NUREG/CR-6220

SAND94-0769

An Assessment of Fire

Vulnerability for Aged

Electrical Relays

Prepared by

R. A. Vigil, S. P. Nowlen

Sandia National Laboratories

Operated by

Sandia Corporation

Prepared for

U.S. Nuclear Regulatory Commission
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NUREG/CR-6220

SAND94-0769

An Assessment of Fire

Vulnerability for Aged

Electrical Relays

Manuscript Completed: June 1994

Date Published: March 1995

Prepared by

R. A. Vigil,* S. P. Nowlen

Sandia National Laboratories

Albuquerque, NM 87185-0737

Prepared for

Division of Engineering Technology

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, DC 20555-0001

NRC Job Code A1833

*Science & Engineering Associates, Inc.

6100 Uptown Blvd. NE

Albuquerque, NM 87110

Abstract

This report details testing to assess the impact of aging on the fire vulnerability of Agastat and General

Electric relays. Both aged and unaged relays were tested. Aged relays were subjected to operational

cycling under rated load and thermally aged for sixty days. All relays were exposed to one of three

different fire temperature profiles in the Severe Combined Environments Test Chamber located at Sandia

National Laboratories. The ability to operate properly in the given fire environment was monitored.

Results for the aged and unaged relays were examined to determine the impact of aging on the relays'

ability to sustain operation under the test conditions. Overall results indicated that the aged relays'

performance was not significantly different from that of the unaged relays.

-iii- -'Ii-NUREGICR-6220

Table of Contents

Page

Executive Summary ............................................................................................................................ 1

1.0 Introduction and Objectives .................................................................................................. 2

2.0 Relay Selection Basis and Results ........................................................................................ 3

3.0 Experimental Arrangement .................................................................................................. 5

3.1 Relay Aging Procedures ................................................................................................ 5

3.2 Relay Fire Testing ......................................................................................................... 5

3.3 Relay Operational Assessments .................................................................................... 7

4.0 Experimental Results .......................................................................................................... 9

4.1 Aging ............................................................................................................................. 9

4.2 Therm al Exposure Results ........................................................................................... 9

4.2.1 Agastat GPI Results ........................................................................................ 10

4.2.2 General Electric HM A Results ........................................................................... 11

4.2.3 General Electric HGA Results .......................................................................... 12

4.2.4 General Electric I-FA Results .......................................................................... 14

5.0 Conclusions ............................................................................................................................. 17

6.0 References ............................................................................................................................... 18

Appendix A SCETCh Temperature Exposure Plots for All Relays Tested .................................. A-1

Nt)REG/CR-6220
List of Figures

Page

Figure 1 Schematic of a typical armature style relay ....................................................................... 3

Figure 2 Severe Combined Environments Test Chamber (SCETCh)

at Sandia N ational Laboratories ...................................................................................... 5

Figure 3 SCETCh temperature exposure profiles ........................................................................... 6

Figure 4 Measurement schematic for each contact pair and measurement matrix ............................. 7

Figure 5 Agastat Al relay with normally open contact stuck because of a melted contact carrier ...... 10

Figure 6 General Electric HMA Relay B-3 after thermal exposure ............................................... 12

Figure 7 General Electric HGA Relay C-1 failure of the spool's top plate ...................................... 13

Figure 8 General Electric HGA Relay C-4 failure of the armature because of blockage ................. 14

Figure 9 General Electric tFA Relay D-1 after thermal exposure ................................................. 15

List of Tables

Table 1 R elay identification schem e ............................................................................................... 4

Table 2 O verall relay test results .................................................................................................. 16

NUREG/CR-6220-U -,%i °
Executive Summary

The purpose of this test program was to assess

whether the fire vulnerability of electrical relays

increased with aging. The sequence followed for

the test program was to: identify specific relay

types, develop three fire scenarios, artificially age

several relays, test the unaged and aged relays in

the fire exposure scenarios, and compare the

results.

The relays tested were Agastat GPI, General

Electric (GE) HMA, HGA, and HFA. At least

two relays of each type were artificially aged and

at least two relays of each type were new. Relays

were operationally aged by cycling the relay under

rated load for 2000 operations. These relays were

then thermally aged for 60 days with their coil

energized.

Temperature exposure testing was conducted in

Sandia's Severe Combined Environments Test

Chamber (SCETCh). Three exposure profiles

were developed for this test program, which were

representative of a generic mild, moderate or

severe thermal exposure. The exposure profiles

consisted of two phases: The initial phase

consisted of a temperature ramp to either 250 TC,

350 TC, or 450 TC, a 10-20 minute dwell at the

desired temperature, and then a temperature

decrease toward ambient. The second phase

began shortly after the end of the first phase and

consisted of a temperature ramp at a rate of 10 TC

per minute until failure was observed. The second

phase was only performed if the relay survived the

first phase.

Results for the Agastat GPI relays indicated that

aging would not significantly affect the thermal

vulnerability of the relay. All of the relays tested

were observed to fail at temperatures ranging

from 206 to 250 TC. In fact, of the relays tested,

only one-an aged sample-survived the initial

phase of the mild exposure profile. Failures were

generally traced to either the coil rectification

circuit or the base socket.

Results for the GE HMA relays indicated that the

aged samples were, in fact, somewhat more

rugged than the unaged samples. During

exposures to the moderate exposure profile, an

unaged sample was observed to fail whereas an

aged sample survived the initial phase of this

profile. All failures were attributed to failure of

the armature. In three of the four cases, actuation

of the armature failed because of an accumulation

of an unknown substance that formed on the top

of the coil's spool just below the armature. The

final failure was attributed to the armature

becoming fused to the relay's housing.

Results for the GE HGA relays indicated that

aging did not impact the thermal vulnerability of

the relays. However, one of the aged samples

displayed a unique failure in that it failed during

the cool-down portion of the first phase of the

moderate exposure profile. The remaining three

relays survived to temperatures in excess of

450 'C. Three of the relay failures were attributed

to the accumulation of an unknown substance that

formed on the top of the coil's spool just below

the armature. The final failure was attributed to

deformation of the coil top plate.

