The OperatorIf you have read my previous blog posts regarding the blast machinery, you know that the machine is made up of individual components, working in harmony to achieve a desired end result. Without each of these components working properly and as designed, then the other components cannot work as they should. Therefore, it is so important to have regular inspections (daily, weekly and monthly) and preventative maintenance programs to ensure small problems do not turn into larger problems. Beyond this, however, it is even more important to have in place the right people overseeing the operation of the machine. A well-trained operator knows more than just pushing buttons and filling abrasive when the machine is running low. The right operator will make the job of the maintenance staff easier, keep cost down while maintaining a consistent and acceptable clean.
For the purposes of this article, I will focus on wheel blasting since there is more of an opportunity for an operator to affect the overall maintenance, and therefore costs, of running the machinery. While air-blast certainly has controllable components that will impact the cost of maintenance, it is usually less and from my experience, and does not compound as quickly as in a wheel blast machine.
The operator role, when it comes to centrifugal blasting, would seemingly be less involved then that of air-blasting. Afterall, nobody is manually doing the blasting. One would think that the operator needs only to make sure the product is fed into the machine and there is some abrasive in the machine. However, there is so much more that an operator can do that will add value to the operation and therefore, the operator him/herself. Below is a list of suggestions that, as an operator, can be accomplished quite easily and how it can affect the bottom line or prevent further issues.
Beginning and during the operator’s shift:
• Check the level in the hopper (both the feed hopper and automatic adder hopper if applicable):Maintaining the required amount of abrasive in the machine is key to keeping the operating mix balanced and consistent. If the level is allowed to go too low, the mix begins to shift toward the fine side and the abrasive will not impact the parts as needed to break of sand, scale, etc. Often, when this happens, an operator will add all new abrasive to the mix to bring up the hopper level. However intuitive this is, it is not the best way to bring the operating mix back into balance. A better approach would be to add some new abrasive along with some spillage from the floor (properly sifted of rocks and trash) or even some of the discard from the separator drum. From there, you can start adding new abrasive in small, frequent additions. Adding all new abrasive, known as “slugging” the machine, can throw off the blast pattern, which can damage other areas of the machine and cause inconsistent cleaning. Of course, if the machine has a properly working addition hopper, it will be easier to maintain the operating mix, provided you keep the addition hopper full of new abrasive. However, regular checks of the feed hopper should still be carried out to ensure the addition hopper is properly working.
• Check the separator:The separator, as written about in a previous post, is responsible for maintaining the operating mix balance. A properly balanced operating mix will have a mix of large, medium and small abrasive particles. In order to maintain this, as the abrasive starts breaking down, the separator will push out particles that are deemed too small for blasting (known as fines) along with the dust and sand. Coupled with small and frequent additions of new abrasive, the balance of large, medium and small particles will remain consistent throughout the blasting cycle. While the machine is blasting, check the separator(s). There should be a curtain of abrasive that fills the entire length of the opening with no gaps. This curtain should be fairly thick but not too much so. A good rule of thumb is that if you can just barely see through it, it is usually pretty good. If there are gaps, the air will tend to circumvent the abrasive and travel more through the gaps. If the curtain is too thick, then air cannot get through to push the fines and dust out. On the contrary, if the curtain is too thin, then too much good abrasive can be pushed out, which is money out of the machine. In addition, check the screen under the separator. If there are blockages, clean those out so abrasive can flow freely through the screen. If there are holes in this screen, they should be repaired so that large debris cannot get to the wheels and cause a failure.
• Check the operating mix.As stated above, a well-balanced mix will contain large, medium and small particles and be free of dust and fines. The best way to check for the correct ratio and maintain the proper balance is to use a sieve test at least once per shift. The sieves required will be dependent on the abrasive in use. W Abrasives offers a full blast check kit customized to your abrasive, which contains everything needed to check the operating mix.
• Check the cleanliness.Take a look at the parts as they come out of the machine. Are they as clean as is required? Are they consistent from piece to piece? If the answer to either of these questions is no, an investigation is needed to determine why as it could be a number of reasons, from the blast pattern to the operating mix or more. It is important to stay on top of this as it affects productivity when reblasting is required. If you can catch it early and remedy the issue, less time is lost.
• Finally, listen to the machine running.Does it sound as it always does? If you have driven the same car for a while, you know when something does not sound right. It could be a rattle or vibration or any number of things that stand out. It can be the same with any machinery. When an operator is around a machine for several hours, day in and day out, they can get attuned to the normal sounds of the running machine, so much so that when these sounds change, they stand out prominently. Just like a car, an off-sounding machine should be cause for further investigation to make sure everything is working correctly.
Referring to my sports analogy from my article regarding the wheel, if the machine is the Chicago Bulls of 1995-1998, then the operator is the great Phil Jackson, responsible for ensuring everyone does the job they were enlisted to perform. A good operator of a blast machine will make sure all the components are performing as expected on a regular basis and can greatly help maintenance by identifying small issues as they arise.
More information on the W Abrasives range of services can be found here: https://www.wabrasives.com/en/WCare-a-range-of-services.html
W Abrasives Technical Team has years of expertise and offer full service and training packages for your operators.
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Technical Service Advisor, NAO