TRAINING MANUAL PIPING

THERMAL INSULATION

Uhde India Limited

DOC No. : 29040-PI-UFR-0033

Rev. : R0

Page : 1

CONTENTS

Page

0.0 Cover Sheet 1

1.0 Introduction 2

2.0 Purpose 2

3.0 Heat Transfer Principle 2 4

4.0 Determination of Insulation Thickness 3 5

5.0 Insulation Type 5 6

6.0 Insulation System 6 9

7.0 Applicable IS Standards 9

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TRAINING MANUAL PIPING

THERMAL INSULATION

Uhde India Limited

DOC No. : 29040-PI-UFR-0033

Rev. : R0

Page : 2

1.0 INTRODUCTION:

Heat Transfer is one of the most common unit operations in Process Industry. In an idealsituation one would want to achieve heat balance between the Source and Sink without anyloss of heat energy to the atmosphere. Unfortunately the above can not be achieved inabsolute terms, even though an attempt can be made to control the Heat Transfer in such away so as to limit the heat loss to atmosphere to a minimum by employing Insulating Materialover the metallic surface exposed to atmosphere. Besides, there could be some other factors(e.g. condensation and subsequent freezing of moisture over the exposed surface) which maynecessitate using Insulating Material depending upon the operating conditions of the Systemunder question. The cost considerations do however prevail upon, in deciding the appropriatelevel of Insulation that would prove to be most effective from an overall angle.

2.0 PURPOSE:

The objectives of providing the Thermal Insulation can be summarized as follows:

To prevent Heat Loss from hot surface.

To prevent Heat Gain by the cold surface.

To prevent condensation (and subsequently ice formation) on cold surface.

To provide Personnel Protection against accidental contact of human body with hotmetallic surface.

3.0 HEAT TRANSFER PRINCIPLE:

The Heat Loss in case of a hot insulated circular pipe takes place due to heat flow through thefollowing 4 steps refer sketch (Figure-1, Exhibit 39.1) below

Figure-1 (Exhibit 39.1)

TRAINING MANUAL PIPING

THERMAL INSULATION

Uhde India Limited

DOC No. : 29040-PI-UFR-0033

Rev. : R0

Page : 3

1. Heat flow Q1 from fluid to inside surface of the metal wall by way of Convection2. Heat flow Q2 across the metal wall by way of Conduction.3. Heat flow Q3 across Insulation Layer by way of Conduction4. Heat flow Q4 from the outer surface of metal wall to the atmosphere, predominantly by

way of Convection.

Under steady state condition the rate of Heat Transfer through the above 4 steps will besame.

i.e. Q1 = Q2 = Q3 = Q4

In case of Heat Gain, by a cold insulated pipe the direction of heat flow will be opposite to thatof the hot insulated pipe.

Rate of Heat Transfer = K A * t Where K = Thermal ConductivityBy Conduction A = Surface Area

t = Temperature Gradient per Unit length= t / R Cond R Cond (Thermal Resistivity due to conduction)

= 1/ KA

Rate of Heat Transfer = h A *T Where h = Convection Heat Transfer CoefficientBy Convection

= t / R Conv R Conv (Thermal Resistivity due toConvection)= 1/ hA

T = Differential temperature

Applying the above basis equations to the Insulated Pipe Cross Section and ignoring thethermal resistivity R Conv and R Cond for heat transfer in Step 1 and 2 (i.e. assuming that Step 1and Step 2 practically offer no resistance to Heat Flow)

The Heat Loss across the Insulation

Q3 = K * 2L * t1 (Eq 39.1) Ln (D2/ D1)

Where:D2 = Outer Diameter of InsulationD1 = Inner Diameter of InsulationL = Length of Insulated Pipet1 = Temperature differential between

inner and outer surface of Insulation.

The Heat Loss from Insulation Outer Surface to the Atmosphere

Q4 = h * D2 L *t2 (Eq 39.2)

Where:t2 = Temperature Differential t between

the Insulation Outer surface andthe Atmosphere.

