AS 3961:2017 pdf download.The storage and handling of liquefied natural gas.
The location of the discharge point and the direction of discharge from a safety valve or other pressure-relief device shall be such that hazards from venting vapours are minimized. Vapour impingement on tanks or piping shall be prevented. The direction of discharge shall be vertically upwards except where another direction is necessary to comply with this Clause, e.g. to avoid impingement.
A safety valve and any associated discharge piping shall comply with the following requirements when installed:
(a) The size of any discharge piping shall be sufficient to ensure that the required discharge capacity of the safety valve is achieved. Refer to AS 1271.
(b) Irrespective of any provisions for recycling vapour discharges from pressure-relief and pressure control devices, the design shall ensure that the required discharge capacity of a safety valve will be released without restriction in an emergency.
(c) The outlet shall not be vulnerable to physical damage.
(d) Provision shall be made to prevent the accumulation of rain, dew, or foreign matter within the safety valve in such a manner as to cause backpressure or render the valve defective. For pressure tanks, the point of discharge shall have a self-closing device designed so that no parts become separated if a discharge occurs. Where a weep hole or drain is provided in order to comply with this requirement, the overall design shall be such that any ignited discharge cannot impinge on the tank, adjacent tanks, piping, or equipment. A deflector or a drainage discharge pipe may be provided; any such piping shall not incorporate a valve.
Monitors and alarms shall be provided for installations described in Clause 2.5.1, located where an abnormal condition of a potentially hazardous nature is likely to occur.
Any such systems shall comply with the following requirements:
(a) Continuously monitored low-temperature sensors or flammable-gas detection systems shall initiate an alarm at the plant site and at a constantly attended location if the plant site itself is not continuously attended. Flammable-gas detection systems shall initiate this alarm at not more than 25% of the lower explosive limit of the gas or vapour being monitored.
(b) Fire detectors shall initiate an alarm at the plant site, and at a constantly attended location if the plant site itself is not continuously attended. In addition, if deemed necessary by an evaluation in accordance with Clause 7.2.5, fire detectors may activate appropriate portions of the emergency shutdown system.
(c) Portable flammable-gas indicators shall be available.
2.8.3 Remote transfer connection
Remote transfer connection provisions for liquid, vapour, or vapour return service, for either filling or withdrawal, shall comply with the following requirements:
(a) The appropriate valve system as specified in Clause 3.3.2 shall be provided at the tank.
(b) An anchorage shall be provided for the remote filling point, of sufficient strength to ensure that the piping and valves between the anchorage and the tank will not be damaged before the drive-away protection fails or releases.
(c) Drive-away protection complying with Clause 2.8.4 shall be provided between the point of connection and the anchorage, as close as possible to the anchorage.
(d) The piping between the tank and the remote transfer connection shall be provided with a connection to a blow-down line arranged to discharge at a safe place. Control shall be by means of a valve and a flow restriction equivalent to an 8 mm orifice.
(e) A non-return valve shall be located as close as practical to the anchorage. Where outflow is required, an emergency shutdown system with excess flow protection shall be provided.
2.8.4 Drive-away protection
A transfer connection shall be provided with shear points or the equivalent, designed in conjunction with the support to ensure that if the tanker is driven away without disconnecting, break-away can be relied on to occur at that shear point before valves or piping are damaged.AS 3961 pdf download.