Gp17. Piping Sys Gen

”Super-Man”/Basic Edition/Part II Copyright NSA

SUPERINTENDENT’s MANUAL “Super-Man”

Part II - Technical Part

Main Group 1 - General Items

Gp 17 - Piping Systems General


SUPERINTENDENT’s MANUAL PART II - TECHNICAL PART Table of Contents Page

17 PIPING SYSTEMS GENERAL 1

170 GENERAL 1 170.0 General Guidelines 1 170.01 Definitions and abbreviations 1 170.1 General about Piping Systems 2 170.10 General 2 170.2 Inspection of Components at Sub-Supplier’s 2 170.3 Preparation of Pipes and Components prior to Installation on Board 3 170.30 General 3 170.32 Pipe shop inspection 3 170.4 Section/Block Building 4 170.40 General 4 170.5 Check Points 4 170.50 General 4 170.6 Suspension, Clamping and Expansion 5 170.60 General 5 170.7 Installation/Fitting of Pipes 7 170.70 General 7 170.71 Pipe fittings 7 170.72 Expansion/flexible couplings 7 170.73 Installation of valves 9 170.74 Packings/gaskets 9 170.75 Vent/Drain Systems 10 170.76 Access 10 170.77 Inspection on board 10 170.8 Control and Maintenance of Cargo Pipes 11 170.80 General 11 170.81 Inspection of cargo pipes from the inside 11 170.9 Bulkhead penetrations 12 170.90 General 12

171 PIPING ARRANGEMENTS 13 171.0 General Guidelines 13 171.1 Flow Conditions/Branch Pipes 13 171.10 General 13 171.2 Galvanic Corrosion 15 171.20 General 15 171.3 Erosion 15 171.30 General 15 171.4 Special Arrangements 15 171.40 General 15 171.41 Piping systems in the accommodation 16 171.42 Vent- and sounding pipes 16 171.5 Marking/Labeling 16


171.50 General 16

172 BENDING, WELDING AND JOINING OF PIPES 17 172.0 General Guidelines 17 172.1 Bending of Steel Pipes 17 172.10 General 17 172.11 Cold bending/annealing 17 172.12 Hot bending 18 172.13 Induction bending 19 172.2 Welding of Steel Pipes 19 172.20 General 19 172.21 Adjustment of pipe ends prior to joining by welding 20 172.22 Welding connections/joints - general 20 172.23 Types of joints/welding grooves 20 172.24 Preheating 22 172.3 Welding Methods 22 172.30 General 22 172.31 Acetylene welding 22 172.32 Electric (manual) welding 23 172.33 Automatic welding 23 172.34 Inert gas welding 24 172.4 Heat Treatment after Welding 24 172.40 General 24 172.5 Branch pipes 25 172.50 General 25 172.6 Welding of flanges 25 172.60 General 25 172.7 Finishing Welding Work 27 172.70 General 27 172.71 Welding faults/repairs 27

173 PIPE MATERIALS 28 173.0 General Guidelines 28 173.1 Copper/Copper Alloys Piping 28 173.10 General 28 173.11 Bending of copper/copper-alloyed pipes 28 173.12 Soldering 29 173.13 Preparatory work/welding joints 30 173.14 Welding methods 31 173.2 Stainless Steel Piping 31 173.20 General 31 173.21 Bending 31 173.3 Non-Metallic Piping 31 173.30 General 31 173.31 Plastic piping 32 173.32 Transport and storage 34 173.33 Installation and repairs 34 173.4 Flexible Hoses 34 173.40 General 34 173.41 Hoses of non-metallic material 35


173.42 Hoses of metallic material 35

174 PUMP TYPES 36 174.0 General Guidelines 36 174.1 Centrifugal Pumps 36 174.2 Piston Pumps/Displacement Pumps 36 174.3 Gear Pumps 36 174.4 Screw Pumps 37 174.5 Wing Pumps/Sliding Vane Pumps 37 174.6 Inspection of Pumps 37 174.7 Installation on Board 37 174.71 Connections 38

175 INSPECTION PROCEDURES/PRESSURE TESTING/PREPARATION FOR OPERATION 39

175.0 General Guidelines 39 175.1 Lube Oil Systems and Hydraulic Oil Systems 39 175.10 General 39 175.2 Lube Oil Piping for Main Engine and Aux. Engines 39 175.20 General 39 175.3 Pressure Testing 40 175.30 General 40

176 SAFETY REQUIREMENTS 41 176.0 General Guidelines 41 176.1 High Temperatures – Insulation 41 176.10 General 41 176.2 Fire and Explosion Hazards 41 176.20 General 41 176.3 Installation Precautions affecting Electrical Systems 41 176.30 General 41 176.4 Flexibility, Vibrations and Deflections 42 176.40 General 42 List of Figures (Figures and sketches are inserted directly in the text where relevant).

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17 PIPING SYSTEMS GENERAL 170 GENERAL 170.0 General Guidelines Group (Gp) 17 contains the following Sub-Groups (SGps): * 170 - General * 171 - Piping arrangements * 172 - Bending, welding and joining of pipes * 173 - Pipe materials * 174 - Pump types * 175 - Inspection procedures, pressure testing, preparation for operation * 176 - Safety requirements SGps 177-179 are “vacant” numbers and may be utilised for later updating. As explained in “Introduction” to Part II of the Manual, MGp 1 of the standard “SFI Group System” (GS) is not relevant for “Super-Man”, and has therefore not been applied for MGp 1. However, there is an obvious need for a code/numbering system where information of a more general nature and common to several systems or types of equipment on board a ship, can be gathered in a logical manner. MGp 1 as applied in the Manual, has therefore been designed to serve this purpose. In Gp 17 is given a general description of piping systems and to some extent also of pumps, which is largely applicable to the majority of such ship systems, e.g. ballast and bilge systems, loading and discharging systems for liquid cargo, cooling systems, fuel- and lube oil systems etc. For further details, reference is made to the respective groups. This implies that the users of the Manual should also read the information given in Gp 17, when studying any of the particular systems mentioned above and their respective Groups. It should further be mentioned that some overlap naturally would have to exist between descriptions given in Gp 17 and the specialised groups. This type of repetition has been difficult to avoid without extensive efforts. Such recurrences are hopefully not reducing the value of the info given, in an adverse manner. Figures and diagrams are inserted in the text where relevant and practical. 170.01 Definitions and abbreviations * BS : British Standard * GRE : Glass fibre reinforced epoxy * GRP : Glass fibre reinforced polyester * NDE : Non-destructive examination * NDT : Non-destructive testing * NS : “Norsk Standard” (Norwegian Standard)

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170.1 General about Piping Systems 170.10 General Pumps and piping systems should always be planned together. This relates to choice of material, dimensioning, arrangement and details. Pipes can be classified as: * Regular pipes * Special pipes such as high pressure steam pipes, pipes for gas carriers etc. Material descriptions and, if available, analyses of all components must be filed on board, to make future repairs easier. For cargo piping and pumps this is also vital in relation to the type of cargo the vessel can carry. Such documentation, when correctly applied, will also ensure that all materials are properly dimensioned and well suited for relevant pressures and liquids. Also make sure that flange material and pipe material go together. The Class rules (e.g. DNV Pt.2 Ch.2 (Materials), Pt.2 Ch.3 (Welding) and Pt. 4, Ch.6 Sec. 6 - Pipes, Pumps, Valves etc.) generally contain information which can help determining correct type, thickness etc. of pipes when designing the respective systems. 170.2 Inspection of Components at Sub-Supplier’s 170.20 General Most defects are found during testing on board. It would, however, be advantageous both to yard and shipowner if defects appear at an earlier stage. By “preventive inspection”, damages to the system can be avoided and improvements facilitated. Components like pumps with power units, heat exchangers, filters, pressure vessels, valves, strip- and bilge ejectors, should as far as possible be inspected at the sub-supplier’s. This to ensure that the equipment meets set quality criteria and is suitable and prepared for installation on board. This is especially important when defects may cause delays, if not revealed prior to installation. The following should be adhered to during inspection at sub-supplier’s: * All welds to be visually examined. * NDE/NDT records to be reviewed for compliance with specified requirements. * Hydrostatic tests to be witnessed; alternatively test records to be reviewed for

compliance with specified requirements. * Shot blasting to be verified to comply with specified requirements, alternatively

corresponding inspection reports to be reviewed. * Corrosion protection externally as well as internally to be verified to be in compliance

with specified requirements. * Pumps, valves and other essential equipment to be functionally tested. * Pump capacity tests to be witnessed, alternatively test records for individual pumps to

be reviewed to verify compliance with specified requirements/operating conditions.

