Using proper best practices for transfer station and MRF operations will increase production and efficiencies while keeping maintenance, fuel and floor costs low.
Tom Griffith
We all know that transfer station and MRF applications are harsh and challenging. Trying to meet safety, production and efficiency goals while keeping costs low, confront transfer station and MRF operators every minute of every day. The following are a few best practices that I have seen and worked with in the past 20 years with our transfer station and MRF customers to help them lower costs while achieving operational goals.
Safety
One of the harshest environments that people and machines can work in, waste applications have inherent safety risks. For transfer stations, it is all about garbage in/garbage out. For an MRF, it is not only about garbage in/garbage out, but recovering money-making materials that can be recycled. To put it in context, these applications are busy, busy, busy with very little margin for error. Most transfer stations and MRFs are inside buildings that are cramped, have poor lighting, slick floors, and do not forget all of the inbound/outbound vehicles and foot traffic. Therefore, safety is the most important thought process from beginning to end of shift.
As discussed in my previous article on landfill best practices (Waste Advantage Magazine, March 2018), safety programs that are not just lip service or “check the box” provide a growing ‘safety culture’ that does not end when the employee goes home for the day. Programs should create and sustain a culture of safety excellence. A good safety program should: measure and manage the right safety activities, recognize workers for what they do right and ensure that all levels of the organization are involved/engaged in the safety system. During a discussion with Caterpillars Cat Safety Services Commercial Manager, he closed with the following three challenges to ensure a great safety program. “There should be visible commitment from top leadership; there should be a strong accountability system and there should be total engagement of those closest to the safety concerns or hazards.”1
One last comment, always wear proper personal protective equipment (PPE)—reflective vests, hard hats, eye protection, steel toe or enclosed shoes, gloves, hearing protection, etc. Again, these environments have so much going on that being seen and protected is a must.
Tire Spin
Let’s get right to the point of one of the highest costs in these applications besides operator and fuel—tire cost. The combination of slick floor, rough floor, bucket contact with the floor, loads of different materials that cause friction and you cannot help but sometimes spin the tires. Depending on the tire, especially the hard rubber that most transfer station and MRF customers use, that cost can be upwards of $40,000+ per set. I have had operators brag about burning the tires off in less than 900 hours. What are best practices that can get us from 900 hours to 3,000+ hours before having to buy another set? Purchase machines that have either a computer-aided traction control, manual traction control or computer-aided rim pull control for the wheels. These systems help the operator lower his tire spin and keep traction. Train your operators that once they start to spin, adding more power does not help them. Adding more power is a common fallacy and adds more spin. Experienced operators will back off power to gain traction and keep themselves engaged with the waste they are handling. Some operators will take a mattress or green waste and ‘sweep’ the floor to try to dry the floor out. Other operators will make ‘cleaning’ runs with their buckets (flat as possible) about every third or fourth push. (Note: tilting the bucket at a 30 to 45-degree angle to clean the floor or push might get desired results, but it adds friction to the floor, spins tires, uses more fuel, wears floors quickly and wears the cutting edge quickly.)
Pushing Material
Best practices in pushing material is simple. Take as much as you can without spinning tires or losing material around the edges. This is not easy with floors that get really slick after kindergarten milk runs in the afternoon. Some of the best operators engage the pile of waste to be pushed with a flat bucket on the ground. Once they make good contact, they will raise their bucket about ½ inch to 1 inch to clear the floor and “slide” the load. This technique helps prevent: friction, wheel spin and lowers fuel burn. Pushing in straight lines is a must since the wheels and tractive capability of the machine are in line, which is the strongest power to the ground. Trying to push something while arced only adds to fuel burn, tire spin and damage to the machine with less production.
One last item—have your operators be aware of what we call favorite side turns or ‘forced’ turns. In transfer stations or MRFs, sometimes operators must always turn a certain direction to stockpile or load haul vehicles, or they prefer to turn a specific way. This practice wears out tires, cutting edges, center pins in wheel loaders. Push straight, slide the load, govern your wheel spin, take only as much as the bucket can push without losing material, are all part of efficient push techniques. In excavators/wheeled excavators, favorite sides keep the machine turning through the same arc, which could wear swing bearings unevenly.
