4

NAT L INST, OF STAND & TECH R.I.C.

• Reference

A111D3 M3DMMD

IMBSIR 81-2324

NIST

ICATIONS

*1. FIE OOPY'^

00 NOT TAKE

Boiling Tests of Non-Asbestos-Based

Thermal Insulation Used in Air-Conduit

Underground Heat Distribution Systems

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Building Technology

Washington, DC 20234

September 1 981

Prepared for; Naval Facilities Engineering Command

U.S. Navy

Washington, DC 20390

Directorate of Civil Engineering

U.S. Air Force

Washington, DC 20330

c

Offir.p of Chief of Engineers

ton, DC 20314

LuSi' 0:

1 n0(
(II
NBSIR 81-2324

6

"-

BOILING TESTS OF NON-ASBESTOS-BASED

THERMAL INSULATION USED IN AIR-CONDUIT

UNDERGROUND HEAT DISTRIBUTION SYSTEMS

T. Kusuda

W. M. Ellis

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Building Technology

Washington, DC 20234

September 1 981

Prepared for: Naval Facilities Engineering Command

U.S. Navy

Washington, DC 20390

Directorate of Civil Engineering

U.S. Air Force

Washington, DC 20330

Office of Chief of Engineers

U.S. Army

Washington, DC 20314

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director
< I';!) 1

V

Ik'

[F’'jf '4 V ^. ' Kiaa«« :

a«iA»»«.WS»S8A?M'OM IQt'tTSa'f^ aWi

' *iSiJQiw:?3 ":i A » 0SMJ WOSTMUaw s

r'/ i ~'v t

'

'

' *

y-KdjBIOtK.ei -^'0 ;,'

^s^tO'S :r,i^'oi

' i IS5

SiWA

;‘:^ut>oD ^Xh

(O'*

.nriesAip-n-^'l • y.iO

mzQ'i ;oc:,u;, ^dl't'-

« '^^-W 1

;^'-

;g!Ti?;^, >0.

%M '*

-'^ ,1 - “' 4

:"’< '! r

AzZ:',:., 'Z.:\ '^^::
ABSTRACT

Non-asbestos-based thermal insulation around steam carrier pipes is commonly

used in conduit underground heat distribution systems for many of the Triservice installations. When the conduit fails, the insulation is expected to

undergo severe boiling action due to the possible Ingress of underground water.

If the insulation is properly fabricated, it should withstand the prolonged

boiling such that its thermal performance would be restored when the ground

water is drained and the system dried.

Several selected insulation systems were boiled in an open tank as well as in

the conduit to test their ability for retaining the original insulation

capability

.

Although most of the calcium silicate-based insulation systems fell off the

carrier pipe under the open tank boiling within 72 hours, they were able to

withstand 96 hours of continuous boiling in the conduit. When drained and

dried, these systems restored their thermal insulation performance to within

10 percent of the original value.

Key words: boiling test; conduit system; pipes; thermal insulation;

underground heat distribution systems.

iii
PREFACE

This report summarizes the test results of open-tank and in-condult boiling

tests on non-asbestos-based thermal insulation used in the Tri-Servlce-type

air-conduit underground heat distribution systems. Systems of several selected

manufacturers were listed at the request of the Tri-Service committee on underground heat distribution systems since 1976, results of which have been reported

in seven successive NBS Letter Reports, as listed below.

Boiling test of calcium silicate Insulation for underground heat

distribution systems.

Conduit boiling test of the insulation in underground heat distribution

systems

.

Part I Part II

Part III

Part IV

Part V

Part VI

Kaylo System.

Thermo-12 System

Pabco System

Wesolite System

Eagle-Picher System

Celotemp-1500 System

Also included in this summary report are the results of the last series of

tests, where the conduit boiling continued up to 64 days.

Commercial names are used in this report to identify for the sponsor the

specific materials tested. Such identification does not imply recommendation or endorsement by the National Bureau of Standards, nor does it imply

that the materials or equipment identified are necessarily the best

available for the purpose.

Iv
TABLE OF CONTENTS

Page

1. OPEN TANK BOILING TEST 1

1.1 Introduction 1

1.2 Bolling Test Apparatus 2 1.3 Open-Tank Bolling Tests 2

1.3.1 Kaylo Insulation 2

1.3.2 Pabco Super Caltemp Insulation 3

1.3.3 J-M Thermo- 12 Insulation 3

1.4 Summary of the Open Tank Boiling Test 4

2. CONDUIT BOILING TEST 30

2.1 Introduction 30

2.2 Description of Test Apparatus 30

2.3 Test Procedure 38

2.4 Tri-Servlce Evaluation Criteria 39

2.5 Test Results 40

2.5.1 Kaylo-lO System 40

2.5.2 Thermo-12 System 40

2.5.3 Pabco System 48

2.5.4 Wesolite System 55

2.5.5 Epltherm System 55

2.5.6 Celotemp System 64

3. SIXTY-FOUR-DAY CONDUIT BOILING TEST 73

4. COMPARISON WITH CALCULATED PIPE HEAT TRANSFER FACTORS 101

5. REFERENCES 105

V
LIST OF TABLES

Page

Table 1. Sixty -four-day Conduit Boiling Test of Six Insulation

Materials 74

Table 2. Comparison Between the Calculated and Measured Heat Transfer

Factor C 104

LIST OF FIGURES

Figure 1. A schematic of the open-tank boiling test apparatus 5

Figure 2. KAYLO #1 system before the boiling 6

Figure 3. Pipe side view of KAYLO #1 specimen before boiling 7 Figure 4. Conduit side view of KAYLO #1 specimen before boiling 8

Figure 5. KAYLO #1 system after 5 hours boiling 9

Figure 6. KAYLO #2 specimen before boiling 10

Figure 7. Conduit side view of KAYLO #2 specimen before boiling 11

Figure 8. Pipe side view of KAYLO #2 specimen before boiling 12

Figure 9. KAYLO #2 system after 72 hours boiling and 24 hours drying ... 13

Figure 10. KAYLO //2 after 72 hours boiling and 24 hours drying 14

Figure 11. PABCO #1 system before boiling 15

Figure 12. A close-up of PABCO itl system before boiling 16

Figure 13. Conduit side view of PABCO #1 specimen 17

Figure 14. Pipe side view of PABCO //I specimen 18

Figure 15. PABCO #1 system after 1 hour boiling 19

Figure 16. PABCO //2 system before the boiling 20

Figure 17, Conduit side view of PABCO #2 specimen 21

Figure 18. Pipe side view of PABCO #2 specimen 22

Figure 19. PABCO #2 system after 3 hours boiling 23

Figure 20. A close-up of PABCO #2 system after 3 hours boiling 24

Figure 21. J/M system before the boiling 25

Figure 22. Conduit side view of J/M specimen before boiling 26

Figure 23. Pipe side view of J/M specimem before boiling 27

Figure 24. J/M system after 72 hours boiling and 24 hours drying 28

Figure 25, Close-up of J/M system after 72 hours boiling and 24 hours

drying 29

Figure 26, A schematic diagram of conduit boiling test for underground

heat distribution system 32

Figure 27. The thermal conditioning box for the conduit boiling

test apparatus 33

Figure 28, Baffle plates along the air passage to obtain uniform

temperature around the test underground conduit system 34

Vi
LIST OF FIGURES (Continued)

Page

Figure 29. Header plates for the underground conduit insulation boiling

tests: one for the electric heating (left) to measure pipe

heat loss; the other for the steam heating (right) to provide

boiling 35

Figure 30. Instrumentation and power control panel for the insulation

boiling test 36

Figure 31. Immersion electric heaters for the heat loss test 37

Figure 32. Heat loss and temperature data during the test for Kaylo-10

insulation 41

Figure 33. Longitudinal distribution of the conduit surface temperature

before and after the Kaylo-10 boiling tests 42

Figure 34. Kaylo-10 insulation after the boiling tests shows severe erosion due to the boiling action 43

