20 HEIMBACHANDRITZ When rolls really matter Image 1: Measuring
membrane and ‘multiplexer’ in close-up
Pulp Paper & Logistics
G
ive us the facts – that’s quite rightly what customers demand from
Heimbach’s TASK (technical assistance, service and know how) department. Just like in a recent case in which a customer noticed irregular CD moisture profiles in his felts over a long period of time. This is a problem that is regularly discussed while undertaking customer service and one that certainly needs to be addressed when it occurs. After all, in most cases the CD moisture profile can also be observed in the sheet. As always the question is: Where does the difference in water content come from? Clarity comes from nip profile measurement. As might be known, Heimbach
customer service personnel regularly check felts running on the machine, measuring and
November/December 2017
Experts from Heimbach provide some tips for optimising nip dewatering, and why precise measurements are vital to a positive outcome
calculating CD moisture profiles. Ideally each position should be measured more than once over the lifetime of a felt. In the case of this particular customer the service colleague measured the relevant data and handed the results over to TASK.
Valuable initial discussion The issue was initially discussed on site with the mill operations manager who reported interesting occurrences: While both 1st and 2nd press felts operated without problems, in the third press the CD moisture profile was uneven again and again (see Figure 1). On a machine with a width of 4.5 metres the areas around the edges – front side (FS) and back
side (BS) – clearly showed more moisture than in the centre. The TASK department could establish right from the start that the two press rolls are aligned perfectly in parallel so that ‘crossed alignment’ could be excluded as a source of the fault.
Investigating the causes It was equally clear that the fault had nothing to do with any of the machine clothing. Figure 1 shows the moisture profiles of three press felts from different clothing suppliers (water content in grams per sq m of felt). Besides the Atromaxx Connect felt, a competitor’s products had at other points in time been installed in the same position.
The result was the same, however with differences in moisture content in the cross direction. Heimbach therefore concluded that the cause of the problem must be in the configuration of the press – even though, as already mentioned, parallel alignment had been checked. At this point the nip profiles had to be investigated further. Here, as always, the principle ‘safety first’ is paramount. After all, there is a drop of four to five metres under the seam felt, and you can never be sure that it is strong enough to support a fall.
Hightech unwrapped Besides using special software on high-performance laptops, Heimbach TASK also use a ‘multiplexer’ which allows to pick up data from so-called ‘sensor membranes’ (see Image 1). This device, a kind of plug unit, is
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