Results for the GE HFA relays indicated that

aging did not significantly impact the thermal

vulnerability. Both aged and unaged samples

were observed to survive the initial phase of the

mild exposure profile while failing during the

initial phase of the moderate exposure profile. All

failures were attributed to failures of the armature.

In general, it was concluded that aging did not

adversely affect the thermal vulnerability of relays.

Depending on the type of relay, the effect of

exposure to even mild temperature excursions

(>200 'C) may degrade relay performance

regardless of the relay's age. Failure mechanisms

were generally attributed to failures in the

armature.

I 1 ~NtREG/CR-622
1.0 Introduction and Objectives

There has been some concern that, as nuclear

power plants age, protective measures taken to

control and minimize the impact of fire may

become ineffective, or significantly less effective,

and hence result in an increased fire risk. One

objective of the Fire Vulnerability of Aged

Electrical Components Program is to assess the

effects of aging and service wear on the fire

vulnerability of electrical equipment. An increased

fire vulnerability of components may lead to an

overall increase in fire risk to the plant.

Because of their widespread use in various

electrical safety systems, electromechanical relays

were chosen to be the initial components for

evaluation [1]. This test program assessed the

impact of operational and thermal aging on the

vulnerability of these relays to fire-induced

damage. Only thermal effects of a fire were

examined in this test program. The impact of

smoke, corrosive materials, or fire suppression

effects on relay performance were not addressed

in this test program.

NUREGICR-62202 2
2.0 Relay Selection Basis and Results

An earlier study performed as a part of the Fire

Vulnerability of Aged Electrical Components

Program identified and prioritized nuclear power

plant electrical equipment potentially vulnerable to

age-related increases in fire vulnerability[1 ]. This

study included an evaluation of industry practices

and component count totals. As a result, relays

were identified as one of the high priority

components.

Relays used in safety-related applications can

typically be divided into four categories:

protective, auxiliary, control, and timing.

Protective relays serve to protect electrical

distribution systems from electrical overloads.

Auxiliary relays serve to assist protective relays,

especially when loads up to 35 amps are present in

the distribution system. Control relays serve as

direct controlling mechanisms for various

mechanical components. Timing relays perform

similarly to control relays with the exception that

these relays are combined with a timing device

that actuates the contacts after a time period has

passed from the receipt of a control signal [2].

The dominant aging-related stress for relays

identified in Reference I is the thermal aging of

synthetic parts caused by continuous energization

or elevated cabinet temperatures. Reference I

also identifies the following possible failure modes

and causes:

Relay Failure Modes:

* Failure to actuate when commanded

* Actuates without command

• Does not make or break current

* Failure to carry current

* High contact resistance

• Set-point shift

* Time delay shift

Relay Failure Causes:

* Phase-to-ground short

* Coil insulation breakdown

* Contact wear

* Binding of contacts because of carrier warpage

* Pitting, corrosion, and accumulation of

contaminants on contacts

* Wear of moving parts

" Loss of integrity of relay pin/socket connection

* Vibration damage: contact chatter, loosening of

connections

• Shift in resistance and capacitive values affecting

time delay and relay set-point values

Reference I identifies those relay models having

the greatest numbers in nuclear power plants. In

particular, three General Electric (GE) models are

identified as the most widely used in industry: the

GE model HFA (21%), GE model HGA (12%),

and GE model HMA (7%). General Electric

supplies approximately 52% of all

electromechanical relays to the utilities that

responded to the survey[l], which also noted that

Agastat/Amerace relays provided 10% of all

relays. In light of the survey results, the following

relays were chosen to be tested in this program:

" GeneraIElectric 12HFA51A49F

" General Electric 12HMAIllA9

" General Electric 12HGAIIA70F

* Agastat/Amcrace GPI

5 relays tested

4 relays tested

4 relays tested

6 relays tested

All the relays chosen are armature style relays and

are rated for operation at I 15V and 12 amps

(except for the Agastats which are rated at

10 amps). Figure 1 shows the basic components

of a typical armature style relay.

Armature

Normally Closed Contact

-Normally Open Contact

Coil

Input

Figure 1 Scheniatic of a typical armature style relay

The relays tested in this program were obtained

directly from the suppliers. They are effectively

3 NUREG/CR-6220
Relay Selection

identical to UL recognized and Class 1E qualified

devices sold to nuclear power plants, although

they were not procured to Class IE specifications.

The major difference lies in the traceability of the

relay production.

General Electric relays are constructed with either

the standard life coil design or the Century series

coil design. Further analysis of the survey data

from Reference 2 indicates that both types of coil

designs for these relay models are in use in various

systems in nuclear power plants. The GE HGA

and HFA relays tested in this program were

constructed using the standard life relay coil

design. The GE HMA models tested in this

program were constructed using the Century

Series coil design.

Basic design features of the Century Series coil

include the following: the coil's spool is

comprised of high thermal strength, glass-filled

polyester for extended life at elevated

temperatures; the wire insulation is a polyamideimide wire coating (180 'C rating) that retains

insulation integrity and mechanical strength at

elevated temperatures; the encapsulation is

described by the manufacturer as polybutadiene,

solventless, and impregnant.

Accelerated life tests conducted at an elevated

temperature and maximum voltage have

established a projected service life of 40 years at

55 TC and 110% of rated voltage for this coil

design. The standard life coils are simple coil

designs with a phenolic spool and an exterior tape

wrap. The wire insulation is similar to that of the

Century Series.

The Agastat GPI relays are constructed using an

electromagnetic core. A W-shaped mechanism is

connected to the core to provide contact switching

movement. The coil provides a low mean turn

length and assists in heat dissipation. The GPI

relays also have a built-in rectification circuit that

retains the dc efficiency of the electromagnet. The

current peak upon coil energization is also

eliminated through the use of a capacitor. The

GPI relays require a screw terminal molded socket

for operation. Note that there are two socket

models available. The model number of the socket

used in this test program was CR0067.

In all, 19 relays were tested as a part of this

program. Table 1 lists the scheme used to identify

each of the relays tested.