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The best support for such inspections is approved drawings and specifications. Most professional suppliers have procedures for workshop inspections and tests, which in most cases should be accepted. These should be checked against the Class rules and specified standards to verify compliance with these. 170.3 Preparation of Pipes and Components prior to Installation on Board 170.30 General It is essential that all parts subject to corrosion protection are adequately cleaned/descaled prior to application of the protective coating. If shot/grit blasting is effected, all sensitive equipment must be properly protected. The dry film thickness of any applied coating should be verified to establish compliance with the coating specification. Welding is not recommended on galvanised, zinc coated or “aluminiumised” pipes. If this cannot be avoided, then it should be ensured that the “metal coating” is removed in way of the weld zone. A suitable corrosion protection coating should subsequently be applied in and around the weld zone. 170.31 Unscheduled inspection during manufacture of pipes Following check points to be observed and adhered to: * All welding of pipes to be carried out by qualified welders using approved welding

procedures. * Check that piping materials are identical with those specified on approved drawings.

Materials for Class I, II and III pipes shall have respectively Class Certificate, Works’ Certificate and Test Report according to the Class rules.

* Preheating of steel pipes and post heat treatment after welding to be carried out if required

according to recognised standards or by the Class rules. 170.32 Pipe shop inspection For relevant check points, see 170.20. It is recommended that check lists are prepared for these inspections to ensure that all required and relevant aspects are covered. E.g. when “Dresser” couplings are used on inside protected pipes, the inner side of the coupling and the outer part of the pipe under the coupling, should be protected. Painting of the pipe in way of the coupling to be avoided.

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However, pipe systems must be inspected on board as well, because section joints and welds will damage preparation done ashore. If the follow-up on board is good, coating damages will be reduced, thus causing less corrosion. 170.4 Section/Block Building 170.40 General Most yards build their ships in rather large sections, trying to outfit these as much as practically possible. This implies that the “connecting-up” time often is very short, thus increasing the workload on the newbuilding superintendent (Supt.) as to verification of the effectiveness of the coating inside pipe fittings/valves. Depending on the yard’s building methods and size of ship, the pipe systems may therefore either be put together and completed part by part on board, or large sections with piping included, may be prefabricated prior to assembly in building dock or on berth. See also MGp 3/Gp 35. The latter method may be easier to follow up and control, but since the time available for inspection generally is very limited, the Supt. must be present to check that there are no damages on the inner coating or in any pipe fittings/valves before the system is closed. 170.5 Check Points 170.50 General Independently of building method, following items should be checked/controlled: * Check clamping and support of pipes, filters and valves. Clamping and support must not

obstruct painting. Make sure that the pipes will endure the dynamic shocks and longitudinal forces exerted by liquid in the pipes. Check that the distance between clamps is not too long. For guidance see table in 170.60.

* Anchoring of pipes should be arranged as required. This is particularly important where

patent type couplings are used. * Pipes should not rest directly in the clamps, but on a layer of Teflon or similar

(applicable for large pipes). * Point loads on pipes must be avoided, and the support loads must be distributed as

widely as possible. * When assembling pipes, flanges must be parallel and bolt holes aligned. * There must be sufficient expansion joints and drain- and inspection plugs in the pipe-

lines. Draining must be effective, especially if freezing may occur. Avoid “dead ends”. * Good access for maintenance and repair of pumps, filters, valves etc.

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* Where necessary, sufficient head-room for use of lifting tackle must be provided. * Good access for manoeuvring of valves, maintenance of filters, mud boxes etc. * Pipes must be arranged to facilitate effective cleaning. * Number of pipe joints should be kept at a minimum. * Large diameter pipes should have a minimum clearance to deck of about 400 mm, and

the smaller ones about 150 mm. * “Aluminiumised” pipes should in particular rest on Teflon (PTFE) or similar materials,

to prevent damage of coating. * Check correct type of bulkhead penetrations. * All valves must be marked with name and number, according to the pipe diagrams. * Inspect the installation of hydraulic systems, and test remotely controlled valves. All

newly installed hydraulic pipes must be well cleaned and inspected before being connected to the remainder of the system.

* Control the attachment and placement of pipes on deck. In some cases it may be

feasible to place the largest pipes towards the ship’s side, and the smaller towards the centre line, this to protect against damage in rough weather. See also MGp 3/Gp 35.

170.6 Suspension, Clamping and Expansion 170.60 General Steam pipes must be laid so that thermal expansion does not cause high stresses in pipes or in connected components/machinery. Clamps and suspension arrangements should be placed on straight parts of the pipe line, and not at bends where internal stress already may be a problem. Clamps etc. placed on bends may also reduce the flexibility of the bend. All pipelines must be suspended in such a way that the weight of pipes and flowing medium is evenly distributed to the clamps. Clamps must be of a solid design. On large pipelines the clamps must not be welded to unstiffened plate panels. This is generally valid for all clamps and fittings carrying weight of any magnitude. For copper and aluminium brass pipes, copper bolster plates should be used. Lead may also be used, but is quickly worn out. Sliding pads of Teflon or similar should be used.

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Make sure that heavy valves and armatures are suspended in a solid way and not supported by adjoining pipelines. Suspension clamps and pipelines must be designed to absorb any possible extra loads caused by e.g. dynamic shocks. For pipe lines with built-in flexibility, make sure that the pipe suspensions are according to approved drawings and calculations. It is especially important that placement and adjustment of spring suspensions are as specified. For elastically supported engines and machinery, adjoining pipes must be flexible. Recommended clamping distances as a function of pipe diameter and wall thickness are given in the table below (Source: DNV). (The wall thicknesses are for guidance only).

Pipe Steel Pipes Cu and Al/Brass Pipes Diameter Wall thickness

min. (mm) Clamping Distance

max. (m) Wall thickness

min. (mm) Clamping Distance

max. (m)

6 8 10 15 20 25 32 40 50 65 80 90 100 125 150 200 250 300 350 400 450 500 550 600

2.0 2.3 2.3 2.8 2.8 3.2 3.5 3.5 3.8 4.2 4.2 4.2 4.5 4.5 5.0 5.8 6.6 6.9 7.9 9.5 9.5 9.5 9.5 9.5

1.0 1.2 1.4 1.6 1.8 2.1 2.4 2.6 2.8 3.2 3.4 3.6 3.8 4.1 4.5 5.1 5.6 6.1 6.4 7.0 7.2 7.5 7.7 8.0

1.6 -

1.6 1.8 2.0 2.0 2.0 2.0 2.0 2.6 2.6 2.9 3.2 3.5 4.0 4.5 - - - - - - - -

0.87 -

1.0 1.2 1.4 1.6 1.8 1.9 2.0 2.4 2.6 2.7 2.9 3.3 3.5 4.0 - - - - - - - -

Wall thickness of cargo pipes to be according to Class rules and operating pressure. Where local pittings, acceptable remaining local thickness to be checked with the Class.

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170.7 Installation/Fitting of Pipes 170.70 General Pipes should not rest against plate edges in penetrations, etc. unless satisfactory supported and protected. Make sure that no stresses or forces, which can harm pipes, valves or adjoining machinery, are built into the system. When pre-stressing is specified, make sure that this is carried out according to approved specification/drawings. If pre-stressing is not necessary, make sure that flanges are parallel, and with bolt holes aligned. Pipes should not be forced into position in a way that may cause additional stresses in connected pipe lines, machinery, bolts, fittings, armatures etc. Pipes should as far as possible be arranged to avoid cutting holes in stiffeners and deck beams. 170.71 Pipe fittings Check the Class rules for relevant requirements. For most screw connections the pipes should be cut straight, and the ends polished. Applied tightening torque must be correct. There must be a certain straight pipe length on each side of the coupling. Where possible, make sure that various screw connections are of the same type, this to make repairs easier. Branch pipes with nominal diameter up to 50 mm, are often fabricated as screw- or H-soldered fittings. For pipes above 50 mm, welded branch pipes are normally used. See also 171.1. 170.72 Expansion/flexible couplings Piping systems have to accommodate movements caused by thermal expansion and by hull deflections, dynamic and static. The movements caused by thermal variations will approximately be as stipulated below: Carbon steel pipes 1,16 mm per ˚C per 100 m Austenitic steel pipes 1,35 mm per ˚C per 100 m Copper alloy 1,42 mm per ˚C per 100 m GRP 2-3 mm per ˚C per 100 m

(Manufacturer will advice) Hull deflections during sea conditions may affect the piping more than the effect of the thermal movements, particularly for piping fitted on deck and near bottom. These movements must be absorbed by expansion elements, slide joints or bends.

