Aggregates Manager Digital Magazine
Issue link: http://read.dmtmag.com/i/742224
AGGREGATES MANAGER / November 2016 27 strainers need to be inspected regularly and cleaned or replaced as necessary. The spray system should be equipped with a pressure gauge. A decline in spray pressure indicates a dirty strainer and will provide maintenance personnel with a metric for frequency of inspection. Most conventional spray systems use centrifugal pumps that are self-lubricating and do not require any regular maintenance. If you have a 'fog' system that uses a positive displacement pump, it will require regular oil changes and may be more susceptible to wear. It's also a good idea to have a spare pump and motor on hand in case of a mechanical failure or freeze damage. Solenoid valves can be another sore point, particular- ly when the water supply is dirty or contaminated with sand. Dirt and grit that build up on the valve seat can prevent it from closing properly. If spray nozzles keep on running or dripping after they have been shut off, that's a good indication that the solenoid is dirty and needs to be cleaned or replaced. If you are thinking about installing a spray system, here are some guidelines to reduce spray system main- tenance: 1. Use heavy-duty components designed to operate in an abusive environment. 2. In cold weather climates, house the pump in a heated enclosure. 3. Use the cleanest water possible. Using dirty pond or river water will make nozzle, filter, and pump mainte- nance a nightmare. 4. Install drain valves at all the low points. Frozen lines can delay start-up on a cold morning and that means lost production. 5. Put nozzles where they can be seen and are easy to access. Out of sight is out of mind. 6. Consolidate all moving parts in a central location with the pump. Solenoids and filters out in the plant are more likely to be damaged or freeze and take more time to inspect and maintain. 7. Most nozzle pluggage occurs from the outside-in due to deposition of wet fines that blow back onto the nozzle — particularly at crusher discharges. Install nozzles so that they are out of the way of this "blow- back" or put a dust curtain in front of them with a small hole that nozzles can spray through. 8. Keep a list of all nozzles and their locations to facilitate ordering and replacement. Baghouses Most modern baghouses are "pulse-jet" that periodically and sequentially pulse reverse air through the filter media to keep them clean. The differential pressure across the filter bags, as measured by a magnehelic or photohelic gauge, is an indicator of perfor- Deposition on spray bars is a common cause of nozzle pluggage. Workers get their greatest exposure to silica-containing dust when they have to clean up spillage resulting from inadequate enclosure. Protect nozzles from depostion that can plug them up by install- ing a dust curtain that protects them from the "blowback" of mist and wet fines.