Cold Thermal Insulation Specification

This content provides you with a sample cold thermal insulation specification that is applied in industrial plant construction.


1.1. SCOPE

This Engineering Specification covers the minimum requirement for design and material of external cold insulation for piping and equipment, for purpose of cold heat conservation, low temperature maintenance, for use in industrial plant.

The deterioration caused by corrosion under insulation is addressed in API RP 571 corrosion and material course. The inspection requirements for piping corrosion under insulation and pressure vessel corrosion under isolation are addressed by the API 570 piping inspector course and API 510 pressure vessel inspector course.

This Engineering Specification defines the cold thermal insulation to be used for equipment, and piping system including:

  • Insulation types.
  • Insulation materials.
  • Thickness to be applied.
  • Fastening materials.
  • Jacketing systems for insulation protection.
  • Technical application methods to be used.

1.2. References - Cold Thermal Insulation Specification

Throughout this Engineering Specification the latest edition of the following codes, standards and engineering specification are recommended:

1.2.1    Codes & Standards

  • Unfaced Preformed Rigid Cellular Polyurethane Thermal Insulation ASTM C 591
  • Code of Practice for Thermal Insulation of Pipe Work and Equipment     BS 5970 (In the temperature range –100 °C to +870 °C)
  • Method of Specifying Thermal Insulating Materials on Pipes, Ductwork and Equipment  BS 5422 (In the temperature range -40 °C to +700 °C)

1.2.2   Engineering specification - Cold Thermal Insulation Specification

Note: Definition of terms used in this engineering specification shall be in accordance with ASTM C 168.

2. Design Basis on Cold Thermal Insulation Specification


Design ambient temperature for cold insulation: Tac = +48  °C

  Maximum direct sunshine temperature:                 85º C

The temperature for which the piping to be insulated shall be the operating temperature indicated on the Line List.

The temperature for which the equipment is to be insulated shall be the operating temperature indicated on the equipment Engineering Drawings. 

2.2. Insulation Purposes 

2.2.1 Insulation shall be provided on all equipment, piping and instruments etc., containing fluid or vapor, for which it is necessary to:

(1) In order to maintain low temperature for process control.

(2) Avoid surface condensation.

(3) Conservation of refrigeration.

2.2.2 The system, including the insulating material, the method of fixing, and the finishing material, has to be capable of giving effective service during the required life period of the installation. At all times the system shall have good resistance to vibration, mechanical damage and thermal movement, and it should retain its physical effective mass and stability in service.

2.3. Insulation Code 

Cold insulation shall be marked with code M on relevant documents.

2.4. Insulation Data on Cold Thermal Insulation Specification

2.4.1 Insulation data shall be indicated on the following documents:

1) Equipment insulation  : Equipment List 

2) Pipe insulation     : Line List

2.4.2 Piping, equipment, storage tanks and vessels requiring insulation shall normally be specified on the following project documents:

1) Piping and Instrumentation Diagrams (P&IDs).

2) Piping arrangements and Isometric drawings.

3) Instruments Piping Details and Schedules.

4) Vessel, Exchanger, Storage Tank documents and Insulation Schedules.

5)   Line List

2.5. Extent of Insulation on Cold Thermal Insulation Specification

1) Insulation around valves and instrument shall be provided so that insulation does not interfere its operation.

2) All pipes, valves, flanges, and fittings shall be insulated.

3) Valves shall be insulated up to the packing gland.

4) All equipment attachment and projections such as vessel supports, steel structures attached to vessels, piping supports, instrumentation lines, equipment trim line and instruments connections directly, to be cold insulated up to a distance of 4 times (minimum 300 mm) the insulation thickness.

5) Insulation shall extend down the outside of vessel skirt for a distance 4 time (minimum 500 mm) the insulation thickness as measured from inside bottom tangent line.

6) All flanged joints, manhole covers, etc. shall be cold insulated with removable box insulation.

7) Insulation on exchangers shall be stopped at a sufficient distance from each flange to permit the removal of the flange bolts and shall be finished with a bevel of sealer.


The following piping components & equipment parts shall not be insulated unless otherwise specified.

(1) Visible parts such as code, inspection and nameplate, stampings, sight glass and level gauge.