Table I Relay identification scheme

Relay Identification Model Number Aging Condition

Al Agastat GPI Aged

A2 Agastat GPI Aged

A3 Agastat GPI Unaged

A4 Agastat GPI Unaged

A5 Agastat GPI Unaged

A6 Agastat GPI Unaged

BI GE 12HMA111A9 Aged

B2 GE 12HMA111A9 Aged

B3 GE 12HMA11A9 Unaged

B4 GE 12HMA1 IA9 Unaged

C1 GE 12HGAIIA70F Aged

C2 GE 12HGAI1A70F Aged

C3 GE 12HGAI IA70F Unaged

C4 GE 12HGAIIA70F Unaged

DI GE 12HFA5lA49F Aged

D2 GE 12HFA51A49F Aged

D3 GE l2HFA51A49F Unaged

D4 GE 12HFA51A49F Unaged

D5 GE 12HFA5lA49F Unaged

NUREGICR-62204 4
3.0 Experimental Arrangement

3.1 Relay Aging Procedures

A general aging procedure was established based

on the information contained in IEEE C37.105-

1987, Standard for Qualifying Class 1E Protective

Relays. This procedure included both operational

and thermal aging. Radiation aging of the relays

was not included in the aging procedure.

The relays to be aged were cycled individually

under rated load for 2000 cycles to fulfill the basic

operational aging requirements defined in IEEE

C37.105-1987. The relay coils were energized

every minute for 0.4 seconds. After each set of

500 cycles, the coil resistance was measured for

each relay.

After completion of the operational aging, the

relays were thermally aged in an oven for 60 days

at 110 'C. During this entire period, the coil of

each relay was energized to simulate the

additional thermal load produced by the

self-heating effects of the coil. (Note that the two

Agastat bases were not included with the relays in

the thermal aging portion of the test.)

The thermal aging was intended to provide for a

generic aging condition for the relays overall, not

a specific aged condition for any one of the

various relay materials. If an activation energy of

1.15eV is assumed (typical of polymers) then the

aging conditions would be equivalent to 40 years

of exposure at a 58 'C ambient.

3.2 Relay Fire Testing

The fire exposure tests were conducted in Sandia

National Laboratories' (SNL's) Severe Combined

Environments Test Chamber (SCETCh). The

SCETCh facility, shown in Figure 2, is able to

simulate both transient and steady-state thermal

conditions. The SCETCh facility was designed to

simulate fire environment effects. Additional

capabilities of the SCETCh facility include steam

testing and hydrogen burn simulation. It may be

h temperature/pressure vessel. The

Figure 2 Sev•re Combined niironments Test Chamber (SCETCh) at Sandia National Laboratories

5 5 NUREGICR-6220
Experimental Arrangement

SCETCh facility is designed to operate at elevated

temperatures as high as 1500 0C.

The SCETCh chamber is a cylindrical chamber

measuring 24-inches long by 18-inches in

diameter. The shell and cover plates are

constructed from Inconel 625. The elevated

temperatures are generated by a series of quartz

lamps mounted around the chamber. Resistance

coil heaters are used to heat incoming fresh air for

the chamber. The desired temperature exposure

profiles are achieved using a computer-controlled

480 Vac power supply.

Each of the sample relays was tested using one of

three thermal exposure profiles. These profiles

were intended to be representative of generic

mild, moderate, and severe thermal exposures,

respectively. That is, the profiles were intended to

represent various commonly identified generic fire

scenarios, rather than any given specific fire

scenario. Transient profile ramp rates, peak

exposure temperatures, and profile durations were

determined based on the results of available test

data and actual nuclear power plant fire event

reports.[3-7]

Each of the three profiles consists of two phases

as shown in Figure 3. During the first phase of

the exposure:

* the exposure temperature was increased from

ambient at a rate of approximately 20 'C/min

(initial ramp);

* upon attaining a predetermined temperature

the exposure was held constant for a specified

time (plateau);

" exposure temperature was then decreased

toward ambient conditions over a period of

approximately 20 minutes (cool-down).

For the mild exposure profile, the initial ramp

lasted for approximately 10 minutes, reaching a

plateau temperature of 250 0C, which was held for

an additional 10 minutes. For the moderate

6WO

500

G- 4001

4300 U

E

p200

100

0

0 10 20 30 40 50

Time (min)

60 70 80 90

Figure 3 SCETCh temperature exposure profiles

NUREG/CR-62206 6
exposure profile, the initial ramp lasted for

approximately 15 minutes, reaching a plateau

temperature of 350 TC, which was held for an

additional 15 minutes. For the severe exposure

profile, the initial ramp lasted for approximately

20 minutes, reaching a plateau temperature of

450 'C, which was held for an additional

20 minutes.

The second phase of each exposure profile

consisted of an upward ramp in temperature at a

rate of 10 °C/min until relay failure was detected.

The relay under test would undergo the second

phase if and only if it had survived the first phase

of the exposure profile. This second phase of the

exposure profile was intended to assess the

relative margin by which a relay had survived the

initial phase of the exposure profile. For example,

if the relay failed at a substantially higher

temperature than the first phase plateau

temperature, then it could be concluded that the

Experimental Arrangement

relay had survived the first phase with significant

margin.

3.3 Relay Operational Assessments

During each exposure, the test relay was operated

under a 1 amp load for each contact set and was

periodically required to actively switch this load.

In particular, each 60 second measurement cycle

consisted of a period of 50 seconds during which

the coil was energized and 10 seconds when the

coil was de-energized. The relay's ability to

switch the load was monitored to verify

operability.

Additional measurements made during each

measurement cycle included the relay's coil

resistance, contact set resistance, and leakage

currents. An electrical schematic of the simulated

load and performance monitoring circuit used for

each contact set is shown in Figure 4. The

120 Vac

Output

Measurements

-I

Output Measurements Coil Coil

For Each Contact Set Unenergized Energized

1 Load Current Measurement Leakage Current Measurement

2 Leakage Current Measurement Load Current Measurement

3 Contact Resistance No Measurement

4 No Measurement Contact Resistance

Figure 4 Measurement schematic for each contact set and measurement matrix

7 7 NUREG/CR-6220
Experimental Arrangement

measurement matrix is also included for

clarification.

It was recognized that this mode of operation is

not representative of typical in-plant applications.

