1
GENERAL
1.1
This specification covers the technical requirements for the design and installation of thermal insulation on piping and equipment at cryogenic operating temperatures, e.g. LNG Production Plants and Terminals.
1.2
Cryogenic services are defined in this specification as piping and equipment at normal operating temperatures, continuous or intermittent, in the temperature range from -100°C to -200°C, where reduction of heat gain and/or prevention of surface condensation is desired.
1.3
These design and installation requirements shall be considered as basic requirements in relation to all cryogenic / LNG piping and equipment for process control, preventing undesired heat gain and/or surface condensation.
It is realised that for special constructions, such as FPSO and Module Fabrication extra attention shall be given to preservation meeting the off-shore conditions.
1.4
Where piping or equipment at cryogenic operating temperatures, do not require thermal insulation for process reasons but whose location presents a personnel hazard, the surfaces shall be provided with a physical barrier (e.g. emergency blow off lines). Ref. CINI 1.3.02a par. 2.3.6.
1.5
At temperatures below -180 °C, the danger of oxygen liquefaction and spontaneous combustion must be considered. Therefore, only inorganic insulation materials shall be used.
1.6
This specification shall be read and applied in combination of CINI 1.3.02a+b.
2
MATERIALS
For cryogenic insulation systems closed cell insulation materials shall be used.
The following materials are applicable:
2.1
Insulation materials
2.1.1
Polyisocyanurate/Polyurethane (PIR/PUR)
a) Polyisocyanurate foam (PIR)
The material shall comply with the minimum requirements as specified in CINI 2.7.01.
It will be applied as slabs and preformed sections.
The thermal conductivity figures are based on aged values, i.e. after 180 days. In case of time constraints, the manufacturer shall submit proven records of proper production and be able to provide reliable quality figures in advance.
b) Polyurethane rigid foam (PUR)
The material shall comply with the minimum requirements as specified in CINI 2.7.02.
It will be applied for in situ application on piping, equipment and fittings.
Spacers (PIR) shall be applied for the installation of the formwork / removable cladding.
c) High Density Polyisocyanurate / Polyurethane rigid foam (HD-PIR / HD-PUR)
The material shall comply with the minimum requirements as specified in CINI 2.7.03.
It will be applied for insulated pipe supports with nominal densities of 160 to 320 kg/m3.
2.1.2
Cellular Glass (CG)
The material shall comply with the minimum requirements as specified in CINI 2.9.01.
Application as slabs and preformed sections.
2.1.3
Flexible Elastomeric Foam (FEF / EPDM)
The material shall comply with the minimum requirements as specified in CINI 2.3.01.
Available in sheets, tubes and tapes.
Remark: see restriction as described in par 3.3
2.1.4
Non-organic mineral wool
For cryogenic applications with an operation temperature below the liquefaction point of oxygen (-183°C at atmospheric pressure, i.e. piping and equipment for liquid nitrogen, oxygen, argon, helium or hydrogen), loose mineral wool used as void filler insulation material, shall meet the requirements as specified in CINI 2.1.04. In addition the oil content shall be less than 0.2% by weight, in accordance with EN 13820 and have a pH value of 8 to 9.5.
Loose fill insulation material shall be suitable for hand packing of cryogenic service cold boxes, expansion- and contraction joints.
2.2
Vapour barrier
To prevent water or water vapour from penetrating into or through the insulation system, a vapour barrier is applied at the outside of the system, as the primary vapour barrier.
As a second line of defence, in multi-layered insulation systems, a secondary vapour barrier is applied between the outermost layer and the next layer inward. The following materials are applicable:
2.2.1
Multiplex foil
The material shall comply with the minimum requirements as specified in CINI 3.3.10
2.2.2
Butyl rubber tape with aluminium foil backing
The material shall comply with the minimum requirements as specified in CINI 3.3.06
Where metal jacketing is to be used, type B or C (polyester layer outer surface) shall be applied.
2.2.3
Vapour barrier mastic
- Latex based material in accordance with CINI 3.2.02
- Elastomer based material in accordance with CINI 3.2.03
- Bitumen based material in accordance with CINI 3.2.04
- Polymer based material in accordance with CINI 3.2.12
The mastic layers shall be reinforced with fabric in accordance with the manufacturer’s specifications.
2.3
Jacketing
The jacketing will protect the vapour barrier from mechanical damage and weather impact.
The following materials are applicable:
2.3.1
Aluminium in accordance with CINI 3.1.01
Note: Aluminium jacketing shall not be used in combination with passive fire protection.
2.3.2
a) Aluminized steel, type T2M-300 in accordance with CINI 3.1.02
b) Aluminized steel, type T1M-300 in accordance with CINI 3.1.02 (aluminium-silicon coating)
Type T1M-300 is recommended for inland, non-corrosive environment only.
Note: Aluminized steel is sensitive to corrosion especially in coastal areas and near ammonia plants.
2.3.3
Stainless steel in accordance with CINI 3.1.05
2.3.4
GRP (Glass-fibre Reinforced Polyester) in accordance with CINI 3.2.11
2.3.5
Flexible elastomeric membrane (CSPE) elastomeric sheet in accordance with CINI 3.2.13
2.3.6
Sealants / adhesives in accordance with CINI 3.2.05 through 3.2.09
2.4
Auxiliary materials
For the application of insulation materials, vapour barrier or jacketing several auxiliary material can be used, which shall conform to the minimum requirements as indicated in CINI 2.25.01 or CINI 3.25.01.
3
DESIGN OF INSULATION SYSTEMS
The design of the cold insulation system depends on several parameters, such as operating temperatures, ambient conditions, material selection etc. as indicated in detail in the CINI Manual.
The following insulation systems can be applied:
3.1
PIR/PUR Insulation Systems
| 1)
2) |
PIR/PUR Preformed sections and slabs
In-situ sprayed / poured PIR/PUR foam Shop sprayed / poured PIR/PUR foam |
in accordance with CINI 2.7.01
in accordance with CINI 2.7.02 |
3.2
Cellular Glass Insulation Systems
In accordance with CINI 2.9.01.
3.3
FEF /EPDM Insulation Systems
In accordance with CINI 2.3.01 / CINI 2.3.02.
FEF/EPDM material is considered applicable in cryogenic applications for small bores, i.e. up to 2” diameter, or for specific non-critical applications, only by exception and to be indicated by the Principal. The additional employment of a vapour barrier is required.
