Proper preventive maintenance can save expensive repairs and keep pumping units in production.
Pumping unit preventive maintenance isn’t rocket science, but it does require thorough attention to details. It’s an important service, because proactive is always less expensive than reactive, says Michael Romines, president of Acme Oilfield Services in east Texas.
“We recommend having it done every six months – after the harshest seasons of winter and summer,” he says. Most of Acme’s customers contract for the twice-yearly maintenance, though once a year is occasionally enough for units that don’t run 24/7.
Acme handles about 750 full-service pumping unit inspections and maintenance calls per year, utilizing a specially designed truck that includes 500-gallon clean and dirty gear oil tanks, a grease keg, a 500-pound crane and an air compressor. The truck allows workers to do eight to 10 inspections a day.
On a typical call, technicians take 45 to 90 minutes to inspect the structure with the AcmeServ 26-point inspection system. “Basically it’s twofold, a visual inspection of the structure’s condition and all the moving parts – the bearings, the gears and things of that nature,” Romines says.
He outlines the process his company follows:
- Lock out and tag out to shut down the pumping unit.
- Visually inspect the exterior of the unit and the engine/motor. Is the unit level and aligned? What is the condition of the belt and brake? Are there any structural cracks? Is the bridle frayed?
“It’s very important because the pumping unit is tied to the bottom hole pump in the well,” he says. “The bridle is holding the rod string that’s in the well directly connected to the bottom pump. So just a crack can throw a little tweak in how that pumping unit rotates and the revolutions it makes.”
Meanwhile, the prime mover (gas engine or electric motor) continues to move, which can result in a broken pitman arm or wrist pin freeze-up. “We’ve seen pumping units throw a beam 10-15 yards across the location,” Romines says.
The worker rates the condition and makes notes of any problems he sees on all of the unit’s parts.
- Remove caps and inspect grease and gear oil for metal shavings or contaminants on the main structure and the gearbox.
“On the structure and structural bearings, we lubricate all the moving parts on every trip,” Romines says. The only thing not automatically changed is the gear oil that lubricates the gear string. The oil lasts a couple of years on well-made pumping units, and since larger units take up to 55 gallons, it adds to the cost. Most of Acme’s clients preauthorize workers to change the gear oil as they deem necessary. Others require a call for approval.
- Once the lubrication is completed and the inspection form is filled out, the worker starts up the pumping unit and does a general cleanup of the area (part of Acme’s service package). If there are serious problems, he keeps the unit turned off.
Customers are sent a copy of the form if there are no serious issues. But if there are failing grades for anything, an Acme customer manager calls the customer to set up a meeting to make recommendations about changing bearings, gaskets and seals, and other services.
“Typically, the most common [serious] thing we find is the need for wrist pins to be changed out,” Romines says. “They are the most vulnerable, because they are the connection point between the elevated piece of the unit and the heavy-duty gearbox. If they have a failure, so many things can be further damaged.”
At $2,700 to $3,500 wrist pin replacement may seem high, but it’s much better than the alternative – major breakdowns.
That happened recently to an operator who didn’t think regular maintenance was necessary, Romines notes. Acme received a call because the unit “wrecked” – it wasn’t going up and down. Something gave way on the pumping unit – most likely a bearing failed or froze up so it quit running in circles. And when it quits the prime mover continued to move, and in this case it pitched the beam off the pumping unit. The customer faced a $15,000 to $22,000 repair.
“Had we been out there three months ago, we might have seen that a bearing was not properly lubricated and was starting to fail in the wrist pins,” Romines says.
It makes the case for preventive maintenance services, he adds, “to result in more run time, less downtime."