Section
6 Oxy-acetylene plants for welding and cutting
6.1 General
6.1.1 LR classed oxy-acetylene welding and cutting plants that have been constructed,
installed and tested under LR’s Special Survey in accordance with this Section and
Pt 1, Ch 3, 23 Notations and Descriptive Notes will be
eligible for the special features class notation OXY. All parts of
oxy-acetylene welding and cutting plants are to comply with this Section.
6.1.3 Operating instructions for the oxy-acetylene welding and cutting plant are to be
supplied by the equipment vendor(s) and kept on board.
6.1.4 Operating instructions are to include the instruction that when the oxy-acetylene
welding and cutting plant is not in use, all valves in the plant are to be kept
closed.
6.2 Compressed gas consumables
6.2.1 Portable gas cylinders and other pressure vessels used to transport and
store liquids or gases under pressure, e.g. acetylene and oxygen, are to comply with
an acceptable National or International Standard, see also
Pt 12, Ch 1, 8 Compressed gas utility systems.
6.2.2 Further guidance, which should be consulted, is given in Chapter 9.17 of
the 2009 MODU Code - Code for the Construction and Equipment of Mobile Offshore
Drilling Units and also the following documents from the British Compressed Gas
Association (BCGA):
- BCGA Guidance Note GN2 Guidance for the
storage of gas cylinders in the workplace
- BCGA Code of practice CP7 The safe use of
oxy-fuel gas equipment (individual portable or mobile cylinder
supply)
- BCGA Guidance Note GN11 Reduced oxygen
atmospheres.
6.2.3 Means are to be provided to secure portable gas cylinders at all
times.
6.2.4 Portable gas cylinders are to be stored in accordance with Chapter 9.17
of the MODU Code - Code for the Construction and Equipment of Mobile Offshore
Drilling Units. Portable gas cylinders are to be stored in a well-ventilated area.
The storage area should be protected from wave impacts and located away from sources
of heat, sparks and fire risk. Cylinders should be stored upright and well
secured.
6.2.5 Oxygen cylinders are to be stored in an area free from combustible
material. When stored in open locations, oxygen and fuel gas (e.g.
acetylene/propane) cylinders are to be stored in separate open locations in
accordance with a recognised Standard see
Pt 12, Ch 1, 8.1 Recognised codes and standards for compressed gas utility systems. Where two or
more cylinders of oxygen or fuel gas are intended to be carried in enclosed spaces,
separate dedicated storage rooms should be provided for oxygen cylinders and for
fuel gas cylinders, with the storage rooms constructed of steel. Provision should be
made for the expeditious removal of cylinders in the event of fire. Alternative
proposals to cool the cylinders in-situ with a drencher system in the event of a
fire will be specially considered.
6.2.6 Gas cylinders are not permitted to be stored in the engine-room.
6.3 High-pressure piping systems between gas cylinders and regulators
6.3.1 Acetylene pipes are to comply with the following:
- Pipes are to be of stainless steel. All pipes are to be
seamless. Piping and accessories are to be certified for use up to 300
bar.
- Copper or copper alloys containing more than 65 per cent
of copper are not to be used in connection with acetylene. In plants where
two or more cylinders of acetylene are connected to a manifold, the supply
pipes between the cylinders and the manifold are to be fitted with
non-return valves that comply with an acceptable National or International
Standard, see
Pt 12, Ch 1, 8.1 Recognised codes and standards for compressed gas utility systems.
6.3.2 Oxygen pipes are to comply with the following:
- Pipes are to be of copper. All pipes are to be seamless.
Piping and accessories are to be certified for use up to 300 bar. In plants
where two or more cylinders of oxygen are connected to a manifold, the
supply pipes between the cylinders and the manifold are to be fitted with
non-return valves that comply with an acceptable National or International
Standard, see
Pt 12, Ch 1, 8.1 Recognised codes and standards for compressed gas utility systems.
Note 300 bar is related to a maximum gas cylinder filling pressure of 200 bar at 15 °C.
Where it is proposed to use cylinders with a higher filling pressure, the pressure
to which piping and accessories are to be certified is to be agreed with LR.
6.3.3 Safety valves fitted at gas supplies are to discharge to a vent point on the open
deck. The vent point is to be in a safe place at a height of minimum 3 m above
deck.
6.4 Low-pressure piping systems downstream of regulators
6.4.1 Pipes are to be seamless, made of ST 35 material with a wall thickness of minimum 2,0
mm or equivalent and/or in conformity with the requirements of a recognised
Classification Society. Pipes on the open deck are to have a thickness of at least
2,5 mm.