(2) Parts having moving element, such as expansion and swivel joint, and sliding valves.

(3)   The parts dislike cold exposing such as gland of valves.

(4) Flange connections in hydrogen service.

2.7 CLEARANCES - Cold Thermal Insulation Specification

(1) Insulation shall be designed to provide an absolute minimum clearance of 25 mm between the outside surface of any insulation finishing material and adjacent surfaces.

(2) Where insulated piping is supported on steel shoes, the height of the shoe shall be such that the underside of the insulation finishing material is clear of the supporting structure upon which the shoe rest by 25 mm minimum.

3. INSULATION MATERIAL - Cold Thermal Insulation Specification


1) All material (Insulation, Jacketing and ancillary material) shall be of high quality, new, and good appearance.

2) The insulation material shall be resistance to degradation. This requirement can have wide implications, from resistance to vermin and fangoid attach, to freedom from fire hazard. Also it will include resistance to the required environmental conditions, e.g., adequate weather resistance for outdoor service as well as resistance to accidental spillage of oil or other chemicals. The insulating material itself should not tend to dissociate nor to disintegrate. 

3.2 SELECTED INSULATION MATERIAL - Cold Thermal Insulation Specification

Rigid Cellular Polyurethane as per ASTM C-591 TYPE-2 shall be used as cold insulation material.


The operating temperature shall be used to determine the insulation thickness.

Multiple layers shall be provided for thickness above 75 mm.

Annex 1 Thickness table for heat conservation (cold) Rigid Cellular Polyurethane.


Panels, blankets, blocks, preformed shells, cut shells, slabs, etc. according to the equipment and pipe sizes and forms.

Preformed insulation shall be used for pipes up to 12” NPS.


3.5.1 Welded Pins (needles)

To maintain insulating materials on storage tank storage shells.

They shall be made of black annealed steel MARTIN types, : 3mm.

3.5.2 Plates

For attachment on needles and handling in place insulating material.

They shall be made of black spring steel.

3.5.3 Wires

They are used to hold pipe insulation materials in place.

Dimensions to be used:

N° 8 (1,3mm.)

Type: 304 stainless steel

3.5.4 Straps / Fasteners

They shall be suitable for the insulation materials selected and the metal jacketing used.

Type: Stainless Steel type 304.

3.5.5 Metal Straps

They are used to hold the insulation materials in position on, equipment and materials and where it is no possible to use needles.

Dimension to be used:

Width 12mm for pipes.

Width 19mm for equipment, ducts.

3.5.6 Strap Fasteners

They shall be adapted to the straps on which they are used.

3.6 Metal Jacketing on Cold Thermal Insulation Specification

3.6.1 Aluminum Jacketing

Aluminum jacketing shall be used as weather protection cover, over the insulation unless otherwise specified. 

Thickness shall be:

(OD: external insulated diameter of equipment or piping)

OD < 350 mm.    = 0.6 mm.

350 mm < OD < 600 mm.   = 0.8 mm.

600 mm < OD < 1600 mm.   = 1.0 mm.

OD > 1600 mm.   = 1.2 mm.

Flat sheet with 0.5 mm thickness for equipment head and transitions.

Type: ASTM B209 Alloy 3003-H16 or approved equivalent, with factory applied polykraft vapor barrier.

3.6.2 Aluminum Foil

Aluminum foil shall be used to protect Stainless Steel surface.

Thickness shall be: 0.19 mm

For securing Aluminum foil on stainless steel surfaces, Aluminum band 24 SWG thickness with 

19 mm wide shall be used.

3.6.3 Commercial Forms to be used 

Flat sheets shall generally be used, but corrugated cladding may be used on large surfaces and storage tanks.

3.7 Jacket Fastening on Cold Thermal Insulation Specification

Blind rivets shall be used for attaching metal jackets together and screws for fixing metal jackets to insulation supports. The material of blind rivets and screws shall be adapted to the material nature of the metal jacketing.

3.7.1 For Attaching Metal Jackets Together

Form: Blind rivet.

Size: Æ = 4mm x 10mm.

3.7.2 For Jacket Fastening To Insulation Supports

Form: Hexagonal heads with washers. (Self-tapping type)

Type: Stainless steel 304 or 304L

Size: Æ: 7 mm. x 13 mm. long for Æ  < 1500 mm.