Typically, a relay would be called upon either to

hold its current position throughout an event, or

to switch positions once and hold the new

position. However, the objectives of this test

program require that the relative performance of

the aged and unaged relays be compared. Hence,

it was important to assess both the timing of relay

failure during a particular exposure profile as well

as the fact of survival or failure. To meet this

objective, it was necessary that the relays be

operated periodically to assess the continuing

operability throughout the exposure.

NUREG/CR-6220 8
4.0 Experimental Results

4.1 Aging

No anomalies were recorded during the

operational cycling of the relays. The coil

resistance varied less than 4% during the cycling

for each of the relay types. No coil failures or test

equipment anomalies were detected during the

thermal aging of the relays.

However, after the thermal aging, it was noted

that the armature of the HGA relay was

malfunctioning. As the HGA coils were

energized, the armatures for each relay easily

switched from the normally closed to the normally

open position. However, when the coils were deenergized, the armature did not completely return

to the normally closed position. It was

hypothesized that the thermal aging might have

caused the degradation of some unknown

lubricant in the pivot. (However, the

manufacturer stated that no lubricant was used in

the armature.) The manufacturer hypothesized

that particulates from outgassing during the

thermal aging may prevent the armature from

returning to the normally closed position.

Another possibility for the improper operation of

the relay was the failure of the return spring. The

return action of the armature was controlled by a

spring attached to a slotted flange on the

armature. A spring from an unaged relay was

substituted for the one from the aged relay. With

the new spring in place, the relay still did not

return to the normally closed position, which

indicated that the spring itself was not the cause of

the problem. The spring from the aged relay was

returned to the original position on the aged relay.

The spring was in the original slot position, which

was the middle slot on the flange, during

operational and thermal aging. As the spring was

adjusted to provide the greatest closing force, the

first relay still would not return to the normally

closed position.

By using low pressure air, the armature from the

first aged relay was cleaned to try to remove any

particulates that might be hampering the armature

movement. After the pressurized air cleaning and

the adjustment of the spring's position, the

armature returned to the normally closed position

when the relay's coil was de-energized. The

second relay was also cleaned with pressurized

air, and it also had the spring adjusted to provide

maximum closing force. Likewise, this relay now

performed as required. The position of this spring

remained in the slot that provided the greatest

closing force so that the remainder of the test

program could be completed. The exact cause of

this failure was not fully determined during this

test program, but it may warrant further

investigation. The remaining relays did not

experience any problems upon completion of the

thermal aging.

4.2 Thermal Exposure Results

For each relay type, the first exposure was

performed using the unaged samples followed by

testing of the aged samples. For each group the

first relay sample was subjected to the moderate

exposure profile. Based on the result of this

exposure, the next sample was subjected to either

the mild or severe exposure profile. That is, if the

first sample survived the entire first phase of the

moderate profile, then the second sample was

subjected to the severe profile. Conversely, if the

first sample failed during the first phase of the

moderate profile, then the second sample was

subjected to the mild profile. Certain exceptions

to this general test sequence were exercised as

described below.

In preparation for testing, relays were energized

for approximately 5 minutes prior to the thermal

exposure. Failures were determined by either a

loss of load-switching capability or the opening of

a 1 amp fuse located on the coil input. Upon

indication of failure, the experimental control

program was allowed to complete another full

measurement cycle to verify that a persistent

failure had occurred. The power to the SCETCh

chamber, the relay load, and the coil power was

9 NUREG/CR-6220
Results

then shut off. The test relay remained in the

chamber until the chamber's temperature

decreased.

Each relay type was tested in its expected

mounting position. The mounting hardware

included with each relay was used during the

testing. Complete panels were not used, only

frame supports as necessary to provide for

mounting.

The complete results for all relays tested can be

found in Table 2 at the end of this chapter.

Temperature exposure profiles of each relay can

be found in Appendix A. The specific details for

each relay type are discussed in the following

sections.

4.2.1 Agastat GPI Results

The Agastat Al relay survived 64 minutes into the

mild thermal exposure, failing during the second

phase temperature ramp. The temperature at the

time of relay failure was 250 'C. Post-test

analysis revealed two failure mechanisms. The

first failure was detected in the base where two

terminals were shorted together because of

warpage of the base socket. The second failure

discovered was a melted contact carrier that

prevented the armature from returning to the

normally closed position, as shown in Figure 5.

During the previous test program [7] an Agastat

GPI relay displayed a similar contact carrier

failure at a temperature of approximately 210 'C.

(Note that this earlier program utilized a slowly

increasing temperature profile until failure was

detected.)

The second aged Agastat relay, A2, survived

approximately 24 minutes, failing during the early

stages of the cool-down period. The peak

exposure temperature was 241 'C, and the

temperature at the time of failure was 210 'C.

A previous test program, which evaluated relay

functionality during exposures to secondary

environments created by a fire, indicated that the

Agastat relays were not likely to survive the mild

exposure profile[7]. Therefore, all of the Agastat

samples were tested in the mild exposure profile.

Figure 5 Agastat Al relay with normally-open contact stuck because of a melted contact carrier

NUREG/CR-6220 110
Results

Post-test analysis revealed that a capacitor in the

coil rectification circuit had a visible burnt crack at

the top portion of the device. A continuity check

of the coil rectification circuit indicated an open

circuit.

The unaged Agastat relays, A3 and A4, failed

approximately 11 and 14 minutes into the

exposure, respectively. In each case, the failures

occurred early in the plateau period. The

temperatures at the time of failure were 206 'C

and 221 'C, respectively. The failure mode was

similar to that of relay A2, namely, an open circuit

in the coil rectification circuits. The capacitors

did not display visible cracking as in A2.

Agastat unaged relays A5 and A6 failed

approximately 11 and 12 minutes into the

exposure, respectively. In each case, the failures

occurred early in the plateau period. The

temperatures at the time of failure were 215 'C in

both cases. In each case the failures were traced

to the bases. Post-test analysis revealed that a

short had occurred between two terminal sockets

in each base. The short caused each relay to fail.

Contact resistance measurements for all Agastat

relays were typically below 70 mQ. The highest

recorded contact resistance for any relay was

86 mQ. Load currents remained stable until

failures were observed. Open contact leakage

currents were generally erratic and provided

limited information.