Figure 35. The joint of Kaylo-10 insulation jacket was eroded out by the

boiling action of water outside the carrier pipe 44

Figure 36. Crumbs of Kaylo-10 insulation found in the conduit space

after the carrier pipe and insulation jacket were removed .... 45

Figure 37. Heat loss and temperature data during the boiling test of

Thermo- 12 46

Figure 38. Longitudinal distribution of the conduit temperature before

and after the Thermo-12 boiling test 47

Figure 39. Thermo-12 insulation removed from the conduit after boiling

for 192 hours and drying 49

Figure 40. The waterline during the conduit boiling of the Thermo-12

system 50

Figure 41. Heat loss and temperature data during the boiling test of

Pabco system 51

Figure 42. Longitudinal distribution of the conduit surface temperature

before and after the Pabco boiling tests 52

Figure 43. The insulation damage due to 192 hours conduit boiling test

and subsequent drying (Pabco System) 53

Figure 44. The Pabco thermal insulation system immediately after removal

from the conduit where it underwent 192 hours boiling and

subsequent drying tests 54

Figure 45. Heat loss and temperature data during the test for Wesolite ... 56

Figure 46. Longitudinal distribution of the conduit surface temperature

before and after the boiling tests for Wesolite system 57

Figure 47. Wesolite on pipe after removal from conduit after 96 hours

of boiling 58

Figure 48. Close-up of opening at joint after conduit boiling of

Wesolite 59

Figure 49. Wesolite after boiling showing deterioration at the bottom

of pipe below the water level 60

Figure 50. Condition of Wesolite after removal from pipe after boiling .. 61

Figure 51. Heat loss and temperature data during the test of Epltherm ... 62

Figure 52. Longitudinal distribution of the conduit surface temperature

before and after the boiling test of Epitherm 63

vii
LIST OF FIGURES (Continued)

Page

Figure 53. Epitherm on pipe after removal from conduit after 96 hours

of boiling 65

Figure 54, Close-up of Epitherm at the bottom of the pipe after boiling

(below the water level) 66

Figure 55. Close-up of Epitherm at the top of the pipe after boiling

(above the water level) 67

Figure 56, Heat loss and ten5)erature data during the test of the

Celotemp system 68

Figure 57, Longitudinal distribution of the conduit surface temperature

before and after the boiling test (Celotemp system) 69

Figure 58. Insulation on the pipe after removal from conduit after

96 hours of boiling (Celotemp system) 70

Figure 59. Insulation after boiling showing deterioration at the bottom

of the pipe below the water level (Celotemp system) 71

Figure 60, Crumbs of insulation found in the conduit space after the

carrier pipe and insulation jacket were removed (Celotemp

system) 72

Figure 61. Celotemp 1500 after 8 days of boiling 75

Figure 62. Celotemp 1500 after 16 days of boiling 76

Figure 63. Thermo-12 after 16 days of boiling 77

Figure 64, Thermo-12 after 24 days of boiling 78

Figure 65. Thermo-12 after 32 days of boiling 79

Figure 66, Thermo-12 after 64 days of boiling 80

Figure 67. Epitherm 1200 after 8 days of boiling 81

Figure 68, Epitherm 1200 after 16 days of boiling 82

Figure 69. Epitherm 1200 after 24 days of boiling 83

Figure 70, Epitherm 1200 after 32 days of boiling 84

Figure 71, Epitherm 1200 after 64 days of boiling 85

Figure 72, Wesolite "D" after 8 days of boiling 86

Figure 73, Wesolite "D" after 16 days of boiling 87

Figure 74, Wesolite "D" after 24 days of boiling 88

Figure 75. Wesolite "D" after 32 days of boiling 89

Figure 76, Wesolite "D" after 64 days of boiling 90

Figure 77. Super Caltemp after 16 days of boiling 91

Figure 78, Super Caltemp after 24 days of boiling 92

Figure 79. Super Caltemp after 32 days of boiling 93

Figure 80. Super Caltemp after 64 days of boiling 94

Figure 81, Kaylo-10 after 16 days of boiling 95

Figure 82. Kaylo-10 after 24 days of boiling 96

Figure 83. Kaylo-10 after 32 days of boiling 97

Figure 84, Kaylo-10 after 64 days of boiling 98

Figure 85. End view of plywood box used to house the conduit 99

Figure 86. Inside of plywood box showing baffles to regulate air flow ... 100

Figure 87, Cross-sectional view of the Tri-service "air conduit"

underground heat distribution system 102

viii
UNIT CONVERSION

The text is written using English units to be consistent with the current U.S.

practice in underground heat distribution engineering. The units most

frequently appearing in the text have the following conversion multipliers to

SI units:

1 inch

1 ft

1 psig

1 Btu/h.ft'^.F

1 Btu-in/h.f t^ ,F

1 Ib/ft^

1 °F

0,254 cm 0,305 m

6.89 kPa above 101.2 kPa

1.728 W/m.K

0.144 W/m.K

16,028 kg/m^

(F-32)/1.8°C

ix
*

••^^ ,:. f'> ..; m -

Of viHVt':•T^i/S^^^ 1^

"*'

I* ':

' V^* ^ •'t *'/> »'• <4 •

' 4^'.

.. . .. :vf. '.i

.

.e»ir; .iv^.^^00 0.it^. ; ''' '/ . ^

I't-.t.^n 'T :r

’••'" V 'T'' 1””^’..; ^.v J ^Hfc .I'Ta :

. c A - 4.'''' - ii

f\'4 -* 'ffc'i^.swrJ 5 '-f'' ' >' ‘ *

kT''.,“ :?ti

‘ •’. ' .’ ' i '" V* •UV *'>JFi^' 7 < * ' ^ •*/*. 'y.' T

‘ *' ‘ * ” * .’F " ' .

> ;% r —•; u,K(?.r vi rti.t^t sd;' :;‘H/., v<. > > V* ; Y.y “ •: • *"

»•' n»r<i '

>

• -•..•.A'i.-i*^

' *T<x \ vf "•?<•< «

1

y''f K**- * ' ''

•’!!3

'’^

*.i T-' A'^ 't^^lSIBSi ,'• -* *• ;'' ^'' ',J -'-. 4

. ' “ :- \'v

'

V’ '^vr. * :>. %,r:;r4 i;^f "“C-'

' i Ki'?

*''•'/ ’ ' • *^P|ydl^ ' ’'® ..Ar,i 'I* 1 '€04\

^:» I,.;: i.:^,

^ f -r-.^ 'C' >. s

.i:''"'* > , i", ,.

r

'(I V 't i ^ y,Tt i -'k ".! »,«i i%'i,^Airv'

IS ...y:

>: V,

»

Sphsp
1. OPEN-TANK BOILING TEST

1 . 1 INTRODUCTION

At the request of Tri-Services* engineers, the Thermal Engineering Section of

the National Bureau of Standards conducted laboratory boiling tests on several

commercial brands of asbestos-free calcium silicate insulation. Most of the

calcium silicate insulations tested over the past few years have satisfied the

boiling and drying requirement when the asbestos was used as a binder for the

calcium silicate, but because of the recent ban of the use of asbestos material,

synthetic fibre type binder is now being used throughout industry. Since some difficulties have been experienced in the field on this new type of insulation

material, the Tri-Services requested NBS to conduct the boiling test on the new

types of calcium silicate insulation. The purpose of the investigation was to

clarify misgivings as to the performance of asbestos-free calcium silicate

insulation in the "air conduit system** when the conduit is flooded, due

mostly to the ingress of ground water.

According to the Tri-Services Guide Specification (TS-15P28) the insulation

material in the conduit system should withstand the boiling and should be able

to assume the pre-boiling thermal resistance value after the ground water is

drained off. In order to assure this requirement, the Tri-Services, with the

cooperation of NBS, previously developed a laboratory boiling test procedure

for the acceptance of the conduit system insulation. [Specification for HeatDistribution System, March 24, 1958]. The Tri-Service/NBS test procedure is

summarized as follows:

The test insulation specimen is installed around 4-inch pipe immersed

in a water tank with the top of the insulation being 2 inches below the

water surface. The insulation is then boiled for 72 hours by maintaining

125 psig of steam in the pipe.

If portions of the insulation fall off of the pipe, if the insulation

becomes eccentric at the center lines of the pipe, if the longitudinal or circumferential joints open up significantly, or if cracks or ruptures

occur in the insulation wide enough that the pipe surface can be seen,

the insulation will have failed the test.

