Well Completion & Stimulation
Frac Pump Maintenance
Best practices prolong frac pump life and improve safety
Structuring a Maintenance Program
Fluid End Maintenance
July 29, 2011
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.