Failures for the Agastat relays were attributed to

three failure modes: shorting of the base, failure of

the built in rectification circuit, or warpage of the

contact carriers. The manufacturer recommended

operating-temperature range for this relay is 0 'C

to 60 °C. All the failures observed occurred at

temperatures in excess of 200 *C.

The aged samples survived longer in the test

environment than the unaged samples, which

suggests that the aging protocol enhanced the

relay's ruggedness. It is suspected that the aging

process annealed the coil rectification circuit

components, increasing their tolerance to thermal

exposures.

4.2.2 General Electric JIMA Results

The first aged relay, B I, was tested in the

moderate profile and failed at the end of the cooldown portion of the exposure. The peak

exposure temperature was 352 °C, and the

temperature at failure was 129 'C. The failure

observed was associated with an armature

actuation failure. Post-test analysis revealed that a

substance, apparently released from the coil's

spool, accumulated on the top of the coil and

prevented the armature from actuating.

The second aged relay, B2, was tested in the

severe profile and failed early in the plateau

period. The temperature at the time of failure was

447 'C. The mode of failure was identical to that

of relay B 1.

The first unaged relay, B3, was tested in the

moderate profile and failed midway through the

plateau period. The temperature at the time of

failure was 348 'C. The mode of failure was

again associated with an armature failure.

However, in this case a closer inspection revealed

that the armature had fused to the relay's housing.

The point of the fusing is shown in Figure 6. The

armature arm was separated from the housing

when slight pressure was applied. However, it

still did not actuate freely because of warpage of

the relay's housing.

The second unaged relay, B4, was tested in the

mild profile. The relay survived the entire first

phase of the exposure and failed during the second

phase. The temperature at the time of failure was

approximately 400 0C. The mode of failure was

identical to that observed for relay B 1.

It was evident from these results that the aged

specimens performed slightly better than the

unaged specimens. Three of the four failures,

including both of the aged and one of the unaged

samples, were attributed to the accumulation of

11 11 NUREG/CR-6220
Results

Figure 6 General Electric HMA relay B-3 after thermal exposure

an unknown substance on top of the coil and

under the armature. The fourth failure was

attributed to fusing of the armature to the relay

housing.

Contact resistance measurements for all GE HMA

relays were typically below 60 mfn. Load

currents remained stable until failure was

observed. Open contact leakage currents were

generally under 0.1 amp until failure occurred.

Note that during an earlier test program [7] an

IMA relay (without a cover) was also tested.

During this test, failure occurred at approximately

400 TC. However, this failure was attributed to

the external coil power lead wires shorting

together, rather than to a failure in the relay itself.

This failure also caused the lead wire to ignite,

and the resulting fire destroyed the relay.

4.2.3 General Electric HGA Results

The first aged relay, CI, was tested in the

moderate profile and failed during the late stages

of the cool-down. The peak exposure

temperature was 353 TC, and the temperature at

the time of failure was approximately 150 'C.

(Note: data during the cool-down portion of the

exposure were not recorded because of a data

logging error. The time of failure was recorded

by the test operator, but the final temperature was

not recorded. The temperature shown in Figure

A- 11 of Appendix A is an estimate based on other

profiles.) The failure was caused by warpage of

the top plate of the coil's spool, which curled

upwards and prevented the armature from

actuating as shown in Figure 7. Note that this

was the only instance in which this particular

failure mode was observed.

Since the first aged relay, C 1, failed on the

cool-down prior to completing the first phase of

the moderate exposure, a decision was made to

deviate from the nominal testing protocol. In

particular, the second aged relay, C2, was also

tested in the moderate profile. This deviation was

implemented in order to verify the results.

The second aged relay, C2, survived the first

phase of the profile and failed during the second

phase. At an exposure temperature of 480 'C, the

specimen self-ignited. Shortly thereafter, failure

of the relay was observed. The failure was

associated with a loss of armature actuation

NUREG/CR-6220 121
Results

Figure 7 General Electric JIGA relay C-1 failure of the spool's top plate

capability. Inspection of the charred remains of

the coil and the armature showed that the

armature and coil had become fused together

because of the accumulation of an unknown

substance beneath the armature. (Recall that

similar behavior was noted in three of the four

HMA relays tested.)

The first unaged relay, C3, was tested in the

moderate profile and survived the entire first

phase of the exposure. Failure was noted during

the second phase at a temperature of 488 °C.

Failure was attributed to the accumulation of an

unknown substance underneath the armature on

top of the coil's spool. This substance prevented

the armature from actuating. (Note that similar

failure mechanisms occurred for the two different

coil designs, the GE JIMA and GE HGA.)

(The C3 relay was the first GE relay tested from

among all relays. The control program used in

this test was identical to that used for the Agastat

tests. Because of the variation between the actual

and the intended profile, the control program was

modified to compensate for this variation. The

variation can be observed by comparing

Figure A-13 to A-I I or A-12. The difference was

determined to be caused by the controlling

thermocouple's location relative to the chamber

and the test specimen. The remaining relays were

tested using the new control program, which

produced exposure profiles that were very similar

to the desired exposure profiles.)

The second unaged relay, C4, was tested in the

severe profile and failed at the end of the plateau

period . The temperature at the time of failure

was 453 'C. The failure mode was identical to

that of relay C3; namely, an accumulation of an

unknown substance underneath the armature

prevented the armature from actuating. This

substance can be seen in Figure 8.

Based on the time to failure and final temperature,

the two unaged relays appear to have performed

slightly better than the aged relays, given these

temperature profiles. However, the difference in

13 13 NUREGICR-6220
Results

Figure 8 General Electric HGA relay C-4 failure of the armature because of blockage

the results for the aged and unaged relays is not

significant.

Contact resistance measurements for all GE HGA

relays were typically below 60 mfl. Load

currents remained stable until failure was

observed. Open contact leakage currents were

generally under 0.1 amp until failure occurred.

4.2.4 General Electric HFA Results

The first aged relay, D 1, was tested in the

moderate profile and failed early in the cool-down

period. The peak exposure temperature was

359 'C, and the temperature at failure was 349 'C.

The failure of two of the six contacts pairs was

noted in load current measurements. Upon

inspection, it was noted that the armature was

warped or bowed. This warpage was severe

enough to prevent the closure of two of the six

contact pairs. However, the coil remained

functional during post-test analysis.