When the pipe insulation withstands the boiling test, the tank will be

drained and the wet insulation will be dried with steam at 350° (125 psig)

for 24 hours. A representative cross section of the insulation will be

taken and put into an oven at 215°F until its weight becomes constant.

TRI-Services represent Naval Facilities Engineering Command; Directorate

of Civil Engineering, U.S. Air Force; and Office of Chief of Engineers,

U.S. Army.

The "air conduit system" is one of the Tri-service approved underground heat

distribution pipe systems whereby thermal insulation around the carrier pipe

is protected by a metallic conduit with an airspace.

1
Three commercial types of calcium silicate insulation were tested in this

investigation; Owens-Corning "Kaylo," Pabco "Super Caltemp," and Johns-Manville

"J-M Thermo-12."

1.2 BOILING TEST APPARATUS

Since the original boiling test facility constructed in 1961 at the old NBS

site in Washington, D.C. was no longer available at the present Gaithersburg

campus, a new facility was built, and is shown in figure 1 with the following

components being identified;

A steel tank , 10 ft long, 20 in wide, 24 in deep, 1/2 in thick, is mounted

on dolly wheels with a drain in the bottom and with fill and overflow connections on one end. A constant water level float assembly was used during

the test. A piece of 8-ft long, 4-ln pipe was installed inside of the

tank. The 125 psig steam is supplied to this pipe through the 1-in diameter

line (J) • Also installed onto this 4-in pipe are a 1/2-in vent line @ at the

outlet end of the pipe, and a pressure gage @ at the inlet end. Two condensate traps (T) , were used on the outlet of the steam pipe; one small trap

(T) is for use when the tank was not filled with water (or when the insulation

is not boiling), and a larger trap (s) is for use when the tank was filled with

water (or when the insulation is boiling). Another condensate trap (?) was used at the inlet of the steam supply to the 4-in test pipe in order to supply

dry steam to the test pipe.

The three condensate lines from these t^ps (7) » (E)» CE) were separately

introduced into the condensate cooler (l^ by coij^ed copper tubings. Cold tap

water was used as a coolant. A platform scale flS) was used to weigh the

amount of condensate during testing of insulation. Water from the condensate

cooler, the condensate collection can , and overflow from the boiling tank

was dumped into the floor drain inside^Building 226. The sump pump

was used when the gravity drains for condensate collection would not take

care of all of the condensate and cooling water.

In addition, copper constantan thermocouples were used to measure the pipe

surface temperature, insulation surface temperature, tank water temperature,

and ambient air temperature.

1.3 OPEN-TANK BOILING TESTS

1.3.1 Kaylo Insulation

Two Owens-Corning "Kaylo" specimens were tested in the first test — the

insulation was tied onto the 4-in pipe with 16-ga. bare copper wire on 9-in

centers, as shown in figure 2. A one-half-section piece is shown (both sides)

in figures 3 and 4, and figure 5 shows the results after 5 hours of boiling.

This insulation started to crack off of the pipe after about 30 minutes of

2
boiling. The density of this batch of insulation was 13.58 Ib/ft^ and had a moisture content of 6.3 percent.

The second test specimen of "Kaylo" insulation was installed on the 4-in pipe

with 32-ga. stainless steel straps 1/2 in wide on 9-in centers, as shown in

figure 6. One half section is shown (both sides) in figures 7 and 8. The

result of 72 hours boiling and 24 hours drying is shown in figures 9 and 10.

The top section of the center piece was about 60 percent off of the pipe, the

bottom section was broken, and the straps had cut into the insulation as shown.

The piece at the trap end of the pipe was broken, but did not fall off of the

pipe. The density of the second batch of insulation was 13.69 Ib/ft^ and the

moisture content was 6.9 percent.

Representatives of Owens-Corning witnessed the installation of the second

insulation test specimen to confirm that the installation procedure used in the

test was the same as that used in the actual application.

1.3.2 Pabco Super Caltemp Insulation

For the first test with Pabco insulation, 1/2-in wide stainless steel bands, were strapped around the pipe on 18-ln centera, as shown in figures 11 and 12.

One half section piece (both sides) is shown in figures 13 and 14. This insulation started to break off of the pipe after approximately 20 minutes of boiling and all of it came off within one hour. The results are shown in figure 15.

The density of this insulation was 13.79 Ib/ft^ and the moisture content was

5.9 percent.

The second test of Pabco insulation was conducted with the insulation installed

on the 4-in pipe with 32-ga. stainless steel straps 1/2 in wide on 9-ln centers

instead of 18 inch, as shown in figure 16. One half section (both sides) is

shown in figures 17 and 18. The results of 3 hours boiling are shown in

figures 19 and 20. The density of this insulation was 14.40 Ib/ft^ and the

moisture content was 3.4 percent.

1.3.3 J-M Thermo-12 Insulation

The insulation specimen tested came with canvas covering, which was removed

before the test. This insulation was Installed on the pipe with 32-ga. stainless steel straps 1/2-in wide on 9-ln centers, as shown in figure 21. One half

section piece is shown (both sides) in figures 22 and 23. The results of 72

hours of boiling and 24 hours of drying after the water was drained from the

tank are shown in figures 24 and 25. Figure 24 shows that the straps have cut

into the insulation about 1/2 in or more. Figure 25 shows a closeup of a crack

of approximately 5/16-ln width in the inlet end piece of insulation. The straps

cut into the insulation. All of the individual pieces of the insulation remained

intact after testing, with only one section broken. The density of the

insulation was 13.31 Ib/ft^ and the moisture content was 3.0 percent.

Throughout the text, the "moisture content" is defined as amount of moisture

percent of the dry weight material.

3
1.4 SUMMARY OF THE OPEN TANK BOILING TEST

All three of the commercial asbestos-free calcium silicate thermal insulations

for the underground heat distribution system tested for this investigation

failed during the boiling test in the open tank.

The Tri-Services Committee evaluated the test results and determined that the

open tank boiling is probably too severe, and advised NBS to repeat the boiling

test inside the conduit.

4
NBS

INSULATION

BOILING

TEST 5

Figure

].A

schematic

of

the

open

tank

boiling

test

apparatus
Figure 2. KAYLO #1 system before the boiling.

6
Pipe side view of KAYLO #1 specimen before boiling ,

7
Figure 4. Conduit side view of KAYLO #1 specimen before boiling
4

Figure 5. KAYLO #1 system after 5 hours boiling

9
Figure 6. KAYLO #2 specimen before boiling

10
Figure 7. Conduit side view of KAYLO #2 specimen before boiling

11
i
13
10. KAYLO #2 after 72 hours boiling and 24 hours drying

14
15
Figure 12. A close-up of PABCO #1 system before boiling

16
Figure 13. Conduit side view of PABCO #1 specimen

i!

I,1

j

I

17
Figure 14. Pipe side view of PABCO #1 specimen

18
! Figure 15. PABCO #1 system after 1 hour boiling

19
(

Figure 16. PABCO #2 system before the boiling

20
Figure i/. Conduit side view of PABCO #2 specimen

21
Figure 18. Pipe side view of PABCO #2 specimen

22
Figure 19. PABCO #2 system after 3 hours boiling

23
Figure 20. A close-up

iof PABCO #2 system after 3 hours boiling

24
Figure 21. J/m system before the boiling

25
Figure 22. Conduit side view of J/M specimen before boiling

26
27
Figure 24. J/M system after 72 hours boiling and 24 hours drying

28
Figure 25. Close-up of J/M system after 72 hours boiling and 24 hours drying.

29

before and after the boiling. Special consideration was given to the

fabrication of the test apparatus in such a manner that the temperature around

the conduit is uniform and that the carrier pipe with the insulation can readily

be removed from the conduit for inspection after the boiling test.

The apparatus used for the boiling test is illustrated diagrammatically in

figure 26. It consisted of a reinforced plywood box for supporting and enclosing the conduit specimen, immersion electric resistance heaters for determining

the heat transfer rate, a steam supply system and the necessary piping, pressure and level gages, and controls for temperature and water level in the pipe.