TRAINING MANUAL PIPING

THERMAL INSULATION

Uhde India Limited

DOC No. : 29040-PI-UFR-0033

Rev. : R0

Page : 4

Under steady state condition

Q3 = Q4

K * 2L * t1 = h * D2 L * t2Ln (D2/ D1)

Conduction Heat Transfer Coefficient for Insulating Material K is typically 0.02 0.04 W/ m. O CConvection Heat transfer Coefficient for Air (natural convection) is typically 15 20 W/ m2 .O C

4.0 DETERMINATION OF INSULATION THICKNESS:

The selection of Insulation Thickness is done based on 1 of the following cases for the givenfluid and ambient temperature, wet bulb temperature (considered for cold insulation only) andwind speed (accounted for in the convection heat transfer coefficient for heat flow frominsulation top surface to the atmosphere).

Case 1:To maintain the temperature of the outer surface of the Insulation to a specified value fromprocess angle (i.e. for controlling the heat gain) in case of Cold Insulated Piping.

Case 2:To maintain the temperature of the outer surface of Insulation above wet bulb temperature toavoid condensation and subsequent freezing of the atmospheric moisture in case of ColdInsulated Piping.

Case 3:To maintain the temperature of the outer surface of Insulation from personnel Protection pointof view in case of Hot Insulated Piping. A maximum temperature of 52 O C is considered to beacceptable.

Case 4:To maintain the loss of Heat Energy to a specified value from the point of view of limiting theplant operating cost in case of Hot Insulated Piping. A value of 100 Kcal/ hr m2 is generallyassumed to be satisfactory from the point of view of rationalizing the Annual CapitalInvestment vis--vis Annual Plant Operating Cost.

The calculation of Insulation Thickness for Cases 1 to 3 is done in following steps

Step 1: Assume an arbitrary Insulation Thickness.

Step 2: Determine Q4 based on the predetermined value of t2 (i.e. differential between thegiven temperature of outer surface of Insulation and the ambient) and the assumed value ofInsulation Thickness in Step 1, as per equation (EQ 39.2)

Step 3: Equate Q3 = Q4

Step 4: For the value of Q3 arrived above, calculate the value of Insulation Thickness as perequation (Eq 39.1)

Step 5: Based on the calculated value of Insulation Thickness recalculate Q4

Step 6: Repeat Steps 3 to 5 until the value of Q3 and Q4 becomes practically same.

TRAINING MANUAL PIPING

THERMAL INSULATION

Uhde India Limited

DOC No. : 29040-PI-UFR-0033

Rev. : R0

Page : 5

Step 7: Select the Insulation Thickness as calculated in Step 4 corresponding to the steadystate achieved in Step 5.

The calculation of Insulation Thickness for case 1 is done on the similar principle as for case1 to 3 with a minor variation in the approach, which is as follows

Step 1: same as above

Step 2 and Step 3: Not required since the Heat Loss (i.e. Q3 = Q4) is already specified.

Step 4: For the specified value of Q3 = Q4 calculate the value of t1 (i.e. temperaturedifferential between the inner and outer surface of Insulation) based on the assumed value ofInsulation Thickness in Step 1.

Step 5: Calculate the temperature of the outer surface of the Insulation based on the innersurface temperature as fluid temperature and t1 calculated in Step 4 above.

Step 6: Calculate t2 (i.e. differential between the calculated temperature of outer surface ofInsulation in Step 5 above and for the given ambient temperature).

Step 7: Calculate Insulation Thickness based on t2 calculated above and the specified valueof Q4.

Step 8: Repeat Steps 4 for the calculated value of Insulation Thickness in Step 7 above andspecified value of Q3 = Q4 to arrive at a new value of t1

Step 9: Repeat Steps 5 to 7 to arrive at the new value of Insulation Thickness

Step 10: Repeat Steps 8 and 9 until a steady state condition is achieved (i.e. calculatedInsulation thickness in step 7 becomes constant)

5.0 INSULATION TYPE:

Based on the functional requirements, the Insulation Material is classified into 2 types asbelow

Hot Insulation:

Insulation used on hot surfaces for the purposes of Heat Conservation or for the purpose ofPersonal Protection.

