Getting the gunge from a gundriller

One of the biggest usages for this type of gundrilling centre is the creation of biomass pellets for biomass boilers.
One of the biggest usages for this type of gundrilling centre is the creation of biomass pellets for biomass boilers.

European precision mechanical engineering business Mollart Engineering Ltd is now installing Eclipse Magnetic’s Micromag magnetic filters on the majority of the multi-spindle gundrilling centres it designs, manufactures and supplies. As a major player in the manufacture of gundrilling centres for the pellet die industry, Mollart produces machinery used to make dies to create pellets from a variety of materials including wood, coal and animal feed.

Blocked pumps

One of the main materials used to make the dies is a chrome alloy steel called XC40 which naturally produces a large amount of dust when drilled at high feed rates. Contaminated oil settling in the tank of the gundrilling centre creates a thick paste-like substance which can block its pump, making it inoperable.Mollart approached magnetic filter specialists Eclipse Magnetics, who recommend its Micromag filter.

Ian Petitt, sales director for deep hole drilling systems at Mollart Engineering Ltd said: “We have been very successful with the Micromag in this application. It has resolved a lot of problems; it’s been a very good, usable tool for us. Not many machines go out without it now.”

On occasions where Mollart fit only one Micromag, it is used to polish the oil after it has gone through another form of media, usually paper, first. The oil is passed through the filter, and then through the heat exchanger in order to reduce the temperature. This is a continuous process; for machines that have a 2000 - 3000 litre tank, for instance, Mollart may only be using 100 - 250 litres per minute of oil. The filter itself is not directly in the high pressure oil line, therefore it is allowed to work at its own pace, and even if the machine isn’t working the polishing of the oil is still being carried out.

The XC40 chrome alloy steel is a martensitic material but contains chrome, which is non-magnetic. However, the ferrite particulate that is collected gathers to form a ‘beard’ on the magnets within the filter, which helps them to catch even the non-magnetic particles, and therefore work efficiently.

In some systems, a series of six Micromag MM20s are used as a pre-filter, which vastly reduce the cost and usage of the paper media. The flow rate of the systems is up to 300 litres per minute, and as the filters have a flow rate of 90 litres per minute, they have three in action and three on standby. There is a changeover mechanism incorporated in the form of a three-way valve so that the filters used can be changed over live without stopping the equipment, enabling continuous 24/7 production.

Pumps cost approximately £3000 each as a minimum, and can cost up to £5000 for larger pumps, therefore protecting them is a must. Customers who used paper filters as a primary method of filtration alone were experiencing problems with the build-up of dust and debris in the machine, which put their pumps at risk. In some instances, pump failure would occur due to contamination. A secondary filter, therefore, was required to remove sub-micron particulate from the oil and keep it as clean as possible was essential.

Disposable costs disposed of

Ian Petitt continues “The good thing about Eclipse filters is that you don’t have disposable filtration elements, and that makes a big difference to disposal costs and general running costs. My main aim is to make sure my customers’ pumps work not only work effectively, but stay alive for as long as possible. Running costs are always high on the agenda. The pumps are very expensive pieces of equipment, and when they go down it puts a huge amount of stress on the business, as well as costing a fortune to replace. The Micromag prevents that situation, and by reducing the amount of media used by the customer, their running costs are kept down.

I recently liaised with a customer in France that was using one of our gundrilling centres. The particular material they were using was creating an awful lot of dust during the drilling process. They initially ran the machine using 20 micron filter paper which was doing its job to start with, butsix months down the line it was being choked by dust. We gave them a Micromag and it immediately and completely eradicated the problem. Wherever there is a dusty drilling problem with ferritic material, these filters can be very useful!”

One of the biggest usages for this type of machine is the creation of biomass pellets for biomass boilers. As an industry that is still growing, the demand for biomass fuel continues to increase. Biomass pellets are created by pushing wood pulp through a die, which is crushed by heavy rollers to produce pellets. The holes that are formed in the die are drilled using the gundrilling centre, producing a precise and accurate hole suitable for the creation of the biomass pellets.

Depending on what the die is going to be used for, up to 200,000 holes may be required on a single die and some produce several hundreds of tonnes of pellets an hour. Due to this high level of use, the dies wear out and need to be replaced, and are, therefore, consumables.

It is imperative that the holes in the dies are drilled effectively and accurately with a good surface finish. This is dependent on the maintenance of the plant to a high standard, including ensuring that the drill is kept in good shape and the oil remaining clean.