Conveying Conventional Conveyor Wisdom....
A conveyor is a conveyor is a conveyor... some people would argue that a conveyor is merely a "commodity" in the packaging industry, suggesting that the only differentiator in the marketplace is price. On the contrary. Done the right way, there are many considerations which go into correctly configuring a conveyor for a particular application. Don't be persuaded otherwise. Bargain basement conveyor prices mean that you get what you get, and that doesn't typically involve much customization or consideration for your particular application. Companies who sell "cookie cutter" conveyors aren't interested in your needs and expect you to figure out how to make their standard product fit your application. At LPS we take the opposite approach. Essentially, we start from scratch every time we begin to engineer and configure the right conveyor for your application.
The first step in the process of configuring a conveyor is to be clear about its purpose. Not so much to yourselves, because it's your plant, your products and your process. Nobody is more intimately familiar with what purpose the conveyor is needed than you. Rather, your mission is to be clear with suppliers about its purpose, first and the various and sundry other attributes the conveyor must have. To the extent that you can clearly lay out the parameters of what you need, it will go a long way towards preventing the "mutual mystification" process that sometimes occurs when you are shopping for suppliers.
The four purposes of a conveyor from our perspective here at Liquid Packaging Solutions are:
- Transporting products from one operation to another
- Accumulation of products between operations to ensure smooth flow throughout the packaging line
- Converging flows of product from multiple lanes into one lane
- Diverging flows of product from one lane to multiple lanes
- Cooling or curing (Closely related to Accumulation)
The next logical step is to understand the size of the conveyor. There are several attributes related to the size:
- Conveyor Length
- Conveyor Height (distance from floor level to belt or chain top)
- Belt or Chain width
- Fully Loaded Weight
Conveyor Length
Conveyor Length is directly impacted by the sizes of containers you will be moving down the line. Example: Suppose you are moving containers on an "in-line" packaging system and the Filling Machine you are using is a 12 Head Filler, filling 6.0" Motor Oil Bottles, the "set" of bottles exiting the Filling Machine at the end of the Fill Cycle will equal 72" (6'-0"). So, if you were configuring a conveyor for a Filling Machine, you would want the length to be, at minimum, 216" (18'-0"). Specifying this length allows for enough space to always have one set of bottles waiting to be filled, another set being filled, and enough space for the filled set to exit out of the machine.
Using the same information above, but specifying an accumulation conveyor instead of a transport conveyor, your choice may be different. Let's say that the Motor Oil in our example above is filled "hot", and because the containers must cool down by 10-20 degrees F. before applying a Two-Sided Panel Label. In this case, the issue is still the 6'-0" length of a set of bottles, but equally important is the amount of time it takes for the bottles to cool down enough to be labeled. Time between operations is the key here. Sometimes we can compress cooling time by utilizing Serpentine Conveyor layouts, or having the conveyor run through a cooling tunnel.
Conveyor Height
Conveyor height is determined by the height of the containers. Clearly, if a Cubetainer of 12" in height is being filled or capped, it is probably prudent to specify a conveyor which is closer to the floor, instead of the commonly used dimension of 32"-36". Some plants specify even taller conveyor heights. This is a critical, but often overlooked attribute mostly because the amount of vertical adjustment on a given Automatic Filler, Automatic Capper, Induction Sealer, or Labeler is usually not greater than 12" of vertical adjustment. Suppose you wanted to Label 5 Gallon pails and One Pint Metal Cans. If you specify a conveyor height which accomodates the 5 Gallon Pails, say 12" from floor level, when you get to the point where you want to change the line over to run the pint containers you may find that there isn't enough adjustment to get the pint cans close enough to the machines. Unless you're taliking to us!
Belt Or Chain Width
As it turns out, there is a difference between Conveyor "Belt" and Conveyor "Chain". The rub is that the difference is not visual. The uninformed among us can look at a conveyor and point to the conveyor belt, and call it a conveyor belt. However, different manufacturers call out their products as "belt" or "chain". Internally at LPS we know the difference because our suppliers have indoctrinated us with their own use of those terms. For the purposes of our discussion about this topic, however, we will use the term "conveyor belt"!
