Differential Hydraulic Flow Indicators

As a torque motor is engaged and resistance is applied against it (helical pier installation), hydraulic fluid into and out of the unit must increase as resistance increases. Measuring the hydraulic flow rates and difference between inflow and outflow sounds simple enough, but how does that correlate to torque? That is where the manufacturer of the torque motor comes into play. Torque motor manufacturers provide specifications that indicate the amount of resistance being applied to the drive unit based upon the differential hydraulic pressure. That is the connection.

However, there is a drawback to using this method. Torque motors can deviate over time up to 15% from the manufacturer’s original specifications. This condition requires the torque motor to be re-calibrated on a somewhat regular basis. Many times engineers will add a 20% safety factor on installation torque for this very reason.

Summary

Hydraulic differential torque indicators are easy to set up and install and offer real time pressure readings. These, of course must be converted into torque using a chart of some sort. They are reasonably accurate, but they do require periodic calibration. Differential torque indicators cost more than shear pins but less than strain gauges. Some models can output data to Microsoft Excel for analysis and archiving - which can be a big plus. Torque should be carefully monitored by every helical pier installer and these products get the job done.

Differential Hydraulic Flow Indicators: