Section 5 Process Pressure Vessels and Liquid,

Piping Systems

Vapour, and Pressure

501. General

1. The requirements for cargo tanks in by the Society. If so required the

Sec 4 may also apply to process pressure vessels if required term "pressure vessels" as used in Sec 4 covers both in-

dependent cargo tanks and process pressure vessels.

2. Process pressure vessels are to meet the requirements in Pt.5 Ch.5 of the Rules or recognized pres- sure vessel codes.

502.

Cargo and process piping

1. General

(1) The requirements of 502. to 505. apply to product and process piping including cargo gas pip- ing and vent lines of safety valves or similar piping. Instrument piping not containing cargo is exempt from these requirements.

(2) Provision are to be made by the use of offsets, loops, bends or similar suitable means to pro-

tect the piping, piping system components and cargo tanks from excessive stresses due to ther- mal movement and from movements of the tank and hull structure. Where mechanical expansion joints are used in piping, they are to be held to a minimum.

(3) Low-temperature piping is to be thermally isolated from the adjacent hull structure, where neces-

sary, to prevent

hull material.

(4) Where tanks or should be made

the temperature of the hull from falling below the design temperature of the

piping are separated from the ship's structure by thermal isolation, provision for electrically bonding both the piping and the tanks. All gasketed pipe joints

and hose connections should be electrically bonded.

(5) Suitable means are to be provided to relieve the pressure from cargo loading and discharging headers and other cargo pressurized lines to the suitable location prior to disconnecting from the loading or off loading facility.

(6) All piping or components that are pressurized with cargo and may be isolated are to be pro- vided with relief valves.

(7) Relief valves discharging cargo from the cargo piping system are to discharge into the cargo vent system.

2. Scantlings based on internal pressure

Subject to the conditions stated in Par 4, the wall thickness of pipes should not be less than:

where:

= theoretical thickness (mm

with:

= design pressure (MPa) referred to in Par 3

= outside diameter (mm )

= allowable stress (N mm ) referred to in Par 4

= efficiency factor equal to 1.0 for seamless pipes and for longitudinally or spirally welded pipes, delivered by approved manufacturers of welded pipes, which are

considered equivalent to seamless pipes when non-destructive testing on welds is carried out in accordance with Recognized Standards. In other cases an efficiency factor of less than 1.0, in accordance with recognized standards, may be required depending on the manufacturing process.

= allowance for bending (mm ). The value of should be chosen so that the

stress in the bend, due to internal pressure only, does Where such justification is not given, should be:

not exceed the allowable stress.

with :

= mean radius of the bend (mm )

= corrosion allowance (mm ). If corrosion or erosion is the piping should be increased over that required by

expected, the wall thickness of other design requirements. This

allowance should be consistent with the expected life of the piping.

= negative manufacturing tolerance of thickness (%).

3. Design pressure

(1) The design pressure in the formula for in Par 2 is the maximum gauge pressure to the system may be subjected in service.

(2) The greater of the following design conditions are to be used for piping, piping systems and components as appropriate:

(A) the MARVS of the cargo tanks and cargo processing systems; or

(B) the pressure setting of the associated pump or compressor discharge relief valve; or

(C) where liquid loading or discharge is used, the maximum total discharge or loading head of the cargo piping system; or

(D) the relief valve setting on a pipeline systems.

4. Permissible stresses

(1) For pipes, the permissible stress to be considered in the formula for t in Par 2 is the lower of the following values:

or

where:

= specified minimum tensile strength at room temperature (N mm

= specified minimum yield stress at room temperature (N mm

If the stress-strain curve does not show a defined yield stress, the 0.2 % proof stress applies. The values of and should be shown on the International Certificate of Fitness for the Carriage of Liquefied Gases in Bulk and have values of at least = 2.7 and = 1.8.

(2) The minimum wall thickness should be in accordance with Recognized Standards.

(3) Where necessary for mechanical strength to prevent damage, collapse, excessive sag or buckling of pipes due to superimposed loads from supports, ship deflection or other causes, the wall thickness should be increased over that required by Par 2, or, if this is impracticable or would cause excessive local stresses, these loads should be reduced, protected against or eliminated by other design methods.

