Safety is something many take for granted. The Society of the Plastics Industry says 2000+ accidents occur in the plastics industry each year. The majority are from workers falling, getting caught in machinery, and electrical accidents. The attitude that “it won’t happen here” has got to be discarded. It is not a matter of ‘if” but rather “when”. Discipline and procedures must be maintained when it comes to the safety of workers operating machinery.
BASIC SAFETY PRECAUTIONS
The extruder looks innocent enough, but it’s always potentially dangerous. Loose-fitting clothing or a necktie are not appropriate for working on the line. Safety shoes and glasses are a must for everyone. A small die may weigh only 30 pounds, but dropped on a foot unprotected by safety shoes, it could do serious damage.
The extreme heat of the die represents another serious risk. I’ve seen workers adjust dies without gloves, but it only takes one little touch to get a burn that may take three to four weeks to heal. Die temperatures range from 350 to 600F.
Electricity also deserves respect. Every piece of auxiliary equipment should be grounded, including the hopper dryer, hopper loader, preheater, extruder, pumps, puller or conveyor, cutoff saw or knife, marking machine, takeup reel for flexible profiles (and pipe), refrigerator unit, and any other unit drawing power. This grounding should be done only by a qualified electrician.
The extrusion line can be especially dangerous with water on the floor, water is a great conductor of electricity. Starting up a line or a break in the line will often result in spilled water. To minimize the risks of a wet floor around the cooling trough, a wood platform alongside the trough and floor drains are helpful. A wet/dry vacuum cleaner and floor squeegees can be a useful item. Keep in mind that workers walking on a wet floor will have wet shoes, and they could slip easily anyplace they go.
Next to the cooling trough is usually a belt puller or a conveyor. It is very easy to injure a hand or fingers on a puller. In a startup, many times the product is hand fed through the water trough and onto the puller. A safer alternative to this practice is to use a starting line. For example, a small plastic pipe or rod cal be threaded through the puller belts while stopped and threaded up to the die head. As the hot extrudate comes from the die, it is attached to the starter line. In this way, the line worker does not have to lead the new product through the cooling trough or puller. Puller belts should always have guards.
Care must be exercised when the extruder is started. Workers should always wear glasses and special gloves to handle the hot extrudate. No one should be standing directly in front of the machine on startup. Air and gas can be trapped in the cylinder or die and, as hot material is moving through, the barrel will occasionally spit out hot plastic. If it’s a vented barrel, the operator should never look into the vent. On startup, the die may need adjustment, which always requires gloves.
In production, problems inevitably pop up. A pressure buildup at the head may go unnoticed. If the pressure is great enough, the clamp bolts will break or the rupture disk will blow. In replacing either, workers may fail to use the correct item. It is also important to check that the pressure gauge is working. Newer extruders usually have a signal light or buzzer to indicate abnormal pressure rises.
Beyond the puller belt or conveyor belt, proper guards must be in place on the cutoff saw or knife. Cutoff-saw shavings accumulate quickly. A shallow box under the saw reduces the hazard of slipping, but constant sweeping is also necessary.
Many lines have marking or stamping units. Some use ink or a hot stamp. Ink can make a mess on the floor that is quite slippery. This hazard can be minimized by providing a catch pan under the marker (above the floor). Hot stamps are cleaner, but if not properly guarded they can burn fingers.
Once in a while, the line will break. This is the time when the machine operator needs help. When working on a line, place a panic button at the puller. When it was pushed, a loud horn would go off and help would come. It is a simple device to install. Panic buttons could be located anywhere along the line. There could even be more than one connected to the same horn.
On an extrusion line, there are many places for accidents. It is common to see plastic pellets and oil on the floor in a plant. Those pellets are like small ball bearings—it doesn’t take many to have someone slip; and oil is a great slipping agent. Line operators must constantly be on the lookout for hazardous conditions such as these. They should never use an air hose to blow away dust or pellets. Instead, a broom and dustpan should be kept at each end of the line for fast cleanup. Well-stocked first-aid kits for treating minor injuries should also be at each line.
Newer pieces of equipment have numerous safety signs regarding the machine. They are not there for decoration, and they should never be removed. Experienced line operators may know most of the areas that can be unsafe, but what about that new operator who has never seen this kind of equipment before?
Although OSHA has been doing a good job in making plants conform to safe practices, there are many small operations that remain lax in this area. Proper safety guards are not always in place; control-cabinet doors and cylinder enclosures are left open. Keep in mind that if a worker is injured due to negligence on management’s part, there are always repercussions. Management could be held legally responsible, and even in less serious accidents the worker’s job performance could be affected.