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Subchapter 1. Unfired Pressure Vessel Safety Orders
Article 6. Anhydrous Ammonia

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§514. Installation of Refrigerated Storage Containers.

(a) Containers shall be supported on suitable noncombustible foundations designed to accommodate the type of container being used.

Adequate protection against flotation or other water damage shall be provided wherever high flood water might occur.

Containers for product storage at less than 32 F. shall be supported in such a way, or heat shall be supplied, to prevent the effects of freezing and consequent frost heaving.

(b) A check valve shall be installed in lieu of the required excess flow valve on the fill connection, except when flow is needed in both directions, and a remotely operated shutoff valve shall be installed on all other connections located below the maximum liquid level.

(c) The filling density for refrigerated storage containers shall be such that the container will not be liquid full at a liquid temperature corresponding to the vapor pressure at the start-to-discharge pressure setting of the safety-relief valve.

(d) Safety-relief valves shall be set to start-to-discharge at a pressure not in excess of the design pressure of the container and shall have a total relieving capacity sufficient to prevent a maximum pressure in the container of more than 120 percent of the design pressure. Relief valves for refrigerated storage containers shall be self-contained spring-loaded, weight-loaded, or self-contained pilot-operated type.

The total relieving capacity shall be the larger of:

(1) Possible refrigeration system upset such as (A) cooling water failure, (B) power failure, (C) instrument air or instrument failure, (D) mechanical failure of any equipment, (E) excessive pumping rates.

(2) Fire exposure determined in accordance with Compressed Gas Association (CGA) S-1, Part 3, Safety Relief Device Standards For Compressed Gas Storage Containers, 1959, except that "A" shall be the total exposed surface area in square feet up to 25-foot above grade or to the equator of the storage container if it is a sphere, whichever is greater. If the relieving capacity required for fire exposure is greater than that required by (1) of this subdivision, the additional capacity may be provided by weak roof-to-shell seams in containers operating at essentially atmospheric pressure and having an inherently weak roof-to-shell seam. The weak roof-to-shell seam is not to be considered as providing any of the capacity required in (1) of this subdivision.

If vent lines are installed to conduct the vapors from the relief valve, the back pressure under full relieving conditions shall not exceed 50 percent of the start-to-discharge pressure for pressure balanced valves or 10 percent of the start-to-discharge pressure for conventional valves. The vent lines shall be installed to prevent accumulation of liquid in the lines.

The valve or valve installation shall provide weather protection.

Atmospheric storage shall be provided with vacuum breakers. Ammonia gas, nitrogen, methane, or other inert gases can be used to provide a pad.

(e) Appurtenances shall be protected against tampering and physical damage.

(f) Containers of such size as to require field fabrication shall, when moved and reinstalled, be reconstructed and reinspected in complete accordance with the requirements under which they were constructed. The containers shall be subjected to a pressure retest and if rerating is necessary, rerating shall be in accordance with applicable requirements.

(g) Precaution shall be taken against damage from vehicles.

(h) The total refrigeration load shall be computed as the sum of the following:

(1) Load imposed by heat flow into the container caused by the temperature differential between design ambient temperature and storage temperature.

(2) Load imposed by heat flow into the container caused by maximum sun radiation.

More than one storage container may be handled by the same refrigeration system.

(i) A minimum of two compressors shall be provided, either of which shall be of sufficient size to handle the loads listed in Section 514(h)(1) and (2). Where more than two compressors are provided, minimum standby equipment equal to the largest normally operating equipment shall be installed. Filling compressors may be used as standby equipment for holding compressors.

Compressors shall be sized to operate with a suction pressure at least 10 percent below the minimum setting of the safety valve(s) on the storage container and shall withstand a suction pressure at least equal to 120 percent of the design pressure of the container.

(j) Each compressor shall have its individual driving unit.

An emergency source of power of sufficient capacity to handle the loads listed in Section 514(h) (1) and (2) shall be provided unless facilities are available to safely dispose of vented vapors while the refrigeration system is not operating.

(k) The refrigeration system shall be arranged with suitable controls to govern the compressor operation in accordance with the load as evidenced by the pressure in the container(s).

An emergency alarm system shall be installed to function in the event the pressure in the container(s) rises to the maximum allowable operating pressure.

An emergency alarm and shutoff shall be located in the condenser system to respond to excess discharge pressure caused by failure of the cooling medium.

All automatic controls shall be installed in a manner to preclude operation of alternate compressors unless the controls will function with the alternate compressors.

(l) An entrainment separator of suitable size and design pressure shall be installed in the compressor suction line of lubricated compression. The separator shall be equipped with a drain and gaging device.

An oil separator of suitable size shall be installed in the compressor discharge line. It shall be designed for at least 250 psi and shall be equipped with a gaging device and drain valve.

(m) The condenser system may be cooled by air or water or both. The condenser shall be designed for at least 250 psi. Provision shall be made for purging noncondensibles either manually or automatically.

(n) A receiver shall be provided with a liquid-level control to discharge the liquid ammonia to storage. The receiver shall be designed for at least 250 psi and be equipped with the necessary connections, safety valves, and gaging device.

(o) Refrigerated containers and pipelines which are insulated shall be covered with a material of suitable quality and thickness for the temperatures encountered. Insulation shall be suitably supported and protected against the weather. Weatherproofing shall be of a type which will not support flame propagation.

NOTE: Authority cited: Section 142.3; Labor Code.


1. New section filed 3-28-75; effective thirtieth day thereafter (Register 75, No. 13).

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