3.4
Combined Insulation Systems
A combination of single/multi inner layer(s) of preformed PIR and single outside layer of cellular glass (CG), can be used for specific insulation system as described in par. 5.6.3.
In a combined insulation system the multiplex foil secondary vapour barrier acts also as a slip layer between the different insulation materials.
3.5
Design guidance for insulation systems
3.5.1
Depending on the operating temperatures, the possibility of Corrosion Under Insulation (CUI) of carbon steel or stress corrosion of stainless steel shall be taken into account, when selecting an insulation system.
The phenomenon of CUI is often underestimated, as it will occur years after completion of a project. The potential cost and safety implications are enormous and therefore insulation systems shall be designed according to the vulnerability to CUI.
In cryogenic operating piping and equipment, occurrence of CUI may also be applicable during extended shut-down periods, even if the risk is limited under normal operating conditions, apart from specific areas such as equipment supports along which important thermal gradients occur.
In CINI 1.2.04 the recommended combinations of corrosion protection and insulation systems to prevent CUI in relation to the operating temperatures are indicated.
European Federation of Corrosion (EFC) “Corrosion under insulation (CUI) the Directive 55 entitled ‘Corrosion Under Insulation (CUI) guidelines) of the EFC Working Party 15 ‘Corrosion in the Refinery and Petrochemical Industry’ or in NACE SP-0198 “Control of Corrosion Under Thermal Insulation and Fireproofing Materials.
3.5.2
Design of insulation details shall be such that the system is not susceptible to water ingress. This includes validating that adequate expansion and contraction provisions are provided and that the performance (water tightness) of vapour stops, vapour barriers and jackets particularly around protrusion and nozzles are assured.
3.5.3
Contraction joints, when required, have to be installed at well defined positions and/or distances.
For more detailed sketches, see CINI 10.5.11 through CINI 10.5.13
The contraction joint application may differ for all systems; the intention of the contraction joint is to:
– minimize heat gain,
– reduce eventual material stresses,
– guaranty to integrity of vapour barrier (as well inner as outer).
A detailed description on movement of insulation material at service and the effect has to be demonstrated for all systems.
In CINI 10.2.02 a description of contraction joints for different materials is included.
3.5.4
Vapour stops shall be combined with supports, in order to secure a barrier at a point without movement between insulation and pipe. (ref. par. 5.6.4.3)
3.5.5
Metallic jacketing on piping require due consideration in terms of emissivity and water ponding.
The lower emissivity of (bright) metal results in an increased insulation thickness compared with non-metal weather protection. For design purposes the emissivity shall be considered as ‘aged’. For emissivity coefficients reference is made to CINI 6.1.02.
If metal cladding is applied, it shall be an “open” jacket, with drain holes at the bottom to allow condensation water at the inside of the cladding to drain. Drain holes to be drilled before installation of the metal jacketing to avoid damage to the vapour barrier. Distance between jacketing and insulation will support the drainage of water and reduce the risk of crevice corrosion and moisture build up.
Another possibility to avoid / reduce crevice/ pitting corrosion is to apply a coating or moisture retardant barrier at the inside of the metal jacketing. In specific cases the Principal may decide to apply such type of jacketing.
3.5.6
Non-metallic jacketing in piping require due consideration in terms of specific fire resistance requirements and mechanical protection by the Principal.
3.5.7
Weather Conditions
The weather conditions shall be achieved from available local metocean data. If not available reference can be made to EN 1473-table 4.
3.6
Guidance for Mechanical Design in relation to insulation systems
The thicknesses of cryogenic insulation systems are quite significant and do increase the outside pipe diameter several times. Especially small diameters may increase more than 10 times.
This shall be taken into account in the early stage of the mechanical design and lay-out of pipe racks, including the minimum 75 mm clearance around insulated cryogenic/LNG piping, including pipe supports, fittings, nozzles length, cryogenic valve extensions, vertical contraction joints, etc., including considerations of operational pipe movement.
4
INSULATION THICKNESS AND EXTENT
4.1
Insulation Thickness
The thickness of cold insulation systems and for each diameter will be established in accordance with calculations based on VDI 2055, ISO 12241, ASTM C680.
Principals or Plant Owners may select design parameters and standards for insulation thickness calculations.
4.1.1
The thickness of cryogenic insulation systems shall be calculated for both of the following cases.
The thickness shall be determined by the most stringent requirement of both.
For these calculations, parameters such as ambient temperature, wind velocity and relative humidity are required. Further the air film coefficient of the jacketing is of importance for this calculation. For emissivity coefficients ref. CINI 6.1.02.
a) Reduction of heat gain (heat ingress) for piping and equipment shall be determined by the Principal. If information is not available the heat gain shall be:
- maximum 25 W/m2 for liquefaction/export LNG plants.
- maximum 36 W/m2 for import terminals.
The solar radiation may be specified at 1000 W/m2, for specific conditions and if so indicated by the Principal.
For most calculations the outer surface of the insulation systems can be set at 70°C.
b) For prevention of surface condensation to arrive at an economically justified cryogenic insulation thicknesses, surface condensation will be allowed during 5% of the time. (Principals may decide for a rate of max.10%)
Weather design condition data need to be considered in such way that in 95% of the time surface condensation is prevented. In general the principal is responsible to provide the relevant data. When weather design condition data is not available it is recommended to consult the ASHRAE handbook.
4.1.2
The thickness and type of insulation will be indicated on the piping list and equipment lists/data sheet in accordance with diameter and operating temperature.
The extent of all types of insulation should be shown on the isometrics.
4.1.3
The insulation thickness of fittings shall be the same as the insulation thickness or the larger of the adjoining pipe. (i.e. DN250 to DN200 Reducer, the DN250 equivalent shall be taken) The thickness of insulation for protruding parts shall be based on the process temperature of the pipe to which the part is attached and the size determined as follows:
- For cylindrical attachments use the nearest pipe size, in the insulation thickness table appropriate to the insulation type, this corresponds to the diameter of the attachment.
e.g. a DN 200 weld neck flanges is equivalent to a DN 200 pipe. - For structural shapes use the longest dimension(of the nominal section size) corresponding to a pipe size, e.g. a 150 x 100 mm angle is equivalent to a DN 150 pipe.
4.1.4
For personnel protection (SS) metal mesh or perforated (SS) sheet metal shall be applied with keeping the distance between cryogenic surfaces and the mesh equal to 50 mm for diameter
< DN 100 (4” OD) and 75 mm for diameters ≥ DN 100 (4” OD) and equipment.