Following material are typically used as Hot Insulating Material

Material Thermal Conductivity AdmissibleTemperature

(mW/ Cm O C ) Range (O C)

Mineral Wool (unbonded) 0.48 (Note 1) 600Mineral Wool (bonded) 0.43 (Note-1) 750Glass Wool 0.43 (Note-1) 450Calcium Silicate 0.55 500

Notes: 1) Thermal Conductivity at 50 O C

TRAINING MANUAL PIPING

THERMAL INSULATION

Uhde India Limited

DOC No. : 29040-PI-UFR-0033

Rev. : R0

Page : 6

Cold Insulation:

Insulation Used on cold surface for the purpose of Cold Conservation or for the purpose ofavoiding Condensation.Following Materials are typically used as Cold Insulating Materials

Material Thermal Conductivity AdmissibleTemperature

(mW/ Cm O C) Range (O C)

Polyurethane Foam 0.29 (Note-1) -150 to 110Expanded Polystyrene Foam 0.32 (Note-1) -150 to 80Expanded Perlite Foam

Notes: 1) Thermal conductivity at 0 O C.

6.0 INSULATION SYSTEM:

Insulating Material:

Normally the Insulating Materials are available in unbonded mats and bonded or foamedpreformed Pipe Sections/ Slabs to suit various applications. Polyurethane Foam andExpanded Perlite Foam can also used by in-situ foaming.

Protective Coating:

Normally thermal Insulation is provided with an external covering for protection against entryof water or process fluid, mechanical damage, exposure to fire and ultraviolet degradation (incase of foam material). The protective cover could be in the form of

Coating (asphalt, polymer or resin) Membrane (felt or paper) Sheet Material (fabric, metal or plastic)

Vapor Barrier:

Cold Insulation Systems operating at subzero (below 2 O C) are normally provided with VaporBarrier and sealed at the joints to prevent condensation and vapor transmission. Metallic Foilsand Mastic embedded Glass Fabric are commonly employed for this purpose.

Insulation Thickness Selection

Uhde Standard provides the recommended thickness for various pipe sizes for the followingInsulation Systems

Cold Insulated Piping System Hot Insulated Piping System Personal Protection System

Insulation Material Properties:

Insulation Material in general shall be chemically neutral, rot-proof and free from impurities. Inaddition following properties are required to be considered in selecting the Insulating Material

TRAINING MANUAL PIPING

THERMAL INSULATION

Uhde India Limited

DOC No. : 29040-PI-UFR-0033

Rev. : R0

Page : 7

Mineral Wool/ Glass Wool

Thermal Conductivity Density Fire Resistance (to be rated as incombustible) Chloride Content Sulphur Content Moisture Absorption Shot Content Recovery after Compression Heat Resistance

Foam Insulation/ Thermocole

Thermal conductivity Density Compression Strength and Hardness Water Vapour Permeability Auto Ignition Fire Resistance Heat Resistance

Application:

Following steps are followed while applying Thermal Insulation on Piping/ Equipment Items.

Insulation Supports in the form of Ring, Lugs are welded to the Vertical Vessels andTanks as per UN 200006 Part 1 Page 1 (for Hot insulation) and as per UN 2000-06 Part1 Page 2 (for Cold Insulation).

Horizontal Vessels will not require Insulation Supports

In case of Cold Insulated Vessels the Insulation will extend up to 5 times the insulationthickness where there are protrusions (e.g. skirts/ leg supports etc.). Supports andBrackets in case of hot insulated Equipment are normally not insulated.

The materials forming part of Insulation System (e.g. Cement, Coating, Fabric etc.) shallbe free from Asbestos except mill board used for avoiding metal to metal contact.

The Carbon Steel and Low Alloy Steel surface to be insulated shall be painted (forcorrosion protection) with paint system as per Painting Specification recommended for theservice.

The Insulation Work shall commence only after the Hydro Test on Equipment/ Piping iscompleted and the items handed over for Insulation.

