API RP 5A3
Recommended Practice on Thread Compounds for Casing, Tubing, and Line Pipe
|Publication Date:||1 June 1996|
The purpose of this recommended practice is to provide means for evaluating the suitability of thread compounds, regardless of composition, for use on API round thread and buttress casing, tubing and line pipe connections in high-pressure service. The tests outlined herein are used to evaluate the critical performance properties of thread compounds under laboratory conditions. When evaluating the suitability of a thread compound, the user should consider full size connection test results and field experience in addition to the results of reduced scale (bench top) test methods ike those described herein.
1.2 PERFORMANCE OBJECTIVE
The performance objective of this recommended practice is to provide laboratory means with which to compare the performance of thread compounds to a standard that has demonstrated successful performance over a wide range of service conditions and a significant period of time.
The thread compound formulations specified in obsolete API Bulletin 5A2 (Sixth Edition, 1988) were originally developed by the Mellon Institute of Industrial Research, under an API sponsored research project, to meet the following performance objectives:
a. Adequate lubricating qualities to prevent galling in threaded connections during makeup.
b. No tendency to disintegrate nor undergo radical change in volume at temperatures up to 300° F (148.9° C).
c. No tendency to become excessively fluid at temperatures as high as 300° F (148.9° C).
d. Sealing properties sufficient to prevent leakage at temperatures as high as 300° F (148.9° C).
e. Absence of any deleterious instability and of any drier or hardener that will evaporate or oxidize, thereby changing the thread compound properties.
f. Resistance to water absorption.
g. Sufficient inert filler to prevent leakage of API round-thread casing and tubing joints under pressure as high as 10,000 psi (68.9 megaPascals).
h. Readily applicable by brush to pipe threads in cold weather.
The "API Modified Thread Compound" has been generally accepted by the industry for a wide range of service conditions over a period of many years. Therefore, the API Bulletin 5A2 modified formulation is utilized as the basis for the Reference Standard in this recommended practice and may be found in Appendix A. This recommended practice replaces API Bulletin 5A2.
Another API sponsored research project, API PRAC Project 88, 89, 91-51, Investigation of Pipe Thread Compounds, indicates that limitation of particle size, solids content, grease thickeners and oil viscosity of API Bulletin 5A2 modified thread compound to the nominal range of tolerance is required in order to replicate performance properties. Therefore, in addition to the requirements found in API Bulletin 5A2, the Reference Standard is further limited to nominal parameters, as found in Section A.6, Appendix A, Reference Standard Formulation.
Note: It should be recognized that the service requirements for thread compounds can exceed the obsolete API Bulletin 5A2 requirements of "cold weather" application and 10,000 psi (68.9 megaPascals) and 300° F (148.9° C). Therefore, the extensive range of service conditions can require full size connection testing, field evaluation and engineering judgement to achieve acceptable performance.
1.3 METRIC CONVERSION
Metric conversion of US Customary units are provided throughout the text of this specification in parentheses, e.g., 6 in. (152.4 mm). The factors used for conversion of US Customary units to metric values are:
The following formula was used to convert degrees Fahrenheit (°F) to degrees Celsius (°C):
° C=5/9 (°F minus 32)