So, basically what to do here is, so this is a setup of the double acting steam hammer, you can see two cylinders one is the upper cylinder, other one is a lowest cylinder. Now in the upward stroke what you do is, you supply air into the lower cylinder. So, when you supply into this, this is a lowest cylinder, when you supply air into the lower cylinder, the hammer which was earlier in the lower cylinder will be pushed up into the upper cylinder.
So, the hammer is pushed up into the upper cylinder, the air which was already there in the upper cylinder will expel out to the exhaust. So, the air which was already there in the upper cylinder will be expelled out through the exhaust. So, basically what you are doing here is you supply air into the lower cylinder. So, that will push your hammer upward into the upper cylinder and the air which was already in the upper cylinder will be released through the exhaust, now your upward stroke is complete.

So, what are you doing the downward cylinder? You supply air through the inlet into the upper cylinder. So, when you are supply air into the upper cylinder, the hammer which was already there will be pushed into the lower cylinder. And air which was already in the lower cylinder will be expelled out through the exhaust. So, now that completes a downward stroke, so alternatively you are supplying air into a upper cylinder and the lower cylinder, so that you can have the rising and falling.

So, another important thing we need to know with respect to double acting hammer is in this most of the blow energy is the derived from the steam energy. Both for the upward stroke as well as for the downward stroke, the blow energy is derived mainly from the steam energy. So, 90% of the blow energy is derived from the action of air or the steam. So, that is why, for the double acting hammer we need not for a heavier hammer.
We can go for lighter hammers, smaller in size and you can go for the shorter stroke or shorter height of fall.

And this hammer is basically designed for lighter conditions, lighter conditions in the sense. So, it is basically designed for light to medium weight piles and for soil with normal frictional resistance. So, very tight clay, hardened clay with very high frictional resistance, so we are not supposed to use these double acting hammers. Because these double acting hammers are designed for lighter conditions, that means for light to medium weight piles and for the normal soil with normal frictional resistance.

So, these double acting hammers, they basically have a very high blow rate, if you look into the blow rate, you can see that the blow rate will be 95 to 300 blows per minute. So, it is very high when compared to the single acting hammer. So, such a high blow rate may can easily damage the concrete pile. So, that is why it is not recommended for the concrete pile.

So, let me summarize what we discussed, so your use of steam energy in driving the ram allows use of shorter stroke and compact hammer than single acting hammer. So, when compared to single acting hammer these hammers are more compact smaller in size, lighter in weight and they have a shorter stroke. And they are designed for lighter conditions, they can deliver a blow rate of 95 to 300 blows. This lighter ram and highest striking velocity maybe suitable for driving light to medium weight piles into soil having normal frictional resistance.

So, we cannot recommend this hammer for a tough soil condition with very high frictional resistance. And not always preferable for concrete piles, as I told you high blow rate can result in damage of your concrete pile, which is basically weaken tension. So, it is not recommended for concrete pile but you can use it for steel piles.