How often should a tensioning jack be calibrated?
2 Answers
Tensioning jacks should be calibrated every 6 months. Introduction to tensioning jacks: A tensioning jack is a specialized hydraulic jack used for tensioning prestressed tendons such as steel strands. The tensioning jack must be used in conjunction with a tensioning oil pump, with both the tensioning and retracting power provided by the high-pressure oil from the pump. Depending on their structure, they are categorized into front-clamp jacks and through-hole jacks. Tensioning jacks feature compact structures, stable operation during tensioning, high oil pressure, and substantial tensioning force, making them widely used in prestressed construction projects such as highway bridges, railway bridges, hydroelectric dams, and high-rise buildings. The accuracy of the tensioning force value of a prestressed tensioning jack directly affects project quality and safety. Therefore, calibration to provide accurate and reliable testing data is crucial. Calibration precautions: Appearance and accessories: The main body of the jack and its major components should have nameplates indicating the product name, model, serial number, manufacturer, etc. Jack equipment should be calibrated and used as a matched set; recalibration is required after replacing major components. Indicator: For analog indicators, the dial scale and markings should be clear, with no loose or bent pointer. During force application, the pointer should move smoothly without sticking or jumping. Operational adaptability: The oil pump of the jack should apply and release force steadily, without pressure fluctuations that hinder readings, and without impact or vibration.
I've been in this line of work for almost twenty years, dealing with jacks every day. According to the regulations on our site, the calibration cycle mainly depends on two indicators: either after 200 uses or every six months, whichever comes first. I recommend being even more diligent, especially during the rainy season with high humidity or when working in high summer temperatures—it's best to check every three to four months. Last week, one of our pump stations had a sudden pressure drift of 10%, all because calibration was delayed too long. Don't skimp on the inspection fees; if calibration fails, the entire prestressed beam will need rework, and the loss would be enough to buy ten new jacks. Also, make sure to regularly check the hose connections and pressure gauges yourself, and stop using them immediately if any issues are found.
