Marine Survey Practice: Preparation for Survey:
Preparation for Survey
Before starting survey work, authorization and scope of inspections are to be clarified, the necessary tools and personal equipment items to be prepared, and the safety precautions are to be arranged.
1. REQUEST FOR SURVEYS
It is important that the procedures listed below are observed when a survey request is received and that they are carried out before the ship is visited for the survey.
1.1 Nominated surveyors or those that belong to an organization recognized by the Administration should check who requests the survey and ensure that they are authorized to do so. For example, a survey request may be made by:
- the owner or master of the ship (or his agent), for a periodical survey, including a mandatory annual survey and an intermediate survey, or occasional survey in the case of damage to the ship's structure or equipment;
- the port State, for clarification of possible non-compliance of the ship's structure or its equipment;
- the Administration of a State whose flag the ship is entitled to fly, for verification of the ship's condition.
1.2 Ensure that it is known which international requirements, which national regulations and which other orders and decrees are applicable to the requested survey.
1.3 If necessary, contact the Administration or organization responsible for issuing SOLAS-related certificates to which special requirements and/or instructions apply, such as:
- national requirements laid down by the Administration which are additional to the international convention, e.g. regarding a dead-man stopping device at winch controls etc., the use of asbestos, which is banned by many authorities although there may be varying interpretations of this ban, a remote starting of fire pumps on ships having unattended machinery space etc.,
- exemptions from the international convention's requirements, e.g. fixed fire extinguishing system of cargo holds,
- different survey methods and procedures accepted by the national authority, e.g. in-water survey (divers' survey) instead of the dry-docking of a ship, and non-traditional methods of surveying machinery such as surveys based on condition monitoring,
- different procedures for reporting to the Administration, to be followed by the surveyor.
If the request for a survey is made by the port State authority, the surveyor should obtain the full background to this request, including the authority's point of view, before visiting the ship.
1.4 Check and study the drawings, data, past survey records and reports, as far as necessary and at hand.
2. TOOLS AND EQUIPMENT
For hull surveying purposes a few personal standard parts are necessary for the surveyor, whereas for special inspections additional tools or checking devices may be required.
Surveyors must be familiar with the equipment and tools used in hull survey procedures. Ship equipment can be used, and in addition, a shipyard may provide necessary devices. Before using measuring devices, calibrations and zero adjustments should be carried out, if necessary.
2.1 Standard Equipment Personal Property
- notebook for recording and/or small dicta-phone
2.2 Other Tools and Equipment Used in Survey
Testing hammer:
Note that hammers made of steel must not be used in gas dangerous or gas suspected areas. Here the use of alloy hammers/tools is required to avoid that sparks are initiated by hammering or when tools slip out of hand and fall down.
Measuring tools:
Dial gauges, welding gauges, and feelers may be required for measuring clearances, welding seam heights, indents or deflections of hatches etc.
Portable oxygen and explosive content meters are necessary in areas where petroleum liquids or others are carried and where compartments with limited oxygen content shall be inspected. If ship's instrument is used, proper calibration of the instrument should be confirmed by a suitable testing method or by the latest calibration record issued by a recognized testing firm.
Thickness measurement instruments:
Such instruments use ultrasonic testing methods and calibration of the instrument is usually built in, otherwise it must be gauged separately.Vibration measurement equipment usually available through a shipyard or at major offices or testing institutes is to be used with reference to the relevant instructions and application procedures. There are numerous devices developed and suitable for hull vibration measurements and for recording vibrations exercised by running machinery.
Camera:
Photographs can greatly aid proper reporting if a suitable camera is available. The use of flashlights, however, is limited in areas where explosion risk exists.
3. SAFETY PRECAUTIONS
The surveyor must pay due attention to his own personal safety as well as to that of other persons on board. The following is i.e. an extract from "Guidance Manual for the Inspection and Condition Assessment of Tanker Structures" (pages 3 ff). Sections 3.2 - 4.5 may serve as a guideline for general safety aspects when tankers and product carriers are inspected.
Safety during surveys:
Before commencing any survey, the owner and all personnel involved in the survey must ensure that appropriate safety procedures are specified.
Safety standards often vary from owner to owner and vessel to vessel. While many owners maintain strict onboard safety procedures, survey personnel including Classification Society surveyors and subcontractors must still be aware of what constitutes minimum acceptable standards for tanker inspection to protect themselves from potentially hazardous working conditions.
