Since the HDD market has improved considerably over the last two years, new rigs and remanufactured equipment are headed back into the field. There are still some “bones” out there to pick up that can save an operator some money if he is careful in what he purchases.
I penned most of the following article three years ago, but I have had enough calls recently that I thought it might be beneficial to revisit this topic once again.
In many instances, mud pumps have sat idle in this industry for up to five years. Given the fact that most of them did not have proper maintenance during their service life, they have sat with emulsified oil for a considerable period of time in extreme weather conditions. This is extremely detrimental to both the power frame, as well as the internal components. Rust could literally destroy a pump on the inside while the exterior could look reasonably good.
Pumps that run in continuous service generally do not have the problem with moisture forming in the power end. They tend to operate at the same temperature. Also, these type pumps are generally serviced on a regular schedule. Pumps that operate only sporadically will build moisture in the power end even if all their seals are good. The heating and cooling of the unit combined with the relative humidity of the air will form water. This is the precursor of rust.
Cost of a Used Pump
Just because an auctioned pump may sound cheap, once you factor in the cost necessary to rebuild a power end, it may be more cost-effective to purchase a new power end completely. It is the same thing as going to a car dealership and purchasing every component of a new car. It would be cost-prohibitive.
The only way to know what you are really getting for your dollars is to do a partial inspection. By removing the inspection cover, you can tell a great deal about the integrity of the power end. By running a magnet through the bottom of the cradle, any ground up shavings can be picked up. If there is a large amount of metal on the magnet, it would be probably better to let that one go. Also, a pump that has sat for a extended period of time, will show signs of rust on the walls of the power end, as well as the crank and other areas. If the power end seems relatively clean, it may be worth purchasing the pump if the price is right.
If the interior of the power end is rusty, it will be necessary to remove all parts and bead blast the interior. After it is properly cleaned, apply a new coat of rust inhibitor paint to the inside and install the power end components.
Of all power end components, the crankshaft will most likely be the most expensive. If the crankshaft is pitted in a few places, it may be possible to use fine emory cloth and polish the journals on the crank. Since a reciprocating pump runs at a slow rpm, a new set of connecting rod bearings may last for a considerable period of time and make this move cost-effective. The connecting rod bearings should be relatively inexpensive.
Cross heads and connection rods can generally be bead blasted and used again. Give the connecting rods a good coat of primer and they’ll probably be as good as new. In most instances, the cross head pin bushing is a form of bronze and the cross head pin is hardened and polished steel. If there is any pitting on the cross head pin or slack in the bushing, they will need to be replaced. This area is the smallest and has the greatest load bearing area of the entire power end. This fitting task is a precision task and must be performed correctly.
The main bearings are a critical area. If there is any pitting on either the bearing or the race, it needs to be replaced. At the same time, the correct shim setting on the crankshaft is necessary. This information will be available from the pump manufacturer, as well as all the other torque requirements for the power end components. This information should be available by request to the manufacturer, providing the serial number of the pump is supplied.
The next area to consider is the liquid end. Most of the liquid ends in this industry are manufactured out of ductile iron. Ductile is a great material. It is inexpensive and works well in an HDD application. However, there is nothing that can be done with ductile as far as repair. The same can be said for the ductile iron crankshafts.
The remainder of the liquid end expendables: valves, seats, valve inserts, plungers, plunger packing, pistons and liners are replaceable and should not be cost-prohibitive. Since most valve assemblies are manufactured from some form of stainless, they should be able to run again providing they are not washed and are equipped with new valve inserts. The plungers, in most cases, are some form of ceramic. Provided they are not pitted or scored, they should be reusable. Plunger packing should be considered expendable and replaced with new packing.
The same can be said of the pistons; they need to be replaced as time and temperature are their enemy. Piston liners manufactured out of ceramic (aluminum oxide) are probably good to go again. However, if the liners were manufactured out of hardened steel or are chrome-lined, they are probably no longer usable. Stuffing boxes and glands are also a consideration. Check to see that the threads on the gland, as well as the stuffmg box are still useable. A visual inspection of the interior of the stuffing box will be required. If the box is badly pitted or worn due to packing, it will be necessary to replace the box. The same procedure should be followed when inspecting a piston pump.
Ron Lowe is a marketing representative with Myers-Aplex, a Pentair Pump Co. All Drillmaster Reports are reviewed by the Drillmaster Advisory Board: Lowe; Frank Canon, Baroid Industrial Drilling Products; Richard Levings, Ditch Witch; Ed Savage, Vermeer Mfg. Co.; and Trevor Young, Tulsa Rig Iron.