Durcor® Design & Specification


Expansion Data

Durcor Wall Thickness Calculations Based on ASME B31.3 Chapter VII

Ref. Section A304.1.2 "Straight Pipe Under Internal Pressure"

For RTR (Filament Wound) and RTM (Centrifugally Cast) Pipe

t = PD/(2SF + P)

Based on Section A302.3.2, the design stress (S) is determined by one-tenth of the minimum tensile strength of Durcor. The tensile strength of Durcor is 43,500 psi, therefore, the (S) is determined to be 4,350 psi. The conservative service (design) factor is 0.5.

Wall Thickness
In all cases, wall thickness exceeds minimum pressure
design thickness using the 0.5 service (design) factor.
Size (in) Gage Pressure Calculated Wall (in) Actual Wall (in) Actual/
1 275 .080 .160 2.00X
1-1/2 275 .115 .155 1.35X
2 275 .140 .150 1.07X
3 225 .172 .215 1.25X
4 200 .198 .240 1.21X
6 175 .256 .285 1.11X
8 150 .288 .325 1.13X

Design for Expansion and Contraction

Simple supported Durcor piping can be easily designed by considering the degree of thermal expansion along straight runs of pipe and any possible pressure thrusts created by closed end systems.

Length changes due to thermal expansion in an unrestrained condition

All piping materials will expand linearly with increasing temperature when in an unrestrained condition. Durcor piping exhibits extremely low expansion rates with increasing temperatures. However, these changes do need to be considered in piping design. The amount of linear thermal expansion of Durcor pipe is consistent over the operating range and is determined to be 6.7 X 10-6 in/in/°F (1.2 X 10-5 in/in/°C).

The formula for determining expansion:

Delta L = a*L * Delta T

Example: Determine how much thermal expansion to expect when installing 300 feet of Durcor piping at 70°F intended to operate at 200°F.

Expansion formula example

Thermal Expansion

The effect of thermal gradients on piping systems may be significant and should be considered in every piping system stress analysis. Pipeline movements due to thermal expansion or contraction may cause high stresses or even buckle a pipeline if improperly installed. Several piping system designs are used to manage thermal expansion and contraction in above ground piping systems. They are listed below, according to economic preference:

  1. Use of inherent flexibility in directional changes
  2. Restraining axial movements and guiding to prevent buckling
  3. Use expansion loops to absorb thermal movement
  4. Use mechanical expansion joints to absorb thermal movement

To perform a thermal analysis, the following information is required:

  1. Isometric layout of piping system
  2. Physical and material properties of pipe
  3. Design temperatures
  4. Installation temperature (final tie-in temperature)
  5. Terminal equipment load limits
  6. Support movements
Durcor® vs. Competition
Temperature Change (°F) Durcor Fiberglass PVC CPVC Carbon Steel Stainless Steel
25 0.20 0.31 0.90 1.14 0.22 0.27
50 0.40 0.61 1.80 2.28 0.44 0.54
75 0.60 0.92 2.70 3.42 0.65 0.82
100 0.81 1.23 3.60 4.56 0.88 1.09
125 1.00 1.54 4.50 5.70 1.10 1.36
150 1.21 1.84 5.40 6.84 1.32 1.63
175 1.41 2.15 6.30 7.98 1.54 1.90
200 1.61 2.45 7.20 9.12 1.76 2.17

Unrestrained Piping

Unrestrained Durcor piping will not exhibit a measureable change in length due to the thrust effects of internal pressure. This is unique for fiberglass reinforced piping. Typically, accommodations for growth must be factored for FRP piping as the axial elastic modulus of typical FRP piping is significantly less than the radial elastic modulus. Due to this anisotropic property and combined with Poisson’s ratio, growth for typical FRP piping from internal pressure thrusts from 150 psi can be from 1/4” to 1/2” per 100 feet of piping.

The axial elastic modulus of Durcor piping (2.76 X 10,6 psi) is over 50% greater than that of typical FRP pipe. With a radial elastic modulus of 2.10 X 106 psi, the axial component accounts for the majority of the stiffness of the pipe. This relativity results in un-measureable growth from internal pressures. Length growth from pressure thrust in unrestrained Durcor piping is only .03-.06 in/100 ft.

Unrestrained Thermal Expansion Uninsulated
Change in Temperature (°F) Pipe Change in Length
(in/100 ft)
25 0.20
50 0.40
75 0.60
100 0.81
125 1.00
150 1.21
175 1.41
200 1.61