(4) Flanges, valves and other fittings should comply with recognized standards, taking into account the design pressure defined in Par 3.

(5) For flanges not complying with a standard, the dimensions of flanges and related bolts should be to the satisfaction of the Society. Design calculations, materials, dimensions and gasket data

are to be submitted for nonstandard flanges.

5. Stress analysis

A complete stress analysis, taking into account all the stresses due to weight of pipes, including acceleration loads if significant, internal pressure, thermal contraction and loads induced by hog and sag of the ship for each branch of the piping system is to be carried and submitted to the Society.

In any case, consideration is to be given to thermal stresses. The analysis may be carried out cording to ASME B 31.3 or equivalent acceptable to the Society.

6. Materials

The materials used in piping systems are to comply with the requirements of the Pt 2 of Rules and Sec 6 of this Guidance, if low temperature applications are involved, taking into

ac-

the ac-

count the minimum design temperature. Materials having a melting

be used for piping.

point below 925°C are not to

503. Tests of piping components

1. Valves are to be subject to the following tests.

(1) Type tests

Each size and type of valve intended to be used at a working be type approved. Type tests to the minimum design temperature lower than the maximum design pressure foreseen for the valves

temperature below -55°C is to or lower and to a pressure not is to be witnessed in the pres-

ence of the Society’s representative. Type tests are to include hydrostatic test of the valve body

at a pressure equal to 1.5 times the design pressure, seat and stem leakage test at a pressure equal to 1.1 times the design pressure, and cryogenic testing consisting of valve operation and leakage verification at the design temperature.

For valves intended to be used

required.

(2) Production tests

All valves are to be tested at

at a working temperature above -55°C, type approval is not

the plant of manufacturer in the presence of the Society’s

representative. Testing is to include hydrostatic test of the valve body at a pressure equal to 1.5

times the design pressure, seat and stem leakage test at a pressure equal to 1.1 times the design pressure.

In addition, cryogenic testing consisting of valve operation and leakage verification at the design temperature for a minimum of 10% of each type and size of valve for valves intended to be used at a working temperature below -55°C.

As an alternative to the above, the manufacturer may request the Society to certify a valve sub- ject to the following:

(A) The valve has been type approved as required by (1) for valves intended to be used at a

working temperature below -55°C, and

(B) The manufacturer has a recognized quality system that has been assessed and certified by the Society subject to periodic audits, and

(C) The quality control plan contains a provision to subject each valve to a hydrostatic test of the valve body at a pressure equal to 1.5 times the design pressure and seat and stem leak- age test at a pressure equal to 1.1 times the design pressure. The manufacturer is to main-

tain records of such tests, and

(D) Cryogenic testing consisting of valve operation and leakage verification at the design temper- ature for a minimum of 10 % of each type and size of valve for valves intended to be

used at a working temperature below -55 °C in the presence of the Society’ representative.

504. Piping fabrication and joining details

1. The requirements of this Article apply to piping inside and outside the cargo holds. Relaxations from these requirements may be accepted, in accordance with recognized standards, for open-ended piping.

2. The following direct connection of pipe lengths, without flanges, may be considered:

(1) Butt-welded joints with complete penetration at the root may be used in all applications. Butt welds are to be either double welded or equivalent to a double welded butt joint. This may be accomplished by use of a backing ring, consumable insert or inert gas back-up on the first pass. And, backing rings are to be removed.

(2) Slip-on welded joints with sleeves and related welding, having dimensions in accordance with recognized standards, are only to be used for open-ended lines with external diameter of 50 mm or less and design temperatures not lower than -55°C.

(3) Screwed couplings complying with recognized standards are only to be used for accessory lines and instrumentation lines with external diameters of 25 mm or less.

3. Flanges in flange connections are to be of the welded neck type and are to comply with recog- nized standards as to their type, manufacture and test.

4. Piping connections, other than those mentioned in Pars 2 and 3, may be accepted by the Society in each case.

5. Welding, post-weld heat treatment and non-destructive testing.

(1) Welding should be carried out in accordance with 603.

(2) Post-weld heat treatment is to be required for all butt welds of pipes made with carbon, car- bon-manganese and low alloy steels.

(3) All butt welds are to be subject to 100 % radiographic testing.

