Posted on August 24, 2016
In any sawmill anywhere in the world breakdowns are going to happen. Troubleshooting why the mill won’t run is a skill that takes experience, knowledge and let’s be honest, a little luck sometimes.
Downtime can be a time to learn and grow as an operation and can become something that is managed well and minimized at every opportunity. There are several factors that can cause downtime but there are also many recurring ones that can potentially be avoided and shortened if the operation takes the time to focus on some simple tasks to resolve some downtime issues.
Mechanical breakdowns are usually quite simple. A broken chain or shaft, a belt comes off, no big deal. Fix and get running. But with these types of breakdowns you should always take a step back and try to determine if the breakdown was the symptom of another problem, more so if it repeats itself. Did the chain break because the bearings on the tail-shaft are worn out? Sometimes a broken part is trying to tell you that something else is actually the problem and the breakdowns will continue to worsen until the actual problem is fixed. Or it could just be a faulty or worn out part, but you need to take the opportunity to answer that question before the issue comes up again.
Some mechanical problems will show themselves in the lumber. Saw marks, saw deviation and poor saw cutting performance can indicate worn or broken parts. A good technique to troubleshoot issues with canters and saw lines is to use an infrared heat gun. Hot spots on one side may indicate alignment issues or cylinders that are not holding the lumber effectively. Hot bearings may mean loss of lubrication and pending failure. Better to spot these while you are still running, and schedule a closer inspection for a weekend or graveyard shift to be ahead of these types of breakdowns.
Electrical breakdowns are far more complicated to troubleshoot, especially when you have optimizers, multiple photocells, encoders, VFD’s and PLC controlled equipment. You need a good PLC guy to be able to look inside the program and see what the stoppage is. Sometimes it’s a faulty electrical part, other times it’s a safeguard of some sort that has been reached and is doing exactly what it is supposed to do which may be the indication of a whole new problem. Having the knowledge and experience of the mill at times like this is priceless.
A key learning that I adopted in my experience is to never over complicate the problem. The more complicated the mill’s equipment is, the more likely it is that the people charged to get the mill running will default to the most complicated solution. Technology today is less likely to fail and cause issues although it can still happen. I’ve seen a mill go down for several hours only to realize an emergency stop in the basement of the sorter was pushed in by mistake.
Quality issues are sometimes tough to figure out because the mill is running, production is adding up but the quality is suffering and nobody wants to stop a running mill to fix a problem they can’t see. Decisions need to be made if you can run this way to the end of the shift or to the weekend to allow time to fix the problem without affecting production. In most cases the decision will be to stop and try to find the problem, in other cases, you run until the shift is done.
If you decide to stop the mill and try to find the problem, have a plan in place to look at specific pieces of the process.
While you are running, back track to see where the problem originates from and then determine what it “could” be and what exactly you want to check before stopping. Also, have all the tools you might need ready so time isn’t wasted waiting for someone to run to the shop to grab a wrench. Then stop the mill, check the items you determined to be potential causes and again decide if it’s a simple fix worth taking downtime or something that you can live with until a more suitable time. Ideally if it’s a small problem, fix it and get going.
In any case, there are a few different breakdown conditions that can be looked at when deciding where to start troubleshooting.
- First is the scenario where the mill is running and has been for hours or days and then all of a sudden, things grind to a halt. Nothing has been changed or modified. Here is where knowledge and experience of the mill’s equipment pays off. Has this happened before? Did anyone see or hear anything abnormal before the stoppage? Is there smoke or burnt smells? Is power lost to any equipment or area of the mill? These are the questions that need to pop into your head, the “outside the box” type questions that will generate dialogue and check items off the list before you call the vendor’s service line.
- Next is the scenario where it’s the start of the shift and a certain piece of equipment will not start. First thing to ask is did anyone work on the equipment overnight or over the weekend. Are all the power disconnects re-activated? Is everything plugged in that needs to be plugged in? A good maintenance program will ensure any equipment that is worked on is tested and runs before the job is considered complete no matter how small the job is. Clean-up should have the same process. Run the equipment to ensure all disconnects have been re-activated, no photocells have been bumped or damaged during clean-up and all tools and equipment have been removed from the area. Assume nothing and again, don’t overcomplicate the issue. It may be a simple fix or it may be a major issue, but you won’t know until you look. Look at the basics and work towards the more complicated possibilities. Check the items you own before calling the vendor and incurring an expensive service call just to find out your clean-up person knocked a photo eye from its mount.
- Another scenario is the mill is able to run but it cannot because one of the conveyance systems has failed. This can be a broken conveyer in the basement, plugged or full chip bin or anything that hampers the removal of accumulating by-products from the process of cutting lumber.
Someone needs to inspect these systems when they are running to ensure there are no indicators of pending failure. A documented scheduled inspection process is ideal to ensure eyes are on everything at acceptable intervals. If you plan to run a weekend shift or longer hours, make sure the trucks that handle these products are called ahead of time and preparations are made to address these products. A checklist for extending hours or running weekends will minimize the likely-hood of any costly oversights in this department.
One basic principle with computerized equipment issues is to always re-boot the computers first. If you are experiencing non desirable results in the lumber, check the scanners and if nothing obvious exists, do a calibration. Parameters and optimizer set ups do not change on their own, ever. Scanners get bumped and moved; computers freeze and changes get made without communication. Timing and encoders can have issues as well. It’s asking the right questions and performing basic troubleshooting tasks that can effectively correct a high percentage of issues in a short time.
One thing a lot of mills lose sight of is the learning that can come from any downtime situation.
- Keep a log of the things that cause you downtime. Generally, the same thing will happen again and most likely on another shift or time where the people it happened to before are not on site.
- Having a reference that describes what happened and how it was fixed will do a couple of good things.
- it will get the mill running quicker.
- it will show on paper that this is a recurring problem that the maintenance department needs to look at and make sure that whatever is causing it gets fixed for good.
Also keep in mind that fixing a problem to get the mill running may not fix the problem that caused the issue or the fix might not be the corrective action required for the long term. Anytime a broken part is welded or repaired during the shift, someone needs to go back when the mill is not running and inspect the repair that was done (under the pressures that come with downtime) and determine if more work is needed or new parts need to be installed to ensure the fix itself doesn’t lead to further downtime later.
Nobody likes it when the mill is broken down and not running but it will happen for whatever reason. Having the skills and experience to effectively troubleshoot a problem and get the mill running comes with how you deal with each and every occurrence. Treat each event as an opportunity to learn and to grow your maintenance program, inevitably resulting in fewer occurrences of downtime and shorter durations.
Robert – Process Expert