Plus a closed loop steam system is almost self sustaining, which improves the efficiency.

It just keeps going back and forth – feed water -> steam -> work -> condensate -> feed water.


combustion in a boiler

Combustion junction what’s your function?

Combustion will be represented by #1 on the drawing. A post just went up last week maybe, covering combustion in detail, way more that we’ll get into here. And we also talked about generating or creating steam even more recently here.

Combustion takes place inside the boiler. Forget the class of boiler, we’ll just say fire happens inside a bundle of sealed metal tubes, water surrounds these tubes. Tubes get hot due to the combustion of natural gas, water boils, and steam is generated. That is area #1 of the drawing. Steam is produced here.

Main Steam Header

Area #2 of the drawing above.

This is where the steam from ALL of the boilers (serving that area) is collected and distributed.

Most times it looks like a large single pipe against a wall. It can be almost like a slender barrel of pipe.

The steam pouring out of the top of the boilers gets delivered via pipes to inlets on the steam header, also called a a manifold. Then, on this same manifold/header, are outlet pipes that deliver the steam to where it will do its work.

It’s a collection and delivery station.

Doing Work Yeah What

steam header picture

Image of what a steam header looks like.

You sing that part. To the tune of the Car Wash song. Try it. Get Car Wash going in your head. Do it. Going to the car wash, going to the car wash yeah. Doing it? Same tune, now, doing work yeah, doing work yeah what.

Maybe it’s just me.

Area #3 is where steam does work. It can be or do anything baby. It is versatile, agile, mobile, and hostile.

It can turn a turbine and generate electricity for a city, it can propel a massive aircraft carrier larger than a football field through the ocean.

In buildings, steam often goes out to places like hot water heaters or heating units out in rooms or offices.

In hot water heaters, they are like little boilers. Except roles are reversed! Dum dum dummmm!

This time, the steam might be INSIDE the sealed nest of tubes with the water from the hot water system surrounding them. Now the hot water gets hot and goes and does its work!

The steam arriving at the hot water heater for example, is all primed right? Carrying as much thermal energy as possible yeah? The hot water system, throws its own water over the tubes where the steam is shooting through and they exchange heat like strangers in the night. Oh so briefly. It is magical though.

The hot water exits out of its pipes on one side toastier than it was before, the steam leaves, dejected, after giving most of its thermal energy in the form of heat to that pouty hot water.

The steam is so exhausted, it gives up. It condenses.

Picture a pot of covered boiling water. With that lid on, you see maybe a cloud of steam start to form, maybe it condenses on the inside of the lid. As soon as you lift it off and relieve that pressure what happens?

basic steam cycle drawing

Relieving that pressure.

Like a quick puff right? And then it’s gone. That steam expanded suddenly when you took the lid off. It expanded so quickly that it “became” so much more, it had more surface area, more chances to exchange heat with the AIR molecules, it was gone.

Steam goes through its work cycle, whatever it is, and expands, and then like you are putting the lid back on, you capture as much as you can.

This is collected, usually drains to strategically placed tanks, and through gravity, fills them up.

This is condensate. This is represented by the blue shading above. This is where the awesome efficiency kicks in.

As much as possible is collected right after it does its work. The temperature difference between say our hot water and the steam causes it to condense right then. Then it falls and drains into condensate tanks.

The condensate tanks usually, or should, have float sensors. Ones that trigger the operation of a condensate pump when the tank level hits a set point. These pumps deliver our now condensed steam to a feed water tank – Area #4.

Feed Water

The feed water portion of a steam system is especially important.

This is where we take low pressure steam condensate, run it through a feed water pump, and deliver it into a high pressure boiler. Remember our pressure fundamentals stuff, the inside of the boiler is operating at over 100 psi right? We need a pump that can take our used up steam, and get it inside there.

The purpose of the feed water tank is to collect and store condensate. It also de-aerates the water, removes oxygen, and in the case of a boiler feed water tank, it usually is a point where chemicals are added for water treatment purposes.

boiler feed water system

A feed water arrangement.

The feed water tank stores it for use, the feed water pumps deliver it.

This is already nice and primed, hot water. None of this peasant untreated stuff straight from the city if we can help it. The water from the city may be 60 F. This huge tank of water is at 200 F. Think of how much energy we’d expend getting that city water up to boiling temperature, 212 F? See how efficient it is to collect the condensate?

We only have to go from 200 F to 212 F now. It is awesome.

Then the whole process repeats over and over. Just like life. Think about it. It’s deep.


This was a fun post to write. Touched on a whole bunch of subjects from earlier posts and mildly tied some together. Mainly though, this was about looking at a basic steam cycle drawing and having an explanation to go along with it.

There are four stages in this drawing – steam generation, collection and delivery, work and condensate, feed water.

Just like the hot water heater we used in the example, there are SO MANY systems that tie into the steam system that it is anything but basic. As the site grows, we’ll continue to get into it hopefully.

Actually it would rock if anyone reading this would like to help contribute something of value. Ideas, posts, how to, whatever, hit me up. Leave a comment if you are so inclined.

Leave a Reply