16 October 2008
Phillippe Bermot

The first cut is not always the deepest, but you still want to prevent it. Our hands are fundamental tools we rely on, and damage to them can lead to long periods off work or worse; lacerated nerves can rob whole hands of their sense of touch. 

Employees handling sharp materials in industries from manufacturing and recycling to catering and security work need protection against the stabs, slashes and grazes that come from regular contact with points, sharp edges, blades and roughened surfaces.

There are basically two types of cuts:

• edge cuts, caused by edges made sharp either deliberately, as in knife blades or chisels, or incidentally, as in clean-edged sheet glass, broken glass or ceramics
• abrasive cuts, from materials such as rough-edged sheet metal, glass
  or timber.

Both types involve movement of the edge across the hand or vice-versa. Less common, but still important, are impact cuts, where the sheer pressure of an edge (a falling piece of glass or metal) against the hand causes the laceration. Impact cuts are common in the "crotch" between the thumb and first finger.

Standard wording

The European standard for cut resistance is EN388, which also sets the standards for a material's ability to resist heavy rubbing, tearing and puncture by pointed objects.

The cut-resistance test for any given material, not surprisingly, involves placing it under a blade, which rotates and is pressed down onto the material by a fixed weight. The test records the number of cycles the blade takes to cut through the material. This figure then translates to one of five cut-resistance categories, which must then be displayed on any gloves made from the material. As the table opposite shows, those at the lower end of the range offer relatively low levels of resistance and would only really be adequate where there is a slight risk of light contact with anything sharp. At the top level though, level 5 (and some manufacturers' gloves comfortably exceed the level 5 standard in tests), the materials will protect users against heavy plate glass slipping through their fingers.

Abrasion resistance is measured using what's known as a Martindale tester, which rubs a sample of the material in a circular motion with an abrasive head. The test result records the number of cycles it takes to make a hole in the fabric. The number of cycles translates into the levels in the table. Where a material is made up of multiple layers, they are all tested separately and the result used is that of the most resistant layer. By contrast, cut-resistance values are based on testing the whole composite material.

Safety glove packaging must state the EN388 test level if the gloves claim cut or abrasion resistance.

Material values

Gloves whose primary protective purpose is cut resistance are most commonly knitted, rather than woven or moulded. Knitting allows highly cut-resistant materials, some of which would be impossible to use in solid form, to be spun as yarns, giving better fit and flexibility.

Knitting creates a matrix of the protective material, which brings various advantages, including allowing the yarn to move or "roll" under light pressure from a sharp edge, making it more difficult for the edge to cut it.

Knitted gloves are also breathable, reducing sweating and discomfort; though there is an inevitable trade-off between the thickness of the gloves and their protective ability, and thicker gloves make for hotter hands, especially when workers are exerting themselves. The balance of comfort and protection is something that you can only judge by risk assessing the activity (and refining the assessment in the light of experience) then looking for gloves that provide the maximum protection for the lightest knit.

There is a baffling range of materials and combinations of materials used in safety gloves now, but the usual suspects for cut resistance include the made-made materials Kevlar, as used in body armour, and Dyneema, which is up to 15 times stronger than steel.

Yarns of these materials may be combined with steel wire or given ultra-thin glass or ceramic coatings to render them further proof against cuts.

Missing the point

One of the things knitted gloves are less proof against is puncture wounds from sharp objects that can penetrate the weave. To protect against puncture, you'll need some kind of barrier coating on top of the cut-resistant material. EN388's five ratings include tests for puncture resistance, which measures the force in Newtons needed to push a rounded point through the assembled material.

Barrier layers are also required where the risk of sharp edges and objects may be combined with other materials you'd want to keep away from employees' skin, as in sewage work or some chemical manufacturing environments. Uncovered knits may also be risky where they could get caught on moving machine parts and draw an operator's hand in.

These barrier coatings, especially where they are thick enough to repel sharp points, limit dexterity, which used to be the problem with all cut-resistant hand protection before the invention of materials such as Kevlar and Dyneema slimmed it down to the size and shape of domestic gloves. Inflexibility, inducing a form of clumsiness, brings its own risks, so it's important not to be tempted to over-specify gloves for a level of protection your risk assessment doesn't justify. If you have to go for the thickest option, make sure employees have exactly the right sizes and that the gloves are closely fitted to their hands.

Hold tight

Where coatings are needed to add extra grip to potentially slippy knits, or because employees will be handling small fiddly objects such as nuts or screws, consider whether the coating needs to cover the whole surface of the glove or whether grips on the palm and fingertips will do the job, or even rubberised dots across the whole glove, which leave the rest of the hand to breathe.

Most gloves stop at the wrist, but where employees could suffer blows to their forearms that the sleeves of their overalls or other workwear would not protect them from, you need either longer gauntlets or separate, elbow-length sleeves made of cut-resistant fabric.

A good supplier will be able to help you translate your risk assessment into hand protection that is suited to the task and fits well. Of course, the best people to advise you on what works in action are your intended users, so it's worth letting them try out any proposed purchase for a short time on the job to see that it works and is wearable.

The users are also your best monitors for replacement cycles. You have to drum into employees that when a glove is cut through or seriously abraded, it's time to change it even where they have not suffered any injury, since its protective value will be compromised and the nature of repetitive manual work is that lightning often strikes twice in the same place.

Philippe Bermot is marketing director, EMEA, for glove specialists Showa.

Categories:
Personal protective equipment (PPE), Article, Manufacturing / engineering