The plywood box measuring 4 ft wide x 4 ft high x 19 ft long (shown in figure

27) was used to maintain a stable temperature around the pipe similar to that

encountered in the underground environment. Nine baffle plates, as shown in

figure 28, were installed in the plywood box to obtain uniform airflow and

temperature around the conduit system.

The conduit specimen was supported in a level position along the longitudinal

axis of the box and protruded through holes cut in each end of the box to fit

the heater plates. The conduit extended about 3 inches beyond either end of

the box. The conduit was wrapped with a blanket of glass fiber insulation

1/2-in thick and fastened at the lapped joints to simulate the thermal resistance of approximately 2 ft of earth cover.

The ends of the conduit were closed with flanged metal plates and secured with

bolts. The joints between the end plates and the exterior of the 4-in steam

pipe were fitted with gland seals to prevent leakage. Holes for 1-in pipe were

provided at the top and bottom of each of the end plates, and one of the end

plates was provided with two additional holes for 1/2-in pipe, for attachment

of a sight glass. The 1-in pipe connections at the top and bottom of the end

plates were used for filling and draining, for venting of steam, and for attachment of a pressure gage, as required. The details of the end plates and the

openings in them are illustrated in figure 29.

The 4-in steam pipe was operated as a closed boiler with immersion electric

heating elements during the periods when the heat transmission rate of the

specimen was being measured. Conventional pipe flanges were attached to the

threaded ends of the 4-in pipe. Steel plates 3/4-in thick were bolted to the

flanges at each end. Each of these plates was drilled and tapped to receive a two-element immersion electric heater located along the center line of the pipe.

In addition, holes for 1/4-in pipe were drilled and tapped at the top and

bottom of each of the steel plates such that they were approximately tangent

to the interior surface of the 4-in pipe. A third hole was provided near the

top of the pipe in either end to establish the water level when the pipe was being used as an electric boiler.

Each of the immersion electric heaters consisted of two hairpin elements of

6 ft length each with a maximum capacity of 3,000 watts (6000 W per heater).

The four elements were wired to provide individual control and each element

was connected to a separate watt-hour meter through a disconnect switch, as shown in figures 30 and 31.

31
osMMoQou

(/)

LiJ

CDZo

GO2O

-J

Z)cn

i/)

QQ

32

Figure

26. A

schematic

diagram

of

conduit

boiling

test

for

underground

heat

distribution

system.
Figure 27 . The thermal conditioning box for the conduit boiling test apparatus.

33
Figure 28. Baffle plates along the air passage to obtain uniform

temperature around the test underground conduit system -

34
AN

APPARATUS

FOR

STUDYING

THE

EFFECT

OF

BOILING

ON

PIPE

INSULATION oz

t—<LUX<

UJ

c/) —>az

UJ

u

R•*••

•• "

-o

iJr

r oz

»—<

UJXu>Oz

UJ

35

SIDE

VIEW,

ELECTRIC

HEATING |

SIDE

VIEW,

STEAM

HEATING

Figure

29.

Header

plates

for

the

underground

conduit

insulation

boiling

testsone

for

the

electric

heating

(left)

to

measure

pipe

heat

lossthe

other

for

the

steaia

heating

(right)

to

provide

boiling.
Figure 30. Instrumentation and power control panel for the

insulation boiling test*

36
I

37

Figure

31.

Immersion

electric

heaters

for

the

heat

loss

test.
The electric heaters were actuated by a pressure controller connected to the ! 4-in pipe. The power supply was arranged so that either 230 volts or 115 volts I could be applied to the heating elements. A second pressure controller served

as a safety device and was used to disconnect all of the electric heaters by 1 means of a magnetic switch if the pressure reached a preselected value above j the operating pressure level. 1

Additional plywood boxes were built around the ends of the conduit that

protruded through the main box. These boxes were filled with vermiculite

insulation during the heat loss measurement test, to minimize the end heat loss.

| A steam supply of 125 psig was connected to the 4-in test pipe during the ' boiling cycle, since the electric heaters were of inadequate capacity for this

j purpose. For the boiling period, the steel plates containing the electric i| immersion heaters were replaced by two other steel plates. One of these two ij plates was drilled at its center and fitted with a 1 1/4-in steam supply pipe. ij This supply pipe extended into the 4-in steam pipe about 18 in and projected ,j about 6 in beyond the steel plate on the outside. The inner end of the 1 1/4-in

pipe was capped, and several 1/4-in holes were drilled through the sides of this i 18-in segment to make the total opening area to be the same as that of the ij cross section area of the 1 1/4-in pipe. The other end of the 1 1/4-in pipe | was connected to the steam supply. The steel plate on this end of the 4-in j pipe was provided with a hole for a 1/4-in pipe at the top, and a second hole ij for a 3/4-in pipe at the bottom. The upper connection was used as an air vent ,||

and as a connection for a pressure gage. The 3/4-in pipe connection was used [ to drain condensate. The condensate pipe was connected to a steam trap and to

a water-cooled heat exchanger to cool the condensate to room temperature. The

ends of the conduit were not insulated during the boiling cycle.

All insulation specimens were provided in the shape of 3-ft-long half cylinders l| of 2-in thickness, and were held around the 4-in carrier pipe by 1/2-in wide i 32-gage stainless straps, wrapped around the insulation at 9-in on-center

distances, as seen in figures 26 and 27.

2.3 TEST PROCEDURE

f At the beginning of a test the 4-in pipe was operated as a closed steam boiler. \ The electric energy consumption of the immersion heaters was used to determine

the heat transmission rate of the insulation before and after boiling. To J prepare for this test, all openings in the conduit flanges except one vent were

closed, and the 4-in pipe was completely filled with water, leaving one of the j openings in the end flange at the top of the pipe open for the air venting.

When the pipe had been filled with water, the vent was closed and the electric Ij heaters were energized at a low rate of heat input. One of the openings, * about a half inch from the top of the pipe, was opened slightly through a valve, and water was allowed to escape slowly as it expanded and as the steam j pressure built up. When the steam began to escape from this opening, it was assumed that the water level had reached the level of the opening and the valve i was closed completely. The steam pressure was then raised to 125 psig to attain

a steam pipe temperature of 350®F. A thermocouple clamped to the 4-in pipe at one end was used as an indicator for setting the pressure control for the

I

'

38
electric heating elements. Thereafter, the pressure in the steam pipe was kept constant, and the energy input to the electric heaters was measured at

regular intervals (twice during the working hours). The heat transmission

test was terminated when the heat transfer rate, as measured by the electric

energy used, became steady for 24 hours.

After the steady-state heat loss of the specimen was determined, the electric

heaters were removed and the alternate steel end plates were bolted to the

flanges on the 4-in steam pipe, thus permitting the boiler to provide steam

for the system.

The steam trap and heat exchanger were connected to the outlet end of the 4-in

pipe. The Insulation space of the conduit was filled with water to saturate

the insulation, after which enough water was drained out to lower the level to

the half-full mark, as indicated by the sight glass.

Steam from the boiler was admitted to the 4-in pipe to raise the gage pressure

to approximately 125 psig as rapidly as possible. The steam pressure was maintained essentially constant for a period of 192 (or 96) hours, during which the

water in the insulation space boiled vigorously. The steam produced in the

insulation space was allowed to escape from one of the vents in the end plate,

and cold water was fed into the insulation space to maintain a constant water

level.

At the end of 192 or 96 hours of boiling, the water was drained from the annular

space between the conduit and carrier pipe, and compressed dry air was introduced

into the conduit for 48 hours with 125 lbs of steam in the 4-in pipe to dry out

the insulation. After the 48-hr drying period, the steam boiler and steam trap were disconnected from the 4-in pipe, and the alternate steel plates containing

the electric resistance heaters were again attached to the pipe. As before,

the 4-in pipe was operated again as a closed steam boiler at a pressure of

125 psig, to determine the post-boiling heat loss. The heat loss test was continued until a new value for steady-state heat transfer rate was obtained.

2.4 TRI-SERVICE EVALUATION CRITERIA

The Tri-Service criteria specify that any one or more of the following kinds

of damage to the insulation constitute cause for rejection.

(1) Portion fallen from the pipe.

(2) Eccentricity of the insulation relative to its original position.

(3) Significant opening of the longitudinal or circumferential joints.

