154.814—Facility requirements for vessel vapor overpressure and vacuum protection.
(a)
A facility's vapor collection system must have the capacity for collecting cargo vapor at a rate of not less than 1.25 times the facility's maximum liquid transfer rate for cargo for which vapor collection is required plus any inerting, diluting, or enriching gas which may be added to the system, unless the vapor growth for turbulent loading of the most volatile liquid handled by the facility is less than 25 percent.
(b)
A facility vapor collection system must maintain the pressure in a vessel's cargo tanks between 80 percent of the highest setting of any of the vessel's vacuum relief valves and 80 percent of the lowest setting of any of the vessel's pressure relief valves for a non-inerted tank vessel, and between 0.2 psig and 80 percent of the lowest setting of any of the vessel's pressure relief valves for an inerted tank vessel. The system must be capable of maintaining the pressure in the vessel's cargo tanks within this range at any cargo transfer rate less than or equal to the maximum transfer rate determined at the pre-transfer conference required by § 156.120(w) of this chapter.
(c)
The pressure measured at the facility vapor connection must be corrected for pressure drops across the vessel's vapor collection system and the vapor collection hose or arm.
(d)
A pressure sensing device must be provided which activates an alarm when the pressure at the facility vapor connection exceeds either the pressure corresponding to the upper pressure determined in paragraph (b) of this section or a lower pressure agreed upon at the pre-transfer conference required by § 156.120(w) of this chapter.
(e)
A pressure sensing device must be provided which activates an alarm when the pressure at the facility vapor connection falls below either the pressure corresponding to the lower pressure determined in paragraph (b) of this section or a higher pressure agreed upon at the pre-transfer conference required by § 156.120(w) of this chapter.
(f)
A pressure sensing device must be provided which activates the emergency shutdown system required by § 154.550 of this part and closes the remotely operated cargo vapor shutoff valve required by § 154.810(a) of this subpart when the pressure at the facility vapor connection exceeds 2.0 psi, or a lower pressure agreed upon at the pre-transfer conference required by § 156.120(w) of this chapter. The sensing device must be independent of the device used to activate the alarm required by paragraph (d) of this section.
(g)
A pressure sensing device must be provided which closes the remotely operated cargo vapor shutoff valve required by § 154.810(a) of this subpart when the vacuum at the facility vapor connection is more than 1.0 psi, or a lesser vacuum set at the pre-transfer conference required by § 156.120(w) of this chapter. The sensing device must be independent of the device used to activate the alarm required by paragraph (e) of this section.
(h)
The pressure sensing devices required by paragraphs (d) and (f) of this section must be located in the vapor collection line between the facility vapor connection and the manual isolation valve, if required by § 154.810(h) of this subpart, unless an interlock is provided which prevents operation of the system when the isolation valve is closed.
(i)
A pressure indicating device must be provided which indicates the pressure in the vapor collection line.
(j)
If a compressor, blower, or eductor capable of drawing more than 1.0 psi vacuum is used to draw vapor from the vessel, a vacuum relief valve must be installed in the vapor collection line between the compressor, blower, or eductor and the facility vapor connection, which:
(1)
Relieves at a pressure such that the pressure in the vapor collection system at the facility vapor connection does not exceed 1.0 psi vacuum;
(2)
Has a relieving capacity equal to or greater than the capacity of the compressor, blower, or eductor;
(4)
Has been tested for relieving capacity in accordance with paragraph 1.5.1.3 of API 2000 (incorporated by reference; see § 154.106) with a flame screen fitted.
(k)
When a facility collects cargo vapor through an undersea pipeline from a vessel moored offshore, the vacuum relief valve may be set at a vacuum greater than 1.0 psi vacuum provided the pressure controls take into account the pressure drop across the vessel's vapor collection system, any vapor collection hoses, and the undersea pipeline as a function of the actual transfer rate.
(l)
If the pressure in the vapor collection system can exceed 2.0 psig due to a malfunction in an inerting, enriching, or diluting system a pressure relief valve must:
(1)
Be installed between the point where inerting, enriching, or diluting gas is introduced into the vapor collection system and the facility vapor connection;
(2)
Relieve at a pressure such that the pressure in the vapor collection system at the facility vapor connection does not exceed 2.0 psig;
(3)
Have a relieving capacity equal to or greater than the maximum capacity of the facility inerting, enriching, or diluting gas source;
(4)
If not designed to insure a minimum vapor discharge velocity of 30 meters (98.4 ft.) per second, have a flame screen fitted at the discharge opening; and
(m)
The relieving capacity test required by paragraph (l)(5) must be carried out with a flame screen fitted at the discharge opening if the pressure relief valve is not designed to insure a minimum vapor discharge velocity of 30 meters (98.4 ft.) per second.