Size of hammer vs boulder size

Hello, I have a bit of a newbie question. We are working in a limestone quarry where the blast they’ve done was very poor in our opinion. We are running a CAT H140 hammer on a 330LN. The blast has produced almost 50% oversized boulders, some as big or even bigger than the excavator. Is there a rule of thumb between the size of the over-sized rocks vs the size of the hammer/excavator? I’m thinking that there must be a quick rule that people can apply. I know you could eventually reduce any material down to size but it doesn’t seem efficient at all. Thanks Liviu

Liviu Popescu said: The blast has produced almost 50% oversized boulders, some as big or even bigger than the excavator. Click to expand... Boulders that size would seem to indicate the need for secodnary blasting in my opinion. Certainly I don't think that a hammer would be an economic method of reducing them to a suitable size to pass through a primary crusher. Is the limestone really hard, soft, or somewhere in between.? Is it easy for the hammer to deal with it.? Are you charging the customer by the hour for hammer work.?

I don't know the in and out of limestone mining, but just general common sense, if the blasting methods used are producing boulders larger than a 300 class excavator then I'm thinking the blasting methods are sketchy. Busting boulders that size with any breaker is not going to be cost efficient.

And you better have a good windshield screen or you're going to be busting some glass. Not to mention all of the paint on the front of the machine is going to be gone from all of the flying breaker chips trying to bust boulders.

Sounds like they need new blasters with a better plan.

Tugger2 said: Sounds like they need new blasters with a better plan. Click to expand... Nailed it!

Tugger2 said: Sounds like they need new blasters with a better plan. Click to expand... And I'm not sure I would be hiring the same blaster that did the original blast. Seems like there could be a conflict of interest there! Kind of like hiring the same mechanic to rebuild an engine who left the drain plug loose when he changed the oil last week!

If you boulders as big as a 330, you have a real mess. While I don't have experience blasting limestone, I do have experience in explosives. It sounds like the blaster didn't drill enough holes and at close enough intervals to prevent the production of such large boulders. The hard part now is blowing those exposed boulders is very dangerous and will send rock everywhere unless you place sand around the boulders to prevent the rock from scattering. Not to mention drilling charge holes into the boulders will be problematic. I am not aware of any rule of thumb for boulder size and breaker size. I think it all comes down to the type of material your breaking, the harder it is the more breaker you want. A breaker may be your only option and that is going to take a while and cost someone a good deal money.

Thank you all for your replies, I’ll take this feedback on board at our further discussions with the clients. It seems there is no rule of thumb, just common sense…

Take a look at Yamamoto rock splitters, I bought one to use in areas where I can't blast . I can split around 150 holes a day and rip them out