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Expansion joints and bellows are subject to approval for their intended use. They are to be so designed and installed that pulling or blowing out is prevented. Pipelines in which expansion joints or bellows are fitted to be adequately adjusted, aligned and clamped. For expansion couplings and flexible couplings the connected pipes must be straight, without burrs and thread damages and well aligned. Common couplings are “Dresser” (see sketch next page), and “NWB” - couplings. All types of compensators and expansion couplings to be carefully aligned and easy to dismantle for inside inspection. Experience shows that compensators are easily damaged during installation, if not especially protected. Hence, relevant precautions to be taken. Damaged compensators must be renewed. Corrosion and erosion are often found at the pipe ends in expansion couplings. When such corrosion or erosion develops, it may reach the sealing surface of the coupling, and the sealing rings start leaking. If such leakage occurs, one may dismantle the coupling and insert a so-called extended coupling, where the seal will land on a non-corroded area. If necessary, the old/corroded ends to be cut off by a pipe cutter before the new extended coupling is mounted. Note that it is absolutely essential that the ends be cut off, as one would otherwise just enhance erosion and shorten the life span of this type of repair. It may be advantageous to have a couple of such extended couplings in spare on board, to handle the problems that may occur in expansion couplings. Also seals and bolts for the ordinary expansion couplings should be kept as spares on board. Pipe bends and spool pieces for suction- and discharge side of cargo pumps should as far as possible be made similar for all pumps, so that spare bends and spool pieces are ready to fit, when needed for any of the cargo pumps. An expansion joint (“Dresser” type) is shown below:

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Typical expansion bellows are shown below:

Axial expansion bellow Rubber expansion bellow with limit stop bolts 170.73 Installation of valves Make sure that all valves and armatures are correctly installed, for easy operation and maintenance. Extension pieces and transmissions to be installed where necessary. Butterfly valves in seawater systems should whenever possible be installed with the spindle in horizontal position. If not, the lower bushing will be quickly worn down because of sand contamination. All pipes must be laid in such a way that they do not obstruct access to or operating of valves and other components. See also 170.76. 170.74 Packings/gaskets Amount and type of packings/gaskets needed as spares must be clarified/specified as early as possible. It should further be evaluated if improved packing/gasket quality may reduce the long term maintenance costs. Rubber gaskets are normally made of Nitrile and are suitable for mineral oils, sea water, light acids and alkalis. Gaskets of Viton are also being used. This quality is more resistant to gasoline with additives, somewhat stronger acids and higher temperatures. Temperature limits with Nitrile gaskets - 30˚C to + 80˚C Temperature limits with Viton gaskets - 30˚C to + 190˚C

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170.75 Vent/Drain Systems Piping systems must be installed in such a way that entrapped air is avoided (especially on the suction side). The highest point must have a vent valve and possibilities of draining from the lowest point. This is especially important for laid up ships. For details, see the respective Groups. 170.76 Access Pipelines to be arranged as neatly and surveyable as possible. Pipes must not obstruct doors, hatches, manholes or normal traffic. An important point is further to fit each pipe in such a way that it can be dismantled without having to dismantle a number of other pipes to gain access. Further make sure that pipelines do not obstruct manoeuvring and control of machinery and equipment. Necessary inspection and maintenance not to be obstructed. Also check that pipelines are made in demountable sections/pieces in the vicinity of machinery and equipment, which normally will be dismantled during periodical overhauls. Piping must also be arranged demountable where necessary for access to other pipe systems or electrical systems. Necessary shut-off valves must be installed where pipe lengths may have to be removed, so that the rest of the system can function as close to normal as possible. However, the number of removable pipe lengths should be kept at a minimum. When arranging piping in the engine room, precautions should be made to facilitate removing pipes and pipe systems if it becomes necessary to transport damaged as well as new propeller shaft or intermediate shafts through opening cut in ship’s side. See also Gp 16. Valves and other armatures, which are welded/fitted on the pipeline, must be easily accessible for maintenance and repair on location. These must also be installed in such a way that pipes can be changed, welded, heated and stress-relieved (normalised) when necessary. 170.77 Inspection on board Following should be checked (see also 170.5): * Leakage test of the piping systems by using at least the relevant working pressure. Pipes

that are normally not tested in the pipe shop, such as heating coils, crude oil pipes etc. to be tested to pressure 1,5 x working pressure or minimum 4 bar. Hydraulic piping should be tested to 1,5 x working pressure or 70 bar above. (For hydraulic piping, see MGp 8/Gp 83).

* Clamping and support of pipes and valves. * Corrosion protection.

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170.8 Control and Maintenance of Cargo Pipes 170.80 General For pipes (especially stainless steel) carrying corrosive liquids like acids etc., and which are only partially filled, the lower part of the pipe will corrode faster than the upper part, with resulting reduced wall thickness. A way to extend the lifetime for such pipes is to rotate them 90° or 180°. The less corroded top of the pipe will then form the bottom, and the pipe will last longer. Internal corrosion and reduction of pipe wall thickness usually start in the lowest part of all horizontally placed pipes, on deck and in cargo tanks and pump room. Corrosion and erosion may also occur in pipe bends on suction- and discharge side of cargo pumps, in raiser pipes from cargo pumps to deck, and in cargo tanks in drop lines from deck. All pipes should therefore be controlled periodically from the outside by ultrasonic measurement, preferably using the same measure points at every control. When the wall thickness is reduced to a certain value (depending on pipe diameter and wall thickness) the pipe should be turned 90°. To allow turning, connected flanges and clamps must be dismantled. In some cases pipes may also be turned inside the expansion coupling, if centring of the pipe is properly done before starting the work. The turning is usually carried out by tackles and by using supports with rollers under the pipe, in order to carry the weight of pipes when turning. To allow turning without to much dismantling, equipment and possibility of turning the pipes should be taken into consideration when the ship is being built. When using pipe materials such as black steel or ductile iron, uncoated inside, experience shows that these pipes may have to be turned 90° after 8-10 years in service and 180° after 12-15 years. Further, the last turning (270°) may have to be done after 17-20 years, depending on type of cargo and pretreatment of pipes. In cases where the pipes are not blasted or coated at the newbuilding stage, blasting and painting after the vessel has been in service for some years, are expensive and time-consuming jobs, compared with turning of the pipes. In many cases this can be carried out on a ballast voyage if the work is correctly planned and necessary tools and work force are available. For corrosion in general, see Part I, Ch. 4 of the Manual. See also 171.2. 170.81 Inspection of cargo pipes from the inside Such inspection can be carried out if the pipe diameter allows a person to move inside the pipe. Before starting the inspection the pipe should have at least two pipe bends removed, one for entering and one for escape. Furthermore, the pipe must be ventilated, cleaned and gas-free.

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For moving inside the pipe, the controller is using a skateboard. Communication to be maintained by walkie-talkies, with one person following the controller and marking on a sketch the results reported, using nearest flange or expansion box as reference points. Quite often local pittings are found, the depth and size of which can be measured or judged by an experienced controller. Max. depth of pittings must also be evaluated based on location of the pipe. (A leaking cargo pipe on deck may lead to greater consequences than a leaking pipe in the tanks). Note: Video inspection is safe and possible for small pipe dimensions. 170.9 Bulkhead penetrations 170.90 General Penetration pieces are not possible to turn. When corroded they are usually to be repaired in place by welding. Repairs to be approved by Class.

