They can use Vanilla Minecraft fuels to operate or EU with an Energy Link. Note that they still require a Redstone signal to run, as do Combustion Engines. You can supply this with Redstone or with Red Alloy Wire from RedPower - it may be more effective.
Steam Engines will never explode unless the engine itself receives too much power. You can leave one running, for example, and it will never explode unless it is receiving power. The temperature is represented by the color of the central pylon. Blue means it's cool, Green means it's warm, Green - Orange toggle means it's beginning to get hot, Orange means that it is hot, and when its an orange -red toggle then it means it's near or in danger of imminent explosion, but its also where the engine runs most effectively (see "using EU as fuel" below)
Steam Engines can be used to run a Quarry, but it's recommended to use 3 or more to run it. It also pumps out 16 items per pump if used to take out items from a chest (Note: It sometimes pulls 52 per pump). If used to take items from an Energy Condenser, however, it will only pump a single item at a time. Like a Redstone Engine, the hotter it gets, the more it will pump. Using this on a Pump will pump out liquids much more efficiently than the redstone engine can. It is debatable whether or not water surrounding it slows down heat building up.
There also seems to be a rare bug in SMP, that when removing any amount of coal from a steam engine, it doesn't come out.
Effects of Temperature
Steam engines, like Redstone and Combustion Engines, pump faster as they get hotter. The table below shows various speeds as compared to a blue steam engine and a blue combustion engine. Please note that all ratios are approximate.
|Temperature||Ratio to Steam||Ratio to Combustion|
|Green||2 / 1||1 / 1 (Same speed)|
|Yellow||4 / 1||2 / 1|
|Red||6.5 / 1||3 / 1|
A red steam engine pumps faster than any other engine in any state. However, the only reliable way to keep a steam engine at this state would be to have a very precise redstone timer hooked up to cycle power from an Energy Link, so as to keep the steam engine just right.
Coal & Charcoal: Each piece equals a total of 32 pumps of the machine. That means with a full stack, it will pull out a total of 2048 pumps. Putting in a stack of this will never cause your engine to explode if you give a buffer time of 5 minutes after the consumption of each stack. However, supplying it with non-stop coal will eventually overheat your engine.
Sticks & Saplings: These last for a total of 3 pumps each. That means that with a full stack, it will pump a total of 192 times. Your pump will NEVER heat up from this, regardless how many you put in.
Planks & Wood (and any other "wooden" item, excluding Sticks and Saplings): These last for a total of 7 pumps each. That means with a full stack, it will pump a total of 448 times.
Your pump will RARELY heat up from this method of fuel.
Lava Bucket: One bucket will last for 260 pumps, however, since you can immediately put a second bucket in to be used "when needed," this effectively means that it has 520 pumps without touching it. A constant supply of lava buckets usually will not overheat your engine, but in a few cases they have. (It is unknown if this is a bug) However, lava costs 832 EMC, so this may not be an ideal solution.
Using EU as Fuel
WARNING, this is bugged in SMP: They will explode with much less power than in Single Player. All the following values are for Single Player, except the note for SMP.
You can power a steam engine with EU by supplying an Energy Link with EU, then plugging the engine directly into the side of the Energy Link, or by using conducting pipe to send the power to the engine. However, supplying the Energy Link with 512 EU/t from an MFSU will blow up a Steam Engine in about 5 seconds. Below is a list of how much EU it takes to consistently run one steam engine at a given temperature. You can easily control the exact number of EU/t going into the Energy Link by using a combination of Low Voltage Solar Arrays (8 EU/t) and Solar Panels (1 EU/t). You can also get the right amount of power by figuring out the correct height to place a Windmill.
Blue: You need a minimum of 3 EU/t to get the engine moving. This is easily produced with a Windmill at low altitude or 3 Solar Panels. You can supply up to 5 EU/t without the engine heating up to Green.
Green: At 6 EU/t, the engine will flash green, after it has been running long enough, though it will be mostly green. At 7 EU/t, it will spend about as much time in Green as a fully warmed up Redstone Engine does in Red. At 8 EU/t, it will stay steady in green, occasionally dropping into blue. It will not heat into yellow.
Yellow: At 9 EU/t, it will flash yellow for one frame every pump. It will steadily increase the ratio of yellow to green until 14 EU/t, when it has one frame green per pump. Note that a Generator will supply 10 EU/t, holding it in Green/Yellow stage. This is advantageous because you can use a Fuel Can filled with Coalfuel Cells to power it for a long time.
If you supply it with 15 EU/t, it will very slowly increase in temperature until it heats up to red (if you don't want to wait, supply far too much power for just a couple seconds). At that point, every fifth pump will have one red frame. 16 EU/t will have 1 red frame every pump, and it will steadily increase until 22 EU/t - the magic number. At 22 EU/t, it will have one yellow frame every pump. This is the most efficient you can possibly make your steam engine and still be perfectly safe (note: In SINGLE player). With 23 EU/t, it will very, very slowly increase in temperature and eventually explode.
WARNING: If the pump is turned off via a switch or something else, but still receives power (EU) it will explode. At 22 EU/t this happens after 18 seconds!
The pump will not explode if it runs out of materials to pump.
You can supply a large number of Steam Engines with one solar array, so long as you evenly distribute the power between the engines. Go back and use an EU reader to check how much EU each Energy Link is receiving. So long as you're not over 22 EU/t, you'll be fine. In the example above, there is one MV-Solar Array (64 EU/t) and 3 LV-Solar Arrays (8 EU/t each) which add up to 88 EU/t. This is divided by the pipes into 44 EU/t, then divided again by the Energy Links so each engines get exactly 22 EU/t. You can see the bottom two engines are in the yellow "flash". These engines will never overheat.
Note: When hooked up to conductive pipes or BC machinery, they will take much more power. In the setup in the picture above, when all four engines were hooked to conductive pipe and machinery, each engine took 34 EU/t without overheating.
SMP NOTE: LV, MV and HV. (May work in single player. Not tested)
You can power a steam engine with HV, MV, or LV EU via an energy link too! Note that an energy link can be switched off on a redstone signal. By keeping the energy link mostly off and pulsing it on only once every 2.5-3 secs (varies in testing) we found steam engines gradually warmed up to red, but did not explode when set correctly.
This can be accomplished by inverting a timer output and setting the timer at 3 seconds. If your engines do not go red, you might try and lower it gradually to 2.5. This timing varied per server. The timing was not much different at different EU values, but did require changing when going from LV to HV.
When you give an steam engine between the 10-14 eu/t on SMP, it will heat up to orange, but wont heat up any farther, tested while I was playing close to that engines, I placed 2 geothermal generators and wired it up to 3 steam engines, and they took it without exploding.
Efficient & Safe Powering
Running a steam engine for long periods of time can be tricky. Although coal and charcoal lasts long and rarely has to be resupplied, the engine has a cooldown period afterwards. One way to avoid this is to feed the engine saplings, which, although not lasting very long, removes the possibility of a catastrophic failure. Having a Mk II Energy collector with a torch on top condensing oak saplings (EMC value: 32), it will supply exactly 2 engines with extremely little off time. This can be useful for safely powering engines in places you rarely come by.
Lava is also fairly safe - one lava bucket powers the engine for at least 100 pumps (didn't sit there to count them all), and in testing found that 8 lava buckets back-to-back still couldn't get it to green temperature. (In some rare cases using about 3-4 buckets back-to-back has made the engine overheat, so be careful!)