Proper maintenance is a must in order to keep headworks screens working correctly and to extend their life
The headworks screens are the first line of defense for any wastewater facility. Their proper operation is crucial to protect all of the sensitive treatment processes that lie within the fence line. Unfortunately, like all equipment, they do not take care of themselves.
Brian Prunty, JWC Environmental’s field service manager from the Service Solutions group, explains what a plant’s operations staff should be considering for the upkeep of their headworks screens.
Q. What is the number one item that causes problems with screens?
By far the most critical item in any in-channel screen is the primary chain. Chains will naturally stretch over time and this is the killer of many screens. If left unchecked the chain will stretch to the point where an expensive catastrophic failure will occur. A little preventive maintenance can head off this type of failure.
Q. What should an operations or maintenance staff be looking for in chain stretch?
There are a few tell-tale visual signs of the chain stretching. One is that the rollers can get oblong as the chain extends. Also the outside of the chain can get shinny spots, indicating that the chain links are scraping on the bottom of the channel. Additionally operators should be looking for rollers that are flattening out over time. Some of this can be corrected by simply tensioning the chain but if there is not adjustment left in the tensioning or the chain is at the end of its useful life then it needs to be replaced.
Q. What are some other maintenance items to be looking at?
For bar type screens like JWC’s Chain & Rake Monster operators will want to make sure that the scraper arm is making good contact with the rakes and removing the solids. Additionally you should make sure that the rake teeth are in good condition and not retaining excessive debris.
For fine screens it is important to look at the brush systems and spray wash used to remove debris from the screening panels. Brushes will wear over time and spray nozzles can get plugged. It is also not uncommon for the plant water supply pressure to change and the spray nozzles may not be removing as much as they were when the screen was installed. If the solids removals elements are not working correctly then carryover of solids can be an issue.
A nice feature that JWC now has available on its Finescreen Monster is a brushless design. By combining our UHMW panels with a dual spray wash system we have been able to eliminate the need for a cleaning brush — and therefore eliminating one maintenance item.
Q. How do you go about a major overhaul on a screen?
There are certainly many schools of thought on this. Some plants will want to take it on themselves, which I think is great if the staff has the time and the training to do so. However, the screen manufacturer obviously does not warrant this work.
A few screen manufacturers have the capability to overhaul screens in various manners. Some companies will require the screen to be removed from the channel and shipped back to the factory for rebuild, which is a pretty costly endeavor.
At JWC, our Service Solutions group has the skills and ability to rebuild the screens on-site. A typical rebuild from JWC would include new chain, new bearings, new chain supports, replacement brushes, new seals and other wear items as well. We basically bring it back to a like-new condition and provide a new one-year manufacturer’s warranty. This is a very economical solution for our customers to significantly extend the life of their headworks screens.