For locations of personnel protection ref. CINI 1.3.02a par. 2.3.6. Ice build-up shall be considered in the pipe design.
4.2
Insulation extent
4.2.1
When cryogenic insulation is required, the entire system shall be fully insulated, including all piping, equipment and their components, like valves, flanges, manholes, nozzles, vents, drains, supports, instrument tubing, etc. to the extent specified
4.2.2
In case of pneumatic or hydraulic bolt tensioning, the insulation system near flanges shall be terminated at a distance such that there is enough space to mount the bolt tensioning tools that no damage to the insulation system on the piping and equipment will occur. The length of the flange box shall be adapted accordingly.
4.2.3
All metal parts, which protrude through the insulation, shall be insulated. There shall be a minimum of 300 mm of bare metal after termination of insulation, to avoid condensation inside the insulation system. If the length of 300 mm of bare metal cannot be realised, a thermal break is to be installed.
Protruding metal parts include, but are not limited to equipment skirts, lugs, saddles, platform trunnion supports, pipe hangers etc.
4.2.4
Nameplates, coding tags, etc. shall be insulated. A duplicate nameplate/coding tag, etc. shall be installed over the outside surface of the insulation system, in consultation with the Principal. The method of attachment used shall not puncture the vapour barrier.
4.2.5
Extend of valve free neck shall be specified by the manufacturer and established in conjunction with the insulation thickness (see CINI 1.3.02-par 2.3.4.2 and CINI 10.7.01)
5
APPLICATION
5.1
Scope
Prior to the execution of the works, a kick-off meeting shall be organised between Principal and Contractor to discuss available documentation, released for construction items, man power levels, work method statements, Inspection and Test Plan (ITP) etc.
The Contractor shall also contact the Mechanical Contractor in an early stage of the project to avoid mistakes and to coordinate possible combined actions, such as installation of pipe supports.
The Contractor shall provide all necessary shelter to protect the insulation works and materials from sun radiation and weather conditions. Attention shall be paid during this period due to high humidity atmosphere.
The Contractor shall coordinate its planning with site construction teams to minimize any potential interference. The installation of insulation shall adhere to site safety rules and observe the requirement of personnel protection and housekeeping.
5.2
Prefab Shop Application
It is recommended, where possible, to insulate straight pipe sections, pipe spools and equipment in prefabrication shops (preferably at an on-site location), including a dress-up application, prior to erection.
In case of pre-insulation, the Contractor shall provide a detailed installation procedure, which will contain required facilities and equipment, fabrication process, transportation and lifting, field joint insulation, quality inspection and materials data sheets.
In case of dress-up application, special care shall be taken for movements and displacement of insulation and jacketing and moisture ingress during transportation, lifting and installation of the pre-insulated pieces, especially when vertical turning and lifting is involved.
This procedure shall be approved by the Principal before the start of work.
Explanation: The above method is often used for run-down lines and modular construction. The modules are then often shipped to the site.
5.3
Field Application
The balance of piping and equipment shall be insulated on site after erection in accordance with the relevant installation instructions.
5.4
Surface Preparation
5.4.1
Operations before insulation.
Piping and fittings shall have all welding completed, including painting where specified, and shall be pressure tested prior to application of insulation.
Flanged connections are tested during commissioning and after approval insulation flange boxes can be installed, which results in a massive operation just before or during start-up. The Principal to decide that flanges can be insulated prior to leak testing /(during commissioning) by the installation of sniffer tubes/ tell tails. (ref. CINI 4.1.27 – leak detection pipes, however in cryogenic services Teflon leak detection pipes are preferred). After start-up the sniffer pipes can be cut off and the hole in the box plugged with a rubber grommet.
Surfaces to be insulated shall be washed down with potable water, to avoid chloride inclusion (residual levels at the surface for carbon steel max 25 mg/m2; for stainless steel max 20 mg/m2) and shall have been allowed time to thoroughly dry out before commencement of insulation application.
Explanation: To test whether the surfaces are free of chlorides, water-soluble salt tests shall be carried out in accordance with ISO 8502-9. In this method, the extraction of soluble salt contaminants for analysis is carried out in accordance with ISO 8502-6 – Bresle’s method. For more information, please refer to Chapter 7 Corrosion protection under insulation.
5.4.2
Insulation cleats
Equipment shall be provided with welded/ mechanically fixed metallic supports, saddles and lugs for insulation installation, as indicated in CINI 5.9.01 and as further indicated. The provisions are installed during the manufacture of the devices according to approved drawings. If the insulation Contractor discovers that the insulation facilities have not been installed, this will be reported to the Principal. Adjustments will be made in consultation with the Principal, as welding can no longer be done after a hydro test of equipment or piping.
5.5
Application of standard insulation systems
Standard insulation systems shall be applied in accordance with the installation instruction.
5.5.1
FEF / EPDM to be installed in accordance with CINI 1.3.51 (see note in par 3.3)
5.5.2
PIR / PUR to be installed in accordance with CINI 1.3.53
5.5.3
CG to be installed in accordance with CINI 1.3.54
5.6
Application of special insulation systems
5.6.1
In-situ sprayed / poured PIR/PUR
5.6.1.1
General
In-situ moulded or sprayed / poured PUR foam should only be applied in exceptional situations by the following methods:
a) Via injection in a temporary mould around piping, fittings or equipment;
b) Via injection in an installed metallic jacketing (box) that acts as primary vapour barrier;
c) Sprayed / poured foam (e.g. shop fabricated piping systems).
Method (a) is the normally preferred method for sprayed / poured PUR foam. After the foam has cured the mould is removed and the quality of the foam can be checked.
Method (b) shall only be used for items that need to be removed for shutdowns (e.g. valve boxes and flange boxes). These boxes are damaged when removed and are considered as sacrificial maintenance items.
Method (c) is normally used for shop fabrication of cryogenic piping (e.g. LNG loading lines).
The quality of dispensed foam depends on several factors, such as the ambient temperature, the temperature of the substrate, the humidity and the qualification and experience of the personnel. To ensure good quality of the foam the mould shall be removed (method a) so that the foam can be fully inspected.
In extreme temperatures and humidity, the advice of the manufacturer shall be sought.
