CHAPTER 5 - INSPECTION OF WATER MEASUREMENT SYSTEMS
9. Weathered and Worn Equipment
Sharp-crested weir blades on older water measuring devices are often in bad condition. Weir blades are seen with dull and dented edges, discontinuous with bulkheads, pitted and covered with rust tubercles, and not vertical. Weir blades have sagged and are no longer level. Staff gages are worn and difficult to read. Stilling well intakes are buried in sediment or partly blocked by weeds or debris. Broad-crested weirs and flumes are frost heaved and out of level. Meter gates are partly clogged with sand or debris, and gate leaves are cracked and warped. These and other forms of deterioration often cause serious errors in discharge measurements. This type of deficiency is difficult to detect because, as mentioned before, deterioration occurs slowly.
Therefore, the person responsible for measuring devices must inspect them with a critical eye. The attitude should be: "I am looking for trouble," rather than: "I will excuse the little things because they are no worse today than they were yesterday." A series of little problems has often accumulated and compounded into large, unknown, and unaccountable errors. Poorly maintained measuring devices are no longer standard, and indicated discharges may be considerably in error. Worn devices should be rehabilitated to ensure true discharge readings.
Repairing or refurbishing a rundown measuring device is sometimes a difficult or impossible task. Fixing small problems as they occur will prevent, in many cases, replacing the entire device on an emergency basis, perhaps at great cost at some later date. Regular preventive maintenance will extend the useful life of measuring devices.