December 2005

Handling with care brings PM some HSE dividends

Faced with the inexorable advance of health and safety legislation including the European REACH rules, metal powder companies could do a lot to clean up their acts by using modern materials handling systems. But although a handful of big players embrace a precautionary philosophy, there are plenty of companies that do not, says Matcon's Hans Pettersson...

In his presentation at EuroPM 2005 in Prague Hans Pettersson made no secret of the fact that he represents a leading materials handling concern. And though he spoke from the "vested interest" corner as it were, that did not detract from the reality and common sense of what he had to say.
It has long been accepted in more aware industrial circles that there is a link between safe working and profitable companies - and vice versa. Safety and profitability are seen to run together since the first illustrates the care that a company puts into running its business in such a way that predisposes it to achieve that second and, from a shareholder's point of view, desirable state.
The other side of the coin, loss of reputation and shareholder confidence, has been seen over the past 20 years in a string of catastrophic incidents that stretch from Bhopal in India through Piper Alpha in the North Sea to Three Mile Island in the United States, interspersed with “lesser” disasters that do not make international coverage.

And yet companies still fail to heed the very real risks they take in terms of employee safety, reputation, and profitability when their workplaces are dirty, unsafe and inefficient. The PM industry has some particular issues, in that metal powders while fine, are also very dense, requiring robust equipment to handle them. Operator exposure should be avoided since some powders are toxic. Other metal powders can be pyrophoric and thus represent a safety hazard.

Hans Pettersson made his case by reference to an unnamed hardmetals powder producer that first embraced intermediate bulk containers (IBC) as a handling methodology a decade ago to take advantage of the production flexibility it offered, reduced operator exposure and reduced risk of error. When the company expanded the decision was made to build on the basis of IBC technology and an IBC formulation concept from Matcon - FlexiBatch - was selected to provide the levels of flexibility and accuracy demanded, combined with low operator exposure.

"It is nothing short of amazing to see how different companies within the same industry deal with the risks of operator exposure," he said. "Most guidelines in this area are nationally derived, but most of them state roughly the same thing.

"Take cobalt as an example. The Swedish, English, German and even American regulations all state accepted exposure levels to be around 0.05 - 0.1mg. Yet when you visit companies handling this material, you see everything between the man (without mask!) and his shovel, up to fully enclosed glove-boxes (making the dosing operation very awkward, but safe!)
"In this project the accepted exposure levels was set at 0.01mg for cobalt and 0.05mg for any other dust in the formulation area. This was deliberately significantly lower than the present regulatory levels, knowing that they will continue to lower as time goes by.

"After all, one fatality will cost the company an awful lot more (both direct and in goodwill and reputation) than a more contained handling system ever will. There are numerous 'risk areas' in a complex formulation system like this. Some of the key areas we had to consider, with agreed solutions for this project, were:

• Drum tipping - Enclosed system and local dust extraction (LDE)
• Manual dosing from drums - Enclosure hoods and LDE
• Major dosing - Dust free cone valve docking to / from raw material containers. Enclosed filling to batch containers with LDE. Continuous hood protection of the open batch container during transport between dosing points.
• Risk removed in blending area by use of IBC Blender.

"These points highlight the main issues during operation. The system was designed to minimise the amount of product lost in dust extraction, but there is still a need to change filters at planned intervals. These filters are located for easy access, and the operator performing this task will have to use personnel protective equipment to assure safety during this operation."
The scope for materials handling in the new facility includes, he said:

• Handling of incoming raw materials
• Drum tipping
• Dosing of minor and major ingredients
• Blending of re-work material
• Controls and automation.

Cobalt and some other components are delivered in IBCs directly from the suppliers, hence removing the need for any kind of manual, open handling. This is unfortunately not possible with all ingredients, hence the "necessary evil" of using a drum tipping device.

There are many machines for drum tipping on the market, but very few that are anywhere near dust-free. With the added complexity of drums ranging from 30 - 200 litres and weights from 50 - 700kg, there was simply no standard off-the-shelf solution available.