The second aged relay, D2, was tested in the mild

profile. The relay survived the first phase of the

exposure and failed during the second phase at a

temperature of 485 'C. The failure was attributed

to severe deformation of the relay body. The

relay's components were misaligned, and the

armature movement was not free enough to

complete contact (make or break).

The relay D3 was tested in the moderate profile

and failed midway through the cool-down. The

peak exposure temperature was 348 °C, and the

temperature at failure was 298 'C. The mode of

failure was similar to D 1.

Relay D4 was tested in the severe profile and

failed midway through the plateau. At an

exposure temperature of approximately 450 °C,

the specimen self-ignited. Shortly thereafter

failure of the relay was observed. The ensuing fire

destroyed the relay.

The final relay tested, D5, was tested in the mild

environment. The relay survived the first phase of

the exposure and failed during the second phase at

a temperature of 440 'C. The test data indicated

that the coil did not actuate when power was

applied. However, post-test analysis did not find

any problems with the coil or the armature. The

NUREG/CR-6220 114
armature was slightly misaligned and slightly

warped, but the contacts were all making contact.

The exact cause of the failure was not evident. It

was noted that when the coil was energized the

relay hummed and chattered loudly. On one

subsequent energization, the armature failed to

actuate. Hence it was concluded that this relay

was subject to an intermittent failure.

From these results, it can be seen that the aged

and unaged relays behaved quite similarly under

the given test conditions. The results of the aged

and unaged HFA relays suggest that the relays will

most likely survive in a fire with an exposure

similar to the mild profile. Survival in fires

corresponding to the moderate and severe profiles

is doubtful.

Results

Contact resistance measurements for all GE HFA

relays were typically below 90 mn. Load

currents remained stable until failure was

observed. Open contact leakage currents were

erratic but generally under 0.2 amp until failure

occurred.

All of the relays tested showed signs of

deformation of the relay body. Many of the outer

shells were cracked. Most of the relay bodies

were also bowed or warped, as can be seen in

Figure 9. The deformation of the relay body was

evident in each of the GE HFA relays, with some

more severe than others. The failures for four of

the GE HFA relays were attributed to warpage of

the armature.

Figure 9 General Electric IFA relay D-1 after thermal exposure

15 15 NUREG/CR-6220
Results

Table 2 Overall relay test results

Relay # Aged Profile Test Survived Time of Peak Temperature Failure

or Order 1st phase Failure Temperature at Failure Mode

Unaged (hh:mm) (0C) (

0C)

Agastat Aged Mild 5 Yes 01:04 250.4 250.4 Stuck contact &

Al Base shorted

Agastat Aged Mild 6 No 00:24 241.1 209.7 Rectification circuit

A2 failure

Agastat Unaged Mild 1 No 00:11 206.4 206.4 Rectification circuit

A3 failure

Agastat Unaged Mild 2 No 00:13 220.7 220.7 Rectification circuit

A4 failure

Agastat Unaged Mild 3 No 00:11 214.4 214.4 Base shorted

A5

Agastat Unaged Mild 4 No 00:12 214.5 214.5 Base shorted

A6

GE HMA Aged Moderate 13 Yes 00:49 352.4 129.1 Armature failed to

B I actuate

GE HMA Aged Severe 14 No 00:23 446.9 446.9 Armature failed to

B2 actuate

GE HMA Unaged Moderate 11 No 00:20 348.2 348.2 Armature fused to side

B3 of relay

GE HMA Unaged Mild 12 Yes 01:19 402.9 402.9 Armature failed to

B4 actuate

GE HGA Aged Moderate 9 No 00:43* 352.6* 150* Armature blocked by

Cl warped top coil plate

GE HGA Aged Moderate 10 Yes 01:38 745.6** 551.9** Armature blocked,

C2 relay destroyed

GE HGA Unaged Moderate 7 Yes 01:40 487.7 487.7 Armature failed to

C3 actuate

GE HGA Unaged Severe 8 No 00:36 453.4 453.2 Armature failed to

C4 actuate

GE HFA Aged Moderate 18 No 00:31 358.9 348.7 Armature warped

DI

GE HFA Aged Mild 19 Yes 01:26 484.7 484.7 Armature warped

D2

GE HFA Unaged Moderate 15 No 00:34 348.2 297.5 Armature wvarped

D3

GE HFA Unaged Severe 17 No 00:34 563.8** 563.8** Completely destroyed

D4 by fire

GE IFA Unaged Mild 16 Yes 01:23 440.0 440.4 Intermittent Failure

D5 I I

* Exact time and temperature of failure not recorded because of a data logging error. Failure occurred during cool-down ramp at the

listed estimated time and temperature. ** Temperatures are higher tlan expected because the relays materials ignited and burncd.

NUREG/CR-6220 161
5.0 Conclusions

This test program assessed the impact of

operational and thermal aging on the thermal

vulnerability of relays. The relays evaluated were

Agastat GPI, General Electric HMA, General

Electric HGA, and General Electric HFA. At

least two relays of each type were tested in an

unaged condition and at least two relays of each

type were artificially aged prior to testing. The

aged samples were operationally aged by cycling

the relay under rated load for 2000 operations.

These relays were then subjected to thermal aging

for 60 days at a temperature of 110 "C with their

coils energized.

Thermal exposure testing was conducted in SNL's

Severe Combined Environments Test Chamber

(SCETCh). Three exposure profiles were

developed for this test program. These profiles

were representative of generic mild, moderate or

severe thermal exposures, respectively.

The Agastat GPI relay results indicated that most

relays would not survive in a mild exposure

(250 'C) environment. However, the aged

samples survived longer than the unaged samples.

Failures were generally traced to the coil

rectification circuit. However, failures in the base

socket were also encountered.

The GE HMA and GE HGA failures were

generally attributed to failure of the armature to

actuate properly. For both relay types, most of

the failures were attributed to an accumulated

substance that formed on the top plate of the coil's

spool just below the armature. One GE HMA

relay failure was attributed to the armature

becoming fused to the relay's housing. One GE

HGA relay failure was caused by the armature

failing to actuate because the top plate of the coil

had curled upwards, preventing movement of the

armature. Aging was not a significant factor in

any of the failures.

