# 255.121 Design of plastic pipe.

- **operation:** document
- **citation:** 16 NYCRR 255.121
- **title:** 255.121 Design of plastic pipe.
- **source type:** regulation
- **agency:** New York State Public Service Commission
- **status:** current
- **official:** true
- **published on:** Not available
- **effective on:** Not available
- **summary:** Transmission and Distribution of Gas. (a) Design formula. Design formulas for plastic pipe are determined in accordance with either of the following formulas:

P = 2StDF/(D − t)

P = 2SDF/(SDR − 1)

Where:

P = Design pressure, gauge, psig (kPa).

S = For thermoplastic pipe, the hydrostatic design basis (HDB) is determined in accordance with the listed specification at a temperature equal to 73°
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**body:**

(a) Design formula. Design formulas for plastic pipe are determined in accordance with either of the following formulas:

P = 2StDF/(D − t)

P = 2SDF/(SDR − 1)

Where:

P = Design pressure, gauge, psig (kPa).

S = For thermoplastic pipe, the hydrostatic design basis (HDB) is determined in accordance with the listed specification at a temperature equal to 73°F (23°C), 100° F (38°C), 120°F (49°C), or 140°F (60°C). In the absence of an HDB established at the specified temperature, the HDB of a higher temperature may be used in determining a design pressure rating at the specified temperature by arithmetic interpolation using the procedure in Part D.2 of PPI TR-3/2012, (incorporated by reference, see section 255.7 of this Part). For reinforced thermosetting plastic pipe, 11,000 psig (75,842 kPa).

t = Specified wall thickness, inches (mm).

D = Specified outside diameter, inches (mm).

SDR = Standard dimension ratio, the ratio of the average specified outside diameter to the minimum specified wall thickness, corresponding to a value from a common numbering system that was derived from the American National Standards Institute (ANSI) preferred number series 10.

DF = Design Factor, a maximum of 0.32 unless otherwise specified for a particular material in this section.

(1) Except as provided in subdivisions (c) through (f) of this section, the design pressure for plastic pipe may not exceed a gauge pressure of 100 psig (689 kPa) for pipe used in:

(i) distribution systems; or

(ii) transmission lines in Class 3 and 4 locations.

(2) Plastic pipe may not be used where operating temperatures of the pipe will be:

(i) below -20°F (-29°C), or below -40°F (-40°C) if all pipe and pipeline components whose operating temperature will be below -20°F (-29°C) have a temperature rating by the manufacturer consistent with that operating temperature; or

(ii) above the temperature at which the HDB used in the design formula under this section is determined.

(3) Unless specified for a particular material in this section, the wall thickness of plastic pipe may not be less than 0.062 inches (1.57 millimeters).

(4) All plastic pipe must have a listed HDB in accordance with PPI TR-4/2012 (incorporated by reference, see section 255.7 of this Part).

(1) For PE pipe produced after July 14, 2004, but before January 22, 2019, a design pressure of up to 125 psig may be used, provided:

(i) the material designation code is PE2406 or PE3408;

(ii) the pipe has a nominal size (iron pipe size [IPS] or copper tubing size [CTS]) of 12 inches or less (above nominal pipe size of 12 inches, the design pressure is limited to 100 psig); and

(iii) the wall thickness is not less than 0.062 inches (1.57 millimeters).

(2) For PE pipe produced after January 22, 2019, a DF of 0.40 may be used in the design formula, provided:

(i) the design pressure does not exceed 125 psig;

(ii) the material designation code is PE2708 or PE4710;

(iii) the pipe has a nominal size (IPS or CTS) of 12 inches or less; and

(iv) The wall thickness for a given outside diameter is not less than that listed in the following table:

Pipe size (inches) | Minimum wall thickness (inches) | Corresponding SDR (values)
1/2″ CTS | 0.090 | 7
3/4″ CTS | 0.090 | 9.7
1/2″ IPS | 0.090 | 9.3
3/4″ IPS | 0.095 | 11
1″ CTS | 0.119 | 11
1″ IPS | 0.119 | 11
1 1/4″ IPS | 0.151 | 11
1 1/2″ IPS | 0.173 | 11
2″ | 0.216 | 11
3″ | 0.259 | 13.5
4″ | 0.265 | 17
6″ | 0.315 | 21
8″ | 0.411 | 21
10″ | 0.512 | 21
12″ | 0.607 | 21

(1) For PA-11 pipe produced after January 23, 2009, but before January 22, 2019, a DF of 0.40 may be used in the design formula, provided:

(i) the design pressure does not exceed 200 psig;

(ii) the material designation code is PA32312 or PA32316;

(iii) the pipe has a nominal size (IPS or CTS) of 4 inches or less; and

(iv) the pipe has a standard dimension ratio of SDR-11 or less (i.e., thicker wall pipe).

(2) For PA-11 pipe produced on or after January 22, 2019, a DF of 0.40 may be used in the design formula, provided:

(i) the design pressure does not exceed 250 psig;

(ii) the material designation code is PA32316;

(iii) the pipe has a nominal size (IPS or CTS) of 6 inches or less; and

(iv) the minimum wall thickness for a given outside diameter is not less than that listed in the following table:

Pipe size (inches) | Minimum wall thickness (inches) | Corresponding SDR (values)
1/2″ CTS | 0.090 | 7
3/4″ CTS | 0.090 | 9.7
1/2″ IPS | 0.090 | 9.3
3/4″ IPS | 0.095 | 11
1″ CTS | 0.119 | 11
1″ IPS | 0.119 | 11
1 1/4″ IPS | 0.151 | 11
1 1/2″ IPS | 0.173 | 11
2″ | 0.216 | 11
3″ | 0.259 | 13.5
4″ | 0.333 | 13.5
6″ | 0.491 | 13.5

(e) Polyamide (PA-12) pipe requirements. For PA-12 pipe produced after January 22, 2019, a DF of 0.40 may be used in the design formula, provided:

(1) the design pressure does not exceed 250 psig;

(2) the material designation code is PA42316;

(3) the pipe has a nominal size (IPS or CTS) of 6 inches or less; and

(4) the minimum wall thickness for a given outside diameter is not less than that listed in the following table:

Pipe size (inches) | Minimum wall thickness (inches) | Corresponding SDR (values)
1/2″ CTS | 0.090 | 7
3/4″ CTS | 0.090 | 9.7
1/2″ IPS | 0.090 | 9.3
3/4″ IPS | 0.095 | 11
1″ CTS | 0.119 | 11
1″ IPS | 0.119 | 11
1 1/4″ IPS | 0.151 | 11
1 1/2″ IPS | 0.173 | 11
2″ | 0.216 | 11
3″ | 0.259 | 13.5
4″ | 0.333 | 13.5
6″ | 0.491 | 13.5

(1) Reinforced thermosetting plastic pipe may not be used at operating temperatures above 150°F (66°C).

(2) The wall thickness for reinforced thermosetting plastic pipe may not be less than that listed in the following table:

Nominal size in inches (millimeters) | Minimum wall thickness in inches (millimeters)
2 (51) | 0.060 (1.52)
3 (76) | 0.060 (1.52)
4 (102) | 0.070 (1.78)
6 (152) | 0.100 (2.54)
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