(4) Significant erosion of the insulation of the joints.

(5) Cracks or rupture in the insulation revealing the pipe surface.

(6) Physical or chemical changes in the insulation which are likely

to impair its function.

(7) Spalling or delamination of the insulation.

(8) More than 10 percent increase of heat loss after the boiling and

drying.

39
2.5 TEST RESULTS

2.5.1 Kaylo-10 System

The heat loss before the 192-hr boiling test was 611 watts, and after the

boiling test It was 747 watts, based on at least 24 hours of steady conditions.

Temperatures and heat transfer during the test are shown In figure 32. The

surface temperature distribution profiles along the conduit during the heat

loss tests before and after boiling tests are shown In figure 33.

The Insulation removed from the conduit after boiling for 192 hours and drying

is shown In figure 34. It can be seen at each end of sections that the insulation scaled and flaked away from the pipe. At some of the joints, between the

insulation segments, the boiling action created large enough holes so that the

bare pipe could be seen (figure 35).

Some of the insulating material that came off during the boiling collected in

the bottom of the conduit, as shown in figure 36.

The insulation was weighed after boiling and there was a loss in weight of

about 3 lbs (3.6 percent of the initial weight, 84.25 lb).

The longitudinal average conduit surface temperatures for pre- and post-boiling

tests obtained from figure 33 are 144.1**F and 157. 9®F, respectively. The large

temperature at the ends and a mid-point temperature hump shown in figure 33 is

due to the pipe support. Assuming the pipe temperature to be 350“F and pipe

length at 20 ft, the overall pipe heat transfer factor of C in the unit of

Btu/h.ft.F is:

C = (3.413) (611) 3 0.506 before the boiling

(20) (350-144.1)

and

C = (3.413) (747) 3 0.632 after the boiling.

(20) (350-157.9)

The pipe heat transfer factor for this particular underground system, therefore,

increased more than 20 percent, which exceeded the Tri-Service criteria of

ten percent. The system is considered to have failed the Tri-Service boiling

test

.

2.5.2 Thermo-12 System

The heat loss before the 192-hr boiling test was 656 watts, and after the

boiling test it was 674 watts, based on at least 24 hours of steady conditions.

Temperatures and heat transfer during the test are shown in figure 37. The

surface temperature distribution profiles along the conduit during the heat

loss tests before and after boiling tests are shown in figure 38.

The same test is repeated later for new insulation specimens, which met

the Tri-Service criteria.

40
Jo‘3dniVd3dl/^31

o

<T> o

00 o

<0 o

in O O

lO o

esj O

o

o

<n O

00 O

u> o

in O

'*

<7*

00

iO

to

CVJ

2 >

<

O

0>

u>

sanoH-DVM

41

Figure

32.

Heat

loss

and

temperature

data

during

the

test

for

KAYLO-10

insulation.
UJo

z

<

K-O

42

Figure

33.

Longitudinal

distribution

of

the

conduit

surface

temperature

before

and

after

the

KAYLO-10

boiling

tests.
; 3

4J Cu 3 •H O a

•3 3

<U 3

•r) •H o

V-i 3

(U 33

cnCO 3 S -3

4-1

J-) 3

33 o •H

cO CO •1—)

4J3 c O o

•H 3

4-1 3

CO 4-1 iH 3 3

CO3 (4-4 •H O o 3

T—( O 1 •H O 4-1 1-3 O3

bO3

M-l •H o I—1

•H

4-t

O 3 43

•HO 3

•r-) x:

4-1 o

4=H ,3 • m

cn3

V43

bO

44
43

Figure

34.

KAYLO-10

insulation

after

the

boiling

tests

shows

severe

erosion

due

to

the

boiling

action.
Figure 36. Crumbs of KA.YLO-10 insulation found in the conduit space

after the carrier pipe and insulation jacket were removed.

45
DRYING

DRYING

ELEC.

HEAT

LOSS

STEAM

&

ENDS

HEAT

LDSS

BEFORE

BOILING

BOILING

TEST

AIR

NO

INSULAT.

AFTER

BOILING

SUnOH-SliVM

46

DAYS
47

Figure

38.

Longitudinal

distribution

of

the

conduit

temperature

before

and

after

the

Theirmo-12

boiling

test.
The insulation removed from the conduit after boiling for 192 hours and drying | is shown in figure 39. It can be seen at each end of the sections that the '] insulation scaled and flaked away slightly from the pipe, which would cause

the heat loss rate to increase; also In figure 39 are shown cracks in the insu- | lation that indicate that with continued boiling the insulation could break and

fall off of the pipe. Figure 40 shows the waterline during boiling, the bands

cut into the Insulation, and pitting along the water line. !

The longitudinal average conduit surface temperatures for pre- and post-boiling | tests obtained from figure 38 are 155. 4“F and 160. 6“F, respectively. Assuming | the pipe temperature to be 350®F and pipe length at 20 ft, the overall pipe

heat transfer factor of C in the unit of Btu/h.ft.F is: i

C = (3.413) (656) = 0.575 before the boiling | (20) (350-155.4)

| and f

C = (3.413) (674) _ 0.607 after the boiling.

(20) (350-160.6)

The pipe heat transfer factor for this particular underground system, therefore,

increased less than 10 percent. The system is considered to have passed the

Tri-Service boiling test criteria.

2.5.3 Pabco System

The heat loss before the 192-hr boiling test was 670 watts, and after the

boiling test it was 689 watts, based on at least 24 hours of steady conditions.

Temperatures and heat transfer during the test are shown in figure 41. The

surface temperature distribution profiles along the conduit during the heat

loss tests before and after boiling tests are shown in figure 42.

The insulation removed from the conduit after boiling for 192 hours and

drying is shown in figure 43. It can be seen that a few portions of insulations were inflated upward against the conduit and cracked. This inflated

and cracked condition can be observed on each of five sections along the 20-ft

test pipe (figure 44).

The longitudinal average conduit surface temperatures for pre- and post-boiling

tests obtained from figure 42 are 155. 4“F and 160. 6®F, respectively. Assuming

the pipe temperature to be 350‘*F and pipe length at 20 ft, the overall pipe

heat transfer factor of C in the unit of Btu/h.ft.F is;

C = (3.413) (670) = 0.601 before the boiling

(20) (350-159.8)

and

C = (3.413) (689) = 0.625 after the boiling.

(20) (350-161.9)

48
49

Figure

39.

Thermo-12

insulation

removed

from

the

conduit

after

boiling

for

192

hours

and

drying.
(

cs

n

50

Figure

40.

The

waterline

during

the

conduit

boiling

of

the

TheT-mo-12
io ‘3univ)i3dNn

O O O o o 03 m ivi <j>

P«4

o>

U>

>-

Oi

<o

ir>

CO

SdnOH - liVM

B

(U kJm

>%

CO

51

Figure

41.

Heat

loss

and

temperature

data

during

the

boiling

test

of

PABCO
c/>

52

Figure

42

.

Longitudinal

distribution

of

the

conduit

surface

temperature

before

and

after

the

PABCO

boiling

tests.
I

53

Figure

43.

The

insulation

damage

due

to

192

hours

conduit

boiling

test

and

subsequent

drying

(PABCO

system)

.
CO u

<U CO x: cu

4-t 4J

4-1 iH

n

cO> 4-1 O d e cu

(U

d

}H cr' cu Pi CO

(U 4J

d

4-1 CO

cO T3d

r4 cO

(U u bC

cO

d

•H •H

'CU I—1

(U •Ho g rO

•H

COPi

<Ud

+J o

CO

CO ’ CM C rH o

•H J-l 4J C

CO cu I—I !3

CO cu C 'O

•H

dd 1—I

cO -u

>-i (U CU ^ S-I cu -C o & u

PQ -Ud

T3

(U

d ^ o H CJ

-CT <r

(Uwd

bC

•H

pH

54
The pipe heat transfer factor for this particular underground system, therefore.

Increased less than 10 percent. The system Is, however, considered to have

failed to meet the TRI-service criteria on account of the physical damage

incurred during the boiling.