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171 PIPING ARRANGEMENTS 171.0 General Guidelines SGp 171 does not deal with theoretical fluid dynamics. Such information may be found in various textbooks, if needed. Pipe dimensions are mainly decided by how the system is operated. If basic conditions are changed, in particular the velocity of flow must be re-checked. Too small dimensions will cause turbulence; too large may cause problems when draining the system. If the flow speed is critical, choice of material is important. Pipes should not pass through tanks and void spaces where a leakage can create problems. (Check with Class). It is also very important to consider the danger of fire. Pressure pipes should normally not pass through void spaces, cofferdams or other rooms where access is limited. It is also very important that pipes, except those necessary for the tank area itself, in general do not pass through any of following spaces/tanks: * Chain lockers * Fresh water tanks and ballast tanks * Fuel oil tanks If pipes other than those needed for the tank itself, pass through a fuel oil tank, make sure that the pipe installation is performed with extra care. If the pipes carry anything else than fuel oil, all pipe joints must be welded. 171.1 Flow Conditions/Branch Pipes 171.10 General Sudden changes in flow direction should be avoided. Pipe bends should have large bending radius and must be without unevenness. The below sketches show typical branch connections. For lager diameter pipes, branch pipes should normally be welded. For copper pipes the welding procedures favour the design shown to the right. However, the angle α should for copper pipes not be less than 70o. This design is also preferable for seawater piping, both from a corrosion and erosion point of view. It is, however, costly, hence a design as shown to the left will in most cases be found acceptable. The branch pipe must not proceed into the main pipe.

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As an alternative to welded branch pipes as shown above, pre-made branch connections can be used. These give smooth transitions and move the welding outside the critical areas. When a large diameter branch pipe requires removal of a substantial part of the main pipe, it may be necessary to introduce a reinforcement to maintain the strength of the pipe connection, see also 172.5. Sudden changes in cross section areas should be avoided. If absolutely necessary, the transition should be made conical with a gradient not exceeding 1: 6. Below are shown poor and favourable designs of transitions between large and smaller pipe diameters, bends and branches.

The figures to the left show wrong transition, bending and connection respectively. Correct solutions to the right.

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171.2 Galvanic Corrosion 171.20 General All components in a system must be evaluated jointly to avoid conditions giving galvanic corrosion. Galvanic corrosion is a bigger problem outdoors than indoors. This because: * The contact area is wet over longer periods of time. * Sea water and pollution create an electrolyte film on the surface which has a high conductance. Note: Some classification societies demand an extra earthing of flanges in cargo systems. 171.3 Erosion 171.30 General Erosion may appear when the flow speed is too high or the flow is turbulent (“Turbulence corrosion”). The protective film that often decides the pipe’s corrosion durability may be worn down and the exposed metal attacked. Erosion corrosion appears among other things in water pipes of copper and copper alloys, also including pipe bends, valves and pumps. To avoid this, the flow speed should generally not exceed: * Pure copper : 1,0 m/s * Admiralty copper : 1,8 m/s * Aluminium brass : 2,2-3 m/s * Copper/nickel Cu 90, Ni 10 : 2,5-3,5 m/s * Copper/nickel Cu 70, Ni 30 : 3,5-4,5 m/s * Galvanized steel : 2,0 m/s 171.4 Special Arrangements 171.40 General Some piping systems must be specially considered, because of large dimensions (e.g. cargo lines), access etc. See also MGp 3/Gp 35 - Loading and Discharging Systems for Liquid Cargo.

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171.41 Piping systems in the accommodation Pipes in accommodation and related areas are made of various materials, such as copper, lead, PVC etc., depending on purpose and price. The pipe system must be completed and pressure tested before the interior work is finalised, and when there is access to the whole system. Supt. should carefully inspect all pipes for leakages and proper clamping. All penetrations must be checked, and defects corrected. When everything is found in order, the insulation work, panelling, deck covering etc. can be completed. Note: Remember that pipes and electric cables can be damaged by careless use of nails,

spikes etc. 171.42 Vent- and sounding pipes Vent pipes from tanks containing flammable liquids and outlets to the atmosphere from safety valves in pipe systems containing poisonous or explosive gases, must not be placed so that gases can be sucked into the vessel’s ventilation system or into air inlets to engine or boiler room. These vents must also be placed in such a way that waste gas cannot harm machinery or equipment, or become a danger to personnel. See also MGp 3/Gp 37, MG 5/Gp 57 and MGp 8/Gp 82. Note: Check the vent pipe diameter regarding filling capacity, and the chances of over-

filling during bunkering.

Sounding pipes for heavy fuel generally to be at least 50-100 mm (50 is min. Class requirement). No other pipes than those necessary for the tank itself should pass through cargo tanks.

171.5 Marking/Labeling 171.50 General Pipelines should be clearly marked to distinguish between the different systems. In addition, valves, pumps, temperature and pressure sensors etc. should be uniquely identified. This identification should correspond to the component identification used on the drawings and schematic diagrams. No stamp marking is allowed. Welds can be marked by paint if required.

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172 BENDING, WELDING AND JOINING OF PIPES 172.0 General Guidelines Requirements as to preparations vary with materials and area of application. Pipes and fittings under high stress must not be exposed to impacts or hammer strokes that can cause local damage. Chips/cuts or other sharp changes of contour that may cause stress concentrations are not to be accepted. The pipe surface must not be polluted by corrosive particles, or other items that may damage the surface. This especially relates to non-iron metals and sulphur alloys. Further, following guidelines to be adhered to: * Steel pipes, flanges and fittings must not at any stage be in contact with non-iron

metals. * Only clean, new fine-grained sand, which has not been used for other purposes, to be used when bending pipes. * Use only steel hammers when preparing for bending. 172.1 Bending of Steel Pipes 172.10 General See the Class rules (e.g. DNV Pt.4 Ch.6 Sec. 7 C) for bending and heat treatment. For bending of copper/copper-alloyed pipes, see 173.11. When fabricating smooth pipe bends, the material in the bend’s outer side is stretched and the inner side is shortened. The reduction in wall thickness at the outer side is approximately: Bending radius r 3D 4D 5D Reduction in % 16 13 10

D = the pipe’s outer diameter

This reduction of thickness must be evaluated when inspecting, and is very important when the pressure is high. When a pipe is bent it becomes oval. The “out-of-roundness” (ovality) should for (high pressure) pipes not exceed approx. 7 %. 172.11 Cold bending/annealing Pipes of carbon steel or alloyed steel in accordance with DIN 1629 or DIN 17175 can be cold- bent. It is normally not necessary to require annealing after cold bending of carbon steel for normal use (exceptions are high pressure steam pipes). Pipes for special purposes must normally be

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annealed after cold bending. If the bending radius is less than 10 D, the entire cold-bent area should be annealed. For details, see Class rules. When annealing steel in accordance with DIN 17175, and St 35 and St 45 in accordance with DIN 1629, the annealing temperature in the following table should normally be applied for a period of 15 minutes.

Steel type Annealing temperature °C DIN 17175 St 35.8 St 45.8 15 Mo 3 13 Cr Mo 44 10 Cr Mo 910 DIN 1629 St 35 St 45

650 - 700 650 - 700 660 - 700 680 - 720 730 - 780 650 - 700 650 – 700

172.12 Hot bending Hot bending of steel pipes is no longer common procedure at modern shipyards. However, carbon steel or alloyed steel according to DIN 1629 or DIN 17175, may be bent at temperatures in the range 850-1000 °C. When forging/upsetting, the temperature should be 950-1000 °C. All pipes should be packed with clean, dry silicate sand before hot bending. Make sure that the pipe is evenly heated in way of the cross section, which is to be bent or forged. During forging or bending, an acetylene burner may be used to maintain correct temperature. Carbon steel pipes with a diameter of 75 mm or less, and chrome-molybdenum steel pipes with a diameter of 50 mm or less, can be heated with a blowpipe/torch before bending or forging. However, every precaution should be taken to make sure that the cross section is heated gradually, to prevent local overheating. It is also important that the heated area is within the specified temperature ranges. Temperature chalk may be used. Heat treatment of DIN 17175 steels, and St 35 and St 45 of DIN 1629 is generally performed according to the temperatures (oC) given in the below table:

Steel type Normalising temp. Hardening temp. Tempering temp. DIN 17175 St 25.8 St 45.8 15 Mo 3 13 CrMo 44 10 CrMo 910*) DIN 1629 St 35 St 45