The following are items of special importance to survey personnel and are included here to highlight the key items of on-board safety. These reflect the present practices and should be treated as a guide rather than a safety standard.
3.1 Safety Meeting - General Considerations
Before beginning any survey the survey team should ensure that a safety meeting is held to discuss all aspects of safety referred to herein with special attention being paid to gas testing procedures, command and communication links, and rescue arrangements.
In pump rooms where cargo vapors may occur due to leakages, pump rooms should be ventilated at least 15 minutes before entering or before the pumps are started.
As most cargo vapors are heavier than air, lower explosive limits (LEL) and/or toxic concentration measurements have also to be taken at floor level and below if inspections are necessary in this area.
Compartments normally not entered, as cofferdams, pipe tunnels, etc., which has usually no fixed ventilation system, should be ventilated by portable equipment.
Especially double bottoms in chemical tankers or product carriers were a risk of minor leakages from cargo tanks above always exists, the double bottoms should be opened at both manhole covers forward and aft and thoroughly ventilated before entering. Then the contents of oxygen, petroleum vapors and/or possible toxic cargoes should be tested before making final access.
The first person entering such a compartment should use breathing apparatus and a life line suitably attached for emergency rescue. A standby team should be trained for this purpose.
A good practice prior to inspecting those double bottom tanks is to fill them with seawater, keep them filled, and pump it out directly before entering.
3.2 Gas Testing for Tank Entry
Entry of tanks for survey should not be permitted until testing indicates that the following criteria are met:
- Gas reading 1% Lower Explosive Limit (LEL) or less (by Explosimeter).
- Maximum Benzene (C6H6) 10 ppm (by Draeger Tube or equal).
- Maximum Hydrogen Sulphide (H2S) 10 ppm (by Draeger Tube or equal) (this figure is under review and likely to be lower).
- Minimum Oxygen (02) 21% by volume (Oxygen Analyzer).
Note: the TLV-TWA for hydrocarbon varies depending on the cargo carried for gasoline the TLV is 300 ppm corresponding to about 2% LEL. Therefore if the TLV-TWA is unknown, a value of about 150 ppm should be used.
- Maximum Hydrocarbons no greater than the Threshold Limit Value - Time Weighted Average (TLV-TWA) for the actual mixture encountered (by Draeger Tube or equal).
- Other limits specific to dangerous cargoes (chemical products), if applicable.
For vessels with inert gas systems, trace amounts of various toxic gases may increase the hazard of exposure for personnel. Normally, a steady 21% by volume of oxygen reading will be sufficient to dilute these gases below their TLV's. However, personnel should be aware of the following limits:
- Maximum Carbon Monoxide (CO) 50 ppm (by Draeger Tube or equal).
- Maximum Nitrogen Dioxide (N02) 3 ppm (by Draeger Tube or equal).
- Maximum Nitric Oxide (NO) 25 ppm (by Draeger Tube or equal).
- Maximum Sulphur Dioxide (S02) 2 ppm (by Draeger Tube or equal).
If gas readings are greater than 1% LEL (Explosimeter), or if other limits are exceeded, the survey team should be instructed not to enter the tank or, if already in it, to stop working and immediately vacate the tank. The Explosimeter used should be calibrated with a low level full scale reading of O to 10% LEL.
The team should arrange with the master to have the tank frequently tested for gas at several locations, say every 2-3 hours. In addition, a member of the team should verify the readings from time to time.
To aid the detection of any local pockets of gas, or lack of oxygen, team members should be encouraged to carry portable hydrocarbon and oxygen detectors with audible alarm features.
3.3 Tank Preparation
Continuous forced ventilation should be supplied to the tank during the inspection. An adequate number of deck fans should be used to supply this air. The fans should, where possible, be ducted to supply fresh air to the tank bottom. The vent fans should be stopped during atmosphere checks. The inert gas fans should not be used to provide fresh air ventilation because contaminants from the inert gas lines could be introduced into the tanks. Inert gas branch lines should be blanked off and the blanking flange interlocks checked at each tank if entry is required while inerting, or gas freeing of other tanks is taking place, or if any other tanks are inerted or contain hydrocarbons.
An alternative to pipe blanking would be to remove a section of the branch line.