6.4.2 Pipes are to be laid freely and be so arranged that they are protected against
damage. They are not to penetrate unventilated rooms, lockers, etc. or be laid in
crew or passenger accommodation.
6.4.3 Expansion loops are to be placed where necessary and piping that penetrates a deck or
bulkhead is to be sheathed in protection tubes of hard plastics or fibre material.
All pipes are to be securely fastened so as to be protected against damage. The
distance between fastening clamps is not to exceed 2,5 m.
6.4.4 Pipes are to be laid with as few joints as possible. In new installations, joints are
to be welded with a tungsten inert gas welding or acetylene/oxygen unit. In existing
installations, joints are to be expertly welded end to end. Joints are to be fitted
in places readily accessible for inspection.
6.4.5 Disconnectable couplings are not accepted as a substitute for welded joints.
6.5 Outlet stations
6.5.1 Outlet stations are to have stop valves, regulators, manometers, safety devices
against backfire and gas backflow (flash back arrestors) and non-return devices and
are to be located in a cabinet or otherwise satisfactorily protected.
6.6 Signs/notices and marking
6.6.2 Entrance doors to enclosures or rooms where acetylene and oxygen cylinders are stored
are to be fitted with warning notices which in writing and illustrations clearly
express:
DANGER GAS UNDER PRESSURE
Fire, open flame and smoking prohibited. Remove cylinders to a safe place in case
of fire.
6.6.3 In the immediate vicinity of gas regulator and cylinders etc, a sign is to be posted
with directions for use and clearly worded text giving the necessary detailed
instructions for their use.
6.6.4 In the immediate vicinity of the regulators, notices are to be posted clearly stating
the maximum pressures in the plant piping permitted between the regulators and the
outlet stations.
6.6.5 Vents from safety valves and similar devices are to be marked with the following
text:
DANGER GAS
Fire, open flame and smoking prohibited.
6.6.6 At the outlet stations, notices indicating the operating pressure are to be posted.
Signs are also to be posted clearly stating that the valves are to be closed when
the installation is not in use.
6.6.7 Pipes are to be colour-coded and labelled in such a way there will be no doubt as to
which gases are conveyed by the pipes. Colour schemes and labels are to be in
accordance with the relevant Statutory Regulations and/or requirements of the
National Administration in the country of registration or the area of operation as
applicable, otherwise in accordance with recognised Standards e.g. ANSI/ASME A13.1,
BS 1710 or ISO 14726. As colour schemes may differ, the title of the regulations or
standards adopted are to be clearly stated by the inlets and outlet stations.
6.6.8 Gas cylinder storage areas are to be clearly marked with signs showing that oxygen
and acetylene cylinders are stored there.
6.6.9 Gas cylinders are to be colour-coded and labelled in accordance with the relevant
Statutory Regulations of the National Administration in the country of registration
and the areas of operation as applicable, otherwise in accordance with recognised
Standards e.g. BS EN 1089-3 and BS EN 7225. As colour schemes may differ, the title
of the regulations or standards adopted are to be clearly stated on the
cylinders.
6.7 The carriage/transportation of gas cylinders
6.7.1 A means of conveyance is to be provided for the carriage of acetylene and oxygen
cylinders on board the unit, and during the transportation of such cylinders to and
from the unit.
6.8 Acetylene and oxygen gas generation plants
6.8.1 Gas generation plants are to meet the applicable requirements of Pt 3, Ch 8 Process Plant Facility and are to be capable of being
demonstrated to be suitable for use in the marine environment by type approval or
other means.
6.8.2 The supply pipes between the generation plants and the manifold are to be fitted with
non-return valves that comply with relevant standards.
6.9 Installation, testing and survey
6.9.1 Prior to the installation of acetylene and oxygen piping, pipes and connections are
to be thoroughly cleaned to remove all grease, oil and other combustible substances.
No combustible or organic solvent is to be used for this purpose. Pipes and
connections are to be blown clean with dry and oil-free nitrogen, after degreasing
and prior to and after installation.Compressed air from an oil-lubricated compressor
or oxygen are not be used.
6.9.2 After completed installation or repairs of the oxy-acetylene plant and otherwise at
five-yearly intervals, all plant piping is to be blown through and be leak tested in
accordance with Pt 1, Ch 3, 23 Notations and Descriptive Notes. The risk of
injury to personnel or damage to the plant from blown-through gas and dirt is to be
considered.
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