INTERPLANT STANDARD - STEEL INDUSTRY

CODE OF PRACTICE FOR THERMAL

INSULATION OF HOT PIPE LINES AND IPSS:1-06-015-17
ACCESSORIES (Third Revision)

IPSS Based IS 14164:1994 Formerly :

IPSS:1-06-015-02
(Second Revision)

0. FOREWORD

0.1 This Inter Plant Standard prepared by the Standards Committee on Pipes,
Fittings, Valves and Piping Layout, IPSS 1:6 with the active participation
of the representatives of all the steel plants and established
manufacturers of thermal insulating materials, was adopted as IPSS
Standard in the year of 1984 & subsequently it was first revised in the
year of 1993 and second revision done in December 2002.

0.2 In view of updating the Indian Standards this IPSS Standard has been
further revised in July 2017.

0.3 Interplant Standards for steel industry primarily aim at achieving rationalization
and unification of parts and sub-assemblies used in steel plant equipment and
accessories, and provide guidance in indenting stores or equipment for existing
or new installations by individual steel plants. For exercising effective control
on inventories, it is advisable to select a fewer number of sizes (or types) from
among those mentioned in this standard for the purpose of company standards
of individual steel plants. It is not desirable to make deviations in technical
requirements.

0.4 In preparation of this standard, the assistance has been derived from the
following :

Sl Indian Description of IS
No. Standard (IS)
1. 277:1992 Specification for galvanized steel sheets (plain
and corrugated) (fifth revision) Amendment-3
2. 737:1986 Specification for wrought aluminum and
aluminum alloy steel and strip for general
engineering purpose (fourth revision)
3. 1322:1993 Bitumen felts for water proofing and damp
proofing (third revision)
4. 3069:1994 Glossary of terms, symbols and units relating to
thermal insulation materials (first revision)

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5. 3144:1992 Methods of test for mineral wool thermal
insulation materials (second revision)
6. 3150:1982 Specification for hexagonal wire netting for
general purposes (second revision)
7. 3677:1985 Specification for unbonded rock and slag wool
for thermal insulation (second revision).
8. 3690:1974 Unbonded glass wool mats for thermal
insulation (first revision)
9. 14164:1994 Code of practice for industrial applicati on and
finishing of thermal insulating materials at
temperatures above 40 deg C and upto 700 deg
C (first revision)
10. 8183:1993 Specifications for bonded mineral wool (first
revision) Amendment-1
11. 9743:1990 Thermal insulation finishing cements (first
revision)
12. 9842:1993 Specifications for pre-formed fibrous pipe
insulation (first revision)
13. 13205:1991 Code of practice for the application of
polyurethane insulation by the in-situ pouring
method.

1. SCOPE

1.1 This Standard covers the method of selecti on and application of thermal
insulation materials to outer surfaces of hot pipe line, flanges and valves
for maximum temperature of 550 oC.

2. MATERIALS

2.1 The insulation material shall be :

a) Unbonded mineral wool made from slag or rock conforming to

IS:3677-1985 or glass wool conforming to IS:3690-1974.

b) Bonded mineral wool conforming to IS:8183 made from slag, rock

or glass. Processed from molten state into fibrous form and
bonded with a suitable binder.

c) Pre-formed fibrous pipe insulation conforming to IS:9842-1993

(first revision). The material shall be mineral wool processed from
rock or glass fibres.

d) In-situ Polyurethane/Polyisocyanurate insulation conforming to IS

13205-1991 (applicable for max operating temperature of 110 oC).

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2.2 The minimum bulk density (Kg/cum) of insulating materials shall be as
given below :

UNBONDED BONDED MINERAL WOOL MAX. HOT

MINERAL Slabs/Mattre Pipe sections FACE TEMP.
WOOL sses Glass Wool Rock Wool DEG C

120 50 85 120 250

150 80 85 120 400
200 120 85 120 550

3. THICKNESS OF INSULATION

3.1 The thermal conductivity of insulation material shall be as given in

respective IS codes. The recommended thickness of insulation, provided
in Table 1 to 3 have been calculated based on the following conditions :

a) Ambient temperature 40 O C
b) Maximum surface 47 o C for OT <=250 oC
Temperature 50 o C for 250 < OT < = 400 o C
55 o C for OT> 400 oC
c) Wind speed 1 m/s
d) Finishing material Aluminum sheet/GI sheet

In case actual site conditions which are expected to vary considerably

over extended periods, or finishing material is other than aluminum,
alternate thicknesses suitable to such conditions can be calculated or
obtained from the manufacturer/applicators.

