Aggregates Manager Digital Magazine
Issue link: http://read.dmtmag.com/i/878969
replaced. Used equipment should always be checked for the integrity of all safety items before use. Avoid unintentional damage Some equipment, especially vibratory, requires re-torqueing of bolts. This is a critical step; if missed, it can cause sig- nificant damage to equipment and prob- able loss of warranty. Check whether you need a torque-multiplier if the torque is higher than available tooling. Also, check what specification, such as lubricated or dry threads, is used. While lubrication schedules vary, check the quantity and type of grease/ oil required. Determine answers to ques- tions such as: is replacement of lubri- cant needed following a fixed time after start-up? Is the period based on environ- mental conditions? A seemingly obvi- ous (but not always heeded) guideline is that Zerk fittings should be cleaned be- fore engaging the gun and dirt cleaned around oil filling points. Inspect spent lu- bricants for contamination. In some cases, analysis should be carried out for tracing specific metals associated with certain types of failure. Don't be too quick to employ a pro- gram of preventive maintenance where teardown and reassembly is carried out 'just to check' — certain failure curves have the highest incidents of fail- ure immediately after initial start-up. Sometimes, the old adage "if it ain't broke, don't fix it" can be the best advice. This can be the case with pump glands, for example. Equipment-specific recommendations So, what equipment-specific things can we watch for in a typical wash plant? Scrubbers/trommels — Apart from lubrication, mounting alignment is very important to prevent permanent dam- age to tires and drives. Checking screen media condition is an obvious mainte- nance activity, but often forgotten are the internal lifters and advancing/retard- ing paddles, which can significantly af- fect performance if their height is below a certain critical point. Material will not rotate and interact effectively. Saving a few dollars by letting the lifter go for a month or so can cost much more in lost/ non-spec production. Screw-shaft based equipment — Wash plant equipment such as log washers, blade-mills, aggregate con- ditioners, coarse material washers, and fine material washers all have a common weakness — the lower bearing. There are various designs — from the complex 'submerged' bearing to the simple out- board pillow-block — and each claims an advantage, but all require lubrication. Paddles and flights need periodic inspec- tion. Any time metal paddles are used, take care, as worn edges can be razor sharp. Wear and fastenings are import- ant to check, as is checking their connec- tion point to the shaft. Check the shaft for run-out and any deflection at the shaft ends, as eccentric motion can cause pre- mature failure of bearings and even the shaft. Shaft straightening should be car- ried out by experienced personnel only. Pumps — These are the heart of a wet process. The correct selection of the materials of construction is critical to long-term, cost-effective service life. There are three key areas in any pump: wet end, gland, and bearings. It is im- portant, particularly with open-vane style impellers, to check the clearance be- tween the impeller and the suction side liner. Too wide a gap leads to bypass in- efficiency and, in slurry pumps, accel- erated wear. Impeller wear should be monitored, as reduction in performance is most likely due to impeller wear. Pump glands seal the pressure gen- erated inside the pump wet end from the outside. They come in various forms, in- cluding the industry standard packed gland, as well as proprietary glands and mechanical seals. Typically, they are 'set- and-forget' and last a full season, but it is critical that they are set up properly in the first place. This is one area of the pump where regular teardown and reassem- bly as 'preventive' is likely to cause more AGGREGATES MANAGER / September 2017 21 Be a cool operator Be a cool operator 1-800-267-2665 • sales@hammondac.com • www.hammondac.com When you work hard in small spaces, you need AC big time! With over 1200 different kits engineered and developed, count on Arctic Wolf™ for factory-style integrated air conditioning systems in ready-to-fit kits. Loaders. Dozers. Excavators. Graders. Tractors. If your equipment has an engine and a cab on it, we can put cool air into it. Call today. 1-800-2 MR COOL or go online at www.hammondac.com and order your system and parts today. 081-178 Equip World 4.5x4.5.indd 1 2016-06-01 2:18 PM Untitled-8 1 8/2/17 10:01 AM