505.

Testing of piping

1. The requirements of this Article apply to piping inside and outside the cargo holds. However, the Society may accept relaxations from these requirements for open-ended piping.

2. After assembly, all cargo and process piping are to be subjected to a hydrostatic test to at least

1.5 times the design pressure. When piping systems or parts of systems are completely manufac- tured and equipped with all fittings, the hydrostatic test may be conducted prior to installation aboard ship. Joints welded on board are to be hydrostatically tested to at least 1.5 times the design pressure. Where water cannot be tolerated and the piping cannot be dried prior to putting the sys- tem into service, proposals for alternative testing fluids or testing means are to be submitted to the Society for approval.

3. After assembly on board, each cargo and process piping system are to be subjected to a leak test using air, halides, or other suitable medium to a pressure depending on the leak detection method applied.

4. All piping systems including valves, fittings and associated equipment for handling cargo are to tested under normal operating conditions not later than at the first loading operation.

506.

Cargo system valving requirements

1. Every cargo piping system and cargo tank are to be provided with the following valves, as appli- cable:

(1) All connections, except safety relief valves and liquid level gauging devices if any, are to be equipped with a manually operated stop valve and a remotely controlled emergency shutdown valve. These valves are to be located as close to the tank as practicable. A single valve may be substituted for the two separate valves provided the valve complies with the requirements of Par 3, is capable of local manual operation and provides full closure of the line.

(2) Cargo handling machinery are to be arranged to shutdown automatically if the emergency shut- down valves required by (1) are closed by the emergency shutdown system required by Par 3.

2. One remotely operated emergency shutdown valve is to be provided at loading/unloading connection point.

3. The control system for all required emergency shutdown valves is to be so arranged that all such valves may be operated by single controls situated in at least two remote locations on the ship. One of these locations is to be the control position required by 1301. 3 or cargo control room. The control system is also to be provided with fusible elements designed to melt at temperatures between 98°C and 104°C which will cause the emergency shutdown valves to close in the event of fire. Locations for such fusible elements are to include the cargo tank valve manifolds and loading stations. Emergency shutdown valves are to be of the fail-closed (closed on loss of power) type and be capable of local manual closing operation. Emergency shutdown valves in condensate piping are to fully close under all service conditions within 30s of actuation. Information about the closing time of the valves and their operating characteristics are to be available on board and the closing time is to be verifiable and reproducible. Such valves are to close smoothly.

4. The closure time of 30 s for the emergency shutdown valve referred to in Par 3. should be meas- ured from the time of manual or automatic initiation to final closure. This is called the total shut- down time and is made up of a signal response time and a valve closure time. The valve closure time should be such as to avoid surge pressure in pipelines. Such valves should close in such a manner as to cut off the flows smoothly.

507.

Ship's cargo hoses

1. Cargo hoses used for cargo transfer are to be suitable for the cargo, pressure and temperature of the cargo. Hoses are to be designed, manufactured and tested in accordance with Recognized Standards acceptable to the Society.

2. Hoses subject to tank pressure,

or the discharge pressure of cargo handling equipment, are to be

designed for a bursting pressure not less than 3 times the maximum pressure the hose will be sub- jected to during cargo transfer.

3. Each new type of cargo hose,

complete with end-fittings, are to be prototype-tested at a normal

ambient temperature with 200 pressure cycles from zero to at least twice the specified maximum

working pressure. After this cycle pressure test has been carried out, the prototype test is to dem- onstrate a bursting pressure of at least 3 times its specified maximum working pressure at the ex- treme service temperature. Hoses used for prototype testing is not to be used for cargo service. Thereafter, before being placed in service, each new length of cargo hose produced are to be hy-

drostatically tested at ambient temperature to a pressure not less than 1.5 times its specified max-

imum working pressure. The hose are to be stencilled or otherwise marked with the date of testing, its specified maximum working pressure and, if used in services other than the ambient temperature services, its maximum and minimum service temperature, as applicable.

508. Cargo transfer methods

Procedures for cargo transfer including emergency procedures are to be submitted for approval. The procedures are to address potential accidents related cargo transfer, and information regarding emer- gency disconnection, emergency shutdown, communication with offshore/onshore terminals etc. are to be included.