June 01, 2015 | SPOC Automation

Safety Features in the IronHorse VFD for Beam Pumps


Safety Features in the IronHorse Variable Frequency Drive for Beam Pumps

The IronHorse drive provides several safety features.

  • Termination point for local field safety shut downs. Most pumping unit installations include local field safety shut downs. These can include: environmental protection (‘enviro-pot’), vibration switches, flow line switches and tank battery shut downs. The IronHorse (IH) provides a termination point for the local field safety shut downs as a standard feature. If the end user has several safety kills they prefer to use at one time, all field safeties can be ran in series and provide VFD shut down.

  • Control (local or remote) lockout. The IH provides an HOA switch (Hand-Off-Auto). This feature lets the pumper prevent a switch from local to remote control (or vice versa), which can very important while working on a well. For example, if the pumper is on site doing a maintenance repair nobody should be able to startup the drive remotely. This is an important safety feature, for both the pumper and the pumping unit itself. It is also important that the pumper be able to switch to local while on site when the VFD unit is not near the pump itself. That way the pumper can adjust settings while directly observing the equipment, and it is important that nobody at this point be able to make changes directly to the drive.

  • High load limit. This safety setting is programmed at startup, specifying the maximum load that the motor provides during normal operations (startup and during peak loads). This limit is set for each individual well, because well and pumping units conditions are unique. High load limit faults indicate a mechanical issue and could possibly require service. If set properly, high load limit can potentially prevent catastrophic mechanical failure of the rod string and gear box. Here are three typical examples of high load limit issues:

    • The pump becomes ‘stuck’ down hole, causing the motor to torque up in an attempt to free the pump. This extra force could result in a rod part. If the running torque limit is set properly, the IronHorse will limit the extentof motor torque to a user-set value.  If  load exceeds these limits and hits the high load limit, the drive will shut down the pumping unit in an attempt to prevent potential downhole damage.

    • An over-tightened stuffing box creates a high load, which the IronHorse senses. The IronHorse shuts the unit down to prevent polished rod damage.

    • The gear box starts to bind up and the motor torques up. The IronHorse senses this and shuts the unit down to prevent gear box damage.

  • Pressure limits. The IronHorse comes standard with a pressure shut down safety function.  The end user can install a pressure sensor on the flow line or casing and tie the sensor back into the IronHorse.  The user sets high and low pressure shuts down limits.  

    • High pressure can be caused by a plug in the flow line, free flowing well, gas build up in the separator. The IronHorse will shut down on high pressure as the pressure builds up and reaches the end user’s setpoint.

    • Low pressure could result from a flow line leak. The IronHorse will shut down when pressure reaches the low limit.

Safety is an on-going concern in oilfield operations. Be sure your drive system is ahead of the curve and provides safety features that address key equipment and personnel risks.