Generally the Insulation shall be applied over the entire metal surface including flangesand stiffening rings etc. except over the parts (e.g. Gland Plate for valve gland packingetc.) which require frequent dismantling for maintenance purpose.

As far as possible and practical the voids due to the profile of the external surface of anyitem (e.g. Valve body) will be filled with loose insulating material.

In case of Cold Insulation the cladding shall be done without using self-tapping screws toavoid rapture of the Vapour Barrier. This however does not apply to in-situ foaming.

TRAINING MANUAL PIPING

THERMAL INSULATION

Uhde India Limited

DOC No. : 29040-PI-UFR-0033

Rev. : R0

Page : 8

Wherever applicable the joints between the Vapour Barrier and steel surface/ claddingare sealed to avoid ingress of moisture.

In case of Insulation Thickness in excess of 75 mm it is recommended that the Insulationwill be applied in multiple plies.

Insulating Material used in the Process Plants in which Nitric Acid or Ammonium Nitrateare produced, shall not contain organic binding materials (e.g. Phenolic Resins).

In the Process Plants with likely hood of formation of volatile flammable vapours, onlyinsulation material with a closed surface (e.g. Foam Glass) shall be used.

In case of application of Insulation in multiple plies, the seams shall be staggered.

Insulation material on vertical or nearly vertical surfaces shall be prevented from sliding bymeans of suitable supports and tie wires or banding.

Closely spaced lines (small bore)or Tubing may be insulated in a common envelop (up to6 lines)

In case of insulation of Heat Traced lines it is recommended to place a thermal shield(metallic foil) between insulation material and the tracing/process pipe for better heattransfer and for preventing the insulation from penetrating between the tracer and theprocess pipe.

Vapour Barrier Foils in case of Cold Insulation shall be overlapped (approximately 50 mm)at the joints.

Installation of Insulation Material is done in following steps:

Spacers:

The purpose of providing Spacers is to enable the cladding to retain its shape andconcentricity with respect to the surface to be insulated

The spacers are required only for mineral fiber mats or for in-situ foaming The spacers are fabricated as per the details given in UN 5001-02 (Part-1) The spacers are positioned (fixed) at the required spacing on metallic/ plastic surface as

per the details given in UN 5001-02 (Part 1) In case of Vertical equipment the spacers are attached to the vessels by means of

Insulation Clips as per UN 2000-06 (Part-1 and Part-2)

Insulation Material:

The Insulation Material in case of Mineral Fiber Mats, is fixed to the cylindrical surface bymeans of metal wire tied in a helical manner around the cylindrical surface.

The Insulation Material in case of Mineral Fiber Preformed Shell or Slabs is glued to themetal surface or held together with closely butted joints.

Insulation Material in case of preformed foam shells and slabs are held in position bygluing the end seams. In case of multiple layers the seams shall be staggered withrespect to each other.

In case of in-situ Foaming the foam is generated within the cavity formed between themetal surface to be insulated and the external cladding.

TRAINING MANUAL PIPING

THERMAL INSULATION

Uhde India Limited

DOC No. : 29040-PI-UFR-0033

Rev. : R0

Page : 9

Packing:

Depending upon the contour of the surface to be insulated, it may be necessary to fill thecavities and voids by means of loose mineral fibers or with the same type of foam

Cladding:

Standard Sheet Metal (Galvanized) shall be used as Cladding Material. Aluminum Sheetcan be used as alternative material (except Caustic Chlorine Plants)

Metal Banding or self-tapping screws may be used for attaching the Cladding. SuitableTurn Buckles or Snap Catches may be used connecting the ends of Banding

Cladding Joints shall be sealed by elastomeric sealing tape.

The Cladding Joints are made by crimping or foalding.

7.0 APPLICABLE IS STANDARDS:

Glass Wool IS 3677 / IS 3690Rock Wool IS 8183/ IS 9842Polyurethane Foam IS 12436Expanded Polystyrene IS 4671Determination of Thermal Conductivity IS 3346Cladding Sheet IS 737