Foam injection application can be executed only after approval of the Principal on the above mentioned methods. It shall not be applied for filling of voids e.g. around valves, flanges and irregular shapes. Foam injection shall not be used for repair of damaged insulation systems.
5.6.2
Shop application of sprayed / poured PUR
5.6.2.1
General
Shop application of sprayed / poured PUR is employed for long stretches of pipe, such as LNG loading lines, BOG lines or rundown lines. In these cases a ‘Shear key/Slide through’ system may be applied.
For this insulation method to be successful the pipe straightness, alignment must be more stringent that allowed in ASTM A312, A358 and A999 (3 mm misalignment on 3 m pipe length). Principal shall require for the bare pipe a straightness of 3 mm maximum on the total pipe length to be insulated in shop by this method. Pipes exceeding this requirement should not be used for this insulation method and can be redirected to applications with conventional insulation systems.
The PUR insulation shall have the properties specified in CINI 2.7.02.
The detailed design shall be prepared with drawings and a method statement, which shall contain application and QA/QC procedures. The design shall cover all aspects, e.g. temporary termination, contraction joints, field welds and pipe supports as well as temporary seal and weather protection during transport and storage to prevent damage and deterioration.
5.6.2.2
“Shear Key/Slide Through” Sprayed / Poured PUR
The system can be described as follows:
- Shear Key
A high density PUR shear key is adhesive bonded to the pipe, with a height equal to the height of the first layer of PUR foam insulation plus the thickness of the underlay of needled glass mat. This serves to anchor the insulation system at this point.
The remaining line portion is basically the slide through system, with the pipe contracting inside the insulation towards the shear key. Hence when two pre-insulated spools are welded together (a field weld) the distance between the shear keys on adjoining pipes decreases and hence the need to have contraction joints in the vicinity of the welded joint assuming equidistant spacing the shear keys Ref. CINI 10.5.08 / CINI 10.5.09 - Slide Through
The line must be allowed to slide easily through the foam during all stages of pipeline cool-down and warm-up when in operation. The insulation shall not be bonded to the pipe or forced to move with the pipe by attachments, branch connections or other restraints.
Ref. CINI 10.5.03 through 07.
The shear key system shall be applied and built up as follows:
- The pipe area where the shear key is to be installed shall be dry abrasive blast cleaned to prepare a proper profiled surface for good adhesion of the cryogenic adhesive. The adjacent areas of the coated pipe shall be protected by masking during the blast cleaning to prevent damage to the coating system.
- Shear keys shall then be adhered to the pipe surface, employing cryogenic adhesive to a 4 mm wet film thickness and temporarily secured by three machine tensioned 20 mm wide x 0.5 mm thick stainless steel bands.
- Temporary bands shall be removed after the adhesive has fully cured. Curing time shall be as per cryogenic adhesive manufacturer’s recommendations.
Subsequently the slide through system shall be applied and built up as follows:
A – Insulation system
- A compressible and resilient layer of needle glass mat of 12 mm thickness, which will be compressed to 8 mm.
- A first layer of PUR foam insulation, using either spray or pouring technique shall be applied, with the desired first layer insulation plus an additional thickness for trimming. The first layer thickness after trimming shall be the same as the shear key thickness. In case of misalignment to such a degree that the first layer does not meet the thickness of the shear key, action shall be taken for correction after approval of the Principal. Based on field experience the maximum allowed deviation is 26 mm. Acceptance criteria shall be based on measurement of the circumference of every layer.
- After trimming of the first layer, a crack arresting barrier consisting of an open weave glass cloth shall be spiral wound, with 50 mm overlaps, on top of the first layer. Alternatively, a self-adhesive PAP multiplex foil can be used with an overlap of 30 mm at all joints.
- On top of the crack arresting barrier, the next layer of PUR foam using either spray or pouring techniques shall be applied as described in step 2.and 3.
- This is to be repeated until desired insulation thickness and stepping is achieved
- After the last layer of PUR foam insulation all layers shall be trimmed and the ends (terminations) of the insulation system shall be finished stepwise, ending at a 250 mm minimum field weld allowance according CINI 10.5.04.
- Finally an aluminium multiplex vapour barrier foil to be installed, before the final mechanical and weather proofing jacketing layer is applied.
B – GRE jacketing system (Glass fibre Reinforced Epoxy)
- To ensure proper adhesion between the outer surface and the first layer of GRE, either an initial spray coat of UV resistant epoxy resin shall be applied to the insulation outer surface or the first layer of GRE shall be applied in higher wetness (lower fibre volume).
- A laminating application of epoxy resin incorporating a layer of chopped strand or woven glass mat shall be spirally wound onto the surface, with a minimum 50 mm overlap. The mat shall be rolled with metal rollers to ensure it is thoroughly wetted out and any entrained air is released. This process shall be repeated until a minimum amount of glass layers is reached to build up the required minimum dry cured thickness
- A final UV resistant epoxy layer shall be pour applied, into which surface tissue is spiral wound with a 50 mm overlap to a minimum thickness of 0.5 mm.
- The GRE coating shall be fully cured by heating at a time/temperature relationship
recommended by the epoxy resin Manufacturer. The heating source should best be obtained by means of infrared radiation. - The stepped ends of the PUR shall be covered with a vapour stop mastic, with a 50 mm overlap onto the GRE jacketing of the pipe insulation. The gap between the insulation and the pipe shall be temporarily sealed with petrolatum tape, 100 mm wide, to prevent water and condensation travelling up the needle felt blanket interface prior to installation of the infill PIR including a contraction joint.
- The epoxy resin shall be suitable for the glass mat filament winding method and shall contain sufficient pigmentation to resist ultra-violet light exposure.
Glass fibre reinforcement mat shall be made of E-glass, i.e. low-alkali glass of first quality and shall have a finish such as silane which is compatible with the epoxy resin. The mat shall have a mass of approximately 450 g/m2 and shall be composed of filaments of 5-20 micron diameter.
The Contractor shall submit all design, engineering and application details and method statements of these systems for the approval to the Principal.
C – GRP jacketing system (Glass fibre Reinforced Polyester)
- For the hand application of UV curing GRP reference is made to CINI 1.3.60.
- For the shop application of a GRP jacketing system a similar procedure as described above for the GRE jacketing system shall be performed. In such case technical specifications, test reports and work methods statements shall be submitted for approval by the Principal.
Recommended thickness of the GRP layer is between 3.0 to 3,5 mm. Detailed stress calculation for the clamping area shall be provided to the Principal to determine minimum GRP layer thickness in the clamping area.