900 - 930 870 - 900 910 - 940

900 - 930 870 - 900

910 - 940 900 - 960

650 - 720 680 - 780

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*) Alternatively this steel can be heat-treated by heating to 900-960 °C with subsequent cooling in oven to 700 °C in one hour. After that, cooling in air. Make sure that the heat-treated parts get correct temperature all through the cross section. The specified tempering temperatures must be kept for at least 15 minutes. During bending and forging, the temperature in the pipe to be checked using temperature sticks, pyrometers or by other reliable means. This to prevent overheating, and to make sure that the forming is done within the correct range of temperature. 172.13 Induction bending The induction bending method is normally used for pipes with large wall thickness and is based on heating the material by using eddy current induced by a fluctuating electromagnetic field. Different current frequencies are used, depending on wall thickness and material type. In principal, all pipes and profiles having a current-carrying capacity can be induction-bent, e.g. carbon, low alloyed and stainless steels. The advantages of this method compared to traditional bending are: * Reduced fabrication- and inspection work * Reduced extent of documentation * Fewer welds, increased safety * The bending radii and angles can be freely chosen, within reasonable limits * Improved medium flow, because of fewer joints and thus a smoother internal surface A general problem is limited availability of induction bending machines at the shipyards, hence subcontractors are often used for this work. 172.2 Welding of Steel Pipes 172.20 General See Class rules. For detailed welding procedures, see Part I/Ch. 4 of the Manual. Welding electrodes used for arc welding as well as for other welding methods should be approved for the actual pipe material. The filler material must give deposited metal of same chemical composition as the base metal. When acetylene welding of carbon steel pipes, the filler material should not contain more than 0,03 % sulphur and 0,03 % phosphorus. When acetylene welding of pipes of 15 Mo 3, 13 CrMo 44 and 10 CrMo 910 in DIN 17175 and armatures in cast steel of GS-22 CrMo 54 in DIN 17245, the filler material must not contain more than 0,02 % sulphur and 0,02 % phosphorus. For welding of copper/copper-alloyed pipes, see 173.1.

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172.21 Adjustment of pipe ends prior to joining by welding Pipe ends and flanges, or other pipe connections, should be in exact alignment prior to and during welding. Make sure that the difference in pipe diameters does not exceed the values stated in the table below. Any misalignment must be kept within the limits given in same table. Out-of-line/misalignment which can result in crack initiations cannot be accepted.

Inner diameter Max. difference inner diameter Above Up to

and incl. With backing

ring Without backing ring

Max. misalignment without backing ring

mm

100 305

mm 100 305 610

mm 0,4 0,4 0,8

mm 0,8 1,6 1,6

mm 0,8 0,8 1,0

Adjustment of the pipe ends by slight machining, drifting or rolling may be accepted. If drifting is to be used, the drift must be slightly conical and the new inner diameter must not be increased by more than 3 %. (Pipe material to be taken into account). If machining is used, make sure that pipe’s inside transition is smooth and that the chamfer is not steeper than 1:4. 172.22 Welding connections/joints - general The pipe arrangement should have as few joints as possible, taking possible later dismantling into account. Joints should as far as possible be welded in the workshop. Onboard assembly joints should be selected with a view to adequate access to facilitate welding and subsequent inspection. 172.23 Types of joints/welding grooves When joining pipes, the weld preparations/grooves should be as shown in below sketches, which depending on the welding method, should be self-explanatory:

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The weld preparations/groove surfaces may be prepared by machining, grinding by emery disk, by chipping or be gouged or oxy/acetylene cut. Make sure that the finished joint surfaces are smooth and without any mill scale, dirt, oil, grease, rust etc. within a distance of minimum 15 mm from the groove. For straight pipelines, make sure that the pipe ends are perpendicular to the pipe axis. For pipes that form an angle to each other, the joint must bisect (halve) the angle between the two connecting pipes. A suitable welding jig to be used to keep the pipes in position, until the weld is strong enough to support the free length of the pipe, making it possible to remove the jig. Temporary alignment arrangements such as lugs etc. should be avoided if possible. This applies especially to alloyed steel pipes. If temporary arrangements cannot be avoided, the welding conditions and procedure must be the same as for the pipe joint. Upon completion of the welding, all temporary fittings such as lugs etc. should be removed. These may be removed by oxy/acetylene cutting and grinding disk or by cutting disk etc. Due care to be taken to avoid over-heating. Care should also be taken to ensure that the full pipe thickness is maintained in way of the weld.

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Tack welds in the welding groove should be avoided. If necessary, tack welds to be ground before final weld. Generally, tack welds should be of same quality and performed according to same procedure as the main weld, and properly fused into the main weld. When welding pipes of different wall thickness or welding pipes to T-pieces, the transition needs to be chamfered when the difference of the two thicknesses exceeds 10 %. 172.24 Preheating Make sure that pipes with wall thickness above 6 mm, of 13 CrMo 4 4 or 10 CrMo 9 10 in DIN 17175, are preheated to 200-300 °C prior to welding. Alloyed steel armatures/fittings must normally be preheated to 200-300 °C prior to welding. Care to be taken when preheating armatures with short stubs/joint pieces, this to avoid overheating of the valve body and associated seals. The weld’s start position should always be well heated. 172.3 Welding Methods 172.30 General It is essential in all welding processes that slag etc. is removed from each weld run/bead before the next one is laid. Start and stop positions require special attention to ensure that these are free from slag inclusions and/or pore holes. It is also essential that all visible defects are ground out or removed by other acceptable means, before applying the next weld bead. See also Part I/Ch. 4 of the Manual. 172.31 Acetylene welding Acetylene welding can normally be used for pipes with diameter not exceeding 100 mm and with a max. wall thickness of 9,5 mm. It can also be used for welding of the root pass. The rest of the weld will, however, have to be completed by an electric welding process. Use a neutral flame for all acetylene welding of steel pipes. When the wall thickness exceeds 4,5 mm and for multiple pass welding, right hand welding with a nozzle that matches the pipe dimension/thickness is normally used. For weld preparations/grooves, see 172.23. For thin-walled pipes with small diameters a total groove angle of about 80-90° and left hand welding is normally used. The root opening should be about 3 mm, and the root face about 1,5 mm. Backing rings not to be used when acetylene-welding pipe joints.

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172.32 Electric (manual) welding Electric manual welding may be used for steel pipes with wall thickness above 3 mm and outer diameter exceeding 75 mm. Electric welding processes may also be used on steel pipes down to 50 mm diam. where the wall thickness exceeds 4,5 mm. Following methods may be applied: * Electric arc welding (“Manual Metal Arc Welding - MMAW”) without backing rings * Electric arc welding with temporary or permanent backing rings * Electric arc welding with acetylene-welded root pass For details, see Part I/Ch. 4 of the Manual. Following guidelines should be adhered to: * Make sure that all temporary and permanent backing rings for welding of carbon steel

are made of mild steel of high quality. For alloyed steel, the rings should be of same material as the pipes. Ceramic backing may also be used.

* Permanent backing rings should be allowed only as an exception. The pipe’s inside to

be as smooth as possible. * Temporary backing rings must be easy to remove after the welding is completed. Make

sure that these have a dimension of about 20 x 4,5 mm. For welding grooves, see 172.23.

* To ensure good fusion, high quality root passes are necessary. The root opening to be

increased as necessary. A max. size electrode should be used for welding the root bead. * When welding without backing rings, the weld preparation/groove should be as shown

in 172.23. The weld should start at the pipe circumference’s lowest point (“6 o’clock”), continue on the pipe’s left side and stop at “12 o’clock”. Same procedure should be repeated on the pipe’s right side. The weld is then completed by applying the necessary number of weld beads/runs.

An acetylene-welded root pass is well suited for providing both good fusion and a small weld (“capping”) inside the pipe. Groove should be as shown in 172.23 for the relevant welding position, and right hand welding should be used. 172.33 Automatic welding Can be used on pipes of most diameters. Automatic welding processes for pipes involve an arrangement where the work piece is set up in a welding jig, which incorporates the weld application tool. There are two main methods

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in use one - where the application tool rotates around the work piece and another version where the application tool is stationary and the work piece rotates. The advantage is that all welding parameters can be accurately controlled and the result is uniform quality in the weld deposit. The disadvantage is the time needed to rig the set up, and the process is therefore most economical for larger diameters, straight lengths of pipe. 172.34 Inert gas welding There are numerous processes where gas shielded welding is approved for joining pipes. See Part I/C. 4. Inert gas welding is often used for root passes. 172.4 Heat Treatment after Welding 172.40 General All steel pipes for working pressure above 10 kp/cm2 or working temperatures above 300 °C, to be annealed after welding. Make sure that the weld is given enough time to cool down to below 100 °C prior to annealing. Annealing is normally not necessary for thin-walled pipes of St 35 and St 45 in DIN 1629, or St 35.8, St 45.8 and 15 Mo 3 in DIN 17175. Exceptions are listed in the previous sections. Pipes fabricated of 13 CrMo 44 or 10 CrMo 910 in DIN 17175 should be annealed. Equivalent heat treatment can be used, as an alternative to annealing. Annealing to be done within the temperatures shown in below table:

Type of steel Annealing temp. (after welding) St 35.8 St.45.8 15 Mo 3 DIN 17175 13 CrMo 4 4 10 CrMo 910

650 - 700 650 - 700 660 - 720 680 - 720 730 - 780

DIN 1629 St 35 St 45

650 - 700 650 - 700

The temperatures given, must be kept for about 15 minutes (holding time), counted from the time when the lowest temperature limit is reached. Annealing should be performed over an area at least 75 mm on both sides of the weld. All annealing of pipes should primarily be done in stationary heating ovens. For long pipes not fitting into the oven, or by annealing on board, a portable, special oven may be used.

