Is Grip the New Safety Feature?

Grip is indeed the new safety feature. But why is grip able to offer the glove user more safety?

The answer to that question is yes: Grip is indeed the new safety feature. But why is grip able to offer the glove user more safety? Surely gloves have always had grip, so how can this be a new thing?

The answer to these questions is the type of grip and the way it's delivered. For many years, glove manufacturers have been developing and producing gloves that have been unable to deliver the type of performance needed. For example, in lightweight assembly applications, such as the ones found typically on automotive production lines, the grip has to be enough to be able to handle the parts, but there shouldn't be too much grip because this can hinder those assembling the parts.

On the flip side, people handle oily components to make, for example, transmissions and suspension systems, which are covered in preserving oils and lubricating fluids. Grip during the past five years appears to be something that the manufacturers' research & development departments have been tasked with improving; much of that emphasis appears to have been focused on delivering improved oil grip. It's not limited to oil grip. There also have been significant advances in assembly gloves in dry areas. Optimized dry grip enables people to pick up small parts while not having too much grip during the assembly activity itself.

The reality is that there has been little on the market, especially for oily environments, delivering the necessary grip in conjunction with the other characteristics required (e.g., dexterity and flexibility). It's the general consensus that the best oil grip is offered by natural materials, such as cotton and leather. While they may offer outstanding oil grip, they are obviously unable to offer the protection from the oil itself. Some get over this by placing the cotton or leather glove over the top of the liquid-repellent and/or chemical resistant glove, but this compromises dexterity, flexibility, and tactility.

The other alternative would be to use a chemical-resistant glove and try to find one with a good grip pattern in the palm. Patterns such as lozenge and sand patch have been quite common, but in reality they offer little, if any, assistance in enhancing their grip.

How have workers coped in the past? They've simply applied their own grip by exerting more force through the hand and arm muscles. Lifting a 1 kilogram (kg) oily weight requires about 40 percent more effort with a standard, unsupported, nitrile chemical-resistant glove versus doing the same lift with the new generation of oil grip gloves.

The Consequences of Increased Muscle Power
People made up for lack of grip through muscle compensation. Why can't workers carry on doing this? Why do we need better gripping gloves? It's now commonly accepted that this way of working can cause long-term health issues if not addressed.

General symptoms typically include aches, pains, tension, and disorders involving parts of the arm, from the fingers to the shoulders and/or the neck. There can be problems with the soft tissues, muscles, tendons, and ligaments, along with the circulatory and nerve supply to the limb.

The symptoms are usually caused or made worse by work. They include problems such as carpal tunnel syndrome, tenosynovitis, and also conditions where there is pain but no recognized condition can be identified. It is more commonly known within the glove business as repetitive strain injury or occupational overuse syndrome. These two commonly used terms can be misleading with regard to the many factors that can contribute to the onset of the conditions, and hence the problem is referred to as upper limb disorder. More concretely, when talking/interviewing your workforce, ask whether they have aches and pains, tenderness in muscles, stiffness, weakness, numbness, cramps, and/or swelling.

A number of factors cause upper limb disease, the most obvious being repetitive work that is carried out for a long period of time and uncomfortable working postures. Both can be addressed by reviewing work flow organization and looking at and adjusting the ergonomics where the activity is being done. Also consider the working environment itself; examine and modify the temperature, lighting, demands, and work breaks (or lack of them).

The point being that gloves can do only part of the job; there must be a holistic approach. Gloves with the appropriate grip have a major impact on the amount of grip force exerted, so it's important to get this right and do your research. Workers are also more likely to suffer an upper limb problem if exposed to more than one risk factor.

Oily Environment
Weight lifted (kg) Without glove With standard glove With new glove
2 11 kgf 8 kgf 5 kgf
4 18 kgf 13 kgf 9 kgf
6 31 kgf 21 kgf 15 kgf
kgf = kilogram force

How Can Grip Help?
To lift something, you have to grab it and hold on to it so it doesn't drop. The energy required to hold anything is closely related to the friction coefficient. A larger friction coefficient makes it easier to lift things, leaving more energy in reserve for getting the job done. For an average male, the arm can deliver up to 60 kg of grip force, which implies that it is possible for an average male to lift a dry weight of only 24 kg on the basis that a 1 kg requires 2.5 kg of hand grip force. Should the item lifted have a thin film of oil, nearly 40 percent more effort is required, reducing the technical lifting limit to 15 kg -- some 9 kg less than in a dry situation.

The new wave of grip products offered by several companies can reduce the amount of force required. The third column in the accompanying table is intended to give an idea of the improvements these new gloves can deliver in oily applications.

At the lower 2 kg weight, the performance versus standard gloves is a staggering 60 percent improvement. Even though this relative improvement reduces with weight, there remains a 40 percent improvement when lifting a 6 kg weight. Given that the trend is for people to be exposed to lower weight limits as robots take the need away for heavy manual handling, this has to be seen as a big step forward in dealing with upper limb disease.

Additional Safety Benefits
There are two other major safety benefits gained by ensuring that workers use gloves with the appropriate levels of grip. The major one relates to cut resistance. Many of the minor cut injuries are dealt with by introducing higher cut resistance in gloves, which has three major negatives. First, it is more expensive to deliver more cut resistance because more, and more expensive, cut-resistant fibers are required. Second, as a consequence of increasing the cut resistance, the gloves nine times out of 10 are thicker, and thicker gloves hinder people from doing their job. If the gloves are not comfortable and/or practical, they will be removed, which leads to the third problem -- increased exposure to cuts. It's strange, but I have seen many times that the introduction of gloves offering more cut resistance does not resolve the issue of cuts. Rather, they remain steady or even increase.

What's the solution? As a first step, focus on resolving the cause of the problem rather than the effect. In the many hundreds of manufacturing facilities that I've seen around the world during my 15 years in this business, few people look at resolving the grip prior to evaluating the level of cut protection necessary. Simply put, if the item being handled doesn't move in the hand, then the likelihood of the glove and consequently the worker being cut is virtually minimal.

Everyone wins. It's easy to compare the cost of good grip versus high cut resistance fibers, and soon you'll see a major cost benefit to your organization. Given the gloves will be thinner, your workers are likely to be happier to wear them, and with higher glove usage accidents should go down, representing another significant savings. The direct cost of a minor injury is today estimated at $342, so bear this in mind when your accident injury rate in coming down.

Today there is still a general misconception that thicker gloves offer more resistance, so you may have to do some educational work as to why you've focused on grip.

Additionally, there may be safety benefits from the reduced risk of dropping the item the workers are tasked with handling. Many foot injuries come from dropped things, so gloves with better grip should reduce the likelihood of this, as well as the budget for damaged goods.

The Commercial Aspect of Appropriate Grip Levels
Have you ever stopped to think how much time and money have been spent on conducting time and motion studies to make the factory as efficient as possible? Did you then think that production process/lines can move only as fast as the people working on them?

The reality is that production lines go only as fast as the people who work between the robots. In this respect, gloves with the correct levels of fit, flexibility, dexterity, and grip have to be seen as investments in productivity. This is especially relevant for those having to work in oily environments.

The largest technological steps in recent years have come in gloves designed for oily environments. Traditional oil grip gloves use tiny convex projections on the flat glove, which helped. The new wave of oil grip protection gloves use a system of micro-craters that act like tiny suction pads, which deliver up to 60 percent more grip force power at lower weights. The gloves you should add to your list for consideration are split into two categories, oily/wet and dry.

This article originally appeared in the August 2011 issue of Occupational Health & Safety.

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