Size: Æ: 7 mm. x 19 mm. Long for Æ  > 1500 mm.

Washers:Æ: 19 mm. Neoprene 2 mm. Thickness.


4.1. Precausions Prior to application 

The following operations shall be performed on equipment and materials prior to application of insulation:

  • Supports installation
  • Satisfactory hydrostatic tests
  • Preparation of surfaces to be insulated.

If insulation work proceeds in advance of hydrostatic testing and inspection, welded joints shall be left uninsulated until hydrostatic testing is completed.

4.1.1. Supports Installation on Cold Thermal Insulation Specification

Generally insulation supports on equipment shall be installed by the Vessel fabricators, and on piping by the piping construction contractor. Support field welding on tested equipment or materials, shall be prohibited unless expressly authorized by the engineering contractor.

4.1.2. Surface Condition on Cold Thermal Insulation Specification

All surfaces to be insulated shall be cleaned in order to remove all contaminates.

Insulation materials shall not be applied to surfaces, which are wet.

4.2. Application of Insulation on Cold Thermal Insulation Specification

4.2.1. General

1) The application methods, given in this engineering specification are general in nature. The construction contractor is responsible for applying an insulating system that to give a satisfactory operational performance and the requirements given herein shall be regarded as the acceptable minimum.

The construction contractor shall carryout the work in accordance with the best practices of insulation application with the minimum of waste and debris and the final job shall have a neat, efficient and workmanlike appearance.

2) Insulation supports shall be provided at least 3700 mm intervals on vertical lines or lines inclined more than 45° from horizontal supports shall be installed above all flanges in vertical lines and located to allow removal of flange bolts.

3) Contraction joints shall be provided on long straight runs of piping at approximately 7 m intervals  and shall be a 25 mm gap for all temperature up-to 180ºC joints shall be packed with glass fiber blanket and adequately sealed.  

4)  Before applying weatherproofing, insulation shall be inspected for open joints, voids, cracks and defacing. Open joints, voids, and cracks shall be adequately filled with insulation and defacing   made good to the satisfaction of the inspector.

5) Special consideration shall be given to application of insulation near pipe supports. The insulation and weatherproofing shall be applied in a manner, which does not restrict thermal expansion or contraction of the piping at its support points.

6) Piping insulation shall be continues at guides.

7) Inner layers in multiple layers pipe insulation and insulation on irregular equipment surfaces (where use of bands and seals is impractical) shall be secured, using wire.

The wire shall be drawn taut to imbed it into the insulation. The ends shall be firmly twisted and the excess cut off. The twisted ends shall be bent over and imbedded into the insulation.

8) Butt and expansion joints shall be staggered for single layer insulation and in both directions all multiple layers of insulation.

9) Hydrostatic tests on pipe, vessels and equipment, if possible shall be completed before insulation is installed. If insulation is applied before testing, all weld and thread joints shall be exposed until completion of testing.

10) Care shall be taken to avoid contact between dissimilar material, which might causes galvanic corrosion.

11) Insulation, which needs to be removed for maintenance purpose, shall be fabricated in such a manner, that it is easily removable and can be remounted with a minimum of work. Quick opening boxes and similar construction shall be used in this case.

12) Single thickness sectional pipe insulation shall be applied with longitudinal joints staggered and shall be secured with wire ties on 230 mm centers.

Double thickness sectional pipe insulation shall be applied with all joints staggered and shall have inner layer secured by at least two wires per section with the outer layer secured by wire ties on 230 mm centers.

13) External stiffing rings on vessel and piping shall be insulated with the same thickness as required for vessel or piping.

4.2.2. Application of Insulating Materials - Cold Thermal Insulation Specification

  • Only sound and dry materials having the correct dimensions, and the required quality shall be installed.
  • Cut outs in insulation shall be clean cut.
  • When more than one layer is provided, the components of each layer shall be staggered and joints of the second layer shall be off set from those of the first layer.
  • Blanket (metal-mesh covered) shall be secured by twisting together the wire mesh or by means of a hook or by tying them together with 0.8 mm diameter wire.
  • Any beveled or rounded edges of insulating component shall be carefully square off before application.
  • Each layer of insulating blanket shall be applied on circular equipment and secured by steel wire or adapted straps with an adequate spacing to hold components in place. (Maximum spacing: 250 mm from center to center).
  • On any sharp angles, a small alloy aluminum angle piece shall be installed to prevent the metal strap cutting into the insulating materials.
  • All insulation components shall be carefully cut and adjusted to follow the exact shape of surfaces, nozzles, manholes, rings, supports, gussets, etc.
  • Stiffeners shall be thoroughly insulated to the required thickness.

