LNG Vapour and LNG liquid leakage into Barrier Spaces
液化天然气蒸气和液化天然气液体泄漏到屏障空间

2.General
2.总则

Under normal operations the IBS and IS barrier spaces are continually swept with nitrogen.
在正常操作下，IBS 和 IS 屏障空间不断被氮气扫过。

A vapour leakage will be detected by the gas sampling analyser
气体采样分析仪将检测蒸汽泄漏

Liquid leakage into an IBS space could develop slowly over a period of days or hours, or may develop suddenly if a major failure of the membrane occurs.
液体泄漏到IBS空间可能会在几天或几小时内缓慢发展，或者如果发生膜的重大故障，可能会突然发展。

3.Failure of Primary Barrier
3.主屏障失效

A major failure in the primary membrane, allowing liquid into the inter barrier space, will be indicated as follows:
主膜的重大故障，允许液体进入屏障间空间，将指示如下：

A rapid increase in the methane content of the affected space.
受影响空间的甲烷含量迅速增加。

A rise in pressure in the inter barrier space nitrogen header, accompanied by continuous venting to atmosphere.
屏障间空间氮气集管中的压力升高，并伴有持续排放到大气中。

Low temperature alarms at all temperature sensors in the insulation below the damaged cargo tank.
在损坏的货舱下方绝缘层中的所有温度传感器处发出低温警报。

A decrease in inner hull steel temperatures.
船体内钢温度降低。

Gas alarms in IBS at 30% by Vol
IBS 中的气体警报率为 30% （按 Vol）

Likely lifting of the Primary Barrier Space (cargo tank) relief valves.
可能抬起主屏障空间（货舱）安全阀。

If a major failure of the membrane occurs, liquid from the tank will flow into the inter barrier space until the levels in both compartments are equal.
如果膜发生重大故障，罐中的液体将流入屏障间空间，直到两个隔间中的液位相等。

Immediately connect the portable liquid level meter to the IBS at the first sign of a liquid leak to assist in determining the height size of the leak by recording the IBS level increase rate, IBS pressure and the cargo tank level pressure.
在液体泄漏的第一个迹象时立即将便携式液位计连接到 IBS，通过记录 IBS 液位增加率、IBS 压力和货舱液位压力来帮助确定泄漏的高度大小。

If the liquid level increases to the cargo tank level before the tank can be pumped out, then extreme care must be taken to protect against over pressurisation of the membrane during the discharge of the damaged tank.
如果在将储罐抽出之前液位上升到货舱液位，则必须格外小心，以防止在卸出损坏的储罐期间膜过度加压。

LNG liquid in the IBS can be removed by either gravity drainage back into the cargo tank as the tank is pumped out, or if that does not work, then by using the IBS drainage system (As per Cargo Manual)
当油箱被抽出时，可以通过重力排水回货舱中去除 IBS 中的液化天然气液体，或者如果这不起作用，则使用 IBS 排水系统（根据货物手册）

Whenever Gas or LNG is detected in IBS (Inter Barrier Space):
每当在 IBS（屏障间空间）中检测到气体或液化天然气时：

Permit nitrogen to continuously flow through the IBS and ensure stable LEL gas concentration in the IBS.
允许氮气持续流过 IBS，并确保 IBS 中稳定的 LEL 气体浓度。

Adjust the flow rate as necessary so that the gas concentration remain less than 10% LEL (desired) or below the maximum value of 30% LEL on both the laden and ballast voyages.
根据需要调整流速，使气体浓度在满载和压载航行中保持小于 10% REL（所需）或低于 30% LEL 的最大值。

Verify and maintain the pressure in the insulation space (IS) at a minimum of 2 mb above the pressure in the IBS of the affected tank to prevent LNG vapour from passing into the IS.
验证并保持绝缘空间 （IS） 中的压力至少比受影响储罐 IBS 中的压力高 2 mb，以防止 LNG 蒸汽进入 IS。

4.Vapour leakage
4.蒸汽泄漏

Leakage of Methane into to the Primary insulation space present NO immediate danger to the tank of the vessel.
甲烷泄漏到主绝缘空间不会对容器的储罐造成直接危险。

On NO96 system, Primary and Secondary barriers are constructed of 0,7mm thick Invar membrane and are liquid and vapour tight.
在 NO96 系统上，初级和次级屏障由 0.7 毫米厚的殷钢膜构成，并且是液态和蒸汽密封的。

The vapour concentration in each primary insulation space is recorded daily to detect any such small but steady change.
每天记录每个主要绝缘空间中的蒸汽浓度，以检测任何这种微小但稳定的变化。

Indicators of serious leakage
严重泄漏的指标

A sudden rise in percentage of methane vapour in on einsulation space:
绝缘空间中甲烷蒸气的百分比突然上升：

Any porosity in primary barrier weld allow passage of methane vapour into the primary insulation space. Amount of this vapour should be kept on minimum by using nitrogen purging.
初级屏障焊缝中的任何孔隙率都允许甲烷蒸气进入初级绝缘空间。使用氮气吹扫应将这种蒸气的量保持在最低限度。

If fracture occurs below the level of liquid in the tank, the vapour concentration will increase rapidly and suddenly.
如果裂缝发生在罐内液位以下，蒸汽浓度将迅速而突然地增加。