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Other alternatives are gas heating or electric heating by induction coils, resistance coils or copper blankets. Heating by manually operated oxy/acetylene burner should be accepted only if other methods are unsuitable or not available. If applied, make sure it is done carefully, so that no local over-heating occurs. Temperature chalk may be used for control. Temperatures should be controlled by thermoelements or other reliable methods. 172.5 Branch pipes 172.50 General Following guidelines should be adhered to: * Special purpose pipes should, whenever possible, have T-pieces instead of welded

branch pipes when the branch pipe’s diameter exceeds 1/4 of the main pipe’s diameter. In special cases, when suitable T-pieces are unavailable, the branch pipe can be welded directly onto a larger main pipe, even if the diameter of the branch pipe exceeds 1/4 of the main pipe’s diameter. See sketches 171.1.

* For thick-walled pipes with small diameter, welding of branches can normally be

allowed, but T-pieces are desirable. * For special purpose piping systems, branch pipes must be welded according to approved

procedures/drawings. Also for normal pipe systems, the joint/groove types to be considered.

* Welding of branch pipes on special purpose pipes should be done indoors, or under

other equally controllable conditions. Also branch pipes on normal pipes should preferably be welded in “indoors” conditions.

All holes/openings in the main pipe for inserting branch pipes should be machined. The weld groove should be made by chipping, grinding or filing. To ease the work, a hand-operated gas burner may be used, if sufficient material remains for chipping etc. Bigger openings in main pipes should be compensated for by reinforcements to maintain the strength. See also 171.10. 172.6 Welding of flanges 172.60 General Below sketches and table (Source: DNV) show recommended welding/attachment of various types of flanges. For nominal pressure above 10 kp/cm2, welded flanges must be of a type A. Weld requirements as for normal butt welds. The inner pipe surface should if possible be ground smooth after welding.

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For pipes with a nominal working pressure below 10 kp/cm2, welded flanges can be of type B. The flange must fit the pipe properly, with a clearance not exceeding 0,5 mm, at any place around the circumference. For C and E, see table below. D is threaded and F shows an attachment where the pipe end is flanged to fix the loose flange. Note: If a welded joint can replace a flange, this is a better solution with regard to

corrosion. However, the need for dismantling of the pipe system for repair or maintenance is to be taken into consideration.

Type of flange connections Steam Lubricating and fuel oil Other media Class of

piping t (°C) Typical flange application

Typical flange application t (°C) Typical flange application

I > 400 ≤ 400

A A - B 1)

A - B A - B

> 400≤ 400

A A - B

II > 250 ≤ 250

A - B - C A - B - C - D - E

A - B - C >250≤ 250

A - B - C A - B - C - D - E - F

III A - B - C - D - E A - B - C - E A - B - C - D - E - F 1. Type B or outer diameter < 150 mm only.

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172.7 Finishing Welding Work 172.70 General Important checkpoints are (see also Part I/Ch. 4): * All welds should have a smooth surface without any undercuts. The weld to have

suitable height/capping. The surface of butt welds must not be lower than the pipe’s surface. If necessary, improvement of the weld must be performed by repeated welding. If so, any previous stress revealing/annealing must be repeated.

* If the weld’s surface is rough or the height/capping is too big, the weld must be ground

as smooth and flat as possible. Make sure that the pipe itself is not ground, and avoid local over-heating (which may cause small surface cracks).

* If access, the weld should be ground smooth also on the pipe’s inside. 172.71 Welding faults/repairs Chipping or grinding may remove minor defects. Removal by gas burner may be acceptable if the area is well ground afterwards. For details, see Part I/Ch. 4.

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173 PIPE MATERIALS 173.0 General Guidelines See Part I/Ch. 4 of the Manual as well as the Class rules. 173.1 Copper/Copper Alloys Piping 173.10 General For pipes of copper and copper alloy with a working pressure above 7,5 kp/cm2, certificates issued by Class may be required. For pipes with working pressure below 7,5 kp/cm2, a Works’ Certificate is normally satisfactory. The chemical composition of applied copper and copper alloys in piping to be according to a recognised norm, e.g. DIN, British Standard or ASTM, and the pipes to be tested as required by Class. When using special alloys, it is important to check the material composition, because minor changes in the composition may cause substantial changes in quality. Small changes in chemical composition may have great influence on the material quality, this being the reason for defining close tolerances in the standards. The Class may allow threaded fittings in pipe systems for non-flammable liquids. Max. diameter 50 mm and max. working pressure about 7,5 kp/cm2, see also 172.6. Couplings with brazed or welded cones, split rings or compression joints of approved make, can be applied for pipes below 50 mm diameter, without pressure limitations. For branch pipes see 171.1. 173.11 Bending of copper/copper-alloyed pipes The bending radius measured from the pipe’s centreline must not be less than 1,5 times the pipe’s outer diameter. For seawater pipelines the bending radius should not be less than 3 times the diameter. Pipes that are not bent over an inner drift or in a pipe-bending machine must generally be packed with clean, dry silicate sand and blinded in both ends with wooden plugs. Pipes with relatively thick walls compared to the diameter, may be bent without filling, when the diameter is less than 50 mm and no ovality occurs in the bend. Cold-bent pipes with a diameter of 25 mm or more must normally be heat-treated after bending and before testing. Recommended annealing temperatures are:

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* De-oxydised copper : 375 - 650 °C * CuNi 90 10 : 600 - 800 °C * CuNi 70 30 : 650 - 870 °C * Aluminium brass : 425 - 595 °C Recommended temperatures for hot bending are: * Deoxydised copper : 850 °C * CuNi 90 10 : 850 °C * CuNi 70 30 : 1000 °C * Aluminium brass : 850 °C However, hot bending of CuNi 90/10 is normally not required, as the hardening will be limited. (For 5% nickel alloys, the temperature may be reduced by 100˚C). There should not be any unevenness in seawater pipe bends. See also 171.1. 173.12 Soldering (For details, see Part I/Ch. 4). For all pipes with pressure above 7 kp/cm2 or temperatures above 95 °C, hard soldering (brazing) to be used, i.e. soldering with working temperatures above 450 °C. Also for pipe systems with CuNi or aluminium brass pipes, hard soldering normally to be used. For other pipe systems soft soldering may be applied. Hard soldering can be done by blowtorch, in a forge or in an annealing furnace. The soldering metal used must be according to applicable standards. For copper pipes, copper phosphorus metals can be used. When applying these metals on copper pipes, soldering paste is not necessary. However, copper phosphorus metals cannot be used when soldering CuNi pipes. These pipes should be soldered with silver-based solder. When using silver-based soldering metal, a soldering paste, e.g. borax must be used. To achieve a good soldering connection, the surfaces have to be well cleaned and without any dirt, grease, oxides etc. The more “shiny” the surfaces are, the better will the connection between the soldering metal and the relevant parts be. Soldered flanges and fittings must be accurately adjusted, with specified clearance to pipes and/or armatures, so that the soldering material is sucked into the soldering groove by capillary effect. The cylindrical clearance between pipe and flange/muff should be about 0,05-0,1 mm. If possible, both sides of a soldered joint should be inspected. The soldering metal must penetrate the clearance all along the circumference. Cleanliness is of vital importance since molten brazing metal will only ad-here to a clean surface. Foreign matter such as oxides, lead and sulphur may cause embrittlement.

30


Material that is to be brazed must be annealed. Stresses in the material either from cold working or imposed during the brazing, may lead to cracking adjacent to the joint. Silver braze according to BS 1845 type 4 or similar with suitable flux, must be used. Any remaining flux after brazing should be removed. 173.13 Preparatory work/welding joints Fillet welds should be avoided for copper pipes. For welding of branch pipes in general, see 172.5. For butt-welding, the weld preparations/grooves may be as shown in below sketch. The Class may allow other joint/groove designs, if these give satisfactory welding.