4.2.3. Vapour Barrier & Weatherproofing (Pipe-work) The entire outer surface of the insulation shall be covered a tack coat of vapour barrier mastic, 1.5 liters per 1.0 m2 with a minimum thickness of 1 mm unless otherwise specified. And nylon fabric embedded into the surface while still wet, avoiding all wrinkles pockets, etc. and overlapping the nylon fabric a minimum of 50 mm.

A finish coat of vapour barrier mastic shall then be applied to the whole surface 3.0 liters per sq.m., with a minimum finished and dried thickness of 3 mm unless otherwise specified, care shall be taken to ensure that all nylon fabric and bands are completely covered. The surface shall be then be smoothed off with a suitable solvent if metal cladding is not to be applied. The vapour barrier mastic and nylon fabric shall extend at least 150 mm beyond the insulation at all metal projections to ensure a good seal. Heavy fillets of mastic shall be applied to all corners and crevices where water is likely to collect. Vapour barrier mastic shall also be used as flashing at all possible sources of moisture penetration such as intersections of insulation, nozzles, building, walls, valve bonnets tees and other protrusions through the surface coating.

4.2.4. Vapour Barrier & Weatherproofing (Equipment) - Cold Thermal Insulation Specification The entire outer surface of the insulation shall be covered a take coat of vapour barrier mastic, 1.5 liters per 1.0 m2 with a minimum thickness of 1 mm unless otherwise specified. And nylon fabric embedded into the surface while still wet, avoiding all wrinkles pockets, etc. and overlapping the nylon fabric a minimum of 50 mm. A finish coat of vapour barrier mastic shall then be applied to the whole surface, 3.0 liters per sq.m. With a minimum finished and dried thickness of 3 mm unless otherwise specified. Care shall be taken to ensure that all nylon fabric and bands are completely covered. The surface shall then be smoothed off with a suitable solvent if metal cladding is not to be applied. At all metal flashing protrusions, insulation terminals, corners and cervices a sealant shall be applied prior to the mastic and nylon fabric, which shall extend 150 mm beyond the insulation to ensure a good seal. Heavy fillets of vapour barrier mastic shall be applied to all corners and cervices where water is likely to collect. Vapour barrier mastic shall also be used at all possible sources of moisture penetration, such as intersections of insulation, nozzles, building walls and other protrusions through the surface coatings.

4.2.5. Application of the Metallic Jacketing

  • After equipment or piping insulation has been applied in a satisfactory manner the insulation shall be immediately jacketed and waterproofed.
  • If bare insulation cannot be jacketed before the end of the working day the system shall be protected with plastic sheets or in shed to prevent water entering.
  • A basic rule concerns the orientation of the metal jacket overlapping.
  • To prevent any ingress of water (or other liquid) under the jacket, it is essential for horizontal joints, that the top sheet overlaps the bottom sheet (like roof tiles).
  • In the case of vertical joints the overlap shall be in opposite direction of the prevailing wind.
  • Laps shall be swaged to increase stiffness and seal efficiency.
  • On equipment, ducts, piping and whenever it is possible, both horizontal and vertical laps shall be minimum 50mm wide, otherwise, they shall be as large as possible.
  • Metal jackets shall be fixed together by adequate screws spaced of maximum 200mm. From center to center.
  • To prevent thermal bridges, insulating fabric bands shall be provided between jacket and support on equipments and at insulation supports.
  • To allow movement due to the differential expansion between equipment or piping and jacket, special arrangement shall be provided (Example: a circumferential lap joint located between 2 supports shall not be fixed).
  • On accessories such as supports, branch connections, nozzles, manholes … where adjustment of jacket is difficult and water infiltration is most likely to happen finishing sheet in 2 parts attached by screws, lapped and swaged shall be provided. Sealing mastic shall also be used.
  • Jacket for vessel heads shall be in section except for small diameters where they may be either flat or Chinese hat type.
  • The outer surface of insulation shall have a regular and smooth finish.