If fracture is above the liquid level, the concentration will exhibit a fluctuating increase.
如果裂缝高于液位，则浓度将呈现波动增加。

An increase of pressure in one Primary Insulation Space:
一个初级绝缘空间的压力增加：

A fracture above the liquid level in cargo tank will allow a direct flow of vapour into the primary insulation space. This flow will vary according to the pressure in the tank.
货舱中高于液位的裂缝将允许蒸汽直接流入主绝缘空间。该流量将根据罐中的压力而变化。

Fracture below liquid leve in cargo tank, resulting in a small amount of liquid vaporising as it passes through the fracture will cause increase in pressure (600:1).
货舱中液体裂隙下方的裂缝，导致少量液体在通过裂缝时蒸发，将导致压力增加 （600：1）。

Small quantity of liquid, which enters in barrier space from any source, vaporises and will have the same effect.
少量液体从任何来源进入屏障空间，会蒸发并产生相同的效果。

Liquid leakage
液体泄漏

In the event of mechanical damage or overpressure of the primary barrier space, a failure of the primary membrane of the cargo tank could occur.
如果主屏障空间发生机械损坏或超压，可能会发生货舱主膜故障。

Primary marrier space will be filled with LNG in a time proportional to size and location of the membrane failure and the height of the LNG in the cargo tank.
主要建筑空间将在与膜故障的大小和位置以及货舱中液化天然气的高度成正比的时间内填充液化天然气。

Liquid lekage may develop slowly over period of hours or days or it may occur suddenly.
液体性lekage可能在数小时或数天内缓慢发展，也可能突然发生。

7.Liquid leakage indications
7.漏液指示

Gas detection alarm in IBS
IBS中的气体检测报警

Rise pressure in the effecte Primary Barrier Space
影响主要屏障空间中的上升压力

Likely lifting of the Primay Barrier Space relief valves
可能解除 Primay Barrier Space 安全阀

Frost of the exaust pipe from the IBS at the vapour dome
来自蒸汽穹顶 IBS 的 exaust 管道结霜

Confirmed by a drop in the recorded temp. of the bottom sensors in the secondary barrier
通过二级屏障中底部传感器的记录温度下降来确认

A general lowering of the inner hull steel temperature
船体内钢温度普遍降低

If any two of above events occur, imediately segregate the gas in PBS from the others and vent it to the atmosphere and maintain the pressure below the IBS releif valves set point 1.0 kPag.
如果发生上述任何两种情况，请立即将 PBS 中的气体与其他气体隔离，并将其排放到大气中，并将压力保持在 IBS 释放阀设定点 1.0 kPag 以下。

8.Liquid leakage indications In secondary barrier space
8.二级屏障空间中的液体泄漏指示

Pressure in Secondary barrier space should be increased to prevent gas contanination from Primary barrier space.
应增加二级屏障空间中的压力，以防止气体从初级屏障空间中污染。

In case the leak is so severe that pressure in SBS cannot maintain above that in PBS than contaminated tank Secondary barrier space should be isolated from other SBSs by closing nytrogen supply valve at the end of the tank.
如果泄漏非常严重，以至于 SBS 中的压力无法保持在高于 PBS 中的压力，则应通过关闭储罐末端的 nytrogen 供应阀将二级屏障空间与其他 SBS 隔离开来。

Hull heating flow rate to be increased as soon as temperature of SBS or inner hull are observed to be dropping.
一旦观察到SBS或内壳温度下降，船体加热流量就会增加。

NO 96 Membrane punching device
NO 96 膜冲孔装置

Messenger system – NO96 Barrier punch
信使系统 – NO96 阻隔冲床

Punch to be Installed on Float gauge pipe
安装在浮法规管上的冲头

Specially designed punch about 30 kg weight
特制冲头约30公斤重

Float attached to messenger line wmarked for refrence
附在信使线上的浮子标记为参考

2.Messenger system – NO96 Barrier Punching device
2.信使系统 – NO96 屏障冲孔装置

Punching device is inserted in to the tank Float Gauge Standpipe after removing float gauge and allowed to gravity fall through the LNG liquid in the pipe (liquid must be there)
取下浮子表后，将冲孔装置插入储罐浮标立管中，让重力通过管道中的液化天然气液体落下（液体必须在那里）

The bottom of the pipe is fitted with a split perforated base allow the Messenger to penetrate through to the membrane.
管道底部装有分体式穿孔底座，使信使能够穿透膜。

Messenger puch hole of 50mm diameter through the primary membrane and box cover.
直径为50mm的信使孔穿过主膜和箱盖。

3.When to use punching device?
3.何时使用冲孔装置？

If the cargo tank were pumped out with a head of liquid remaining in the IBS, severe damage to the membrane would result.
如果将货舱抽出时，IBS中残留了液体头，则会严重损坏膜。

For this reason it is necessary to intentionally puncture the primary membrane when the damaged tank is being pumped out.
因此，在抽出损坏的储罐时，有必要故意刺穿主膜。

Pumping of the tank must be limited so tank level decreases slower than 0.4m/h
必须限制储罐的泵送，使储罐液位下降速度低于 0.4m/h

Approval from CLASS/GTT/Owner has to be obtained before dropping device.
在丢弃设备之前，必须获得 CLASS/GTT/Owner 的批准。