Liquefied Gas Carrier

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Personal protective equipments onboard liquefied gas carrier

Breathing Apparatus: It is always preferable to achieve a gas free condition in a tank or enclosed space prior to entry. Where this is not possible, entry should only be permitted in exceptional circumstances and when there is no practical alternative. In this case breathing apparatus must be worn and if necessary protective clothing must be worn also. There are three types of respiratory protection.
  1. Canister filter respirators
  2. Fresh air respirators
  3. Compressed air breathing apparatus

Canister filter respirators :

These consist of a mask with a replaceable canister filter attached through which contaminated air is drawn by the normal breathing of the wearer. They are simple to operate and maintain, can be put on quickly and have been used extensively as personal protection for emergency escape purposes on ships certified for carrying toxic cargoes.

They are, however, only suitable for relatively low concentrations of gas, once used there is no simple means of assessing the remaining capacity of the filter, filter materials are specific to a limited range of gases and, of course, the respirator gives no protection in atmospheres of reduced oxygen content. For these reasons, the IMO Code requirement for emergency escape protection is now met by lightweight portable package self-contained breathing apparatus.

Fresh air respirators :

These consist of a helmet or face mask linked by a flexible hose (maximum length 120 feet) to an uncontaminated atmosphere from which air is supplied by a manual bellow or rotary blower. The equipment is simple to operate and maintain and its operational duration is limited only by the stamina of the bellows or blower operators.

However, movement of the user is limited by the weight and length of hose and great care must be taken to ensure that the hose does not become trapped and kinked. While in general this respirator has been superseded by the self-contained or air line compressed air breathing apparatus, it will be found on many ships as an always available backup to that equipment.

Compressed air breathing apparatus :

In the self-contained version (SCBA), the wearer carries his air for breathing in a compressed air cylinder at an initial pressure of between 135 and 200 bars. The pressure is reduced at the outlet from the cylinder to about 5 bars and fed to the face mask as required through a demand valve providing a slight positive pressure within the mask. Working duration depends upon the capacity of the air cylinder and the respiratory demand. Indicator and alarm features are usually provided to warn of air supply depletion.

A typical set, providing approximately 30 minutes operation with physical exertion, may weigh about 13kg and the bulk of the cylinder on the back of the wearer imposes some restriction on his manoeuvrability in confined spaces. Although when properly adjusted, the SCBA is simple and automatic in operation, its maintenance requires care and skill. To ensure their serviceability when required, all such breathing sets must be checked monthly and worn and operated during appropriate exercises preferably using special exercise air cylinders in order to keep the operational cylinders always fully charged.

Although modern demand valves are designed to maintain a slight positive pressure within the face mask, it must not be assumed that this feature will prevent leaks from the contaminated atmosphere into an ill-fitting face mask. While face mask materials and contours are designed to accommodate a range of typical facial shapes and sizes, it is essential that, before entry to a dangerous space, the air tightness of the mask on the wearer's face be thoroughly checked in accordance with the manufacturer's instructions. Comprehensive practical tests have shown that it is virtually impossible to ensure continued leak tightness in operational conditions on a bearded face.

Most compressed air breathing sets may be used in the air line version (ALBA) whereby the compressed air cylinder and pressure reducing valve are placed outside the contaminated atmosphere and connected to the face mask and demand valve by a trailed air hose. At the expense of decreased range ability and the need for extra care in guiding the trailing air hose, the wearer is relieved of the weight and bulk of the air cylinder and his operational duration may be extended by the use of large air cylinders of continuous supply cylinder changeover arrangements.

Escape Breathing Sets

One short-duration escape breathing apparatus is useful for each person on board LPG ships. The total number of sets onboard is equal to the number of persona the ship is certified to carry.

The Master is to ensure that all personnel onboard are familiar with the operation and the limitations of these sets. In particular, newly joined personnel are to be instructed in the use of these sets when they sign on.

It is the responsibility of the Second Officer to ensure that the compressed air cylinders are full and that they are checked monthly or more frequently if required. On no account are these sets to be used for operation use, inspection, rescue or fire-fighting support. They have duration of 15 minutes and are to be used only to assist personnel escape from concentrations of toxic vapours.

Protective clothing

In addition to breathing apparatus full protective clothing should be worn when entering an area where contact with cargo is a possibility. Types of protective clothing vary from those providing protection against liquid splashes to a full positive pressure gas-tight suit which will normally incorporate helmet, gloves and boots. Such clothing is also to be resistant to low temperatures and solvents.

Full protective clothing is particularly important when entering a space which has contained toxic gas such as ammonia, chlorine, ethylene oxide, VCM or butadiene.

One complete set of protective clothing is to consist of:
When wearing protective clothing it is important to ensure that neither the sleeves are tucked into the gloves, not the trousers into the boots. This is to avoid low temperature cargo falling into the gloves and boots of personnel working in areas where splashing of cargo of spillage is possible. Sleeves are to pass over gloves and trousers over the boots of all protective clothing.

Suitably marked decontamination showers and eyewash should be available on deck in convenient locations. The showers and eyewash should be operable in all ambient conditions.

Related Information:

  1. Procedure for commissioning the cargo system

  2. Cargo emergency shutdown requirement for liquefied gas carrier

  3. Gas analyzing equipment

  4. Use of cargo as fuel -Cargo conditioning, reliquefaction and boil-off control for LNG carriers

Safety checklist for gas carrier

Reactivity of liquefied gas cargo and safety guideline Procedure for loading Liquefied Gas Cargoes

Procedure for Cargo Conditioning in Liquefied Gas Carriers

Procedure for segregation of Liquefied Gas Cargoes

Procedure for Stripping Liquefied Gas Cargoes

Procedure for Changing Liquefied Gas Cargoes

Displacing Atmosphere with Inert Gas (Inerting)

Preparation for Cargo Transfer

Procedure for discussion prior cargo transfer

External links :

  1. International maritime organization

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