2.5.4 Wesolite System

The heat loss before the 96-hr boiling test was 746 watts, and after the boiling

test it was 781 watts, based on at least 24 hours of steady conditions. Temperatures and heat transfer during the test are shown in figure 45. The surface

temperature distribution profiles along the conduit during the heat loss tests

before and after boiling tests are shown in figure 46.

The insulation removed from the conduit after boiling for 96 hours and drying

is shown in figure 47. It can be seen at a number of places that the insulation had openings at the joints. Figures 48 and 49 show close-ups of the

openings and also the deterioration of the insulation below the water level

during boiling. The insulation at the top (above water level) of the pipe was very easy to crumble and could not be taken off the pipe without breaking up

(figure 50).

The longitudinal average conduit surface temperatures for pre- and post-boiling

tests obtained from figure 46 are 149. 6°F and 150. 4“F, respectively. Assuming

the pipe temperature to be 350°F and pipe length at 20 ft, the overall pipe

heat transfer factor of C in the unit of Btu/h.ft.°F is:

C = (3.413) (746) = 0.635 before the boiling

(20) (350-149.6)

and

C = (3.413) (781) = 0.667 after the boiling.

(20) (350-150.4)

The pipe heat transfer factor for this particular underground system, therefore,

increased less than 10 percent. The system is considered to have failed the

Tri-service criteria on account of the physical damages incurred during the

boiling. A water repellent was added later to help correct the crumbling and

loss of hardness in the insulation after this test had been completed.

2.5.5 Epitherm System

The heat loss before the 96-hr boiling test was 634 watts, and after the boiling

test it was 656 watts, based on at least 24 hours of steady conditions. Temperatures and heat transfer during the test are shown in figure 51. The surface

temperature distribution profiles along the conduit during the heat loss tests

before and after boiling tests are shown in figure 52.

* The PABCO later conducted a separate boiling test at a private laboratory

following the NBS test procedure and successfully met the Tri-service criteria.

55
DRYING

.DRYING

HEAT

LDSS

BDILING

TEST

STEAM

&

I

ELECTRIC

ENDS

HEAT

LOSS

AFTER

BEFORE

BOILING

AIR

I

NO

INSULATION

BOILING

Jo ‘aunivdJdNJi

56

Figure

45.

Heat

loss

and

temperature

data

during

the

test

for

Wesolite,
00

57

Figure

46

.

Longitudinal

distribution

of

the

conduit

surface

temperature

before

and

after

the

boiling

tests

for

Wesolite

system.
58

removal

from

conduit

after

96

hours

of

boiling.
59

Figure

48.

Close-up

of

opening

at

joint

after

conduit

boiling

of

Wesolite.
60

Figure

49.

Wesolite

after

boiling

showing

deterioration

at

the

bottom

of

pipe

below

the

water

level
61
Drying

Drying

electric

Heat

loss

....

steam

&

ends

Heat

loss

before

boiling

air

no

insulation

after

boiling

(Jo JtiniVtl3dN31

SUnDH/liVM

62

DAYS
CONDUIT

SURFACE

THERMOCOUPLES

(«24

COPPER

CONSTANTANI

(U

Vj3

4-1 cO

0)a

(1) o

CO r

g 3 0) W -C

4J *H

•H a, 3 W C CM O O O

4-1 <U CO Si 0)

4-1 4-1

>4H W) O 3

•H 3 iH O *H

•H

O

4J3

Si 0) •H s:

^4 4J

4-t CO V4 •H (U TO 4J

y-4 iH 3 33 T)

•H 3

•3 3 3

4J 3

•H >4 60 O 3 4-1 O 3

CMm3

!-4 3

60

•H

pi4

63
The insulation removed from the conduit after boiling for 96 hours and drying

is shown in figure 53. Figure 54 shows close-up of the insulation at the

bottom of the pipe (below the water level) after boiling. Figure 55 shows

close-up of the insulation at the top of the pipe (above the water level)

after boiling.

The longitudinal average conduit surface temperatures for pre-and post-boiling

tests obtained from figure 52 are 139. 2“F and 140. 1“F, respectively. Assuming

the pipe temperature to be 350°F and pipe length at 20 ft, the overall pipe

heat transfer factor of C in the unit of Btu/h.ft.®F is:

C = (3.413) (634) = 0.472 before the boiling

(20) (350-139.2)

and

C = (3.413) (656) = 0.490 after the boiling.

(20) (350-140.1)

The pipe heat transfer factor for this particular underground system, therefore,

increased less than 10 percent. The system is considered to have passed the

Tri-Service boiling test.

2.5.6 Celotemp System

The heat loss before the 96-hr boiling test was 725 watts, and after the boiling

test it was 782 watts, based on at least 24 hours of steady conditions. Temperatures and heat transfer during the test are shown in figure 56. The surface

temperature distribution profiles along the conduit during the heat loss tests

before and after boiling tests are shown in figure 57.

The insulation removed from the conduit after boiling for 96 hours and drying

is shown in figure 58. Figure 59 shows close-up of the insulation at the

bottom of the pipe (below the water level) after boiling. Figure 60 shows

crumbs of insulation found in the conduit space after the carrier pipe and

insulation jacket were removed.

The longitudinal average conduit surface temperature for pre- and post-boiling

tests obtained from figures 57 are 149. b^F and 157. 7“F, respectively. Assuming

the pipe temperature to be 350®F and pipe length at 20 ft, the overall pipe

heat transfer factor of C in the unit of Btu/h.ft.°F is:

C = (3.413) (725) = 0.617 before the boiling

(20) (350-149.6)

and

C = (3.413) (782) =: 0.694 after the boiling.

(20) (350-157.7)

The pipe heat transfer factor for this particular underground system, therefore,

increased more than 10 percent. The system is considered to have failed the

Tri-Service boiling test.

64

66

Figure

54.

Close-up

of

Epitherm

at

the

bottom

of

the

pipe

after

boiling

(below

the

water

level)
Drying

electric

Jo ‘junivtiJdMJi

oioor^tom^ coe^^ oa oo r~> CO ir>

OA

5 52

0»

E ^

S' E Q CO

0>

04,

I I

o

1 CD |o

Qi X3

1

i —

t

1 1

1 1

r

% t1 1 1

1 1

VJ

1

~i r Tjy

r*

3 - / 1

“t

r

3

I \

li

rs

A

1

r

J

T iJ f rl ^

r 1

1

1 Jj

3£S 1k

T

ri I 1 UJ HS, ’ 5 cc => ^

- “ ^ < z zLU 2 O. z o- ^

^ LU

- ^ B ^ t “ 3E S * X o o o

LJ 1 1

1 — i

r

J

> < I

o ^ CO •

GC 1.J

n ,C| —i

J —

LJ

a- —L

CN

00

>-

GOCO CO

CO CM

CO

GO

CVJ

SHnOH-ilVM

CO

ex

C»4 CM O OO CO ^ CN

Figure

56.

Heat

loss

and

temperature

data

during

the

test

of

the

Celoterap

system.
67

after

boiling

(above

the

water

level)

.
CM

CO

69

AVERAGE

CONDUIT

SURFACE

TEMPERATURE

DISTANCE

(FT)

•

AFTER

BOILING

CARRIER

PIPE

TEMPERATURE,

350°F

O

BEFORE

BOILING
u

<u 4J

0)a.

•H

P-

<U . 4=

4Jco e

Q) um

>>

CO o p. H e u (1) to +J H O P <—t

CO (U P o

00m

cuPP

00 H

pLi

70

removal

from

conduit

after

96

hours

of

boiling.
71

Figure

59.

Insulation

after

boiling

showing

deterioration

at

the

bottom

of

the

pipe

below

the

water

level

(Celotemp

system).
72

Figure

60.

Crumbs

of

Insulation

found

in

the

conduit

space

after

the

carrier

pipe

and

insulation

jacket

were

removed

(Celotemp

system).
3.

SIXTY-FOUR-DAY CONDUIT BOILING TEST OF INSULATION

Six different brands of high temperature asbestos-free pipe insulation were

installed on the 4-in, 20-ft pipe inside of 10. 75-in RIC-WIL conduit. The

test was conducted in the same conduit boiling apparatus as described in sec- tion 2, except that the conduit was filled to the half-full mark with water

and controlled at this level during this 64 days of boiling. The steam pressure

in the 4-in pipe was 50 psi, and this caused the water in the conduit to boil

during the test.