Stockpiling Material
Stockpiling material effectively is an art that many operators have a hard time mastering. Most of the time they are under pressure to get the material in, stockpiled and back out again. They either do not have time to handle the material correctly or do not take the time to do it correctly. Sometimes the building configuration or capacity do not lend to adequate storage of material especially if something goes wrong with outbound haul vehicles. Operators must stack the material as high as they can and as safely as they can. Climbing the pile with the machine is not an option. This leads to incorporation of material into the machine no matter how well it is guarded and eventually could lead to a possible rollover. Operators that know and use best practices will leave one or two loads at the foot of the stockpile and then push them up with the next load sliding material higher on to the stockpile. Another method would be to push up as high as the machine can and as the operator dumps the load, they will make a slight indention in the waste with their bucket to push the next load into. Operators do need to be careful when pushing high with lift arms extended as high as they can with a full bucket. No matter whose machine or bucket, material could fall over the waste rack and crawling down the lift arms and cylinder and contact the cab and glass.
Loading: Haul Vehicles, Bins and Conveyors
All of the above brings us to the inevitable. Stockpiled material must go back out the door and/or get processed in the MRF. First, let’s start with sorting before loading. Having the right tool on the end of the wheel loader or excavator/wheeled excavator to sort reject material is vital. Sorting grapples and grapple buckets are the best for machines to quickly grab, pull, carry and reject unwanted material. Whether it is sorting cardboard or metals prior to loadout in a transfer station or sorting reject materials that could clog the conveyor or hopper in a MRF, operators need to be alert and understand how to use the tools at their disposal.
Best practices for loading outbound haul vehicles in a transfer station and MRF depend on the type of load out for which the building is designed. Below grade or tunnel loading means that the haul vehicle is below the grade the machine is on. Pushing in straight lines, sliding the load, pre-staging material in front of the pit prior to the next haul vehicle all are efficient practices. For a haul vehicle that is half above/half below the level of the load machine, having the pile close by, loading the bucket as full as possible without spillage, (the bucket can only hold so much) running short distances, making as few turns and wheel revolutions, are all best practices. For haul vehicles on the same level as the loadout machine, (this is the most inefficient) operators need to make sure that their stockpile is close, keep distances short, do not overfill buckets and keep straight when approaching the haul vehicle.
Loading conveyors or hoppers inside of an MRF has its own special skills. Prior sorting of the material and fluffing the material are imperative. Fluffing basically means that the machine will pick the material up and dump it loosely in a pile to break it up and reveal reject material. Once this takes place, operators will load the material into the conveyor bin or hopper making sure that they do not overload or over stack the material, slowing the process down. Best practices for excavators and wheeled excavators for load out or loading conveyors/hoppers are: position the machine to the conveyor/hoppers/haul vehicles so that the reach is 35 to 45 degrees of vertical, do not add a lot of down pressure when loading the tool, do not swing more than 90 degrees to load the tool, load the hopper or reject material. If the machine is equipped with a hydraulic cab riser, raise the cab to achieve full visibility to the load area. Be careful during the loading process so that the work tool will clear the sides without contact.
Tamping
Every transfer station and MRF operator wants to achieve “full rated loads” with outbound haul vehicles. To achieve a fully rated load, most operators will ‘tamp’ the load for two reasons: 1) To gain as much weight outbound as possible and 2) To keep the load top flat/level so that the load can be tarped safely. The bottom line is, if you must tamp, be square with the haul vehicle so you do not put side loads in to your machine or haul vehicle. Do not raise tires or track off the floor. Using that much hydraulic power, you add pressure past the design point of the structures of any machine. Eventually, something will fail. Observe how long you are tamping. Keep tamp time short. With an excavator or wheeled excavator, tamp in layers. This will help you gain max load weight. Try to leave the haul vehicle in one piece. Be cognizant of the amount of pressure you are putting downward into the haul vehicle. (do not flex, push or pull sides). One last point, if you have the material and capacity to achieve fully rated loads without tamping, then perform a test of weights with tamping or not tamping loads. You might be surprised at the slight amount of weight you gain for the fuel and stress on the machine you use.
At the End of the Day
Best practices for transfer station and MRF operations are simple:
- Safety first. Include the whole team. Make everyone accountable.
- One of your highest costs is tires. Monitor tire spin. Train your operators on machine systems and ways to keep spin to a minimum.
- Proper push and stockpiling techniques will increase production and efficiencies while keeping maintenance, fuel and floor costs low.
- Whether loading haul vehicles, hoppers or conveyors, using proper sorting, fluffing, (MRFs) and outbound loading techniques, assures lower costs and helps meet production goals.
- Use proper tamping techniques without raising the machine off the ground. Most of all, find out if the the amount of time you tamp justifies the slight amount of weight increase that might take place.
Tom Griffith is a Market Professional of Waste Applications and Products for Caterpillar Corporate Waste Group (Peoria, IL). He can be reached at (309) 675-5463.