British Paper Machinery News


Yankee press loading and bearing change W


almsleys Limited is the most experienced and successful service


company when it comes to looking after Yankee dryers and their bearings and gearboxes. The company offers a service checking mechanical aspects of the press loading system to ensure the controls are accurately calibrated and functioning correctly.


roll loading is available without compromising safety.


Preparing a new Yankee bearing for re-assembly - In the last two years Walmsleys has changed several Yankee bearings and in some cases replaced the main gearbox at the same time. “This is not a simple task and can often involve 2-3 days shut working around the clock,” explains Martin Cunliffe, Service Manager for Walmsleys Site Services. Regular servicing of Yankees and bearing systems can avoid such un-planned shuts


allowing Overloading a press roll onto a


Yankee dryer can be dangerous and damage the main bearings ... but if a press isn’t loaded to the optimum, machine output will be limited. This service ensures the designed maximum Yankee press


Large high flow UK fan project


Salvtech has secured a large high flow UK fan project


S


alvtech Limited has secured another fan project in the UK,


including an installation and commissioning package, for a high flow flue gas bag filter system.


Having represented Pollrich GmbH since 2015 and working with a number of different industries and processes, Salvtech has seen an ever-increasing amount of orders over the last few years. Projects range from small fans with <2kw motors for special ventilation and cooling projects, to fans with motors over 1.5mw for applications such as flue gas venting and tissue machine TAD fans. Pollrich has more than 112 years of experience in numerous projects worldwide. The diverse product range offers solutions for the multiplicity of specifications and requirements around ventilation technology. The company configures its centrifugal


fans for almost every performance range and is therefore able to offer individually optimised and tailor- made solutions.


Several customers in the paper industry have already approached Salvtech for their fan and ventilation needs so, to get ahead of the queue, give them a call today.


Salvtech Ltd Martin Christmas


+44(0)1244 638900 +44(0)1244 638900 info@salvtech.com www.salvtech.com


• Installation checked to ensure loading mechanism is


dimensionally correct to original design drawing


• Loading devices checked to ensure correct bellows/units installed


• Visual inspection of pivot points to check for correct lubrication and wear


• Optical checks of press roll(s) for News and views from the British Paper Machinery Suppliers Association Issue 83


Once all these have been verified and are all correct, the on-machine calibration check can be carried out. All systems have a degree of hysteresis so that when pressures are increased or decreased, the mechanical backlash in the system and regulators will give a slightly different load for the same applied pressure.


Walmsleys Limited Charles Hunnisett


+44(0)1254 830486 +44(0)1254 832181 sales@walmsleys-uk.com www.walmsleys-uk.com


October 2019


this work to be


scheduled during normal shuts.


An even nip - It’s not practical to take a Yankee dryer nip impression and get meaningful results unless the press felt is removed and the dryer cooled. The use of load cells will measure the actual force being applied by a press roll to a Yankee cylinder against loading pressures applied by the loading mechanism. Providing the correct camber has been applied to the press roll, an even nip will be applied at the rated press loading. The load cells have special mounting brackets fitted to the press roll bearing housings such that the reaction forces pass through the centre line of the Yankee dryer.


Press loading errors - Three main areas can cause an error in the press loading.


5


alignment and recording results


• Check mechanism travel is not restricted to limit loading force


• Inspect pans for blockages in drain pipes to ensure excess water not being held


Checking loading control system • On planned machine shut remove loading gauges and verify calibration against a calibrated source such as a dead weight tester


• Check air piping for leaks - on hydraulic systems leakage should be visible


• Remove and set pressure relief valves against calibrated source. Slowly increase pressure until relief valve lifts. Reduce pressure until it closes. Repeat three times, record results


• If system is air on water (to give damping) check liquid is at correct level. With final piston or diaphragm disconnected and supply pipe blanked off, cycle through loading pressure range and observe physical backlash in regulator.


• Mechanical aspects of the press loading


• Changes in actual weight of the mechanism


• Loading signal and equipment calibration


Checking physical installation


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