The purpose of this test was to determine the effect of long periods of boiling

on the insulation inside of the conduit. This test was run for 8 days and was

stopped to remove the 4-in pipe and insulation from the conduit for examination

and for taking photographs. This same procedure was repeated for three more

8-day periods of boiling (32 days total). At the end of 32 days of boiling,

the same procedure was repeated for an additional 32 days, a total of 64 days

of boiling of the insulation on the 4-in pipe inside of the conduit.

The results of this test are shown on Table 1 with references to photographs.

The samples are identified in the photographs by the following numbers:

1. Celotemp 1500, Celotex Corp. Expanded perlite. Figures 61 and 62.

2. Thermo-12, Johns-Manville Co., Calcium silicate. Figures 63-66.

3. Epitherm 1200, Eagle-Picher Co., Mineral wool. Figures 67-71.

4. Wesollte "D", Wesolite Co., Perlite/sodium silicate. Figures 72-76.

5. Super Caltemp, Pabco, Calcium silicate. Figures 77-80.

6. Kaylo-10, Owens/Corning, Calcium silicate. Figures 81-84.
Table

1.

Sixty-four-day

Conduit

Boiling

Test

of

Six

Insulation

Materials

o;

0) 60 • s 3 • rH Cd 'O 0 rH 0 rH a 3 rH 3 rH 3 4J

Cd Cd 3 rH 3 > 3 > 0 -o 3

rH vO T) 43 3 43 3 CO 3 00 1 <U CO • 43 rH rH m 60 o 1 T) o Q) 3 4-) O 3 3 CD 3 3 3 3 • 3 1 •H •H 60 l-i 43 Cd !-i 60 Ul V4 60 Su Ul (D *H 4J Ul

CO CO Cd 3 60 3 3 Cd 3 3 Cd 3 3 M 3 3 3 c >» a 60 •H 60 a 4H 60 a 4J 60 0 3 *H 60 O X Cd •H rH u •H Cd Cd •H Cd Cd •H 3 P 0 •H u a TJ Fn C/D cd fJU Q 3 p 3 M 0 •'-1 P

60

'O 3 3 3 • •H 3 • 0 rH 4J • CO 3 rH 3 p p 3 • m 'O 0 4H 0 m 3 > Ov 3 3 cn

CNJ 1 o 4J vO 3 h*. Cd •iH 42 3 00 1 3 3 CO • 4H rH 3 3 1 3 Qi 3 3 cd 3 <D 3 3 3 3 3 3 3

•H 60 P P 4: 3 60

p 60 3 p 60Mp jjpp

JJ CO Cd 3 60

p Cd 3 Cd CO 3 Cd 3 3 3 0 3 c a cu 60 •H 0 a 60 a 60 a 4H 60 •H 60 O CO Oil •tH rH 3 Cd •H Cd <4H •H Cd Cd •H 0 0 *H O T) cd Pk C/D •H F14 Q 0 F*4 p 3 Fh >“) 4-i p

cu60 • •

Cd •T3 3 3 • a 3 3 •H rH 3

Cd 3 60 41 rH

Cd 3 •H 42 3 a CO CO •H

60 1 -3 • 4-) 0 o^ Cd « cd •H 00 *J CO CM c cs 1 0) 4J vO Cd VO Td 4J P-H 3 > 3 *H 00 1 CO 3 4-J 3 u > 3 <U 3 3 p (D 4H •H 3 u 3 3 3 3

•H <U )-i 60 0 Pu 43 0 p 3 60

p 60 44 Ul o 3 3 3 Cd a 3 60 •T-7 3 •iH Cd 3 3 3 3

PQO 3- 60

a cu 60 •iH 60a 60

a -H 60 3 P- *H Cd 3 •H rH 4J •rH 0 Cd •H 3 0 *H

W

M 3 a CO Pu CO Cd s P P

cd Q

Td

CJCO S cd 5^ o 3 3 • O J3 u 60 rH 3 3 m • CO V 3 43 0 60

<u 3 •H •H •H Cd

r—4 c D, o •H 3 CO 4J

a c o •H CM iJ fO 00 3 cn •H Cd Cd rH 3 •H vO vO a > rH •3 • 00

4-J 'O • rH • 0 rH 3 3

Cd <4-1 <u 0) 3 3 4J a; 3 4J 3 CO CO 3 4J rH CD rH o u 4-) 00 P 43 60 )-i 4J 4: p 4ii 3 p 42 41 Ul

Cd 3 3 >-i 3 3 60 Cd 3 3 60 3 0 •H 3 60 *H 3 C CO y-l 60 3 a 60 •H a 60 •H vH 60 Cd 60 •H 3 60

•H c <4-4 •H

U 3 •H rH Cd •H 0 rH •H

p 3 •H rH »H *H

ft. •H o Cl4 C/D Hd C/D Td Fn CO fn

u •H FZ4 cn > p

60C

•H 0) • 3 • 3 • rH 3 3 rH 3 iH 3

Cd

O 60 3 • 43 0 42 0

<D rH •H Cd 0 rH rH *H •H rH *H *H u Cd CO U a rH 3 Cd CO 4J 3 3 4J rH O *H Cd Cd 3 > CM 0 •H Cd 0 *H 3

00 •H > rH nd 4H vO 43 3 •H > rH •H > iH

T3 CO 3 3 rH CO 3 3 3

0) 0) >> 3 CO

u 3 <v 0) 3 3 CO 3 3

4J

U !-i 43 60 3 43

M 60pp 42 60 3 42 60 3 U 3 CU 3 *rl 60 Cd 3 Cd 0) 3 a Cd •H p 3 *H

Cd Cd 60

a •H cu 60a 4-1 60

aa

4-1

O 3 o rH cu •rl Cd Cd •H 0 Cd 0 0 3 0

C/D Cd 2 T) 4J C/D cd Pu

Q 3 Pi 2 ^3 4.4 Z T3 -u

rH

cd •H <]) 0) CD 3 U u 4J iJ 4J

Q) •H 3 Cd

a Cd Cd

4-) o • rH rH o 0 3 p 0 60 0

Cd o a

U rH 0 M rH • • •H

a •H 3 -H s u <u •H rH CM 3 0 P 0 TJ 3 rH •H rH

1—t o o. > •H rH 43 0 u 0 3 4J •H 3 *H c u (M 3 CO a s CO 4J rH CO U CO o D- 't? 1—1 3 a •r! 3 CD Cd Cd 0 0

•H

a

X 0) t s a

U cu. rH 4JU CD 0 0 a 1-4

u

a

4-) CU 0) 'O

O 1 3 3 1 Cd nH •H 4J •H 3 1 3

Cd 4J c a 3 •H 43 3 p rH rH •H rH lu 0 •H 0 CO o o cd P 3 CJ 4-) rH 3 0 0 rH •H 3 0 0 tH 3 3 3 T—1 & 3 43 rH •H 60 C CO CO u CO P 43 rH >» 3 iH

cn Q) o;

X 43O Cd cu Cd •H 3 3 3 3 cd Cd 3 S 3 C CJ o w H Id CJ td w s s 3 eui CO p 0 0 U M

74
75

Figure

61.

Celotemp

1500

after

8

days

boiling.
76

Celotemp

1500

after

16

days

of

boiling
77

Figure

63.

Thermo-12

after

16

days

of

boiling.
78

Figure

64.

Thermo-12

after

24

days

of

boiling.
79

Figure

65.

Thermo-12

after

32

days

of

boiling.
80

Figure

66.

Thermo-12

after

64

days

of

boiling.
81

Figure

67.

Epitherm

1200

after

8

days

of

boiling.
82

Figure

68.

Epitherm

1200

after

16

days

of

boiling.
iIi)I

I’i<j

llI

iiIiI

83

Figure

69.

Epitherm

1200

after

24

days

of

boiling.
84

Figure

70.

Epitherm

1200

after

32

days

of

boiling.
“'vV f”..

• ^

y^/

^y-iy-'-

- c;.-

t’, -^if "

85

Figure

71.

Epitherm

1200

after

64

days

of

boiling.
86

Figure

72.

