2209.5.4 Venting of Hydrogen Systems
The height (H) and separation distance (D) of the vent pipe shall meet the criteria set forth in Table 218.104.22.168.4 for the combinations of maximum hydrogen flow rates and vent stack opening diameters listed. Alternative venting systems shall be allowed when in accordance with Section 222.214.171.124.6.
CFM at NTPg
> 500 to ≤ 1,000
CFM at NTPg
|> 1,000 to ≤ 2,000 CFM at NTPg||> 2,000 to ≤ 5,000 CFM at NTPh||> 5,000 to ≤ 10,000 CFM at NTPh||> 10,000 to ≤ 20,000 CFM at NTPh|
- Minimum distance to property line is 1.25D.
- Designs seeking to achieve greater heights with commensurate reductions in separation distances shall be designed in accordance with accepted engineering practice.
- With this table personnel on the ground or on the building and/or equipment are exposed to a maximum of 1,500 Btu/hr. ft2,and are assumed to be provided with a means to escape to a shielded area within 3 minutes, including the case of a 30 ft./sec. wind.
- Designs seeking to achieve greater radiant exposures to noncombustible equipment shall be designed in accordance with accepted engineering practice.
- The analysis reflected in this table does not permit hydrogen air mixtures that would exceed one-half of the lower flammable limit (LFL) for hydrogen (2 percent by volume) at the building or equipment, including the case of a 30 ft./sec. wind.
- See Figure 2126.96.36.199.4.
- For vent pipe diameters up to and including 2 inches.
- For vent pipe diameters up to and including 3 inches.
Where alternative venting systems are used in lieu of the requirements of Section 2188.8.131.52.5, an analysis of radiant heat exposures and hydrogen concentrations shall be provided. The analysis of exposure to radiant heat shall assume a wind speed of 30 feet/second (9.14 m/sec) and provide a design that limits radiant heat exposure to the maximum values shown in Table 2184.108.40.206.6(1). The analysis of exposure to hydrogen concentration shall provide a design that limits the maximum hydrogen concentration to the values shown in Table 2220.127.116.11.6(2).
|EXPOSED OBJECT||MAXIMUM RADIANT HEAT||TIME DURATION (minutes)|
|Personnel||1,500 Btu/hr • ft2 (4732 W/m2)||3|
|Noncombustible equipment||8,000 Btu/hr • ft2 (25 237 W/m2)||Any|
|Lot line||500 Btu/hr • ft2 (1577 W/m2)||Any|
|EXPOSED OBJECT||MAXIMUM HYDROGEN CONCENTRATION|
|Personnel, buildings or equipment||50% LFL within a distance of D and H of Table 218.104.22.168.4|
|Lot line||50% LFL within 1.25 times the distance of D and H of Table 222.214.171.124.4|
|H||=||Minimum height in feet (mm) of vent pipe above the ground or above any structure or equipment within distance (D) where personnel might be present.|
|D||=||Distance in feet (mm) to adjacent structure or equipment where personnel might be present.|