Chance Breeze is an outside sales representative for Gardner Denver. During his more than 20 years in the industry, he has worked as a pump mechanic and international field service technician. His areas of expertise include extensive mechanical knowledge of cementing, acidizing, nitrogen and frac pumps.
There are two sides to every story. On one hand are the frac pumps that customers find on websites, in brochures, and at trade shows. These new pumps are pristine, freshly-painted monuments to advances in engineering technology.
However, an often-ignored reality is seen by district managers and maintenance mechanics, who see examples of the damage and abuse that frac pumps take on a daily basis.
These damaged pumps and fluid ends that inspired this article. To ensure the safest possible working conditions for operators in the field, pumps must continue to perform better. Improved performance and reliability are also key factors influencing the bottom line.
Engineering teams across the industry have been hard at work designing pumps that can withstand the conditions imposed by unconventional plays. Now, the industry’s maintenance programs must rise to meet the challenge.
Structuring a Maintenance Program
Having the appropriate tools, resources, and training is the foundation of any good maintenance program. As a start, maintenance managers will need to ensure that operators and mechanics have the correct tools to perform maintenance. This may seem relatively straightforward, until the number of different pump models and brands on the market is considered. Many oilfield service companies will mix and match pumps and fluid ends, further complicating the issue.
In addition to tools, field personnel should also be provided with the right resources and information to properly maintain their pumps. Many of the most successful maintenance programs create booklets that detail important guidelines for pump maintenance. As an example, an effective guide might include:
- A service manual
- A parts list
- Torque and clearance specifications
- A guide to replacing expendable parts
- A guide to removing and reattaching the fluid end
- Any technical bulletins from the manufacturer
- A pump maintenance schedule
As a reminder, this guide should include information covering each power end and fluid end that the operator may encounter on the job because specifications for each brand and model may differ.
If questions remain on how to develop such a booklet, the pump manufacturer will likely be able to help. Finally, it is also a good idea to take field conditions into account. Laminating the pages in any instructional manual will ensure that it remains useful in the dirt and grime of the oil patch.
The final cornerstone of any maintenance program is continual training. Even if operators and mechanics have a wealth of experience behind them, all new maintenance professionals should be trained to your company’s policies shortly after coming on board.
Periodic classes should be held to ensure that skills remain sharp and that maintenance shortcuts are not replacing manufacturer recommendations. Advancing experienced operators from a field role to a training role can also be an effective way to keep the company’s best people challenged and engaged.
Finally, keep in mind that training should be both informative and interesting. Some ways to make training classes more dynamic might include:
- Incorporating both hands-on examples and academic lessons
- Inviting guests such as pump or parts manufacturers
- Using the internet and other technological solutions to increase involvement
Fluid End Maintenance
Maintaining the fluid ends on frac pumps is a difficult process that can be made easier by combining steps. For example, one of the most frequent maintenance procedures conducted on the fluid end is replacing the valves and seats. Operators should use this opportunity to inspect the interior of the fluid end.
After removing the retainer nut, the threading on the retainer nut and the fluid end should be visually checked for cracked or broken threads. Valves and seats should be changed simultaneously once wear on the seat reaches 0.015 to 0.030 inches, or approximately the thickness of a thumbnail.
Another reasonable rule of thumb is to replace valves and seats after every other stage. Valve springs should also be replaced regularly. By combining tasks, the entire process will prove more manageable. When replacing the valves and seats, the seat decks should be inspected for thin cracks or indications of a wash-out. Consistent application of these procedures prolongs the life of frac fluid ends and protects field personnel.
Improper replacement of packing is the second most common mistake made when performing fluid end maintenance. If using adjustable packing, the exterior of the fluid end should be marked to indicate when the packing is fully in place. If employing non-adjustable packing, the packing nut should be flush with the face of the block.
In terms of proper installation, operators should have a visual guide in their training materials that illustrates the direction and order of the particular brand of packing being used. Additionally, all packing elements should be replaced at each change out. Semi-hard elements, such as the junk ring, may seem more resilient than the rubber rings, but experience has shown that it is difficult to detect flaws in these semi-hard elements.
Finally, the operator should take the opportunity to inspect the packing bore for wear patterns that could indicate a wash-out. Giving the plunger, plunger clamp, and packing nut a quick glance before reassembling the unit is an ideal last step to ensure a thorough packing change.
Maintaining the Power End
The next major maintenance area is the power end. Most experienced repair technicians say that 60 percent to 70 percent of damage sustained by the power end is caused by problems with the lubrication system. For a frac pump to function effectively and safely, lubrication oil must be kept pressurized, clean, and cool. Therefore, it makes sense to concentrate resources on this particular system.
Lube pumps should be replaced annually to ensure that no mechanical deficiencies are present. The lube system should be flushed, cleaned, and checked for leaks as specified by the manufacturer or maintenance supervisor. The strainer should be cleaned and the oil filter should be replaced regularly.
Another extremely effective method that has been employed by more advanced maintenance programs is the use of oil sampling. For example, assume that the oil in the frac pumps is changed every 100 hours. One could take a sample of the oil at 70 hours to check for any problems that may be putting the pump at risk before its scheduled maintenance. Keeping the lubrication system fully operational is one of the best investments that a company can make.
Opening the unit to check individual components is also critically important. When operating at such high pressures, one small problem can create hundreds of thousands in damage to a frac pump.
With such high stakes, it is imperative that the internals be examined. Specifically, the rod bearings and thrust seats should be visually checked every three to six months, depending on operating conditions. Moreover, the bull gears, pinion bearings, and pinions need to be checked on approximately the same schedule. These practices may be cumbersome, but they pay dividends to those who follow them.
As a final topic for maintenance, one cannot ignore the importance of checking and retorquing the fastener systems on a frac pump. Driveshaft universal joints should be inspected periodically for wear, and fasteners should be retorqued. Stay rods should also be visually checked for alignment and condition. Finally, the stay rods should be torqued to manufacturer’s specifications in the order specified in the operations manual.
The industry will continue to refine its maintenance programs. Maintenance managers will encounter a variety of limitations—both financial and cultural. Nevertheless, the gradual emergence of the fact that good maintenance procedures are an investment, rather than an expense, will take hold. When service companies rely more heavily on experienced operators, mechanics, and OEM partners, effective maintenance will become a source of pride, rather than frustration.
Upstream Pumping Solutions, Winter 2011