# How to Calculate the Bend Radius of HDPE Pipe

January 24, 2022

Compared to many other pipe materials, high-density polyethylene (HDPE) offers greater flexibility. This unique characteristic allows pipes made from it to be bent to a tighter radius, which can significantly facilitate handling and installation operations since the components can be flexed to avoid obstacles or handle curvatures in the bore path during directional drilling.

The bend radius refers to the minimum (i.e., smallest) radius a pipe can be bent without experiencing kinks, damage, or otherwise degradation. While it is always measured to the inside curve of the bend, it refers to the minimum radius achievable for a long amount of time (i.e., long-term bend radius). Below, we cover how to calculate the minimum bend radius for HDPE pipe.

## Formula for Calculating the Minimum Bend Radius of HDPE Pipe

The minimum bend radius for HDPE pipe can be calculated using the following equation:

R = a(OD)

In the equation, R = minimum bend radius (in inches), a = minimum allowable bend ratio, and OD = the pipe’s outside diameter (in inches). The minimum allowable bend ratio value for a pipe varies depending on the length of time the pipe needs to be bent (i.e., long-term vs. short-term). Reach out to the pipe manufacturer for short term allowable bend ratios.

## Calculating the Minimum Long-Term Bend Radius for HDPE Pipe

The long-term minimum bend radius indicates how much an HDPE pipe can be curved for an extended period (e.g., years or decades) safely. Pipes with thick walls benefit from better resistance to kinking. However, they require greater force to bend and carry a higher risk of springing back forcibly if the proper safety measures are not taken.

The minimum long-term bend ratios for HDPE pipes to use in the above equation are as follows:

• DR 7 to 9 pipes have a minimum long-term bend ratio of 20 (i.e., their smallest allowable bend radius is 20 times their OD)
• DR 11 to 13.5 pipes have a minimum long-term bend ratio of 25 (i.e., their smallest allowable bend radius is 25 times their OD)
• DR 15.5 to 17 pipes have a minimum long-term bend ratio of 27 (i.e., their smallest allowable bend radius is 27 times their OD)
• DR21 and greater (lesser wall thickness) pipes have a minimum long-term bend ratio of 30 (i.e., their smallest allowable bend radius is 30 times their OD)

## Calculating the Minimum Field Bending Radius

When determining the minimum field bend radius, you’ll need measurements for the pipe diameter, wall thickness (DR), and whether or not pipe fittings will be present. The following formula can be used:

RF = minimum field bending radius in ft
D = pipe outside diameter, in (mm)