The GE HFA relay failures were generally caused

by warpage of the armature arm. This warpage

prevented certain contacts from fully engaging.

One GE HFA displayed an intermittent coil

actuation failure. All of the relays tested exhibited

severe distortion of the relay body. Aging was

not a significant factor in the failures.

In general, it can be concluded that the effect of

aging on the fire vulnerability of relays appears to

be insignificant. Depending on the relay type, the

effect of exposure to even mild temperature

excursions (>200 °C) may affect relay integrity

independent of the relay's age.

It was also noted that a relay may function

properly at a high temperature for a period of time

and subsequently fail upon cooling. This was

observed in four of the relays tested in this

program (one sample from each relay type). The

most common failure mode observed was failure

of the armatureto actuate on command because of

blockage or warpage.

17 17 NUREG/CR-6220
6.0 References

1. Lowry, W. and Vigil, R. A., "Prioritization of

Reactor Control Components Susceptible

to Fire Damage as a Consequence of

Aging," NUREG/CR-6103, SAND93-

7107, Science & Engineering Associates,

Inc. for Sandia National Laboratories,

January 1994.

2. Toman, G. J., Bacanskas, V. P., Shook, T. A.,

and Ladlow, C. C., "An Aging Assessment

of Relays and Circuit Breakers and System

Interactions," Franklin Research Center,

NUREG/CR-4715 (BNL-NUREG52017), June 1987.

3. Lambright, J. A., Nowlen, S. P., Nicolette, V.

F., and Bohn, M. P., "Fire Risk Scoping

Study: Investigation of Nuclear Power

Plant Fire Risk, Including Previously

Unaddressed Issues," NUREG/CR-5088,

SAND88-0177, Sandia National

Laboratories, January 1989.

4. Cline, D. D., von Riesemann, W. A., Chavez,

J. M., "Investigation of Twenty-Foot

Separation Distance as a Fire Protection

Method as Specified in 10 CFR 50,

Appendix R," NUREG/CR-3192,

SAND83-0306, Sandia National

Laboratories, October 1983.

5. Nowlen, S. P., "Enclosure Environment

Characterization Testing for the Base Line

Validation of Computer Fire Simulation

Codes," NUREG/CR-4681, Sandia

National Laboratories, March 1987.

6. Chavez, J. M., Nowlen, S. P. "An

Experimental Investigation of Internally

Ignited Fires in Nuclear Power Plant

Control Cabinets: Part 1: Cabinet Effects

Test, Part 2: Room Effects Tests,"

NUREG/CR-4527/V1 & V2, SAND86-

0336, Volumes I & 2, Sandia National

Laboratories, April 1987 &

November 1988.

7. Jacobus, M. J., "Screening Tests of

Representative Nuclear Power Plant

Components Exposed to Secondary

Environments Created by Fires,"

NUREG/CR-4596, SAND86-0394, June

1986.

NUREG/CR-6220 118
Appendix A SCETCh Temperature Exposure Plots for All Relays Tested

In this appendix, the temperature exposure profiles are shown for each relay tested. Each figure contains the desired profile

(mild, moderate, or severe) and the actual temperature profile. Note that the relays were tested in the order listed in Table 2

in the report. The thermal exposures were perfomed in Sandia National Laboratories' Severe Combined Environments Test

Chamber.

A-1 NUREG/CR-6220

Temperature Profile for Relay Al (Agastat)

600

500

400 Failure Occurred

300

-" 200

100

0 . . . . . . * • . . . . . ... . . . . , . . , • .

0 10 20 30 40 50 60 70 80 90 100

Time (H nutes)

Figure A-i SCETCh temperature exposure for relay Al

Temperature Profile for Relay A2 (Agastat)

600

500

2Failure Occurred

300

- 200

100

0

Actual Profile

Mild Profile

0 10 20 30 40 50 60 70 80 90 100

Time (minutes)

Figure A-2 SCETCh temperature exposure for relay A2

A-3 A-3 NUREG/CR-6220
Temperature Profile for Relay A3 (Agastat)

600

500

400

•0 Failure Occurred

V 300

E

1- 200

Actual Profile

100 Mild Profile

0 10 20 30 40 50 60 70 80 90 100

Time (minutes)

Figure A-3 SCETCh temperature exposure for relay A3

Temperature Profile for Relay A4 (Agastat)

600

500

400

o Failure Occurred

300

E

F% 200

Actual Profile

100___ Mild Profile

0 10 20 30 40 50 60 70 80 90 100

Time (minutes)

Figure A-4 SCETCh temperature exposure for relay A4

NUREG/CR-6220A- A-4
Temperature Profile for Relay AS (Agastat)

600

500

400

Failure Occurred

S300

• 200

Actual Profile

100 Mild Profile

0 10 20 30 40 50 60 70 80 90 100

Time (minutes)

Figure A-5 SCETCh temperature exposure for relay A5

Temperature Profile for Relay A6 (Agastat)

600

500

S oo

&400

Failure Occurred

300

E

200

100

Actual Profile

Mild Profile

0 10 20 30 40 50 60 70 80 90 100

Time (minutes)

Figure A-6 SCETCh temperature exposure for relay A6

A-5 A-S NUREG/CR-6220
Temperature Profile for Relay BI (GE HMA)

450

400

350

L 300

S250

200

E

150

100

50

0

0 10 20 30 40 50 60 70" 80 90 100

Time (minutes)

Figure A-7 SCETCh temperature exposure for relay B 1

Temperature Profile for Relay B2 (GE HMA)

450

400

350

SFailure Occurred

250

L 200

E

150

100

50

0 10 20 30 40 50 60 70 80 90 100

Time (minutes)

Figure A-8 SCETCh temperature exposure for relay B2

NUREGICR-6220A- A-6
Temperature Profile for Relay B3 (GE HMA )

450

400

350

-300

1 250

. 200 Failure Occurred

150

100

50

0 . . .. . . . . . . ' . . . . ' . .

