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NATIONAL BUREAU OF STANDARDS REPORT

5655

FIELD TEST OP HYLAG UNDERGROUND PIPE INSULATION AT

PHILADELPHIA NAVY YARD

Report to

Office of the Chief of Engineers

Bureau of Yards and Docks

Headquarters, U. S. Air Force

<^b|>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANOARDS
THE NATIONAL BUREAU OF STANDARDS

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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

1003^20-4881 November 22, 1957 5655

FIELD TEST OF HYLAG UNDERGROUND PIPE INSULATION AT

PHILADELPHIA NAVY YIIRD

by

Selden D„ Cole

and

Paul R. Achenbach

Air Conditioning, Heating and Refrigeration Section

Building Technology Division

to

Office of the Chief of Engineers

Bureau of Yards and Docks

Headquarters, U, S, Air Force

IMPORTANT NOTICE

NATIONAL BUREAU OF STAN!

Intended for use within the Go-, to additional evaluation and revi listing of this Report, either In v the Office of the Director, Natio however, bjr the Government ag

to reproduce additional copies I

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 2015.

tiiy published It is subjected

)roductlon, or open-literature

n Is obtained In writing from

ich permission Is not needed,

epared if that agency wishes

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

FIELD TEST OP HYLAG UNDERGROUND PIPE INSULATION AT

PHILADELPHIA NAVY YARD

by

Selden D, Cole and. P* R, Achenbach

ABSTRACT

A field test was made of a section of underground steam

pipe> at the Philadelphia Navy Yard, insulated with Hyiag

by collecting and weighing the condensate. Investigation

was also made of the moisture content of the insulation

and earth around and above the steam pipe* The results

showed that the heat loss per linear foot of pipe can be

determined by this method when the condensate is cooled

before drainage, if there is a negligible pressure drop

in the section under test. The observed heat loss per

foot of eight-inch pipe was 397 Btu/hr at 59 psig steam

pressure on the first day and 513 Btu/hr at 44 psig

steam pressure on the second day. A rainstorm thtt

occurred between the two tests is the only known variable

that could have increased the heat loss rate on the

second day. The moisture content of the insulation was

I„08 percent and that of the earth was 13 «1 percent

near the surface and 9.7 percent adjacent to the pipe

insulation on the side of the pipe three feet below the

surface at the conclusion of the second test. The wire

mesh outside the insulation was badly corroded and the

bituminous coating had a porous, granular, carbonaceous

appearance. Air spaces as wide as I 1/2 Inches were

observed between the pipe and insulation at the area of

excavation.

Introduction

At the request of the Office of the Chief of Engineers,

Department of the Amy, a field test was made of a section of under'

ground steam pipe, insulated with Hyiag, in operation at the Philadelphia Navy Yard. The amount of condensate produced in a

measured length of pipe was measured; a section of the insulated

pipe was inspected; temperatures were observed in the earth and on

the insulation; and samples of insulation and earth were taken for

moisture determinations.

- 2 -

Descriptlon of Test Specimen

Hylag pipe insulation is produced by the Continental

Coatings Corporation of 10 East 52nd Street, New York 22, New

York* The specimen for this test consisted of about 230 feet

of eight”lnch steam pipe insulated with a covering of Hylag.

The Hylag was reinforced with l/2”ln. hardware cloth and the

surface was covered with a bituminous material for waterproofing purposes. The test section extended from manhole to

manhole and had an offset expansion loop as part of its length.

In the m.anhole at either end there was a suitable bucket type

steam trap. The condensate was released to the atmosphere

rather than to a return condensate line. See Fig. 1 for

location of the expansion loop in relation to the manholes.

The manhole nearest the power plant will be considered the

inlet end of the length of pipe under test, while the other r

manhole will be considered the outlet end. The pipe was

buried in filled ground with an earth cover of about 36 inches.

Test Equipment and Procedure

Each end of the pipe was fitted with a calibrated pressure gage six Inches in diameter. The gages were installed in

both cases in the horizontal 3/4-lnch condensate line ahead of

the steam trap. The scale of both gages ranged from 0 to 300

pounds,” that at the inlet end was '^graduated in five-pound

Intervals and the one at the outTet ejid in two-pound intervals.

In each case there was a loop between the 3/'^-inch pipe and

the gage.

Thermocouples of copper-constantan wire were used with a

Rubicon portable precision potentiometer to Indicate temperatures. The temperature of the pipe was observed at the inlet

and outlet end. The tem.peratures of the earth, and of the

insulation, were recorded during the time of excavating a

hole for the purpose of observing the insulated pipe.

The condensate was collected in a 24-gallon container

resting on a scale. A 50-foot coll of 1/2-inch copper tubing

was connected to the 3/‘4-inch pipe at the outlet of the steam

trap and was immersed in a container supplied constantly with

tap water at a temperature of about 66 °F. This coll cooled

the condensate and thereby prevented evaporation by flashing

or boiling.

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For the first test the condensate was collected for a

period of three hours. For the second test on the following

day^ the condensate was collected for a period of four hours.

At regular Intervals the gage pressure at the Inlet and outlet

ends j condensate weight and thermocouple Indication were

recorded, A preliminary time was devoted to checking the

operation of each of the several parts before the test period

started.

Prior to the first test^ the steam trap In the system_,

about 100 feet ahead of the Inlet end, was bypassed and the

condensate blown to the atmosphere to assure the steam pipe

was dry, and prior to the second test the condensate line at

the Inlet end of the test section was blown. In each case

the results Indicated a dry line, A rainstorm occurred during • the 24 hours that elapsed between the two tests.

