Crushing, Screening & Conveying

Crushing, Screening & Conveying2017-04-04T06:57:13-04:00
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Burned bronze bushings - Gyratory Crusher (4 replies and 1 comment)

Eder Figueiredo
2 years ago
Eder Figueiredo 2 years ago

Hi everybody.
Wondering if somebody could tell me which is the correct type of bronze for bushings applied in the gyratory crusher, such as inner eccentric bushing and bottom shell bushing.
A Brazilian’s supplier has supplied the bushings with the follow composition as shown in the attached table. The problem is due the fact the bushings are burning too easily.
Does anybody have a suggestion about this issue or other points to be investigated in the crusher?
Thanks in advance.

Bronze-bushings-properties.pdf
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William Cullen
2 years ago
William Cullen 2 years ago

Looks like a lube problem. Where does it get lube toward the center. The heat is localized toward the end. how tight is the fit when assembled? The surface where it is held stationary, is it distorted in some way.

Bill

Paul Morrow
2 years ago
Paul Morrow 2 years ago

Check for duck tail on mantle (profile) also fines packing the chamber.

Eder Figueiredo
2 years ago
Eder Figueiredo 2 years ago

Dear Paul and Bill,
We have replaced the mantle due uneven profile. Please see attached photo.
The tolerance fit and the oil flow is according to the OEM recommendations.
I have doubts about the bronze alloy composition.
Thanks for sharing.

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BAUD
2 years ago
BAUD 2 years ago
2 likes by Ian Lim and David

1-Intro
Among critical factors, proper maintenance and right procedure to replace bushings help highly to avoid unplanned downtime and improve the life of bushings. You say you did it. I have axed my attention on the materials.

2- Comments on the analysis results
-By definition, the ultimate tensile strength is higher than the yield strength. This is not the case in the above table. Perhaps, the results have been wrongly placed. They should be corrected.
-The total % in the first column is 99.99 %: this is acceptable. The second column has more than 100 %. There has been a problem with rounding the numbers.
-The obtained results  should have their references (targets) in order to compare easily. This is missing.
-The meaning of the dot and the comma are different in the Metric system compared to the English system.A misuse can create a confusion in the interpretation of the results.
-Globally, these results have not been controlled by the laboratory quality control supervisor.

-If the results have been given by the supplier of the bushings, you should take samples on the bushings and send them to another laboratory for the analysis. Try to avoid the previous laboratory.
-If you sent yourself bushings samples to the laboratory and got the current results, you should take new bushings samples and send them to a renowned laboratory different from the first one.

3- Suggestions
-Standards
When a supplier proposes you a new material, whenever possible, ask the equivalent standard (ASTM, UNS, SAE, EU, ISO, DIN, BS..) or the nearest equivalent. It will save you time in case a problem pops up.
-Structural Metallurgy
On top of the analysis done, it will be very useful to have a micrography of the failed materials.
-According to the above given results, the bronze alloys are in the family of High- Leaded Tin Bronzes. Compared to similar bronze alloys, it appears that the Nickel (Ni) and the Zinc (Zn) is missing. The mechanical properties shown in  the table are very different and far above those of the equivalent bronze alloys.

4-Recommendations
-The current results have not been controlled and have a questionable reliability.
In order to suggest some good materials, it is advisable to have the maker, the type, the model, the speed (including linear speed), the pressure, and the load used in the gyratory crusher.
-Moreover, the item number of the OEM part and its weight are very useful. Most of these elements generally appeared on a conventional drawing of the part.
-The materials are very suspicious according to the results in the table. New tests are necessary. 

 

Eder Figueiredo
2 years ago

Thanks for your advices, Baud. They were very useful for me.
The alloy is ZCUSN10PB10 which is equivalent to US standard C.93700.
As you have recommended, I will prepare the bushing bronze samples in order to send to a lab and check the results.

Regards,

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