5.6.2.3
Field joints / Field welds
On for field welds, pre-formed PIR sections shall be used and shall be finished in accordance with CINI 1.3.53.
The temporary protection at the terminal ends of the pre-insulated pipe spools shall be completely removed just prior to the application of the field weld insulation. Prior to installation of the first layer of field weld insulation, the temporary petrolatum tape shall be removed from the ends of the pre-insulated piping and a needle glass mat shall be applied around the pipe, similar to the adjacent per-insulated sections.
In case a factory made GRE / GRP field joint cover is to be installed by the hand lay-up method, a method statement shall be provided.
5.6.3
Other Special applications
5.6.3.1
Fireproofing
Main application for fireproofing on cryogenic insulation systems is the vessel skirts on aluminium heat exchange columns. In this case it is common practice to apply a layer of cellular glass over the top of the PIR insulation and finished with SS steel jacketing.
When fireproofing requirements are considered for other equipment the Principal and/or the Engineer has to specify:
- Applicable fire scenario: Pool fire per UL-1709, Jet fire per ISO 22899-1
- Fire resistance rating
- Dimensions of object(s), wall thickness and material grade
- Maximum permitted object temperature during the fire-resistance rating time
The proposed cryogenic insulation systems to meet the above requirements, will require documented third party testing in full accordance with the relevant requirements. This test defines the acceptable insulation material in conjunction with a jacketing or finish layer. (e.g. a stainless steel/aluminized steel cladding or an intumescent epoxy coating).
Dedicated fireproof simulation calculation programs, in line with relevant testing, will generate the minimum imposed insulation thickness.
For combined fireproofing / cryogenic application the highest insulation thickness will be selected.
As a general guidance reference is made to API 2218 “Fireproofing Practices in Petroleum and Petrochemical Processing Plants”.
5.6.3.2
Complex configuration, small bore piping
Pipe with a complex configuration of small bore pipes and instrument tubing should be insulated with suitable materials e.g. FEF / EPDM, meeting the operating temperature requirements.
5.6.3.3
Expansion/contraction bellows
Expansion or contraction bellows in insulated pipes systems shall be insulated as well. However, due to the concentrated movement of pipeline sections, the insulation system on bellows is subject to severe erosion and wear. Especially bellows in BOG vapour return lines are, due to cycling operating temperatures, very vulnerable to damage because of degradation and failure of the vapour barriers which results in ice formation in the corrugations of both the primary and the seal bellows. Therefore it is recommended to avoid bellows in such cycling condition pipeline systems and to install loops instead.
Depending on the type of bellow the corrugations are covered or not. If not, a 1.0 mm. thick stainless steel sheet shall be cylindrically formed over the outer diameter of the bellows in order to ensure free movements of the bellows. The cylindrically formed sheets shall be fixed to the bellows flanges. The length of the cylinder shall be the maximum expanded length of the bellows plus twice the insulation thickness. Ref. CINI 10.5.10.
The covered bellows shall be insulated in the same way as the pipe together with contraction joint system, with the same insulation thickness and layering. The system to be verified with a conceptual insulation design drawing.
The Contractor shall submit the bellows insulation design for the approval to the Principal.
In CINI 10.2.11 a typical insulation application/repair procedure for a contraction bellow is described.
5.6.4
Pipe Supports in cryogenic insulation systems
5.6.4.1
General requirements
Insulated pipe supports can be manufactured of moulded or cut high density polyisocyanurate or polyurethane rigid foam. (HD-PIR/HD-PUR).
Supports shall be supplied as complete assemblies to the site, i.e. HD-PIR/HD-PUR cradles and steel clamp, bearing plates and shoes.
The support design shall be consistent with the insulation system and provisions shall be made for a proper seal between the pipe insulation onto the supports. The installation of insulation supports should be a combined effort by the mechanical contractor and the insulation contractor. Ref. par. 5.6.4.3.
The thickness of the insulation at the cold support is to match the thickness of the line insulation, though the thermal conductivity of the HD-PIR/HD-PUR will be slightly higher than the line insulation.
HD-PIR/HD-PUR foam supports shall be designed and furnished as a complete assembly.
Supports shall be designed to withstand all service loads, including:
- thermal stresses resulting from differential contraction of the foam and the pipe,
- thermal stresses resulting from the temperature gradient through the thickness of the insulation,
- clamping forces,
- mechanical loads applied by the piping system,
- any other loading that may be present at the support.
The mechanical (vertical and horizontal) loads should be obtained from the pipe support drawings (e.g. isometric drawings).
The maximum continuous stresses in the foam shall be limited to 0.2 times the ultimate compressive strength, ultimate tensile strength and shear strength respectively.
Incidental peaks loads may exceed 1/5th of the compressive strength only if the elastic range of the material is not exceeded. Typically this would be approx. 3/5th of the compressive strength at break.
This needs to be defined by the manufacturer with data of expected loads by engineer.
The HD-PIR/HD-PUR cradles shall be designed for all specified operating conditions, including differential expansion and contraction between HD-PIR/HD-PUR cradles and pipe.
The design shall also cope with tolerances of the outside diameter of the pipes and the inside diameters of the HD-PIR/HD-PUR supports.
The Contractor shall submit a proposal, supported by data sheets, calculations, test certificates, method statements of installation, etc., which shall cover all related requirements (e.g. thermal conductivity, mechanical properties, stresses, tolerances, etc.) for approval to the Principal .
In case clamp supports around pre-insulated pipes are installed, a compensation layer is required. All loads and stresses have to be confirmed by calculations as indicated in EN-ISO 14692-3, Annex E5.
5.6.4.2
Materials
The material for pipe supports can be HD-PIR/HD-PUR. Depending on the loads, the density shall be between 160-320 kg/m3. The material properties shall be as indicated in CINI 2.7.03.
The material shall be either moulds of applicable sizes or cut from bun stock.
Independent test reports of the mechanical properties shall be submitted to verify the suitability of the service loads, the thermal stresses and the thermal conductivity.
In case of high compression stresses resin impregnated laminate blocks can be applied, to created a thermal break between the pipe and the support. Ref. CINI 3.25.01.
Extra attention shall be given to avoid a cold bridge at the bracket ends.
5.6.4.3
HD-PIR/HD-PUR support structure
HD-PIR/HD-PUR supports may be of either single or multi-layer construction.
