"Can you get 5,000 continuous feet on a jumbo, with a single steel, without every changing the steel?"
Yes. Using Tamrock and Atlas Copco hydraulic drills, drilling 4 inch holes, T-45 drill steel. 800 to 1500 feet per day, depending on rock hardness. First steel is a 14 footer as that is the maximum you can put on the mast. Add 10 footers as you go depending on the depth of the hole. Good driller will go all month without needing additional steel unless he gets into mud-filled cracks which plug the bottom steel (cheaper to change steel and let a laborer in the shop unplug them than let the driller do it.) Using button bits.
Shaft sinkers using pluggers will use 7/8th inch hex, integral steel as it is easier to pull integral steel than tapered steel with cross or button bits. Can not ever recall seeing a shaft sinker break a steel. Plug and stick em yes (and take a ribbing from everyone else on the crew). Many shaft sinkers now using hydraulic jumbos, drilling full face instead of benching. Drill large diameter(6 to 10 inch) pilot hole about 400 feet long as a relief hole then one pass 14 foot steel (yielding 12 foot hole) for blast holes.
My understanding is that Inco and Falco contract out supply of drill steel and bits on a per foot contract basis. Only suppliers are Fagersta and Sandvik. (Condor would know, that is/was his neck of the woods) At Hemlo, Manley and Saxon were also in the running with Sandvik and Fagersta, but they got bot out by an Australian outfit. My buddy in Timmins says this is the deal at Kidd Creek. (using Fagersta).
When I was starting, I was taught to rotate between steel also to allow cooling etc. It is just a pain in the a$$ to do that to-day. especially if you are drilling deep holes and have a carousel!
When I was young, they used to make steel in England. Swedes (Sanvik and Fagersta) were known for the best steel and run them out of the business.
Mitsubishi has made in-roads in Canada (in the Pre-Cambrian shield where the hard-rock is) but as far as I know Mitsubishi is more surface construction and quarrying than mining.
Large blast holes underground at Inco, Falco, Hemlo are drilled using DTH (down-the-hole) hammers. Drill pipe does not take the hammering as the top hammer units provide so different type of material than in drill "steel". suppliers of DTH hammers also supply drill pipe so they are among the suppliers. australian outfit "Digger" has made in-roads here. |
