Tanker Notes ||
Container Ship Operations ||
Ocean Navigation ||
Tanker operation : Measures for pump room inspections & gas detection equipments
A pump room contains the largest concentration of cargo pipelines of any space within the ship and leakage of a volatile product from any part of this system could lead to the rapid generation of a flammable or toxic atmosphere.
The Pump Room may also contain a number of potential ignition sources unless formal, structured maintenance, inspection and monitoring procedures are strictly adhered to.
Before Starting Cargo Operations (including Loading):
• An inspection is to be made to ensure that strainer covers, inspection plates, drain plugs and lighting are in place and in proper order.
• Drain valves in the pump room cargo system, especially those on cargo oil pumps, should be firmly closed.
• Bulkhead glands should be inspected to ensure efficient gas-tight seal between the Pump Room and the machinery space.
During Cargo Operations (including Loading):
• Inspection at regular intervals to check for leakages from glands, pipes, plugs, seals, drain valves, especially those fitted on pumps.
• Where pumps are in use, the absence of abnormal sound, the normal function of local and remote pressure gauges, the integrity of pump glands (where fitted), the bearings, casings should be checked for overheating.
(Pump Glands shall never be adjusted on rotating shafts, while the pump is in service)
GAS DETECTION EQUIPMENT
Gas detection equipment is required for ensuring spaces are safe for entry, work or other operations.
Their uses include the detection of:
a) Cargo vapour in air, inert gas or the vapour of another cargo.
b) Concentrations of gas in or near the flammable range.
c) Concentrations of oxygen in inert gas, cargo vapour or enclosed spaces.
d) Toxic gases
Personnel must fully understand the purpose and limitations of vapour detection equipment, whether
fixed or portable.
Maintenance records for all gas detection equipment onboard are to be maintained by the Chief Officer
. Onboard calibration records and shore
records are to be maintained together for each meter and are to be updated on each occasion that the
instrument is tested or checked.
The importance of careful calibration cannot be over emphasised as the gas detection or analysing
equipment will only give accurate readings if calibration is carried out strictly in compliance with the
manufacturer’s instructions and using the correct calibration gases. Where calibration is carried out
ashore or by shore technicians, a certificate is to be issued and retained onboard.
Instruments must always be checked, zeroed and spanned where applicable before every use as per
the manufacturer’s instructions.
Where calibration is required by the manufacturer’s instructions to be carried out ashore or by shore
technicians, this must be recorded within the vessel’s PMS and all certification issued. In such
circumstances at least one unit for each measurement function should remain onboard available for
use at all times. Where calibration is carried out ashore or by shore technicians, a certificate is to be
issued and retained onboard.
Any equipment not fully operational and/or in good condition, including perished hoses, leaking
aspiration bulbs and out-of-date calibration gases or Draeger tubes should be withdrawn from service
and reported to the management office.
Hoses used with portable gas instruments must be of sufficient length, appropriate to the full depth of
the tank or space being tested. Long hoses must clearly marked at least every 5 meters so that the
user can assess the level of the hose in the space.
Where the atmosphere testing equipment is not of a uniform manufacture with identical hose fittings, a
suitable system is to be created to identify and match the correct hoses with the correct equipment.
Hoses compatible with the equipment should be stowed in the same location as the equipment.
All ships are supplied with a portable oxygen analyser. This equipment is supplied for use in checking
that spaces to be entered have been properly ventilated. It is also to be used on Tankers, Gas Ships
and Chemical Carriers to check that the atmosphere of inerted tanks remains below 7%.
Two tests should be carried out on the instrument prior to use and a permanent record of readings
kept on board.
(a) Zero Adjustment
This is done by using an oxygen-free gas, such as Nitrogen or Carbon Dioxide. Equipment is
supplied for this test. Note that CO2 is paramagnetic and therefore may not give a zero reading
on certain instruments.
(b) Span Adjustment
This must be done in FRESH AIR and the instrument carefully checked that the reading has
stabilised at 21% before the atmosphere of any space is tested.
The maker’s instructions for the particular instrument should be followed carefully to ensure that
calibration procedures are correctly carried out. Calibration checks must be carried out every two
The Explosimeter is the name normally associated with the instrument for measuring hydrocarbon gas
in air at concentrations below the Lower Flammable Limit. Its full name is a Catalytic Filament
Combustible Gas Indicator.