0 10 20 30 40 50

Time (minutes)

60 70 80 90 100

Figure A-9 SCETCh temperature exposure for relay B3

Temperature Profile for Relay B34 (GE HMA)

600

500 Failure Occurred

-400

S300

E 0 Actual Profile

Mild Profile

00 - - "- - Estimated Profile

0 . . 1. 3 0. 4 0 . 0 6 0 7 0 8 0 9 0 1 0

0 10 20 30 40 50 60 70 80 90 100

Time (miinutes)

Figure A-10 SCETCh temperature exposure for relay B4

A-7 A-7 NUREG/CR-6220
Temperature Profile for Relay Cl (GE HGA)

450

400

350 Data logging error

300

P250

K 2o00 2010 - Actual Profile

150

Medium Profile

100 Failure Occurred - Estimated Profile

50

0 10 20 30 40 50 60 70 80 90 100

Time (minutes)

Figure A-1 I SCETCh temperature exposure for relay C1

Temperature Profile for Relay C2 (GE HGA)

800

700 Failure Occurred

600

500

2 Relay Ignited

S400

v300

F200 Actual Profile

100 Mild Profile

0 10 20 30 40 50 60 70 80 90 100

Time (minutes)

Figure A-12 SCETCh temperature exposure for relay C2

NUREG/CR-6220 A-8
Temperature Profile for Relay C3 (GE HGA)

500

450 Failurc Occurred

400

350

300

" 250

200

150

100 - Actual Profile

50 Medimn Profile

0

0 10 20 30 40 50 60 70 80 90 100

Time (minutes)

Figure A-13 SCETCh temperature exposure for relay C3

Temperature Profile for Relay C4 (GE HGA)

500

450

400

- 350

S300 a3 0 Failure Occurred

E 200

•"150

-- n Actual Profile

100

50 Severe Profile

0 -

0 10 20 30 40 50 60 70 80 90 100

Time (minutes)

Figure A-14 SCETCh temperature exposure for relay C4

A-9 A-9 NUREG/CR-6220
Temperature Profile for Relay DI (GE HFA)

450

400

350

300

E 250

K. 2o200

E1% 1o

100

50

0

0 10 20 30 40 50 60

Time (minutes)

70 80 90 100

Figure A-15 SCETCh temperature exposure for relay DI

Temperature Profile for Relay D2 (GE HFA)

600

500 Failure Occurred

• 300

E%' 200

Actual Profile

100 Mild Profile

0 10 20 30 40 50 60 70 80 90 100

Time (minutes)

Figure A-16 SCETCh temperature exposure for relay D2

NUREG/CR-6220 A1 A-10
Figure A-17 SCETCh temperature exposure for relay D3

Temperature Profile for Relay D4 (GE HFA)

600 Failure Occurred

500

400

.2

E 300

E

1- 200

Relay Ignited

100

0 10 20 30 40 50 60 70 80 90 100

Time (minuites)

Figure A-18 SCETCh temperature exposure for relay D4

A-11I A-il NUREGICR-6220
Temperature Profile for Relay D5 (GE HFA)

600

500

6400

300

E

E- 200

100

0

Failure Occurred

0 10 20 30 40 50 60 70 80

Time (minutes)

90 100

Figure A-19 SCETCh temperature exposure for relay D5

NUREGICR-6220 A1 A-12
NRC FORM 335 U.S. NUCLEAR REGULATORY COMMISSION 1. REPORT NUMBER

12-89) (Assigned by NRC. Add Vol., Supp., Rev.,

NRCM 1102, end Addendum Numbers, If &my.)

3201.3202 BIBLIOGRAPHIC DATA SHEET NUREG/CR-6220

(See instructions on the reverse) SAND94-0769

2. TITLE AND SUBTITLE

An Assessment of Fire Vulnerability for Aged Electrical Relays

3. DATE REPORT PUBLISHED

MONTH j YEAR

March 1995

4. FIN OR GRANT NUMBER

A1833

5. AUTHOR(S) 6. TYPE OF REPORT

R.A. Vigil*, S.P. Nowlen

Technical

7. PERIOD COVERED (Inclusive Dates)

8. PERFORMING ORGANIZATION - NAME AND ADDRESS (If NRC. provide Divlsion, Office or Region, U.S. Nuclear Regulatory Commission, and mailing address, if contractor, provide nwe and mailing addrivs)

Sandia National Laboratories *Science and Engineering Associates,Inc.

Albuquerque, NM 87185-0737 6100 Uptown Boulevard, NE

Albuquerque, NM 87185-0737

9. SPONSORING ORGANIZATION - NAME AND ADDRESS (If NRC. type '~Same as above ~ if contractor. provide NRC Division. Office orRegion. US~ Nuclear Regulatory Commission.

9. SPONSO R I NG 0OR GAN I ZATI ON - NAM E AN D AD D R ESS Ilf NRC, ryp "Sarn as above"; if contratr, provide NRC Divsin Office or Regon U.1 Nuclear Regulatory Commisin

and mailing addressj

Division of Engineering Technology

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, DC 20555-0001

10. SUPPLEMENTARY NOTES

11. ABSTRACT f200 words or lessi

This report details testing to assess the impact of aging on the fire vulnerability

of Agastat and General Electric relays. Both aged and unaged relays were tested.

Aged relays were subjected to operational cycling under rated load and thermally

aged for sixty days. All relays were exposed to one of three different fire

temperature profiles in the Severe Combined Environments Test Chamber located at

Sandia National Laboratories. The ability to operate properly in the given fire

environment was monitored. Results for the aged and unaged relays were examined

to determine the impact of aging on the relays' ability to sustain operation under

the test conditions. Overall results indicated that the aged relays' performance

was not significantly different from that of the unaged relays.

12. KEY WORDS/DESCR!PTORS (List words or phrases that will assist researchers in locating the report. I 13. AVAILABILITY STATEMENT

aging, relays, fire vulnerability unlimited

14. SECURITY CLASSIFICATION

(This Page)

unclassified

IThis Report)

unclassified

15. NUMBER OF PAGES

16. PRICE

NRC FORM 335 (2-89)


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NUREG/CR-6220 AN ASSESSMENT OF FIRE VULNERABILITY FOR AGED ELECTRICAL RELAYS MARCH 1995

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NUCLEAR REGULATORY COMMISSION

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