Aditya's Blog

Improving Machine Safety in Cement Plants:-

I am of the opinion that in industries most of the people do their routine jobs very nicely, with full zeal and dedication, but many of them remain frustrated as they feel that their hard work was not recognized and not remunerated properly. For those people my answer is that they get paid for what they did. People should ask a question themselves at the end of the day as to what value addition and incremental improvement in safety, productivity, reliability, stability, MTBF etc. they had done during the day. The gainers would be those whose have a positive answer to the above question. The gainers would be those who attempt to bring improvements day by day by tackling the tasks differently. That is where “Think out of box” concept comes in picture. I therefore repeatedly emphasize on this term.

I am sharing with you my another experience for improving machine safety in cement manufacturing plants.

The lubrication system for Ball Mill Slide Shoe Bearings and Symetrogears has for a number of years been made in such a manner, where the oil flow is supervised by a level switch. In this arrangement a reservoir is made as per the below figure and is placed immediately before the point of bearing lubrication in the lubrication circuit. In that reservoir there is a level switch, whose output (which would be normally HIGH if the reservoir is full due to sufficient oil flow) becomes LOW, if the oil level becomes less from the normal level point due to lack of inflowing oil, resulting the mill to stop as programmed in DCS safety interlocks. The construction of the reservoir is such that some oil would still be there even when low level alarm comes. For ensuring bearing safety, the remaining amount of oil would flow into the bearing during the stoppage of the mill through the drain holes placed below the normal oil level point.

The above arrangement sounds very good at the first sight and it is difficult to foresee any problem in the above. But if we think the worst case, what would happen if the oil output line of the reservoir gets choked over a period of time. The oil would not flow to the bearing but since reservoir output is choked, it would be full and its level would continue to show HIGH. So DCS would continue to understand that lubrication oil is going to bearings, hence it would not stop the mill, until and unless stop command comes from some other safety sensor like high bearing temperature etc. These other safety sensors have their own response time constants and sometimes fail to timely detect the system abnormality resulting in heavy breakdown causing huge production loss and heavy cost impact.

So what could be done to improve machine safety and to avoid such kinds of breakdowns?

After thorough brainstorming a very simple solution to the above problem could be found. The programing in the DCS was modified. To start the Mill, the DCS would first monitor that the signal from the level sensor is LOW, which would ensure that the reservoir is empty and its output line is not choked. Then the lubrication pumps of mill would start and if the oil flow is proper then the level signal would become HIGH and mill would be ready to start. By doing this, in every start / stop cycle the condition of the oil reservoir was monitored. In case the level signal remains HIGH even when the mill and lubrication pumps stop then the reservoir would be cleaned before next mill start up. This way this simple software modification enhanced machine safety.

I hope you must have found this post interesting. If in your plants also, you are struggling with some chronic problems and need simple and cost effective solutions, please contact me at my EMail:- <apagarwal2004@yahoo.co.in>. I am open for consultancy and trainings, including site visits whenever required.

I would be eagerly waiting for your comments and suggestions.

Think out of box (concluding part)

In my last post I had narrated a problem of kiln stoppage every time the coal mill was to be taken under maintenance for turning its rollers’ wear segments. This job was taking 6 hours while the available fine coal stock used to be sufficient for 5 hours only even at reduced kiln output.To avoid the shutdown I did brain storming sessions with the team.

The procedure for this maintenance was to stop the mill. Open the doors. Remove one roller by opening its’ bolts. Take the roller down outside coal mill, near to the another spare roller which was kept ready with all maintenance done. Remove the wear segments from the roller taken out from coal mill and fix those wear segments in turned position on the spare roller (This job used to take 2 hours).Lift the spare roller and fix it in the coal mill. Close the doors and give clearance to run the mill (Total job duration 6 hours). The removed roller was then overhauled, bearings cleaned and inspected, seals replaced during the rest of the day and then it was kept ready for replacement next day.

When I asked team why we can’t fix a set of wear segments on the spare roller and keep it fully ready for replacement, this would save 2 hours and avoid kiln stoppage. Their reply was negative due to the reason as given by them was that the spare roller fitted with a set of new wear segments when fixed inside coal mill would make the mill operation unstable as the other two sets of wear segments on other two rollers were already worn and had different profile. My next question to the team was if we could fix a set of worn out wear segments (which we had scrapped in past) on the spare roller and keep it ready in all respects for replacement. Initially they were speechless and then their eyes were glittering with joy for finding a solution of long pending problem, as this arrangement would not make the coal mill operation unstable.

We started doing the same and on the fourth day of maintenance we used to remove the spare roller fitted with scrap wear segments from coal mill and kept the same ready by overhauling the same for replacement during the next scheduled maintenance.

This clearly shows that many problems looking big and impossible to solve can have simple solutions. The only thing is to think out of box.

Hope you would have found the above blog interesting. This is only one example. During my long tenure in cement industry with rich experience, I had solved many chronic problems in cement plants, which were affecting plant operation and efficiency.

I am open for consultancy. In case of any need, I can be reached on my E-Mail ID:- apagarwal2004@yahoo.co.in

Think out of box

In one of the cement plant where I worked for long, there was a three roller vertical grinding mill for coal. In this the rollers’ wear segments were to be turned (one roller at a time) by 180 degree every month or two months depending upon the wear pattern of metal, after taking shut down of coal mill. For doing this job in one roller it used to take 6 hours minimum. The fine coal stock availability even when hoppers were full, used to be for maximum 5 hours, even when kiln kept running at reduced output. The result was that the plant was to be shut down every time during the above kind of maintenance, resulting in heavy losses. This trend was continuing for long, till I took over. After brain storming for many days we could find out a method to avoid kiln shutdown during the above maintenance. In my next post I would write about the solution what we had adopted. Till then you can also explore, as there could be many other solutions to the above problem. I would love to receive your ideas for possible solution.

My first blog post:-

This blog I have started to share my experience and knowledge which I had attained during my long carrier in Cement Industry. By qualification I am a hard core instrumentation engineer, but I have experience in all the fields of engineering and operations. During my long service span of more than 37 years I encountered and solved many technical problems in Cement Industries. I would be describing those in my subsequent posts one by one. Also I invite suggestions f uhirom readers to make this blog more fruitful, interactive and interesting.

My Introduction:-

I am a graduate engineer from BITS Pilani. After passing out I started my carrier in Indian Cement Industries. Starting as Graduate Engineer Trainee and gaining good experience in all the fields, year by year, I finally attained the post of Plant Head. I have expertise in running Cement Plants effectively at their full capacity, turning around loss making plants to profitable by improving KPI, MTBF Etc. I am retired now and helping cement industry by providing consultancy as well as training.