All cargo pipelines leading to the tank should be checked for oil content and the valves secured closed, immobilized and signposted. Any oil present in the lines should be removed.
All adjacent tanks should be in the same gas free condition as specified above or fully ballasted. Alternatively, and with the knowledge and approval of the owners and the agreement of the survey team, adjacent tanks may be fully inerted or partly ballasted/remainder inerted but with pressure reduced to a minimum. The survey team should be aware of the danger of potential leakage of inert gas through bulkhead fractures or faulty valves.
3.4 Safety Watch and Safety Equipment
The survey team should not remain in a tank unless there is a safety watch by ship's staff with at least one individual stationed at the tank hatch throughout the inspection. The safety watch should have the authority to order the evacuation of a tank and should be responsible for registering the survey team entering or leaving a tank. Communication should be maintained between the personnel in the tank and the safety watch. When underway, the safety watch should maintain communication with the bridge.
Rescue equipment including breathing apparatus, resuscitators, smoke masks, rescue lines, a stretcher, etc. should be laid out at the tank hatch or, if more than one tank is being worked, at a suitable central location on deck.
3.5 Tank Cleaning
Tanks and spaces to be surveyed must be sufficiently clean and free from water, scale, dirt and oil residues to reveal excessive corrosion, significant deformation, fractures, damages and other structural deterioration. Tank cleaning can be performed with an existing Crude Oil Washing (COW) system.
Generally, tank surveys should be avoided in tanks in which de-sludging operations are taking place since these operations can potentially raise gas levels.
3.6 Ballast Transfer
The survey team should not enter or remain in any tank if ballast is being moved in or out of that tank. Consideration should also be given to ballast movement in adjacent tanks.
3.7 Maneuvering
The survey team should not enter or remain in any tank while the ship is maneuvering in congested or confined waters.
3.8 Use of Ultrasonic Measuring Equipment in Cargo Tanks
Most ultrasonic thickness measuring equipment is not intrinsically safe. Its use is allowed only in tanks with a “hot work” certificate or, alternatively, where agreed by the owner, in tanks with gas quality meeting the requirements of section 3.2 above.
In this case, surfaces within cargo tanks that are not sufficiently cleaned of cargo residues are unacceptable for inspection and should be avoided by the survey team. If ultrasonic measurements are essential in such areas, the surface must be cleaned free of all residues for a radius of 1 meter from each reading point.
3.9 Temperature Extremes
When temperature extremes are expected during a survey, the inspection team should review the procedures that the master or safety officer will follow to monitor the exposure of the team to guard against hypothermia, frostbite, heat fatigue, heat stroke, etc.
When the limit are reached or exceeded, the team, in consultation with the master or safety officer, should adjust its work/rest period for the conditions being encountered. In hot climates the survey should be scheduled to avoid the midday heat when the above limit is likely to be exceeded. Some cooling can be achieved by spraying the decks with water during very hot weather.
3.10 Lighting
Whenever possible, natural lighting should be provided in the tank during surveys by opening all tank hatches. Suspended lighting should also be provided to supplement any natural lighting. Each person should carry a torch of the high intensity beam type such as a Wolflite or Halogen light. Torches and lights should be of intrinsically safe design
3.11 Rafting Surveys
Inflatable or rigid rafts should be of a type with sufficient compartment that adequate buoyancy and stability is provided even with one compartment ruptured.
At no time should the water level be allowed to be within one meter of the deepest under-deck web face flat.
Under no circumstances should the raft be used so that it is isolated from a tank hatch. In the case of tanks with swash bulkheads where two tank hatches are not fitted, the survey may be carried out using two rafts. One raft will be in use while the other is secured at the swash bulkhead for emergency escape.
Rafting should not be attempted if there is more than a thin sheet of oil on the water.
Rafting or boating should be discontinued if the rise and fall of the raft or boat within a cargo tank (due to the motion of ballast water caused by rolling) makes the operation difficult or hazardous. In making this decision, the team should consider the degree and period of roll, the proximity of rafting to the deck-head or other structure (that could damage the raft), and expected maneuvering that could add to excessive motion of the ballast water. While it is difficult to set a limit, the rise and fall of ballast water should not exceed one meter, equivalent to about 1.5 to 2 degrees of roll per side on a V/ULCC.