The single layer support shall consist of seamless two half sections with the full thickness. The multi-layer supports consist of segments glued together. Both systems shall have ship lapped longitudinal joints and the circumferential ends at both sides shall be staggered with the correct dimensions to enable proper application of the connecting insulation systems in a later stage.
The factory-assembled support shall have a bonded extended multiplex vapour barrier (with a sufficient overlap of 50 mm) covered with a bonded 1,5 mm thick EPDM pad and 0.6-0.8 mm thick metal support sheet. The top metal sheet shall overlap the bottom metal sheet and the top part of the EPDM foil shall overlap the bottom part and shall be bonded together.
The EPDM foil protects the multiplex foil against mechanical damage.
All layers of HD-PIR/HD-PUR, vapour barrier and metal sheets shall be extended beyond the previous layer, with a minimum of 50mm. Ref. CINI 10.5.01.
For multi-layer systems, the segments or half-pipe sections shall be factory-bonded into one integral unit. The adhesives shall withstand any stresses and strains, accommodate contraction within the foam and remain effective within the required temperature range.
Unless otherwise specified, 360° assembled HD-PIR/HD-PUR supports for all pipe sizes shall have their top and bottom structural cradles fitted with bent lugs or welded angles to accept stainless steel bolts and nuts.
All carbon steel parts of the supports shall be hot dip galvanized (as per ASTM A123 or ISO 1461). Direct electrical contact between noble metal (stainless steel, nickel, copper, etc.) surfaces and less noble metals (zinc, aluminium, or coatings of these metals) shall be prevented by an non-conductive polymeric (rubber, fluorocarbon, etc.) band or sheet installed between the dissimilar metals avoiding localized galvanic corrosion of the less noble metal. Galvanic corrosion can be severe when large noble surfaces are in contact with less noble metals in system that are continuously wet due to condensation, moisture or heavy rain fall.
Hot dip galvanized carbon steel support parts may receive or not an additional painting to improve the durability of the corrosion protective system depending by the specific project requirements in force.
All pipe support units shall be well protected during transport and storage to avoid any damage.
For the installation procedure of the HD-PIR/HD-PUR pipe support see CINI 10.2.12
5.7
Commissioning/Maintenance, Shut down/Heat up Procedures of cryogenic systems
5.7.1
Commissioning and start up
The following actions to be taken:
- final visual check of the condition of the insulation system before start up.
- at locations where modifications have to be executed, the full final completion test/procedures to be performed again.
- check that the insulation systems accommodate the pipe contraction properly, without being damaged.
- Refer to the general commissioning and start-up procedure.
- 2 months after start up, a NDE testing survey (e.g. thermographic) shall be executed to determine potential cold spots, thermal bridges etc.
5.7.2
Before shut-down
A visual inspection of the relevant piping and equipment insulation should be carried out in order to detect the shortcomings with respect to:
- the integrity of the jacketing
- condensation or frost on cold surfaces
- breaks or shrinkage cracks in weather/vapour barriers
- gaps or unsealed joints
Possible failures of the insulation system should be marked (including pictures) and must be repaired during the out of service period.
The pipe supports, in particular the sliding points shall be checked. They must be free from any obstacles, such as soil and ice.
The sliding parts of the supports shall be lubricated with e.g. oil-spray.
Note: In case sliding parts for support are made of stainless steel sheet and PTFE, no lubrication with oil-spray shall be applied.
The entire insulation system incl. primary/secondary vapour barriers shall be dismantled at the following locations of:
- the spectacle blinds to be installed
- the relevant bellows
The build-up ice between the bellows shall be thawed by means of appropriate heaters (e.g. infrared heaters) and/or temporarily electrical tracing, after approval of the Principal. This should be continuously monitored till the metal skin temperature will become above 0°C.
5.7.3
During shut-down
After the warming-up period the following measures should be taken:
The insulation system shall be removed at the location of:
- the projected tie-ins
- the marked spots to be repaired or to be inspected
After removal of the insulation at the above mentioned locations, the adjacent insulation material shall be checked. If the insulation material is dry, the layers shall be staggered, finished smoothly, sealed with vapour barrier mastic sealant and temporarily covered with black plastic.
If the insulation material is not dry, all wet insulation shall be removed, up to the nearest vapour stop.
In the meantime the tie-ins will be installed and tested.
After testing, the insulation system can be re-installed according to the specification.
6
QUALITY CONTROL
6.1
General
The Contractor shall submit to the Principal a quality system manual based on ISO 9001. The quality system shall include specific QA/QC procedures for the work and test procedures for all materials.
The QC procedure shall include an inspection and test plan (ITP) with references to all test procedures, number of samples, hold-points and witness points, acceptance and rejection criteria and frequency of tests.
The Contractor shall provide facilities for the inspection of all materials and application procedures before and during the insulation work, up to the contractual completion date.
Inspection shall be carried out during and after completion of any stage and before commencement of the following stage, beginning with material checks and ending with final performance checks.
Inspections shall be carried out by independent qualified specialists, with experience and skills in cold/cryogenic insulation techniques.
6.2
Inspection
6.2.1
Inspection of Materials
Inspection of materials shall be performed either at the Manufacturer’s works or in the field.
Laboratory test results for various insulation and ancillary materials obtained by independent test laboratories shall be submitted prior to the commencement of the work together with the data sheets, Manufacturer’s instructions and method statements of the Contractor.
Should the material be delivered in multiple production batches, one laboratory test shall be performed at the Manufacturer’s works and the test results shall be submitted. For all other batches a “Compliance Certificate” shall be submitted certifying that the materials are in accordance with the technical specifications of the first production batch. Each batch used on site shall be clearly marked to allow rapid tracing of the origin of the supply should discrepancies be noted.
6.2.2
Pre-Insulation Survey and Inspection
After a piping/equipment system has been “released for measurement”, a pre-insulation survey and measurement of the system shall be performed by the Insulation Contractor to verify the designed system and as-built situation. Deviations shall be notified to the Principal.