When welding Cu and CuNi pipes, pre- and post heating are normally not required, neither is heat treatment after welding. However, a light preheat to 50-100 ˚C will remove any moisture. Butt welding of pipes should normally be done in a horizontal position. During the welding, the pipe should be rotated so that the welding is constantly performed on the pipe top (“12 o’clock”). Pipes of copper and copper alloys may be cut by a gas burner. The groove surfaces are to be ground or filed.

For gas welding t ≤ 1,5 mm El. welding t ≤ 4 mm

For gas welding t > 1,5 mm El. welding t > 4 mm α = abt. 60˚ for copper pipes, abt. 70˚ for CuNi pipes.

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173.14 Welding methods Welding of Cu and CuNi pipes can be done by gas welding or metal arc welding with inert gas. (1) Gas welding When gas welding Cu pipes, the flame must be neutral or slightly oxidizing. When gas welding CuNi pipes, the flame should be neutral or slightly reducing. In both cases soldering paste should be used. Flux material and melting electrodes must suit the relevant copper alloy and have same or better qualities regarding mechanical strength and corrosion resistance. When welding Cu pipes, the flux material and melting electrodes must be copper. When welding copper-alloyed pipes, flux material and melting electrode must be a copper alloy, e.g. Monel. (2) Metal arc welding Metal arc welding with inert gas can be done by melting (MIG) or non-melting (TIG) electrode, and a special flux material. The inert gas can be argon or helium. For CuNi pipes, metal arc welding with inert gas will normally give a better result than gas welding. When metal arc welding Cu/CuNi pipes with inert gas or gas welding Cu pipes, backing rings may prove useful. If such rings are used, they should be removed after the welding is completed. See also Part II/Ch. 4 of the Manual. 173.2 Stainless Steel Piping 173.20 General Stainless steel is according to definition a high-alloyed steel with more than 5 % additives. Special alloyed steel such as stainless steel and acid proof steel are subjected to galvanic corrosion, in addition methods of clamping and jointing must be carefully considered in accordance with the thickness of the material chosen. 173.21 Bending For induction bending see 172.13. 173.3 Non-Metallic Piping 173.30 General For details, see also Part I/Ch. 4. See also the Class rules.

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173.31 Plastic piping Plastic materials to be of approved type and normally only used in areas where the temperature is in the range 0-50 °C. Max. working pressure 10 kp/cm2. Plastic is not allowed in pipelines carrying oil or other flammable liquids or in fire- and bilge lines, feed water and condensate lines or in main cooling water systems. Plastic pipes can not be used in direct connection to sea- and overboard valves, in drain pipes below freeboard deck or as sounding pipes in oil tanks. Application of plastic pipes is limited by IMO`s fire endurance requirements (Appendix 1-2 Res. A.753). Plastic pipes have qualities clearly superior to e.g. steel. Corrosion, in traditional terms, is not an issue, maintenance work is decreased and the system lifetime is increased. However, this is only achieved through proper fitting and operating procedures. Installation is also expensive and time consuming since the demand for accuracy is high. GRP and GRE pipes require special treatment during transport, lifting, storing, installation and operation. If the flow medium temperature may exceed 75-80 °C, GRP should not be used, see maker’s specification. See also Part I/Ch. 2. GRP and GRE pipes may be used for sea water and crude oil inside tanks, cofferdams, void spaces and pipe tunnels. PVC and similar pipes may be used in accommodation for fresh and grey/black water, on the condition that fire integrity is maintained by special deck penetrations. For GRP and GRE piping it is of importance that point loadings due to clamping or supports are avoided. The clamps should be made of steel with an inner pad of soft plastic material. The width of the clamps should be 20-50 % larger than normally specified for flat bar clamps. Correct clamp spacing for GRP piping depends on various factors such as pipe material, diameter and pipe wall thickness, weight and temperature of flowing fluid and potential vibrations. Maximum acceptable clamp spacing will normally vary from 1 to 2 m for small diameters and from 2,5 to 4 m for larger diameters. A minimum of one anchor point for each joint should be used. Flanges are often used as anchoring points for GRP piping. For clamping of PVC and other thermoplastic piping, see NS 6085 as an example of acceptable clamping.

33


An example of supporting and clamping is shown below:

Permissible pressures and temperature limits for thermoplastic pipes (i.e. a “softer” type of plastic) and GRP pipes are given in below tables (Source: DNV):

Thermoplastic pipes. Permissible pressures and temperature limits Permissible working pressure (bar)

Material Nominal pressure 1) PN (bar) - 20 to

0°C 30°C 40°C 50°C 60°C 70°C 80°C

PVC 10 16

7.512

6 9

6

ABS 10 16

7.5 12

7.512

7 10.5

6 9

7.5

6

HDPE 10 16

7.5 12

6 9.5

6

1. According to recognised standards for water supply on shore.

Glass fibre reinforced epoxy 1) and polyester pipes (GRP). Permissible pressures and temp. limits Permissible working pressure (bar) Minimum heat distortion

temperature of resin ISO 75 Method A

Nominal pressure 2) PN

(bar) - 50 to 30°C 40°C 50°C 60°C 70°C 80°C 90°C 95°C

80 10 16 25

10 16 16

9 1416

7.51216

6 9.515

100 10 16 25

10 16 16

101616

9.51516

8.513.516

7 11 16

6 9.5 15

135 10 16 25

10 16 16

101616

101616

101616

9.5 15 16

8.5 13.5 16

7 11 16

6 9.5 16

1. Minimum heat distortion temperature 135°C.

2. According to recognised standards for marine use.

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173.32 Transport and storage Transport must be performed with care, using e.g. wooden pieces to protect pipe ends and between the pipes. When lifting GRP pipes, never use steel wires or chains but straps of canvas or nylon. Pipes to be carefully handled and not exposed to impacts. Pipes should not be stored in temperatures higher than 50 °C. If this cannot be avoided, stacks of pipes should not exceed 2 m, to avoid deformation of the lower pipes. It is important to check that no damages have occurred to the pipes during transport and storing, especially on the machined pipe ends. If storing raw materials for pipe repairs on board, max. storage temperature to be 25 °C. Rolls of glass fibre should be sealed in plastic to avoid humidity absorption, and chemicals must be stored well separated. 173.33 Installation and repairs To be done by specialised personnel only. The specialists’ qualifications should be checked. Temperature when joining or repairing should be approximately 20 °C. All surfaces must be dry. Check maker’s recommendations for detailed procedures. Sliding clamp supports must have PVC saddles, with spacers between the clamp halves. Fixed clamp supports must have rubber liners. Each must have at least one fixed clamp support. Pipes to be protected from welding spatter, sand blasting etc. Under no circumstances, smoking or use of open flame must occur. Painting of GRP pipes is possible but is not necessary or recommended, because paint may hide scratches and damages. Check supplier’s documentation and recommendations for details. 173.4 Flexible Hoses 173.40 General Flexible hoses are frequently applied in hydraulic systems. For motors with elastic supports and high revolutions, including compressors and separators, flexible hoses are used to avoid transmitting vibrations to connected pipelines. Flexible hoses should normally only be allowed when make, type and location are stated on approved drawings. All hoses should be as short as possible, with good access for maintenance and repairs. Maker’s instructions regarding minimum bending radius etc. must be followed.

35


Fuel oil, lube oil and compressed air systems should be arranged so that all hoses are possible to separate and shut off from the rest of the system. Note: If hoses can be avoided and replaced by solid pipes, this is a better solution. Main

problems with hoses are danger of damage, corrosion of couplings, UV radiation of rubber, short lifetime etc.

Also see the Class rules. 173.41 Hoses of non-metallic material Such hoses are normally made of special purpose rubber with cord reinforcement and steel sheathing. Couplings are secured by using special press-shrunk fittings, delivered by the hose manufacturer. In branch lines for cooling water systems, normal stainless hose clips may be used, check with Class. 173.42 Hoses of metallic material These are normally corrugated or laminated tubes, usually of stainless steel with welded or hard-soldered couplings and an outer, braided protective sheathing.