Once the type of survey has been decided upon, it is necessary to consider the means of access available to achieve the goals of the survey.
The need for reasonable access to the upper parts of a tank structure has recently been reinforced by the introduction of the IACS Unified Requirements for the Special Hull Surveys of Oil Tankers. These requirements do not stipulate how access is to be achieved but have specific requirements for close-up surveys of deck-head structure and primary ring structure coupled with thickness determination in these areas.
The following options are available to aid access to the structure for condition assessment:
4.1 Climbing
In general, the free climbing height should be limited to about 3 meters above the bottom or any large stringer platform. If it is necessary to exceed this height, there should be a water bottom to provide a “cushion” or other provisions such as safety lines. The free climbing height above the water surface should not exceed 6 meters.
When climbing in tanks containing water, the surveying personnel should wear “flotation aids”. A flotation aid is a simple form of lifejacket which does not impede climbing.
4.2 Permanent Arrangements
Much can be achieved at the design stage of a vessel by the provision of manholes and ladders. The width of face plates, the location of stringers, the provision of manholes etc., can all contribute to the ease with which a structure may be surveyed and the condition monitored in service.
Some shipbuilders fit limited permanent walkways at the upper parts of the tank either for their own use or at the request of an owner. Often use of existing structure is made for permanent walkways with handrails added. The fitting of such walkways will however incur a cost and deadweight penalty for the operator especially as the walkways themselves and supporting brackets must be substantial enough for the corrosion environment. Walkways can provide sufficiently close access to obtain a general assessment of the condition of the structure and identify suspect areas for closer examination.
4.3 Temporary Staging
Conventional temporary staging within a tank to gain access to deck-heads and bulkheads structure is an option that may be attractive in some circumstances but, as the vessel gets older and survey requirements more stringent, the cost of such staging methods could become prohibitive.
The use of temporary staging restricts the survey to being carried out within the repair yard and does not facilitate a survey at sea for preparation of repair specifications and the like.
4.4 Mobile Platforms
The most common form of temporary staging other than conventional scaffolding is the mobile platform. This consists of a portable, self-elevating platform suspended from wires through holes drilled in the upper deck. If a sufficiently extensive grid of holes is provided, reasonable access to deck-head areas can be achieved.
Alternative designs of mobile platform are mostly based upon an articulated or telescopic arm principle. Such designs would typically incorporate a support turret suspended from a tank cleaning opening or from the tank bottom. The articulated or telescopic arm is supported by the turret and is usually operated hydraulical1y or pneumatically to bring the inspection platform to the desired position. The movement of the platform can usually be controlled by the inspector on the platform. Each platform should be capable of carrying two persons and would typically have an outreach from the turret of about 25 meters.
All forms of mobile platform are highly susceptible to the motions of the vessel and are therefore more readily usable in dry-dock or sheltered conditions rather than at sea. it should be noted that these platforms may have to be certified as complying with local factory inspectorate and International Labor Organization (ILO) requirements, particularly when used within a repair yard.
4.5 Rafting
Although limited in use for some structural configurations, survey of deck-heads from a raft or boat within a partially filled tank is fairly common practice with some operators and is likely to become even more popular as more stringent survey requirements are introduced.
The tank should not be filled beyond a level approximately 1 meter below the deck transverse so that the survey team is not iso1ated from a direct escape route to the tank hatch. This will mean that on larger vessels with deep deck transverses the inspector will still be some distance from the deck-head which may preclude close-up survey.
Filling to levels above the deck transverses should only be contemplated if a deck access manhole is fitted in the bay being examined to provide access to the raft and direct escape to the deck in an emergency.
Fitting of additional deck manholes (with access ladders and platforms) for this purpose should possibly be considered on future designs if rafting is planned as the main means of deck-head survey.
Safety is of prime importance during ratting surveys and likely motions of the vessel must be taken into account at all times.
(Note: above sections 3 and 4 are grouped under the heading "Safety and Access" in Chapter 1 "Survey Preparation Guidelines").
4.6 Opening of manholes
For access to double bottom tanks, pipe tunnels, wing tanks, etc., both manholes should be opened and prepared.
It enables natural ventilation and easier means of escape, if necessary.
In addition, inspections are easier to perform if the tank passage can be made in one way only and when light and tools and fresh air are to be reached from short ends.