For in-situ polyurethane/polyisocyanurate insulation, the recommended

thickness of insulation can be taken as given under column 150 o C
operating temperature (OT) as per Table-1.

4. APPLICATION

4.1 General

4.1.1 All insulating materials shall have intimate contact with the surface.

4.1.2 While applying multilayer insulation, thickness of any layer shall not
exceed 75 mm, all joints shall be staggered and each layer shall be
separately secured by binding wires. Each layer shall preferably be of
equal thickness as far as possible.

4.1.3 Insulation shall be applied to the surface at ambient temperature and

with ample provision for thermal movement. This shall be applied in a

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manner which will avoid occurrence of breaking and telescoping due to
alternate periods of expansion and contraction.

4.1.4 Vertical pipes with diameter of more than 80 mm shall have support rings
at intervals not exceeding 2 m to prevent insulation from collapsing.
Supporting rings or lugs shall also be installed near the pipe bends (refer
Fig 2)(page-15)

4.1.5 Protrusions through the insulation such as pipe lines, supports, piping,
instrument take-off etc shall be covered to same thickness as the
adjacent insulation and extended up to six times the thickness of
insulation (except at hanger rods) and shall be sealed.

4.1.6 All voids, irregularities and joints shall be filled with loose insulation
material and properly packed.

4.2 Sequence of Application

a) Removal of existing insulation, if any

b) Surface preparation as per clause 4.3.1
c) Application of insulation as per clause 4.3.2
d) Finishing as per clause 4.3.3

4.3 Method of application

4.3.1 Surface preparation – Before application of the insulation the surface

shall be wire brushed to remove all dirt, rust, scale oil, etc and dried.
Suitable primer coating shall be provided on the pipe surfaces in case
indicated by the customer.

4.3.2 Application of insulation – The insulation shall be provided with any one
of type described below :

a) Loose mineral Wool – In case of loose mineral wool mattresses,

wire mesh (24 SWG x ¾”) conforming to IS 3150 shall be provided
on both the sides.

All the joints of wire mesh of adjacent mattresses shall be secured

with 20 SWG lacing wire.

NOTE: While insulating pipe of diameter 250 mm and above, lugs of 4

mm dia rods having length 50 mm more than the thickness of
insulation shall be welded at a distance of 200 mm on MS flats 20
x 3 mm shaped in the form of rings to suit the circumference of
pipe being insulated. These lugs shall be bent inside after the last
layer of the insulation and shall remain within the thickness of
insulation. The ring segment shall be bolted together with M 8 x
16 bolts. These rings shall be spaced 400 mm apart on pipe (for
details refer Fig.2)

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b) Bonded Mineral Wool – In case of bonded mineral wool

mattresses, the wire mesh shall be provided on one side. All
circumferential and longitudinal joints of mattresses to be fill ed
with loose wool so as to ensure heat leak proof joints. All the joints
of wire mesh of adjacent mattresses shall be secured with 20 SWG
lacing wire.

The material of the wire mesh/stitching wire/lacing wire shall be

G.I. for interface temperature upto 400 deg C and stainless steel
(IS 6582:1972) for higher interface temperatures.

For general arrangement of insulation pipe system (refer Fig 1)

NOTE: Bonded mineral wool may possibly contain up to approximately

0.01% of chloride. If circumstances can arise in practice such that
chloride concentration can take place on the surface of certain
alloy steels. For example, austenitic steels, then there is a
serious risk of stress corrosion cracking. In such cases, use of
aluminum foil/heat resistance anti corrosive paint, as per IPSS:1-
07-030-85, over the surface before the application of thermal
insulation is suggested.

c) Pre-formed pipe sections – The pre-formed pipe sections shall be

snapped on to the pipe surface in a staggered configuration and
shall be held in position by means of galvanized wire 20 SWG at
300 mm centre to centre (refer Fig 1).

d) In-situ insulation – The technique of insulating with in-situ

polyurethane/polyisocyanurate insulation is a preferred method for
many thermal insulation applications such as for process piping
and other equipments for the range of operating temperatures upto
110 deg C in case of PUF and upto 140 deg C in the case of PIR.
Application of insulation will be carried out as per IS 13205:1991.