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174 PUMP TYPES 174.0 General Guidelines Choice of pumps depends on application area and price. Because of the high number of pumps on most vessels, it is important to evaluate the total need at an early stage, thus making it possible to reduce number of pump types, makes and makers, resulting in a more homogenous stock of spare parts and normally lower prices. For details, see the respective Main Groups/Groups. For cargo pumps, see MGp 3/Gp 35. 174.1 Centrifugal Pumps 174.10 General Centrifugal pumps are normally used when there is a demand for high capacities. When installing, the pump’s limited suction capacity must be considered. It is important to check the pump’s working conditions, and evaluate suction height and possibilities of cavitation. Most centrifugal pumps have mechanical seals, but soft seals may occur. Make sure that the seal is suitable to the pump’s working medium. 174.2 Piston Pumps/Displacement Pumps 174.20 General Piston/displacement pumps are normally used when there is a demand for suction head. Usually driven by an electric motor (or steam). Piston pumps are often replaced by other pump types because of high price and the variable pressure at the pressure side (mainly for larger pumps). 174.3 Gear Pumps 174.30 General Gear pumps are usually applied for smaller capacities, like lubrication, fuel oil and hydraulic systems.

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174.4 Screw Pumps 174.40 General Screw pumps are primarily used as lube oil and fuel pumps, but also as cargo oil pumps and in hydraulic systems. 174.5 Wing Pumps/Sliding Vane Pumps 174.50 General These pumps are mainly applied in hydraulic systems, see MGp 3/Gp 30 and MGp 8/Gp 83. 174.6 Inspection of Pumps 174.60 General Pumps are normally delivered by sub-suppliers. If possible, one should visit the manufacturer and inspect the test runs (for main cooling pumps, cargo pumps, fire pumps etc.). Test programs should include: * Capacity testing * Continuous operation (at least 1-2 hours) * Opening-up for post inspection During capacity testing, the pump’s specifications and characteristics must be noted for later filing on board. When running continuously, bearing temperatures etc. to be controlled. Stuffing boxes must always be thoroughly checked. When opening up for post control, necessary adjustments to be done and possible damaged parts renewed. Minor scratches and burrs to be polished. Impellers must be carefully examined for casting defects. Minor defects can be repaired by welding. 174.7 Installation on Board 174.70 General Pumps are often installed on foundations after launching. Welding stresses, and in particular strain in pipe connections may occur after the pumps are installed on board. The Supt. must therefore check alignment and fitting after all major welding is completed. In some cases it may prove necessary to loosen the pump’s pipe connections to make sure that pipes and pump are still aligned. Check easy access to the pumps for maintenance and repair. Make sure that there is sufficient headroom for use of lifting tackle. See also MGp 1/Gp 16.

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174.71 Connections It is of utmost importance that pipe connections do not create any operating problems. The below sketches show some examples of connections between pipes and pumps, which should be self-explanatory.

Wrong installation w. concentric Correct installation w. eccentric reduction of pipe diameter reduction of pipe diameter

Unfavourable installation with bend Improved installation. before the pump.

Wrong pipe arrangement on Correct pipe arrangement on the suction side. the suction side. Erosion damages must be avoided when the direction of flow is changed. Entrapped air must be avoided by installing the pump above pipe level on the suction side.

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175 INSPECTION PROCEDURES/PRESSURE TESTING/PREPARATION FOR OPERATION

175.0 General Guidelines All pipes, bends, valves etc. must be cleaned and freed from dirt, mill scale, slag, weld splatter, rust etc. before installing on board. 175.1 Lube Oil Systems and Hydraulic Oil Systems 175.10 General Pipes for lube- and hydraulic oil must be thoroughly cleaned before installation. After fabrication of the individual pipe lengths, inner welds on flanges and pipe joints must be grinded and cleaned. The pipes to be acid-washed on the inside, then flushed with fresh water to remove all acid remains, and finally dry-blasted by compressed air. To prevent inside corrosion during storing prior to fitting on board, the pipe may be coated with a mixture of boiled linseed oil and white spirit. Thereafter the pipes must be checked and plugged. Valves and other components in the system should be cleaned the same way. The cleaning of lube oil systems is very important, but the methods may be different from yard to yard. Sand- or shot blasting of the pipes is also done in advance of the acid cleaning. In these cases it is necessary to remove the blasting particles completely. For lube oil systems for main engine, turbine and gear, the cleaning procedure recommended by the supplier of the machinery/equipment should be followed. After installing the lube oil system on board, it must be flushed with hot oil before the system lube oil is applied. The Supt. to make sure that this procedure is followed. For lube oil systems, see also MGp 7/Gp 71. For hydraulic systems, see MGp 8/Gp 83. 175.2 Lube Oil Piping for Main Engine and Aux. Engines 175.20 General After assembling of main- and aux. engines at the maker’s, all built-on pipes must be well cleaned and flushed. See also MGp 7/Gp 71. Procedure and flushing medium may vary, but the Supt. must evaluate the actual procedure and make sure that the result is satisfying. Thereafter the system can be filled up and the oil must be circulated, preferably with extra oil filters at the engine inlet. After installing on board one must be equally careful, and the procedure must be repeated.

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175.3 Pressure Testing 175.30 General All pipe systems to be pressure-tested according to the relevant authorities’ and Class’ requirements. Pressure testing cannot be carried out before all work on the system is completed. It is very important that all attached branch pipes etc. are tested. Prior to testing, make sure that the pipes are satisfactory supported to carry the extra loads from the test pressure and weight of the testing medium. Pipelines that have been fabricated and pressure tested in the workshop, to be leak tested on board. All other pipes, flange joints and armatures installed on board, to be included in the testing procedures carried out after installation (pressure- as well as leak testing). Make sure that the test pressure is maintained long enough, to allow a thorough inspection for possible leakages. Normally, clean fresh water or the pipe’s actual working medium must be used for pressure testing if nothing else is specified. Sea water can only be used in seawater systems. Test pressure and medium generally to be according to below table: Type of Pipe Testing

Medium Working

Pressure (WP) kp/cm2

Testing Pressure kp/cm2

Compressed Air

FW FW

Below 70 Above 70

1,5 x WP

or min. 4 bar Pipes for Heated Oil under Pressure

FW

1,5 x WP

or min. 4 bar Transfer-, Suction and other Low Pressure Piping

FW

1,5 x WP

or min. 4 bar

Heating Coils

FW

1,5 x max. WP or min.4 bar

Hydraulic Pipes for Winches, Steering Gear etc.

Oil

1,5 x max. WP or a

pressure 70 bar above WP

Feed Water- and Steam Pipes

FW

1,5 x WP or min. 4 bar

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176 SAFETY REQUIREMENTS 176.0 General Guidelines SGp 176 primarily deals with hazards caused by high temperatures, fire- and explosion hazard related to liquids with low flash point, operational reliability related to electrical systems, mechanical safety in connection with vibrations, local stresses, expansion etc. 176.1 High Temperatures – Insulation 176.10 General Boilers, exhaust pipes and pipelines, which during operation may reach temperatures of 220 °C or above to be well insulated. If an insulation material that will absorb oil is used, the insulation must be covered with metal sheathing. This also applies to flange joints. Exhaust pipes and boilers not be installed close to bulkheads adjacent to cargo- or fuel tanks, minimum distance should be 300 mm. Steam pipes in shaft tunnels etc. to be insulated so that the surface temperature does not exceed 60 °C. 176.2 Fire and Explosion Hazards 176.20 General Overflow and vent pipes from tanks alternately containing flammable liquids and water ballast, must be treated as pipes containing flammable liquids. Particular attention to be given to pipes carrying flammable liquids under pressure. Pipelines carrying flammable liquids or gases not to be lead through areas containing electrical machinery and equipment, or through fire control- or communication rooms. Further not close to boilers and other hot surfaces. Necessary pipelines carrying flammable liquids or gases in engine rooms or other rooms containing both machinery and electrical equipment must be placed as far as possible from the electrical equipment. 176.3 Installation Precautions affecting Electrical Systems 176.30 General Pipelines containing steam or liquids must be installed in a way preventing dripping, leakage or condensate from harming/destroying the electrical equipment. If this is not possible and the electrical equipment is not satisfactory protected, the pipes must be equipped with covers. These covers must run all around the pipe, and have open ends. The

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ends must not be close to any electrical equipment. Make sure that the covers are strong enough to withstand mechanical stress. For details, see MGp 8/Gps 85-89. 176.4 Flexibility, Vibrations and Deflections 176.40 General All pipeline systems to have sufficient flexibility to avoid that thermal expansion, dynamic shocks, vibrations and deflections in the vessel cause leakages, deformations or fractures in connected equipment. For details, see the respective Gps.

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Documents

Gp17. Piping Sys Gen