After “Released for Insulation” (normally after completion of pressure testing, painting and if applicable testing of electrical/steam tracing), the Insulation Contractor shall inspect the following:
- Surfaces
Are the surfaces coated and clean/dry? In coastal areas, the surfaces shall be washed with potable water to remove salt deposits and shall be dried. - Hangers/Supports
Are all hangers and supports of the correct size and properly located according to the specifications? Are all supports, anchors, guides or hangers on low temperature piping free from obstructions to allow sufficient space for support insulation application and condensation control treatment, and normal expansion and contraction of the system? Are supports properly installed, e.g. for cold insulation in the so-called “hot-mode”? - Expansion/Contraction joints
Are all positions for installation of the expansion/contraction joints in the insulation clearly defined and marked? - Clearances
Has sufficient accessibility and clearance been provided for both the insulation thickness to be applied and the space necessary for workmen to apply it? - Electrical tracing stations/hangers
Is sufficient protection against incoming rain and other water provided (e.g. water deflectors)?
6.2.3
Inspection during installation of insulation systems
Inspections shall be carried out on material and applications to ensure compliance with the specifications. Special attention shall be paid to work areas where a high degree of manual skill is required to cut and fit the insulation to ensure tight joints without voids in the layers. Typical areas which are difficult to insulate include hand cut elbows, tees, unequal tees, vessel nozzles, attachments, etc.
6.2.4
Inspection Procedure for In-Situ Sprayed / Poured PUR
Foam injection shall be done only after the procedure has been examined for each unit to be insulated.
The Contractor shall draw up the inspection procedure and control sheets will be established for each pipe/spool in order to assess the step-by-step inspection status on a continuous basis.
The inspection procedure shall include but not be limited to the following tests, documented in appropriate data sheets and performed daily:
- For each machine each day and before the start of spraying / pouring work, a sample shall be made in a closed mould to simulate conditions in practice. Each sample shall be examined for density, closed cell content, thermal conductivity and visual appearance. Samples shall be tested in accordance with ITP.
- Machine foaming test in free expansion to determine the same values as specified.
- Measuring and recording of all data such as ambient temperature and relative humidity;
- Operating and re-circulation pressures for the pouring machines.
- Inspection of the cavities to be injected for the following:
- Temperature;
- Humidity / water pockets;
- Accessibility;
- Properly placed pouring and vent holes.
- Inspection of the foamed cavities by examination of the quantity and quality of the foam escaping from the vent, drain and injection holes.
- Daily checks by cutting samples. On these samples the compressive strength shall also be tested.
Injection control data sheets shall be maintained for all insulated pipes/spools to record all operating and material data for easy cross-reference in case of failure.
All samples shall be numbered to ensure full traceability and shall be stored by the Insulation Contractor under such conditions that they remain suitable for further testing if necessary, until all dispensing work has been completed.
Test results shall be submitted weekly.
6.2.5
Final Inspection and Release
All parties involved when the system is considered complete or as soon as possible thereafter shall conduct a final inspection. After final completion of a system, a “release for system insulation completion” shall be issued. The Insulation Contractor shall be kept responsible for the performance of insulation system(s) till the contract completion date and warranty period has expired, unless the systems are not operated within the design envelope or are damaged by others.
The application shall be inspected to determine that the insulation is of the proper thickness and that its materials, workmanship and finishes meet the specifications.
Infrared inspection technique may be used after start-up to verify proper thermal performance of the insulation system(s).
Cold insulation systems shall be subjected to thermographic survey, if so required by the Principal, a few weeks after initial start up to identify deficiencies. The thermographic survey shall be executed by a licensed competent person familiar with both the thermographic camera, industrial thermal insulation and the related emissivity aspects.
Deficiencies shall be marked (including pictures) and shall be made good at the earliest opportunity (e.g. the next shutdown).
6.2.6
Inspection in a running plant
Reference is made to CINI 1.3.05 – ‘Quality Control of Insulation Systems’
6.3
Testing
The Insulation Contractor shall submit test reports and adhere to the quality control requirements on all insulation materials, as described in CINI 1.3.05.
For the sprayed / poured PUR activities the Insulation Contractor shall establish a site laboratory to carry out the daily testing in accordance with the QA/QC programme and testing of the foam characteristics. This may be restricted to density, closed cell content, cell structure and compressive strength, in consultation with the Principal.
For each batch of pre-formed foam or whenever a fresh blend of chemicals is used the following tests shall be carried out according to the standards mentioned in CINI 2.7.01 / 2.7.02
- Density,
- Thermal conductivity at ambient temperature,
- Closed cells content,
- Cell structure: uniform and free of voids and bubbles in excess of 1.5 mm in diameter across the rise of the foam, or 5 mm in depth in direction of rise. No more than 5 smaller voids or bubbles per 250 x 250 mm area on any cut standard length of half pipe section or slab shall be allowed. The surface shall be free of striations, sheared cells, and planes of weakness and uncured areas,
- Compressive strength,
- Tensile strength *,
- Flammability *,
- Dimensional tolerances.
* In case on-site testing is considered not feasible, laboratory capacity off-site shall be arranged to achieve these test results, after approval of the Principal.
Results of the above Quality Control tests shall be recorded for two samples of foam from each batch of chemicals and reported to the Principal. Serial number and expiry shall identify batch date or manufacturing date.
In case of non-conformance all defective materials shall be replaced.
6.4
Conflicts
In case of conflict between Principal and Contractor a third party insulation expert can be nominated, to be agreed by both parties. The decision of the third party expert shall be binding for both parties.
6.5
ITP
Prior to commencement of the work an Inspection and Test Plan (ITP) will be submitted to the Principal for approval. In the ITP the QC activities of all stages of the work shall be indicated. For each activity shall be indicated the inspection level and by which party to be executed.
A typical ITP for ‘Insulation & Cladding of Pipework in Cold Service’ is indicated in CINI 10.2.13.
7
MAINTENANCE OF CRYOGENIC INSULATION SYSTEMS
7.1
Introduction
Due to the extremely low temperatures encountered in cryogenic insulation systems the ingress of moisture is a major cause of breakdown and significant damage to the insulation. During installation a lot of attention is paid to details that prevent the ingress of moisture by the construction of multitudes of vapour barriers and vapour stops. Any product lines that thermally cycle, e.g. vapour return lines, are exposed to constant expansion and contraction cycles which further impart stress to the insulation system especially the vapour barriers.
Once moisture finds its way into the insulation there is a constant freezing and thawing action, either driven by product temperature or ambient conditions, that progressively destroys the cell structure of the insulation and results in a progressively increasing ice ball. In some cases this may result in a loss of thermal efficiency but in other cases it may interfere with the correct operation of other mechanical components such as bellows or restrict proper operation of piping systems, e.g., sliding supports. In the case of bellows it may result in premature failure due to ice forming in the convolutes of the bellows which may rupture the convolutes during freeze/thaw cycling with the resulting escape of gas or liquids.
