Tom Blackwood Forum Moderator 18 Posts
Re: How to Avoid a Break in the Main Shaft Screw21 July 2009 at 1:29pm
There are a variety of torque limiting couplings on the market and they all either slip or disconnect to avoid breaking the shaft. Many of the better manufactures will supply a slip clutch or a limiter with the equipment. I would contact your equipment supplier for the best device. If they don't have one, just Google the term "torque limiting coupling." However, a torque limiter may not be the best solution and can cause production problems (product quality, downtime to clean the screw) due to the slip of the drive. It may be better to redesign the screw to avoid high torque. I would do some shear testing of the material over the range of moisture in the screw to see what the correct screw design should be. It may be a more reliable solution to replace or use a different screw design, which will not have periods of high torque.
We have a twin screw conveyor for transferring Na2SO4 as per spec data below. To avoid a break in the main shaft screw, I would like to install a torque limiter for safety device. What is your opinion and is there a best way to do this? Is there any torque limiter product that accommodates our screw design? See the data below: Product to be handled: Sodium sulphate (salt) Chemical formula: Na2SO4 Density at 20 degree C: 2700 kg/M3 Bulk density: 1500 kg/M3 Shape of particles: Rhombic Sieve analysis: - above 0.1 mm: 70% by weight - 0.06 0.1 mm: 15% by weight - below than 0.06 mm: 15% by weight Average particle size: 0.18 mm Specific particle surface area: 68 M2/kg Total throughput: 6000 kg/hrs dry salt, 6250 kg/hrs wet salt Temperature: 40 degree C Residual moisture: 3% - 4% by weight Material of construction: - all wetted parts: SS 316L - all non wetted parts: SS 316L Speed of screw conveyor: Fixed 36 rpm Electrical data: 380/680 V, 50 Hz, IEC standard, IP 53, non explosion proof, F insulation class Spec for geared motor: SEW EURO drive R107DV132M4, 7.5 KW, 36 rpm
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