Rod Pumps and Components - Production Solutions

Each of the three types has inherent advantages that require its use under certain pumping conditions. Each has at
least one limitation that makes its use undesirable under other conditions. In many ways, any one of the three types
may do equally well, but under difficult producing conditions selection of the proper type is of greater importance. In
most cases, the experience of the operators in a given field will be the determining factor in selecting the proper type
of pump for a well. For further information, please see the API PUMPS section beginning on page 13.
The fourth letter is either C or M. A seating assembly employing seating cups is designated as C. A cup seating
assembly has the lowest first cost, and is a reliable means of seating a pump (one time only). When a cup seating
assembly is used, a slight interference fit between the cups and the seating nipple holds the pump down until the
well pumps up. A cup seating assembly has the disadvantage that when the pump is unseated, portions of the cups
frequently will tear away from the mandrel. A strainer nipple should be used to keep this debris from entering the
pump. In addition, on a rod part fishing job when a cup seating assembly is used, it is usually desirable to retrieve
the pump to change cups, even though the parted rod was at a shallow depth. This concern can be addressed with
the use of steel or brass friction rings; this configuration can be seated and unseated a number of times without the
danger of seating assembly failure. It is referred to as “FR” in the API designation nomenclature.
A seating assembly employing a metal seal is designated M. In the case of the API Mechanical Bottom Lock seating
assembly, the seal is generally brass or soft steel. Either of these can be reseated several times without replacing. A
spring lock holds the pump down while the well is pumping up.
In the case of the API Mechanical Top Lock seating assembly, these generally rely on precision ground stainless steel
rings which serve as both the no-go and the sealing ring when they engage a second stainless ring in the top lock
seating nipple in the tubing string. A spring lock holds the pump down while the well is pumping up. The Mechanical
Top Lock, like the Bottom Lock, can be reseated numerous times without replacing.
MonofloALS@nov.com • www.nov.com/ArtificialLift
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IntRoduCtIon