Morgan Hill Municipal Code Part 8 Minimum Threshold Quantity Controls

Responsible persons shall cause materials which do not exceed the minimum threshold quantity as defined in Section 8.40.1020 to be provided with controls specified in Part 2 and Part 8 of this article.

(Ord. 1494 N.S. § 2 (part), 2000)

Storage of cylinders shall be within ventilated gas cabinets, exhausted enclosures or within a ventilated separate gas storage room as defined in the California Fire Code.

Storage of portable and stationary tanks shall be within a separate ventilated room without other occupancy or use. If gas cabinets are provided, the room or area in which they are located shall have independent exhaust ventilation when properly exhausted cabinets are not utilized. Exhaust systems for gas cabinets, exhausted enclosures and separate gas storage rooms shall be designed to handle the accidental release of gas. Such exhaust systems shall be capable of diluting, absorbing, neutralizing, burning or otherwise processing the entire contents of the single tank or cylinder of gas which presents the highest potential hazard. Systems utilized for such processing shall be designed as a treatment system, as described in Section 8.40.1450, below. If a total containment system is utilized, the system shall be designed to handle the maximum anticipated pressure of release to the system when the system reaches equilibrium.

(Ord. 1494 N.S. § 2 (part), 2000)

When gas cabinets are provided, they shall be:

A. Operated at negative pressure in relation to their surrounding area;

B. Provided with self-closing limited access ports or fire-rated windows to give access to equipment controls. The average velocity of ventilation at the face of access ports or windows shall be not less than two hundred feet per minute (FPM) with a minimum of one hundred fifty FPM at any point of the access port or window;

C. Connected to a treatment system;

D. Provided with self-closing doors;

E. Constructed of steel with a thickness of not less than twelve gauge.

(Ord. 1494 N.S. § 2 (part), 2000)

Treatment systems shall be utilized to process all exhaust ventilation to be discharged from gas cabinets, exhausted enclosures or separate storage rooms. Treatment systems shall be designed to reduce the maximum allowable discharge concentration of the gas to one-half IDLH (or 0.05 LC 50 if no established IDLH) at the point of discharge to the atmosphere as specified below. When more than one gas may be emitted to the treatment system, the treatment system shall be designed to handle the worst-case release based on the release rate, the quantity and the IDLH (or 0.1 LC 50 if no established IDLH) for all the gases stored or used. In the event that a revised IDLH is published, the city shall establish a new timetable for existing facilities to upgrade their treatment systems to meet the revised IDLH value.

(Ord. 1494 N.S. § 2 (part), 2000)

Treatment systems shall be sized to process the worst-case release of each gas based on the maximum flow rate of release from the cylinder or tank utilized which presents the highest potential hazard. The entire contents of tanks and cylinders shall be considered.

(Ord. 1494 N.S. § 2 (part), 2000)

Stationary tanks shall be labeled with the maximum rate of release for the gas contained based on any valves or fittings that are inserted directly into the tank.

If multiple valves or fittings are provided, the maximum flow rate of release for the valve or fitting with the highest flow rate shall be indicated. If liquefied gases are in contact with any valve or fitting, the liquid flow rate shall be utilized for purposes of computation of the maximum flow rate of release. All flow rates indicated on the label shall be converted to cubic feet per minute of gas at normal temperature and pressure.

(Ord. 1494 N.S. § 2 (part), 2000)

For portable tanks and cylinders, the maximum flow rate of release shall be calculated based on the actual release data or calculations using actual valve manufacturers specifications. When this data is not available, the maximum flow rate of release shall be calculated based on the total release from the cylinder or tank within the time specified in the table below:

When portable tanks or cylinders are equipped with approved reduced flow orifices in the cylinder valve, the worst-case release may be determined by the maximum achievable flow through the orifice as determined by the valve manufacturer or the gas supplier. Reduced flow and excess flow valves shall be permanently marked to indicate the maximum design flow rate. Such markings shall indicate the flow rate for air under standard conditions. Lettering shall be one-quarter inch high, minimum, and be in contrast to the color it is printed upon.

When cylinders are manifolded together, the maximum release rate shall be the sum of the release rates for all of the manifolded cylinders.

(Ord. 1494 N.S. § 2 (part), 2000)

All primary piping for regulated materials shall pass a helium leak test of 1×10 -9 cubic centimeters/second where practical, or other nationally recognized standard. Tests shall be conducted by a qualified "third party" not involved with the construction of the piping and control systems.

(Ord. 1494 N.S. § 2 (part), 2000)