Wesolite

"D"

after

8

days

of

boiling.
Figure

73.

Wesolite

"D"

after

16

days

of

boiling.
88

Figure

74.

Wesollte

"D"

after

24

days

of

boiling
89

Figure

75.

Wesolite

"D"

after

32

days

of

boiling.
90

Figure

76.

Wesolite

"D"

after

64

days

of

boiling.
91

Figure

77.

Super

Caltemp

after

16

days

of

boiling.
-

:

92

Figure

78.

Super

Caltemp

after

24

days

of

boiling
93

Figure

79.

Super

Caltemp

after

32

days

of

boiling.
f

94

Figure

80.

Super

Caltemp

after

64

days

of

boiling.
95

Figure

81.

KAYLO-10

after

16

days

of

boiling.
96

Figure

82.

KAYLO-10

after

24

days

of

boiling
Mi

97

Figure

83.

KAYLO-10

after

32

days

of

boiling.
98

Figure

84.

KAYLO-10

after

64

days

of

boiling.
99

Figure

85.

End

view

of

plywood

box

used

to

house

the

conduit.
Figure 86. Inside of plywood box showing baffles to regulate air flow.

100
4 . COMPARISON WITH CALCULATED PIPE HEAT TRANSFER FACTORS

While the previous section dealt with the experimental measurement of overall

pipe heat transfer factor C, this section compares the measured data with the

theoretical values determined by the standard pipe heat conduction calculation

procedure.

Referring to figure 87 , which depicts a cross section of the "air conduit system,

the following notations and data are used to calculate the pipe heat transfer

factor C:

D = outside diameter of the carrier pipe, inch

t]^ = pipe wall thickness, inch

t2 = thickness of calcium silicate insulation, inch

t3 = thickness of air space between the conduit and insulation, inch

t4 = thickness of conduit wall, inch

Ti = steam temperature, “F

T2 = temperature at the interface of carrier pipe and calcium silicate

insulation, °F

T3 = temperature at the outside surface of the calcium silicate

insulation, ®F

T4 = temperature at the inside surface of the conduit wall, “F

T5 = temperature at the outside surface of the conduit wall, °F

Q

= overall pipe heat transfer, Btu/h ft

C = overall pipe heat transfer factor, Btu/h ft, "F

h = heat transfer coefficient at the conduit air space,

Btu/hr ft 2 ®F

kp = thermal conductivity of carrier pipe (test pipe) wall, Btu“ln/h

ft2 °F

O kj = thermal conductivity of calcium silicate insulation, Btu-in/h ff^ “F

2 k^ = thermal conductivity of conduit Btu-in/h. ft “F

Using these notations, it is possible to write a steady-state heat conduction

equation as follows:

101
CONDUIT

AIR SPACE

THERMAL INSULATION

CARRIER PIPE

Figure 87. Cross-sectional view of the Tri-service "air conduit" underground

heat distribution system.

102
D-2ti

2tt kp (T1-T2)

12 An( ^^J1_£522 ) D

IT (D+2 t

2

> (h) (T3 - T

4

) 12

2tt kc (T4 - T 5 ) 12 Jln |

D + 2t2 + 2t3 + 2t^

| D + 2t^ + 2t^

= C(Ti - T5)

Rearranging the above equations, the overall pipe heat temperature factor C is

calculated by:

D = 4.5 in

t]^ = 0.25 in

t 2 = 2 in

t 3 = 1 in

t4 = 0.25 in.

Assuming the handbook values for thermal conductivities

kp = 360 Btu-in/hr ft^°F

k^ = 360 Btu-in/hr ft^°F

h = 3 Btu/hr

^ Ric-Wll publication of 1971 entitled "Prefabricated Insulation Piping

System" p. 23.

'h'h !

' Approximate value based on unreported NBS test.

+ in •)/kc 1

For this particular test system, manufacturer's datal./ indicate that:

103
1 = 1.9098 + 0«232 + 0.02

j = 0.000727 + 1*2146

C 360 ki 3 360 ki

By using manufacturers' value of kj, theoretical values of C were calculated

and compared against measured values, as shown in table 2.

The measured heat transfer factor C is considerably higher than that anticipated

from the standard heat conduction calculation, mainly for two reasons:

1. The conduit system has several pipe supports that act as thermal

bridges, bypassing the insulation.

2. As shown in the conduit surface temperature distribution, as indicated in figures 34, 39, 43, 47, 53 and 58, there is a large

amount of end heat loss.

These two factors, especially the end heat loss factor, are very critical when

the test pipe is short — so much so that they could overshadow the effect of

the deterioration of pipe insulation due to the boiling test. Moreover, the

10 percent degradation criterion would favor the test system having higher

total heat loss caused by the thermal bridge effect, because it would permit

the acceptance of a larger heat loss Increase through the Insulated section

of the test pipe. Although the estimation of the heat loss due to the thermal

bridge and the end heat loss is very critical, the data shown in table 2 are

so scattered that it is difficult to perform an error analysis.

Table 2. Comparison Between the Calculated and Measured Heat Transfer Factor C*

Manufacturer's Measured C

System

Name

data of

kx@300“F

Calculated

C

before

boiling

after

boiling

Kaylo 0.46 0.379 0.506 0.632

Thermo 12 0.44 0.362 0.575 0.606

Pabco 0.45 0.370 0.601 0.625

Wesolite 0.44 0.362 0.635 0.667

Epitherm 0.39 0.321 0.472 0.490

Celotemp 0.52 0.424 0.617 0.694

* Calculated from the pipe to the exterior surface of the conduit.

104
5. REFERENCES

[1] Seldon D. Cole and Paul R. Achenbach, "Effect of Boiling of the

Insulation in Underground Heat Distribution Systems," NBS Report 7449,

February, 1962,

[2] TRI-Services, "Procedures for Establishing Acceptability of Underground

Heat-Distribution Conduit Systems," Department of the Army, Corps of

Engineers; Department of the Navy, Bureau of Yards and Docks; Department

of the Air Force, Directorate of CE, July 1, 1964.

105
NBS-114A (REV, 2-8C) U.S, DEPT. OF COMM. 1. PUBLICATION OR 2. Performing Organ. Report No, 3. Publication Date BIBLIOGRAPHIC DATA

SHEET fSee instructions)

REPORT NO.

NBSIR 81-2324

November 1981

4. TITLE AND SUBTITLE

I OILING TESTS OF NON-ASBESTOS -BASED THERMAL INSULATION USED IN AIR“CONDUIT UNDERGROUND

HEAT DISTRIBUTION SYSTEMS

5. AUTHOR(S)

Dr. T. Kusuda and W. M. Ellis

6. PERFORMING ORGANIZATION (If joint or other than NBS, see instructions) 7 . Contract/Grant No. NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE 8. Type of Report & Period Covered

WASHINGTON, D.C. 20234

9.

SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, City, State, ZIP)

, Tri-Services: Naval Facilities Engrg. Council, USN, Washington, DC 20390

Directorate of Civil Engrg., USAF, Washington, DC 20330

Office of Chief of Engrs., US Army, Washington, DC 20304

10.

supplementary notes

Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11.

ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here)

Non-asbestos-based thermal insulation around steam carrier pipes is commonly used in

the conduit underground heat distribution systems for many of the 'Dri-service installar- i tions. When the conduit fails, the insulation is expected to undergo severe boiling

action due to the possible ingress of underground water. If the insulation is properly

fabricated, it should withstand the prolonged boiling such that its thermal performance

should be restored when the ground water is drained and the system dried.

Several selected insulation systems were boiled in an open tank as well as in the con- ! duit to test their ability for retaining the original insulation cabability.

j Although the calcium silicate-based insulation system fell off the carrier pipe uiider | the open tank boiling within 72 hours, most of the systems were able to withstand 96 j hours of continuous boiling in the conduit. When drained and dried, these systems J improved their thermal insulation performance to within 10 percent of the original

value.

12. KEY WORDS fS/x to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolon s) boiling test; conduit system; pipes; thermal insulation; underground heat distribution systems.

13. AVAILABILITY

[331 Unlimited

[XI For Official Distribution. Do Not Release to NTIS

1331 Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C.

20402.

331 Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

15. Price

USCOMM-DC 6043-P80 |

1