At the end of the second test, a hole about 3^5 feet

was dug to expose the pipe and Insulation. This excavation

was about 1/3 the length from the Inlet end, on the long leg

of the expansion loop. See Fig, 1, Temperatures were recorded

of the surface of the earth and at several stations above the

pipe as the hole deepened. Specimens of the earth and Insulation were placed In weighed containers as rapidly as possible after exposure and the containers Immediately sealed

air tight. Moisture content was determined by (l) weighing

container and contents, (2) opening container and heating at

214 F until constant weight obtained.

The length of the specimen pipe under Investigation was

measured with a ^0-ft steel tape and found to check In length

with the figures Indicated on the blueprints of the Installation,

Test Results

The gage pressures observed at the two ends of the test

specimen during two tests Indicated no measurable drop In

pressure for the length of the test specimen. The thermocouple readings Indicated temperatures corresponding to

saturation temperatures of steam at the observed steam pressures ,

-4-

The results of the two condensate tests on successive

days were as follows;

Test Average Steam Saturation Computed Computed

Condensate Pressure Steam Heat Loss Heat Loss

Collected at Outlet Temp. per Sq Ft per

Ib/hr psig °F Pipe Surface

Btu/hr

Linear

Foot

Btu/hr

1 102.7 59 oO 306.9 176 397

2 131c2 44.5 29 I 08 227 513

The heat loss per foot was obtained by multiplying the

condensate collected per hour by the latent heat of the steam

at the corresponding steam pressure and dividing by the total

length of the test specimen in feet.

The temperatures in the earth during excavation were as

follows

72 in. from edge of hole at the earth's surface 55

12 in. deep over pipe 100 F

24 in. deep over pipe ll4 F

32 in. deep to one side of the pipe ll4 F

36 in. deep on exposed insulation surface where an

air space existed between pipe and insulation 155 P

36 in. deep between insulation and earth 183 F

Between pipe and insulation in 1" air space 253 P

Between pipe and Insulation in 1"' air space 249 'F Between pipe and insulation^ no air space 258 F

Saturation temperature by gage pressure 292 F

The temperatures near the outlet end at the earth's surface were;

2 in. deep and over the pipe 60 F

2 in. deep and 6 ft laterally from pipe 54 F

The specimens of earth and insulation as taken from the

hole during excavation contained percentages of moisture

related to dry weight as follows:

"5

Surface (8-ln„ layer)

At top of insulation (S-in^ layer)

At side of pipe (8-in<, layer)

Insulation (entire layer)

13 . 1^

12 . 1^

9 . 7^ 1.08^

About 1 1/2 Inches of the earth adjacent to the insulation had a light color^ was dusty, and appeared to be dry

compared to the surrounding earth„

The bituminous coating on the surface of the insulation

was hard even under heat^ and had a porous, granular, carbonaceous appearance. It appeared to have little waterproofing quality. The wire mesh underneath the bituminous

coating had rusted through in places and was so brittle that

it could be readily broken with the fingers.

The Hylag insulation was not in contact with the pipe

around the entire circumference of the pipe at the area of

inspection. The approximate fit of the Insulation envelope

is indicated in the lower diagram of Fig. 1, The portion of

the envelope indicated by the dotted lines in Fig. 1 was

removed for moisture determination. The air space between

pipe and insulation approximated 1 1/2 Inches in some places.

The insulation was from 1 1/2 to 1 3/'4 inches thick in most

places, but was as thin as 1/2 inch in a few places. Only

about two feet of the pipe were uncovered for inspection.

Discussion

The heat loss of the test specimen can be compared with

the i»equirement s of the current interim OCE Guide Specification by correcting the observed values to a pipe surface

temperature of 350 °F and evaluating the resulting heat loss

rate per square foot of exterior pipe surface. The heat loss

through an envelope of insulation and earth is proportional

to the temperature difference across the envelope if the

thermal conductivities of the m.aterials remain constant for

the two conditions. This would be approximately true for a

change in pipe temperature of 50 degrees.

Correcting the observed heat loss values for a pipe temperature of 350 °F the heat loss per linear foot would be 46,6

Btu/hr and 640 Btu/rir and the heat loss per square foot of

exterior pipe surface would be 206 Btu/hr and 283 Btu/hr for

Tests 1 and 2 respectively under conditions otherwise like

those existing during the tests.

_ 6 -

The low moisture content of the insulation shows that the

Hylag insulation was quite dry, as would be expected for the

temperatures observed on the inner and outer surfaces of the

insulation.

Apparently^, the heat loss per unit length of pipe was

increased 29 percent by the rainstorm that occurred between

the two tests. There is no direct corroborative evidence

for this conclusion^ however^ since the moisture content of

the soil was not observed before the rain. The earth fill

over the pipe was a very porous soil that readily absorbed

water. Handbook data on the effect of moisture content on the

thermal conductivity of soils indicate that the observed

increase in condensate rates between tests 1 and 2 could have

been caused by a 5 to 7 percent increase in the average moisture content of the envelope around the steam pipe.

According to information obtained from the Public Works

Office at the Philadelphia Navy Yard this installation was

made between three and four years ago. Inspection of the

Insulation at this one location indicated that the bituminous

coating had very little waterproofing value at this time.
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TEST SECTION OF PIPING SYSTEM

FIG. I

U. S. DEPARTMENT OE COMMERCE

Sinclair Weeks, Secretary

NATIONAL BUREAU OF STANDARDS

A. V. Astin, Director THE NATIONAL BUREAU OF STANDARDS

The scope of activities of the National Bureau of Standards at its headquarters in Washington,

D. C., and its major field laboratories in Boulder, Colorado, is suggested in the following listing of

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description of the activities, and of the resultant reports and publications, appears on the

inside front cover of this report.

WASHINGTON, D. C.

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NBS