In-situ insulation foaming is particularly suited to:

i) Where complicated shapes are involved which would not

lend themselves to easy insulation treatment using
preformed rigid materials.

ii) Where a joint free insulation is desired or where the

number of joints is to be kept to a minimum.

iii) Where very high disbonding stresses (such as leeward

wind forces) are to be encountered by the insulation
system.

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iv) Where speedy installation coupled with high reliability of
applied insulation is sought.

4.3.3 Finishing – The insulation shall be finished by any one of the methods
described below :

a) Cement plaster – The finishing cement plaster free from asbestos

suitable for indoor/outdoor applications as per IS 9743:1990 shall
have a total thickness of 12 mm applied in two layers and shall be
reinforced with chain link mesh 20 SWG x 20 mm as per IS 3150.

Note : 1) One coat of oil/cement paint may be applied over the

plaster in case of indoor applications.

2) Suitable water proofing compound such as bituminous

shall be applied over the cement plaster in case of outdoor
applications.

b) Sheet metal cladding – Aluminum sheet as per IS 737 or G.I. sheet

as per IS 277 shall be rolled, grooved and retained in place with
self-tapping screws at 150 mm cc, ensuring minimum 50 mm
overlap of cladding sheet at all longitudinal/circumferential joints.
The joints shall be rendered water proof by incorporating 25 mm
wide bituminous water proofing felt (IS 1322:1993) with the joints
being arranged at 8 or 4 O’clock position to shed rain water.
Aluminum sheets of 22 SWG and G.I. sheets of 24 SWG are
recommended.

Note: Sheet metal will be preferred for outdoor applications .

5. INSULATION OF FITTINGS

5.1 Before insulation of fittings is taken up, insulation of the pipe with its
protective finish shall be completed. The insulation o f valves,
bends/elbows, flanges and clamps shall be done using same thickness
as the main equipment/piping (refer Fig 3 to 6).

5.2 At valves and flange fitting location, insulation on pipe lines shall
terminate from the face equal to the overall length of th e bolts or stud
plus two flange thickness so as to permit withdrawal of bolts without
damage to adjacent insulation.

Note: Insulation of flanged fittings and valves shall be carried out after hot
tightening.

6. INSULATION OF TRACER LINES

6.1 Insulation shall be so applied that no insulating material comes in

between the tracer and the process pipe. For steam traced lines, a

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protective barrier layer of 0.1mm thick aluminium foil shall be applied
enclosing the process and tracer pipes (refer Fig 7), only after which
insulation work shall start as per method of application described earlier.

7. PERFORMANCE TESTING

7.1 Performance of the installed insulation system shall be assessed against

the specified requirements by carrying out measurements of following
parameters after commissioning of insulated systems :

Ambient temperature Measured 1 m away from insulated surface

Surface temperature Measured on finished insulation surface
Wind speed Measured nearest to the surface
(within one meter)

Temperature & wind speed shall be measured by suitable instruments

surface contact type temperature indicator, with appropriate bow/leaf
type probe. Wind speed shall be measured by portable mechanical
anemometer. These instruments shall have valid calibration.
Measurement spots shall be selected by sampling, to represent entire
insulated area. Since the reference conditions during the test may not be
same as specified, correlative calculations shall be done to assess and
estimate the insulation performance at sp ecified conditions.

Note – Performance testing shall be done after system is stabilized.

8. SPECIAL CONSIDERATIONS FOR COASTAL LOCATIONS

The following are recommended in consideration of conditions that

prevail in coastal locations (as described in Append ix-I):

8.1 Surface protection prior to insulation – All pipes and metal surfaces to be
insulated shall be cleaned and painted with heat resistant paints suited
to maximum operating temperature. Selection shall be made on the basis
of paints manufacturers recommendations. Stainless Steel surface shall
be protected with aluminum foil 0.1 mm thick applied with minimum 50
mm overlap and secured with 0.4 mm dia stainless steel wires at a
spacing of 400 mm.