The success of any insulation inspection is early detection of problems. If breakdown can be detected whilst it is isolated between vapour stops, e.g. in contraction joints, it is easier to repair. Once breakdown progresses into the main insulation then the work scope increases dramatically and it is much harder to repair, especially, if the line cannot be taken out of service.
For these reasons operators should be trained to observe any evidence of insulation breakdown to ensure early reporting which affords the best opportunity for remedial work. This should also be supplemented by formal inspections at pre-determined intervals.
7.2
Insulation Systems
By nature, a lot of insulation systems are dependent on extensive manual installation in the field, often with semi skilled labour and under adverse weather conditions. A lot of the components rely on a high level of quality control during installation. Similarly, a number of the components do have finite lives if they are not totally protected from harsh environmental conditions including extreme UV radiation. In some cases the installation is sub-optimal for the operating environment it will be exposed to. It is therefore unrealistic to assume that an insulation system will last for the design life of the plant without some maintenance intervention.
7.2.1
Pre-insulated Lines
Pre-insulated lines are most typically used outside of the process areas (Off Plot) where long straight runs of pipes are required to transfer product to the storage tanks and loading jetty.
Some of these lines remain permanently cold whereas others, eg, vapour return line, are in cyclic service. The cyclic lines are most susceptible to insulation breakdown due to the repetitive expansion and contraction as the line temperature cycles.
As permanently cold lines do not cycle they are not as vulnerable to movement induced insulation breakdown. However, bellows insulation will still fail even when there has been minimal movement and ice in the bellows should be avoided due to the risk of rupture of the convolutes if the line ever has to be warmed up.
Provided the outer protective GRE/GRP cladding is correctly installed and includes a robust vapour barrier, the problem areas are generally confined to the contraction joints, bellows, fittings and elbows.
The contraction joint is normally protected by a top hat section which covers a folded butyl rubber vapour barrier. The butyl rubber barrier is applied and bonded to itself for the longitudinal seam and circumferentially to the GRE/GRP with a contact adhesive. Neither the butyl rubber or the contact adhesive can be considered to be reliable for the life of the plant and service history of this detail has shown limited service life.
Similarly, the bellows incorporate a butyl rubber vapour barrier. The amount of travel and repetitive movement that occurs at bellows in cyclic service makes this one of the weakest points of any cyclic insulation system.
Elbows, especially at pipe loops, are designed to accommodate the expansion and contraction of the pipe system. This results in a flexing of the pipe fitting as well as the insulation. Typically, elbows will not be pre-insulated and will have conventional lagged (pre-cut segmented layers) insulation with an outer vapour barrier. Depending on pipe diameter, a butyl rubber vapour barrier contraction joint may be incorporated to accommodate this movement.
7.2.2
Field Applied Insulation
As well as the features identified with pre-insulated systems this system is also vulnerable to breakdown of cladding due to corrosion and failure of the primary vapour barrier. Some metallic cladding, e.g., aluminised steel, is more prone to corrosion when used in corrosive environments.
Galvanic corrosion of the cladding or the recently introduced aluminium foil vapour barriers can occur especially if water accumulates between the vapour barrier and the cladding and there is no polyester protective coating on the aluminium. Once the aluminium is consumed there is no certainty on the performance of the butyl rubber backing as a vapour barrier.
7.2.3
Fittings in both pre-insulated and field applied systems
Valves, flanges, trunnions, manways, nozzles, etc are often compromised in the way insulation has been applied due to difficult geometry or compromised insulation thickness as a result of inadequate clearances provided in design. In other cases inadequate lengths are available where metal protrudes through the insulation. Typical examples are the spindle of a valve in cryogenic service or the platform supports on a cold vessel. In all these cases ice may have formed and a decision is needed as to the risk this ice may pose to the integrity of the overall insulation system. In the case of some ice on a valve spindle it may be acceptable provided that vapour stops have been installed either side of the valve. This will localise any damage to the extent of the valve insulation, however, in locations where vapour stop protection is not applied, repairs should be planned at the first opportunity.
7.3
Inspection
In order to limit the amount of damage that can be caused by an insulation failure it ongoing inspection should be part of day to day operations for operators to be trained to look for any tell tale signs of insulation breakdown as they do their normal duties. This is not to be a substitute for a regular, say, 12 monthly inspection by a trained inspector but will assist to limit the damage.
Signs of possible insulation breakdown or potential areas for water ingress can be seen as:
- isolated cold spots on the cladding which will be evident as condensation or frost (not to be onfused with widespread condensation which may occur due to cladding temperature going below dew point)
- condensation dripping out of the cladding joints or weep holes
- deformed cladding and broken steel bands
- torn, perished or unglued seams on butyl rubber vapour barriers
- water or ice collecting in the bottom of butyl rubber expansion/contraction joints on cyclic lines
- rust staining may also be an indicator
- mechanical damage to cladding may be an indicator for damage to the vapour barrier
Not all defects will be externally visible and part of the inspection should include a sampling of expected problem areas, eg, contraction joints, by removal of top hat sections, to inspect the vapour barrier.
For more rigorous inspection thermographic surveys are a useful tool to identify or confirm problem areas
7.4
Repairs
Where the need for repairs is identified they should be assessed as to the urgency for action. In many cases the repair will be deferred until the next shutdown. In the case of critical repairs or lines that are not subject to shutdown the repair may have to be done on line.
Repairing cryogenic lines in service requires special techniques to be able to strip insulation, remove ice and re-insulate the line. This is best done by specialist contractors experienced with this problem.
8
DEFINITION OF TERMS
| Principal | Owner of the plant / Unit |
| EPC Contractor Contractor | Engineering, Procurement, Construction Contractor Insulation Contractor |
| Manufacturer | Manufacturer of insulation material(s) required for the specified system(s) |
| Supplier | A supplier of insulation material(s) required in accordance with this specification |
| Testing Laboratory | Independent materials testing laboratory appointed by the Contractor and approved by the Principal. All tests performed by this laboratory shall be submitted to the Contractor and the Principal for review |
| Cryogenic | In this specification the temperature range of cryogenic temperatures are set between -100°C through -200°C. It is recognised that in literature different temperature boundaries are used. |
9
STANDARDS
For all standards mentioned in this specification reference is made to CINI 2.50.00.