4.2.6. Insulation of Equipments and Ducts - Cold Thermal Insulation Specification

Insulation elements like blocks and slabs shall be applied with their length parallel to the greatest length of surface being covered.

The base course shall be applied with alternate length blocks so that all successive end joints are staggered.

Skirts supporting equipments shall be insulated outside as part of the equipment area.

Vessel identification plates shall not be insulated.

Finally metallic jacketing shall be applied.

4.2.7. Insulation on Piping - Cold Thermal Insulation Specification

Straight Pipes

The edges of pipe insulation segments shall be cut off square leaving a distance between the insulation segment edge and the flange bolt extremity equal to the bolt length plus 25mm. To ensure enough clearance for bolt dismantling.


Generally, materials shall be cut into suitable segments and joints shall be carefully staggered.

Each section shall be held in position by a metal strap and fastener.

Tees and Branch Connections

Elements shall be carefully cut and adjusted.

When two layers (or more) of insulation are provided, joints shall be staggered as follow:

- 1st layer on secondary branch

- 1st layer on main pipe

- 2nd layer on secondary branch

- 2nd layer on main pipe.

Then metallic jacketing shall be applied.

Flanged Components

Flanged components shall be insulated by means of prefabricated boxes or insulation elements like blocks and slabs.

4.2.8. Insulation on instruments; 

For in-line instruments, gauge and up to block valve of local instruments such as pressure gauges, extend and specification of insulation shall be according to this engineering specification.

For lubing impulse / analyzer line, insulation extend and specification shall be in accordant with Engineering Specification for Control and Instrument.     

Generally local instruments shall be insulated by means of prefabricated removable boxes or insulation elements like blocks and slabs.

Insulation shall be applied as described in paragraphs 4 for instrument pipes.

Insulation must enable controls and adjustments.

4.2.9. Inspection Windows - Cold Thermal Insulation Specification

Adequate number of inspection windows on all strategic locations shall be provided for checking metal corrosion by construction contractor, which will be specified by field engineer.

The removable window shall be of the same basic material and thickness as the rest of the insulation and of sufficient rigidity to withstand handling.

5. Inspection requirements on Cold Thermal Insulation Specification

5.1 All materials furnished and/or used in connection with the insulation work shall be subject to inspection and approved by Owner to assure the use of material of the type and quality, which meet the requirements of this specification. It is the responsibility of insulation contractor to ensure adequate percautions against damage and deterioration are taken during the storage of insulation materials.

5.2 Installation procedure shall be subject to inspection by Owner or by his representative and any material, which has been improperly installed or excessively damaged material shall be removed and replace properly with undamaged material.

5.3 Inspection and approval of materials and workmanship by Owner shall not relieve insulation contractor of any his responsibilities what so ever.

5.4 Prior to insulation work commencing on any particular section, Owner or third party should be satisfied that all insulation supports on vessels, vertical pipelines have been correctly installed. Additionally all refrigerant tracing lines are properly in place and all metals surface are clean and free of foreign or spattered materials.

5.5 All insulation application shall be performed during dry weather, uncompleted and exposed surfaces should be protected at all time against dampnest, condensation or rain. Any exposed ends shall be temporarily protected with weather proofing insulation showing any evidence of moisture shall be removed and replaced.

5.6 Prior to the release of any equipment and piping to the insulation applicator, all valves, gauges, etc., shall be inspected, tested and repaired.

5.7 Care shall be taken to ensure that all moving parts (working parts) of instrument, valves, and equipment are protected when insulation is applied.    

6. Storage Requirements on Cold Thermal Insulation Specification

Insulating materials shall be packed in a manner to ensure no moisture can enter during transport, in transit, and storage at site and also during application.

Preferably, the materials shall be fixed to non-returnable pallets.




INSULATING MATERIAL: Rigid Cellular Polyurethane as per ASTM C-591 TYPE-2.

K = 0.019 W/m °C


Cold Thermal Insulation Specification


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