SEMI F18-95 GUIDE FOR DETERMINING THE HYDROSTATIC STRENGTH.pdf

SEM F18-95
GUIDE FOR DETERMINING THE HYDROSTATIC STRENGTH OF, AND
DESIGN BASIS FOR. THERMOPLASTIC PIPE AND TUBING
Purpose
5.1.1 1 /598-this test method consists of exposing
To identify a test method for measuring the hydrostatic
specimens of pipe/tube to a constant internal pressure
strength of thermoplastic pipe and tubing, a method for
while in a controlled environment. Such a controlled
estimating long-term hydrostatic strength, and recom-
environment may be accomplished by immersing the
mendations for developing design bases
specimens in a controlled-temperature water or air
bath. The time-to-failure is measured
2 Scope
5.1.2 2837- The procedure for estimating long
guide ref
rences the industry-recognized term hydrostatic strength is essentially an extrapola
Standard Test Method for determining the time-to-fail-tion, with respect to time. of a stress-time regression
ure of plastic pipe under constant internal pressure
line based on data obtained in accordance with ASTM
D 1598. Stress-failure time plots are obtained for the
selected temperature and environment: the extrapola
Standard Test Method for determining the long-term tion is made in such a manner that the long-term
hydrostatic strength of plastic pipe in order to obtain hydrostatic strength is estimated for these conditions
the hydrostatic design basis of the pipe material
5.2 PPI Jechnical Report
2.3 This guide references the Technical Report of
icies and procedures for developing recommended 5. 2. I 17-3/92 These policies and procedures are
hydrostatic design stresses for thermoplastic pipe
for development of recommendations for thermoplast
materials from 23'C to 93. 3 C(73F to 200F)
tic pipe compounds based on test data from good qua
ity pipes made by specific processing techniques
3 Referenced Documents
These recommendations may or may not be valid for
3.1 ASTM Standards
pipes made by differing processing techniques
D 1598 Standard Test Method for Time-to-failure 6 Comments
of Plastic Pipe under Constant Internal Pressure
6.I The Hydrostatic Stress Committee of the Plastic
D 283 Standard Test Method for Obtaining Hydro- Pipe Institute(PP])has recommended a minimum
static Design Basis for Thermoplastic Pipe Materials
safety factor of 200% based on the hydrostatic design
3.2 PP1 Technical Remor?
basis. The safety factor is intended to make allowance
for manufacturing and testing variables such as normal
Tr-3/92-policies and Procedures for Developing variations in the material, manufacturing process,
Recommended Hydrostatic Design Stresses for Ther-
nd in the evaluation pi
(ASTM
moplastic Pipe Materials
D2837andD1598
6.2 Appli
4 Terminology
consideration and may require an increased safety fac
Currently this document contains no terminology
tor. For example, with liquid hydrocarbons and other
chemicals, temperature can have a disproportion
5 Summary of Referenced Documents
effect on the long-term performance of the tubing or
5. 1 AST Standards
pipe. No general safety factor has been established for
these types of services, so each case should be
designed on its own merit
NOTE: It is strongly recommended that the user of
Mmericansocieny for esting and