A full understanding of the construction and principle of an Explosimeter is essential for its safe and
efficient use and it is essential that any person using this instrument carefully studies the operating
manual. There is also a detailed explanation in the ISGOTT carried on tankers.
The Explosimeter measures from 0 to 100% of the Lower Explosive Limit (1.4% by volume).
If the gas to air mixture is above the upper explosive limit (6% by volume) the meter reading will
initially rise to give a reading of 100% or above, but will rapidly fall towards zero because the mixture
of gas and air in the combustion chamber is too `rich' to sustain combustion.
The meter must therefore be constantly observed for this phenomenon, as an apparently safe reading
may be obtained when the atmosphere is in fact highly dangerous.
Calibration checks must be carried out at two monthly intervals and when a filament has been changed
in accordance with manufacturers’ instructions. Note that, in general, an explosimeter may be
calibrated by different gases. It is essential that the correct gas is used otherwise an error may result.
Explosimeters will not read hydrocarbon levels in an inert atmosphere.
Although similar to the Explosimeter, the `Tankscope' (or Non-Catalytic Heated Filament Gas Indicator)
measures hydrocarbons in an inert atmosphere. It indicates their presence as a percentage proportion
of the whole atmosphere. The instrument is especially useful during purging with inert gas. It will
indicate when the proportion of hydrocarbons has fallen to a level whereby the atmosphere will remain
below the Lower Explosive Limit (LEL) on the introduction of fresh air.
Calibration checks must be carried out at two monthly intervals.
TOXIC GAS DETECTORS
These detectors measure relatively low concentrations of toxic gases. Such gases may include Carbon
Monoxide or Hydrogen Sulphide.
The type of instrument will normally require a special attachment or tube which the gas is aspirated
through. It is necessary to know in advance what gas is expected in order to choose the correct
detection tube. The readings are to be compared with the occupational exposure limits or threshold
A minimum list of tube types required for specific vessels is included at the end of this section however
additional tubes must be carried appropriate to the hazards identified within the MSDS for the cargo
COMBINED FUNCTION METERS
There are certain instruments which have a combination of functions. Examples of some equipment
which may be carried are:
As with all other instruments the manufacturer’s instructions regarding operation and calibration must
be followed at all times.
- Draeger Combiwarn: this instrument measures and monitors flammable vapours as a
percentage of LEL in the range of 0 - 50% LEL. It also measures
oxygen concentrations. This instrument can be preset to give audible
and visual alarms at specific levels.
- Digiflam 2000: this combines the functions of the Tankscope and an Oxygen meter, its
main use being the monitoring of COW and Inert Gas operations.
- Exotox 40: this is supplied specifically for the use in testing and monitoring the
atmosphere of enclosed spaces. It combines the functions of an
Oxygen monitor, and Explosimeter and a toxic gas monitor for either
Carbon monoxide or Hydrogen sulphide. It provides continuous
monitoring of all three functions and has visual and audible alarms.
PERSONAL MONITORING METERS
Some instruments can be carried in a pocket such as a Personal Oxygen Meter, used for entry into
enclosed spaces. Such instruments are intended only as a personal monitor and will give an audible
and visual alarm if the Oxygen content falls below its preset level.
As monitors, they are not designed (and therefore not to be used) for testing the atmosphere for
oxygen or other gases.
A vessel carrying H2S cargo must maintain sufficient
supply of personal meters to ensure all persons working in the gas-zone are provided with detection
Zero and alarm checks are to be made before each use.
The material and condition of sample lines can affect the accuracy of gas measurements. Sample
tubing which is cracked or blocked or which has become contaminated with oil or other substances may
seriously affect instrument readings.
The tubing must always be checked before and during use and if necessary be cleaned or replaced.
It is also important to realise the length of tubing and compare to the meter manufacturer’s instructions
as to the number of aspirations per metre length. If this is not done there is a danger that the sample
gas may not reach the meter sensor and therefore give a false reading.
Pumproom entry precation Learn basic procedure for pumproom management
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General precautions for oil cargo loading in tankers
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