8.2 Cladding over insulation

8.2.1 Aluminum Cladded system

i) The aluminum sheet shall conform to IS 737:1986 alloy

designation 31000 in the following thicknesses :

Up to 600 mm dia over insulation 0.71 mm

601 mm and above 0.91 mm

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ii) All cladding joints shall have a synthetic rubber based metal
sealant provided in a bead of approximately 6 mm dia.

iii) Securement shall be done with aluminum pop-rivets at a spacing

of 150 mm.

iv) Aluminum bands shall be provided over cladding in the following

sizes at a spacing of 400 mm (max) :

Upto 300 mm dia meter over insulation None

301 to 600 mm 25 x 0.91 mm
601 and above 25 x 1.2 mm

8.2.2 Galvanized/Galvalume sheet cladded system

i) Specification for cladding material shall be as per IS 277:1977 with

class 2 galvanization or galvalume protected steel and thickness of
sheet shall be used as below :

Up to 600 mm dia over insulation 0.6 mm

601 mm and above 0.8 mm

ii) All cladding joints shall have a synthetic rubber based metal
sealant provided in a bead of approximately 6 mm dia.

iii) Securement shall be carried out with galvanized pop-rivets and

steel screws placed alternatively at a spacing of 150 mm.

iv) Galvanized steel bands shall be provided at a spacing of 400 mm

maximum in the following sizes :

Upto 300 mm dia meter over insulation None

301 to 600 mm 25 x 0.6 mm
601 and above 25 x 0.8 mm

8.3 For brief description of special considerations for Coastal Locations see
Appendix- 1

9. GENERAL - Any details not specified in this standard shall be as agreed

between suppliers/applicators and client.

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TABLE – 1

RECOMMENDED MINIMUM THICKNESS (mm) CHART FOR RESIN

BONDED MINERAL WOOL (SLABS / MATTRESSES)
DESIGN CRITERIA
Ambient temperature 40 O C
Maximum surface 47 o C for OT < =250 o C
Temperature 50 o C for 250 < OT < = 400 o C
55 o C for OT> 400 oC
Wind speed 1 m/s
Insulation material (density) 50 kg/cum for OT < = 250 oC
80 kg/cum for 250<OT< = 400 oC
120 kg/cum for OT > 400 oC
Finishing Aluminium sheet/G.I. sheet

Pipe NB Operating temperature (OT), Deg c

mm Upto 150* 151 to 250 251 to 350 351 to 400 401 to 550
15 50 95 95 100 105
20 50 100 100 105 110
25 55 105 105 110 115
32 55 110 110 115 120
40 55 115 115 120 125
50 60 120 120 125 130
65 60 125 125 135 140
80 65 130 130 140 145
100 65 135 135 145 150
125 70 145 145 150 160
150 70 150 150 160 165
200 75 155 155 165 175
250 75 165 165 175 185
300 80 170 170 180 190
350 80 170 170 185 190
400 80 175 175 185 195
450 80 180 180 190 200
500 85 180 180 195 205
600 85 185 185 200 210
x 95 235 235 255 270
* Thicknesses indicated in this column can be used for in -situ polyurethene/
polyisocyanurate insulation also.
NOTE: Pipe NB (x) stands for NB more than 600 mm & flat surface. All thicknesses indicated are in mm.

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TABLE – 2

RECOMMENDED MINIMUM THICKNESS (mm) CHART FOR

UNBONDED MINERAL WOOL

DESIGN CRITERIA
Ambient temperature 40 O C
Maximum surface 47 o C for OT < =250 o C
Temperature 50 o C for 250 < OT < = 400 o C
55 o C for OT> 400 oC
Wind speed 1 m/s
Insulation material (density) 120 kg/cum for OT < = 250 oC
150 kg/cum for 250<OT< = 400 oC
200 kg/cum for OT > 400 oC
Finishing Aluminium sheet/G.I. sheet

Pipe NB Operating temperature (OT), Deg c

mm Upto 150 151 to 250 251 to 350 351 to 400 401 to 550
15 55 105 110 130 135
20 60 110 115 140 140
25 65 115 120 145 145
32 65 125 130 155 155
40 70 125 130 155 160
50 70 135 140 165 165
65 75 140 145 175 175
80 75 145 150 180 180
100 80 155 160 190 195
125 85 160 170 200 200
150 85 165 175 210 210
200 90 175 185 220 225
250 95 185 195 230 235
300 95 190 200 240 240
350 95 195 205 245 245
400 100 200 210 250 250
450 100 200 210 255 260
500 100 205 215 260 265
600 105 210 225 270 270
x 120 270 290 360 365

NOTE: Pipe NB (x) stands for NB more than 600 mm & flat surface. All thicknesses indicated are in mm.