"A lot of 'bespoke' design work was required to arrive at an acceptable solution both with regards to dust levels and ease of operation. The high cost and complexity of containing drum transfers, combined with associated manual handling issues, adds to the benefits of using IBCs for distributing these types of dusty and sensitive metal powders.

"In almost all applications and all industries, there is a need to add very small amounts of minor ingredients. In this case there were up to 12 ingredients that fall within the range of between 50 grams and 15kg. These ingredients are manually dispensed. Emphasis was placed on localised extraction points assuring minimal exposure to the operator, but at the same time not extracting unnecessarily large amounts of product to filters.

"Strict operator procedures, combined with bar coding and operator confirmations of every handling step, assures traceability. Every drum has a unique bar code, and only if the correct drum is scanned, will the system allow weighing to start. The operator accepts correct weight at the screen and then further acknowledges that this amount has been transferred in to the main batch container. A dedicated pallet truck performs the handling of the ingredient drums, making the changes quick and easy.

"About 20 different major ingredients are used, some very frequently, others quite rarely. In order to accommodate all these ingredients with a minimal amount of fork truck traffic there are a total of 19 IBC dosing positions in the plant. Four of these dosing positions are 'traditional', using a vibratory feeder located below an IBC discharge station for dosing. These are dedicated for Cobalt and some other ingredients that are frequently used, but always in smaller quantities. The dosing range here is 3 - 150 Kg with a dosing accuracy better than +/-50 grams. The other 15 positions are based on a flexible IBC formulation ('Flexi-Batch') concept.

"On each position, the dosing is performed by a single cone valve device mounted on a movable trolley. The cone valve moves along on the trolley together with the weigh scale and performs a dust free docking to the ingredient IBC above. Dosing can then be carried out, and when complete, the trolley moves on to the next ingredient. This results in extreme flexibility, relatively small space requirement, and a realistic capital investment. The dosing range in this system is 10 - 800Kg and the dosing accuracy better than +/- 100grams," he said.

Most, if not all, metal powder producers have a need for dry blending at some stage of the process. In this case the blender is used for homogenising "re-work" material, which can then be re-used in the formulation process, once its exact characteristics had been defined.

The biggest benefit of using the IBC blender is that there is no need for powder transfers to or from the blender, reducing the risk of dust escape by unnecessary transfers. This also removes the risk of segregation during discharge of the mixer.

The IBC filled with the re-work material direct from process, is loaded into the blender using a fork truck. Once blending is finished, the blend can be loaded direct on the flexi-batch system.

"The automation philosophy is built in such a way that one operator will be able to handle the complete formulation area. The movement of the batch IBC is fully automated once the recipe is started. This is accommodated by two automatic trolleys and roller conveyors. There are sensors and scanners located at strategic positions to inform the control system at all times where all 'live' containers are. The use of RFID tags was considered for the project, but wasn't deemed to offer any financial or technical benefits versus the well-known barcode technology in this instance."

There are three distinct "control levels" relevant to the formulation system, said Hans Pettersson. The highest level is the warehouse storage control. This level controls and records what is in all incoming drums, once scanned and also what goes into, and out of, the IBCs.

"The second level is the SCADA system for the formulation area itself. The main purpose of this system is to handle the downloaded recipes and, based on these recipes, perform the necessary movements of batch containers, request changing / re-fill of raw material containers etc. Alarm handling and operator interfaces also lie at this level. The third level is the operational PLC level. This is where dosing control logic; dosing parameters and interface to the various scales are controlled, allowing the system to meet the tight dosing tolerances.

"Bar codes are used to track drums and containers. This is a good starting point for a working traceability system. The most important ingredient of the system, however, is still the operator and the system must be designed such that it is easy to work within it, and difficult to go round it. Automated dosing and IBC movement reduces the risk of operator errors. The other aspect of assuring traceability is the emphasis of keeping the facility very clean, avoiding accidental ingress of wrong materials.

"The technology is available from us and others, but yet there are only a handful of metal powder companies using it." And he had one deft thrust for the "old men" at the top.

"REACH regulations or not, the metal powders industry will soon have to catch up on technical and environmental development around us. Young people of today simply won't accept working in the conditions offered to them in a dusty metal powder factory."