- June 01, 2004, by David J. Bentley Jr. RBS Technologies
Last month this column began a series of three articles on safety in the converting industry. It noted that safety concerns in the converting industry primarily are found in three areas: heat hazards, pinching nips, and housekeeping issues. The May column dealt with the most common problems surrounding heat, and this month's edition will cover pinching nips.
A pinching nip is the point in a converting operation where two rotating rolls traveling in the same direction meet. The gap between the spot where these rolls come closest together is extremely small. This feature makes it extremely dangerous. Any new worker at a converting operation that uses nips learns almost immediately not to place his hands anywhere near a nip.
While that certainly is excellent advice, additional factors exist. For complete safety in the vicinity of a pinching nip, workers must be cognizant of many facts. Alertness to the presence of a pinching nip is as important as being aware of heating sources discussed last month.
Because the rolls travel in the same direction, they can easily draw almost anything toward the very small opening between them. Since the rolls are usually metal or some other hard material such as rubber, they readily can crush soft objects such as fingers and hands at the point where they almost touch, i.e., the nip.
People working on pieces of equipment having pinching nips should not wear jewelry on their hands. A ring on a finger caught in a pinching nip easily can amputate that finger when the ring enters the nip. Without the ring, the injury might only be a crushed finger.
Clothing is another important factor when working near nips. Loose clothing such as ties, unbuttoned sleeves, gloves, and similar items can become caught in the nip. A tie caught in a nip actually can strangle an individual. Unbuttoned shirt sleeves also can catch in the nip and cause an arm to enter the nip.
Long hair is another hazard, since it too can become caught in the nip. The simple rules are: Never wear jewelry around a nip, never have loose clothing items around a nip, and never have long hair around a nip.
Cleaning rags or other cloths used near a nip also may become trapped. If the rolls of a nip require cleaning, stop the unit and clean the rolls while they are stationary. The person doing the cleaning should make certain the equipment actually is locked out so another person cannot start it during the cleaning process.
Workers that encounter machinery with pinching nips should always wear safety glasses. While soft items often will go through the nip and simply become crushed, hard items may not totally enter the nip.
Consider a metal screw driver with a plastic or wooden handle. If the metal portion of the screw driver enters the nip, the handle may shatter when it reaches the nip, sending small pieces of plastic or wood flying through the area. These flying missiles can be extreme safety hazards. Wearing safety glasses can prevent these pieces from causing damage to eyes.
When something falls into a nip, the normal tendency is to reach for it rapidly to try and retrieve it. Workers must be alert to this problem constantly and train themselves to avoid this danger. Some machine operators also come dangerously close to nips with various areas of their body when they try to prevent a wrap around a nip, a break to a web, etc.
Always realize the nip is waiting to grab whatever comes too close to it, almost like a hungry animal that senses the approach of a meal.
The best procedure is to place guards near all pinching nips. Workers frequently dislike this approach because it restricts their access to the web traveling on the path through the unit with the nips. This is exactly the reason it is important to have such a guard. Therefore, guards should always be near a pinching nip despite the pleas of operators to remove them.
Next month this column will address housekeeping as the last safety issue.
David J. Bentley Jr. is a recognized industry expert in polymers, laminations, and coatings with more than 30 years of experience in R&D and technical service. Contact him at firstname.lastname@example.org.