As it is with the other attributes, the conveyor belt width is determined by the maximum diameter or width of the containers being transported by it. This is true for all conveyors which run parallel to the machines it feed as it transports containers in and out of Filling Machines, Capping Machines, Induction Sealers, Labelers and other machines. It is a fairly straightforward concept. If the largest diameter of a container being transported on the conveyor is 8", then an 8" wide conveyor belt will be sufficient. If other containers besides the 8" diameter container are transported on the same conveyor belt, for example, a 2" Diameter one, then the Conveyor Rails can be adjusted in to accomodate the smaller container. It's always possible to run a smaller container on a wide conveyor. The converse, however is not a guarantee.
There is another wrinkle in this equation when our discussion turns to molten products filling or candle making machinery. With these applications conveyors are typically wide, slow moving conveyors with a Molten Products mounted perpindicular to the conveyor belt. Typically, the conveyor never starts and stops and filling occurs "on the fly". Molten Products Conveyors are normally utilized as accumulation conveyors, as discussed above, and their width is dictated by the the size of a "set" of filled containers. Suppose that you have a 3" Diameter Pillar Candle and that you are filling 12 Candles at a time. That would make the "set width" equal to 36". Allowing a few inches on either side of the set would put you into a 42" Wide Conveyor.
Once the overall size of the conveyor is correctly specified, the work can now turn to the other equally important attributes, namely:
- Conveyor Belt Or Chain Type (Material, Construction)
- Belt or Chain Sprocket Type
- Conveyor Drive (Motor and Gear Ratio)
- Conveyor Drive Location
- Line Direction
- Conveyor Rail Brackets
- Conveyor Controls and Location
Conveyor Belt or Chain Type
The good news is that there are a plethora of different types of belt and chain on the market. In fact, the array is downright dizzying. Common materials are various plastics, stainless steel, and in the case of candle making or molten products cooling conveyors, wire mesh. While the list is not endless, it does require some thought in terms of getting the right one specified. Some variables to consider are the product itself. Certain types of plastics are better for corrosive materials, like bleach or caustics. The same belt, however, may not be suitable for solvents because they melt. Hazardous Location environments require carbon impregnated belting or stainless steel to conduct static electricity to a grounding stake. These issues go back to the original discussion of purpose.
Belt or Chain Sprocket Type
The choices in this arena are driven by the type of belt or chain selected for the conveyor. In fact, most suppliers of belt or chain specify ther correct sprocket type. In certain environments like the Food, Phamaceutical or Dairy Industries, bearings must be sealed to prevent
Conveyor Line Direction, Drives and Locations
Again, seemingly endless combinations of possiblilities. At LPS our customers projects, if you'll pardon the pun, drive this. We configure conveyor drives based upon required electrical codes (NEMA 4, NEMA 12, Hazardous Location, Class I, Division I, Group D), based upon desired speed of the belt or chain (drive gear ratio) and based upon customer preference (A/C Motor or D/C Motor).
The Location of the drive can be on the front of the conveyor (operator side), nested underneath the conveyor in the middle, or on the back side. Customer preference dictates this, as does transfers from one conveyor to the next.
Locations of conveyor drives is also determined by the direction of the line. Conveyor drives are always located at the downstream end of the conveyor, as they "pull the belt", rather than "push" the belt. Failure to get this communicated properly will result in re-work which is a waste.
Conveyor Rail Type and Bracketry
Conveyor Rail types available are commonly either stainless steel or aluminum. Equally common is an HDPE wear strip. On Corrosive Products Conveyors, the Conveyor Rail is made of HDPE, since both stainless and aluminum won't hold up over time to corrosive products. Bracketry can be as simple as two "L-Brackets" mounted to the conveyor or as fancy as Rod and Block products like the ones that Valu-Guide, Marbett and a few other companies supply.
Conveyor Controls and Location
The type of Controls is determined by the type of Drive Motor. When an A/C Motor is driving the conveyor, we us an A/C Frequency Inverter. This allows for the means to change conveyor speed by controlling frequency drive. Commonly called "Freek Drive" in the industry, which is fun to say! The other predominant type of conveyor controll is a D/C Controller, used of course on D/C motors. The Locations of the controls can be either a discrete controller mounted on the side of the conveyor, or the controller can be mounted inside of a Machine Control Cabinet like a Filler, Capper or Labeler.
Posted: February 19, 2010
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