Pump jacks are essential oilfield equipment that bring petroleum from deep underground to the surface. A specialized load cell mounted on the pump’s polished rod measures the load being lifted – important information for effective pump-off control.
A pump jack goes by many names in the extraction industry: beam pump, sucker rod pump, rod pump, oil horse, oil derrick – to name a few. These units work 24/7, in oilfields ranging from tundra to desert, to artificially lift well fluid to the surface.
Gauges and sensors at critical points in the sucker rod pump system serve to monitor and control the working pressures, exerted forces, and fluid levels. One of the key instruments is the polished rod load cell for pump-off control.
Pump-Off Control for Sucker Rod Pumps
Pump jack with load cell sensor installed on the sucker rod’s bridle (circled)
Located at the top of the sucker rod string, the polished rod is the strongest part of the line that’s inserted into the well’s tubing. The sucker rod moves steadily up and down to draw up well fluid using a system of opening and closing valves. This rod also seals off the well fluid so that it enters the flow line only and does not escape into the atmosphere.
A pump-off control system ensures that the reciprocating pump is operating efficiently and effectively. This technology has become an industry standard because it enhances safety and pump performance. Pump-off control systems:
- Save energy and protects equipment from excess wear by decreasing pumping cycles when the output is lower.
- Maximize production by increasing pumping cycles when the output is higher.
- Help extend the life of wells by controlling the amount being extracted.
- Save money by limiting cycles during peak demand periods (if connected to the electrical grid).
- Save time and maintenance costs by reducing stop-and-start incidents caused by exceeding the beam unit’s rated capacity.
- Protect equipment by preventing the rod from continuing to pull when the sucker rod string becomes stuck in the casing string
For these reasons, today’s sucker rod pumps come preinstalled with pump-off control systems, and older ones are being retrofitted with them.
Load Cell for Pump-Off Control Systems
A pump-off control system is made up of these main components:
- Load cell sensor installed on the sucker rod’s bridle
- Load cell cable to transmit a 2 mV/V signal to a strain gauge amplifier, which provides a 4…20 mA signal to the rod pump controller
- The electrical control unit, which contains the POC (pump-off controller), the VFD (variable frequency drive), and the SCADA (supervisory control and data acquisition) system.
F9870 polished rod load cell
WIKA’s F9870 is a compression (strain gauge) load cell specifically engineered for the polished rods of pump jacks. Its hermetic construction and sturdy steel body, along with shock and vibration protection, allows the polished rod load cell to be used in extreme outdoor conditions and ambient temperatures from −40°F to 175°F. The F9870 is available in the standard ranges of 0…30,000 lbs. and 0…50,000 lbs., with an overload protection of 200% of capacity. This force transducer’s high accuracy (≤ ±0.50% full scale) means precise control and greater reliability, with a proven 2 mV/V output signal.
With an industry-standard mounting configuration, the F9870 is easily integrated into new or existing pump-off control applications and is compatible with most pump-off control units. We also offer washer sets for installation. The F9870 polished rod load cell includes international certifications (CSA, ATEX, IEC, IECEx) for use in hazardous locations.
WIKA USA, Smart Sensing for Pump-Off Control Systems
Among WIKA USA’s product experts are specialists in oil and gas (upstream, midstream, and downstream), force measurement, and pumping systems. The F9870 polished rod load cell is just one of the many force sensors designed and manufactured by WIKA Sensor Technology, which has a state-of-the-art facility near Columbus, Ohio. Contact us for more information about measurement solutions for pump jacks and other artificial lifting systems.
Product mentioned in this article:
• F9870 polished rod load cell