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TABLE – 3

RECOMMENDED MINIMUM THICKNESS (mm) CHART FOR RESIN

BONDED MINERAL WOOL (PIPE SECTION)

DESIGN CRITERIA
Ambient temperature 40 O C
Maximum surface 47 o C for OT < =250 o C
Temperature 50 o C for 250 < OT < = 400 o C
55 o C for OT> 400 oC
Wind speed 1 m/s
Insulation material (density) 85 kg/cum for glass wool
120 kg/cum for rock wool
Finishing Aluminium sheet/G.I. sheet

Pipe NB Operating temperature (OT), Deg c

mm Upto 150 151 to 250 251 to 350 351 to 400 401 to 550
15 40 75 95 100 105
20 45 80 100 105 110
25 45 85 105 110 115
32 45 90 110 115 125
40 50 90 115 120 125
50 50 90 120 125 135
65 55 100 125 135 140
80 55 105 130 140 145
100 55 110 135 145 155
125 60 115 145 150 160
150 60 120 150 160 170
200 65 125 155 165 175
250 65 130 165 175 185
300 65 135 170 180 190
350 65 135 170 185 195
400 70 140 175 185 200
450 70 140 180 190 205
500 70 145 180 195 205
600 70 145 185 200 215
x 75 175 235 255 275
NOTE: Pipe NB (x) stands for NB more than 600 mm & flat surface. All thicknesses
indicated are in mm.

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APPENDIX – I

BRIEF DESCRIPTION OF SPECIAL CONSIDERATION FOR

COASTAL LOCATIONS

1. Most coastal locations involve high wind velocities and cyclonic storms.
Selection of cladding thickness and securement of cladding need special care.
In all cases, specifications shall feature positive securement at sheeting joints,
by pop rivets/self-tapping screws. Insulation systems for large ducts, and such
areas shall incorporate external bands over cladding which are the only means
of preventing dislodgment of sheeting by the heavy leeward (suction) pressures
that are normally encountered.

2. As is well known, atmosphere in a coastal location, in addition to high humidity,

also contains higher levels of electrolytes – thereby increasing the potential for
electrochemical corrosion. From this angle, the following become important :

a) All equipment and piping shall be properly cleaned, surface prepared

and coated to desired protection standards prior to releasing them for
insulation applications. In heated systems, coatings used shall be
selected for suitability for peak temperatures expected in service. Field
welded areas on shop fabricated and shop coated equipment need care
and attention in this regard.
b) All stainless steel surfaces need special attention due to their sensitivity
to chloride attack. Irrespective of the type and nature of the insulant
selected, there is likelihood of high chloride pick-up in storage, handling
and application and hence, positive protection against direct
concentration of leachable chlorides at the interface between the metal
and the insulation is mandatory.
c) All exposed surfaces, such as cladding shall be selected to be of
materials which will not pit, scale or corrode. Aluminum alloy cladding is

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preferred in all cases. Where sheet steel is used for any reason, it shall
be galvanized with sufficient thickness of coating. Some improved
protective techniques such as galvalume treatment or additional coil
coating over galvanizing are available which will provide superior service
life.
d) Bands and securement devices including screws shall preferably be of
the same material as the main cladding. Where they have to be of
different metals, they shall be so chosen as to ensure that they are not
electrolytically dissimilar at the point of contact.
e) Although sealings at joints in cladding and flashing at the terminations in
insulation are important in many systems, coastal areas need special
care in these areas since water seepage through imperfect joints can be
much more serious, since corrosion under insulated systems due to such
occurrence remain undetected till it is too late.

Generally, special care is needed in selecting and inspecting all

materials forming part of the insulation system such as the material,
sealants, mastics and adhesives, etc. since aging and deterioration rates
are higher in aggressive environmental conditions per sec.

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