Vylon Technical Sheet

HDPE RSC to PVC Stiffness Conversion

The ring stiffness constant (RSC) is a term which is calculated using the modulus of elasticity, moment of inertia and diameter for polyethylene pipe.  The pipe properties required for the calculation are normally given by the manufacturer.  The equation for calculating RSC is:

RSC=  Ring Stiffness, lb/ft of pipe

                                                                                                E=       Modulus of Elasticity, lb/in²

                                                                                                I=        Moment of Inertia, in⁴/in

                                                                                                D=       Mean Pipe Diameter , in

The RSC term is not equivalent to pipe stiffness per ASTM D 2412.  RSC can be converted to pipe stiffness for a comparison of pipe strength.  The conversion from RSC to pipe stiffness is calculated using the formula:

PS=     Pipe Stiffness, lb/in²

C=       Adjustment Factor

The C factor in the conversion equation is a term which will vary depending on the pipe material, size, and configuration.  An approximate value of 0.80 can be used to calculate the minimum pipe stiffness.  The pipe manufacturer should be consulted for product specific values.

Minimum Pipe Stiffness for Specified RSC’s

Pipe Diameter (in)	RSC 40 (psi)	RSC 63 (psi)	RSC 100 (psi)	RSC 160 (psi)
18	12.9	20.2	32.2	51.6
21	11.0	17.4	27.8	44.4
24	9.8	15.3	24.4	39.0
27	8.6	13.7	21.7	34.7
30	7.8	12.3	19.5	31.2
36	6.6	10.2	16.2	25.8
42	5.6	8.8	14.1	22.6
48	4.9	7.7	12.3	19.7
54	4.3	6.9	11.0	17.7
60	3.9	6.2	9.8	15.8