Manufacturers of non-API rods should specify the rod's allowable stress. Despite having high strength and a small cross-sectional area, it was expensive and ran into field support problems similar to those of flexible strands and CORODs. The weak point in the string is this rod. Fatigue of rods also was considered in
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This is because it has to support the weight of the rest of the small-diameter rod load, the pump and the very large fluid load on the gross seating nipple area.
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A hand-tight position is attained when full shoulder abutment is made and a 0. This is especially problematic if field welds are made and the rods are used in an inadequately protected corrosive environment.
Proper running, handling, and makeup procedures should be followed to secure maximum service from a rod dpec. Any variation in lubricants or in the surface finish of the threads or mating surfaces drastically changes these percentages, indicating that torque could 11 be a precision makeup method for sucker rods.
One of the earliest means used for designing tapered sucker-rod strings is in the Sucker Rod Handbook. The primary factor determining the proportion of each size of rod in the rod string is the size of the pump. Beforepercentages were calculated so that the unit stress on the top rod of each section from the weight of the rods in air plus the weight of the produced fluids on the gross plunger area is equal. However, typically only one grade of rod is used in the string to avoid mixing during running and pulling operations.
The development of the wave equation for sucker-rod lift by S. Adjustments to the predictions should be made for future troubleshooting and any further design changes.
Replacing a rod string one rod at a time is not normally a good operating spe thus, the economic life of a rod string needs to be considered if rods spef to fail. Non-API sucker rods generally fall into two groups: Society of Petroleum Engineers. This results in a significantly decreased run life. If the manufacturer and rod type are known, the actual yield-strength values should be used.
These rods take advantage of the newer alloys and heat-treating procedures currently available and are based on American Iron and Steel Inst. Sufficient calculations need to be done to assess the economic impact for all wells in a field.
Typically, the rod-string section will be replaced after two or three failures, while the entire rod string may be replaced after three or four failures. This page discusses rod types, design of the rod string, couplings, maintenance and replacement. The diameter sppec the pump plunger determines the fluid load lifted during the pumping cycle.
AISI or type steels, which have high tensile strengths.
Sucker-rod strings are lifting a apii deal of weight every cycle. Zaba  detailed the next refinement of sucker-rod loading, which was the organization of the Sucker Rod Pumping Research Inc.
Columns 6 through 11 in Table D. The primary factors affecting the selection and sizing of rods and the rod system are as follows:. Corrosion pits are one type of stress raiser. This enables operators to run 1-in. However, the ID of the seating nipple determines the fluid load that must be lifted to unseat the pump.
Combining this with the normally corrosive environmental conditions of water, H 2 S, CO 2etc. Torque measurement has been discredited as a sucker-rod-connection makeup method.
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Pony rods are sucker rods shorter than 25 ft, and they vary in length. The top rod in the bottom section normally has zpec highest stress in the string because it has the smallest cross-sectional area.
Because of the increased zpec and lower coefficient of friction, if properly surface treated, coupling-on-tubing wear is transferred from the rods—which are easy and less expensive to replace—to the softer tubing, which is more expensive to replace. Rod strings should be designed to enable the operator to unseat the pump without yielding any rod in the rod string.