Facility Feature
CONVEY '20: Preventive Maintenance of Elevator Legs

Business-aligned reliability is a way to optimize profitability with equipment reliability. Essentially what we want to do is determine the right amount of uptime or reliability that our equipment needs to maximize profitability. To do so, you will need to address the following areas:

• Determine the amount of uptime needed. The best way to accomplish this can vary widely, depending on your situation, company, products, etc. For example, if you’re running a country elevator that is only busy during harvest season, you’re going to take a much different approach than if you’re running an export location, high-throughput elevator, or processing/milling facility that runs 24/7.
• Schedule downtime for safety checks and inspections into your operating plan.
• Consider turnaround timing or seasonal impacts. You want to plan downtime around any type of seasonal impacts or any type of slowdowns in the industry or the plant. Downtime can be very costly, but the costs can be minimized if it is planned well.

This article is based on a presentation by Lucas Reed, director of reliability-centered maintenance, ADM, Decatur, IL (217-451-8026). Reed spoke July 31 as part of CONVEY ‘20, a virtual operations workshop held online by the National Grain and Feed Association (NGFA), the Grain Elevator and Processing Society (GEAPS), and Grain Journal.

• Budget and staff for repair and maintenance. You will need to answer several questions: Are we going to use contractors? Are we going to use internal resources? Do we have the right technical staff to maintain the equipment ourselves? Again, what is the allowable downtime? Are we going to build something standard, or are we going to over-engineer or over-design?
• Project asset life. As equipment ages, there comes a point when we can no longer keep patching over patches. We need a good plan for projecting how long equipment will last and determining when something has reached that point. Then, what will be the plan to replace the equipment, and how much downtime will be involved?

• Determine the level of capital investment needed. Having a capital strategy that’s aligned with your maintenance strategy is key.
• Complete compliance and risk-mitigation measures. From a compliance standpoint, what will cause us to shut down equipment to do inspections? We have to clearly communicate that these things are non-negotiable. The dangers around grain handling are well known, and this is not an area to induce risk to increase throughput.

Consider turnaround timing or seasonal impacts. You want to plan downtime around any type of seasonal impacts or any type of slowdowns in the industry or the plant.

Bucket Elevator Maintenance Tips

There are a few key areas to highlight to maintain bucket elevators and ensure proper operation.

One of the easiest and quickest ways to get more capacity out of a leg is to increase its speed. And while that’s a pretty cheap option, there are some longevity and liability issues to account for. At ADM, we recommend 650 feet per minute for good capacity and a manageable level of stress on the c rotating components of the equipment. As you increase the operating speed of your equipment, you are increasing the rate of degradation exponentially.

When it comes to bearings, we want them to be pillow block and separate from the casing, mainly to prevent any type of heat spreading. We want to use a good-quality belt that’s fire and oil resistant.

We also want to have good inspection doors and openings on the head and tail sections. This makes cleanout much easier and allows for equipment inspections without having to completely disassemble.

Explosion venting and full hazard monitoring systems are recommended to protect your assets.

Component Strategies

With bucket elevators, your approach should be to consider all the different components individually and ask yourself, “How could this fail?” and then develop an inspection or a preventive maintenance plan to address each one of those hypothetical scenarios.

When we do have a failure, we want to perform a formal investigation. The single focus should not be to get things repaired and back in operation as quickly as possible. We need to understand why the failure occurred. Was it because we missed precision maintenance or it wasn’t the right type of maintenance? Was it because of something completely different that we need to look at in our process? I can’t tell you how many times we’ve had bucket issues, and the problem turned out to be grain quality. It had nothing to do with the leg. It had to do with a bin that wasn’t getting cleaned properly. Determining why a failure occurred gives you the information you need to implement good countermeasures.

Precision Maintenance

It is recommended to perform precision maintenance during both inspections and repairs. This applies to belt tensioning, precision alignment, and tensioning and torquing of fasteners.

Drive belt tensioning is something many people believe they know how to do properly, but technology in this area has come a long way to make the process easier. Many manufacturers will actually provide you with the frequency at which you want to install the belt.

You also want to use data and thresholds to make decisions rather than visual observation and opinion. Again, put the science behind it. As the industry continues to lose experienced, veteran employees, it’s becoming increasingly vital to rely on good science and data points to help make decisions.

Maybe you still have that operator or mechanic or superintendent who knows all this. Maybe they don’t need that guidance, but what happens when they retire and take all that knowledge with them? You need to plan for this, and one of the best ways to do so is to document. By documenting your maintenance, it allows someone to come in off the street and be able to make sense of the situation. For example, the picture (on p. 82) of the sheaves shows how a belt should be set in the sheave. This visual resource can be a big help for less-experienced employees to identify dished-out sheave grooves.

We also want to have good inspection doors and openings on the head and tail sections. This makes cleanout much easier and allows for equipment inspections without having to completely disassemble.

As far as belt splicing, there are many ways to do it effectively. I prefer the mechanical splice. No matter your preferred method, you’ve got to make sure to pay attention to the critical pieces of it. Ensure that you have good overlap. Use the right fasteners with the right amount of torque.

When performing belt splices, you really have to look at alignment. This ensures good riding on the pulley. Make sure you’re not going to install your belt in such a way that’s it’s going to want to pull one way or the other.

As far as pulleys and lagging, we recommend slide-lagging. Again, lots of different pulleys work, but we recommend slide-lagging because it’s pretty easy to maintain. Without taking out the whole pulley, you can replace the lagging, slide it in, and slide it inside out. Clips can be welded or bolted. You’re going to cut to length. You want to make sure that you inspect the depth of the lagging as it will wear over time.

Define how much wear is allowable. It’s not about squeezing every bit of life out of it. Downtime is much more valuable than maybe getting a little bit of life out of a belt or some lagging.

Understand that each day that equipment operates, you’re accumulating risk. So, what’s the right level of risk that you can tolerate? What’s the amount of downtime we could tolerate? Answering those questions will help you determine when to replace equipment.

When performing belt splices, you really have to look at alignment. This ensures good riding on the pulley.

Hazard Monitoring

Hazard monitoring systems are essential to preventing catastrophic property damage and injury from malfunctioning equipment. It’s so important to make sure that they’re installed in the right location. These systems – which c include speed sensors, temperature sensors, alignment sensors, plug detection, and vibration – need to be maintained, as well. You can’t just install hazard monitoring systems carelessly and forget about them. They need to be wired in such a manner that they’re going to automatically shut down the system at some point. You don’t want it to require someone to hear an alarm and perform the shutdown manually.

For example, a touch switch needs to be installed so that it will rub the belt. The switch has to be the first thing the belt will touch. You can’t let the belt rub on the casing for a quarter of an inch before it finally touches the touch switch.

It’s not uncommon to hire a third-party contractor to install your hazard monitoring system for you. However, they may not know the correct areas to install each component. You have to determine where things need to be placed. Are you making sure that the alignment sensors are installed in a way that can actually track the belt? In some cases, given the configuration, we may need more than one sensor, and once we get those sensors installed, do we get them terminated properly? Having the sensor installed is one thing, but is it actually talking to our PLC or our DCS system?

To check that your hazard monitoring system is working as intended, we recommend performing annual shutdown testing on all the different hazard monitoring switches.

Reprinted in November/December 2020 Grain Journal