Information Notice 1990-23, Improper Installation of Patel Conduit Seals

Improper Installation of Patel Conduit Seals

ML031210572
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant, Crane
Issue date:	04/04/1990
From:	Rossi C Office of Nuclear Reactor Regulation
To:
References
IN-90-023, NUDOCS 9003280088
Download: ML031210572 (7)

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C.

20555

April 4, 1990

NRC INFORMATION NOTICE NO. 90-23:

Addressees

All holders of operating licenses or construction permits for nuclear power

reactors.

Purpose

This information notice is intended to alert addressees to a possible safety

problem caused by the improper installation of Patel conduit seals as a result

of incorrect selection of grommets based on the wire gauge size.

It is ex- pected that recipients will review the information for applicability to their

facilities and consider actions, as appropriate, to avoid similar problems.

However, suggestions contained in this information notice do not constitute

NRC requirements; therefore, no specific action or written response is required.

Description of Circumstances

On November 6, 1989, the staff at the H. B. Robinson plant notified the NRC that

they had discovered that some of the conduit seal grommets used to seal insu- lated wire conductors entering environmentally qualified instrument housings

were oversized for the application. The seals are used to prevent moisture

from entering safety-related electrical components following loss-of-coolant

accidents.

Use of oversized seals may create potential moisture intrusion

paths into safety-related instrumentation inside the reactor containment.

The problem was attributed to inadequate installation instructions that were

used when the seals were installed in 1986 and 1987. These instructions listed

the grommets by wire gauge size and gave maximum wire insulation diameters for

each wire size (see the first table, page 1, of the enclosed EGS Bulletin 90-1).

In accordance with these instructions, the seals were selected based on wire

gauge alone. However, since the insulation thickness for a given wire gauge

varies from one wire type to another, a more appropriate parameter for choosing

the correct grommet size would have been the minimum wire insulation diameter

for which a particular grommet will achieve an effective seal. The selection

of grommet size based only on wire gauge size resulted in the installation of

some grommets that were too large to provide an effective seal.

As a result, some of the seals failed pressure tests that were designed to simulate post- LOCA pressures.

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IN 90-23 April 4, 1990 During the investigation of the grommet leakage problem, the Robinson staff also

checked the torque on the conduit seal union nuts that are used to compress the

seals.

EGS Corporation recommends that the union nuts be torqued to 50 ft-lb

(EGS Bulletin 90-1).

On approximately half of the 90 seals inspected, the union

nut moved about 1/4 inch when this torque was applied.

One union nut was found

to be quite loose.

EGS Corporation reports that 1/4 inch of movement does not

necessarily indicate a degraded seal but recommends that the correct torque be

verified on a representative sample of installed conduit seals.

Discussion:

In order for these conduit seals to be able to function at accident pressures

and temperatures and for extended periods following an accident, it is impor- tant that the correct installation procedures be established and consistently

applied. In this case, the installation of the seals according to inadequate

procedures could have resulted in moisture intrusion into more than one safety

component during an accident, leading to equipment failures or the display of

erroneous information to the operators.

Although the vendor's use of wire range sizes to designate the grommets appears

to have been intended as an aid in choosing the proper grommet for the appli- cation, differences in insulation thicknesses because of differences in

insulating materials and type of application were not accounted for by either

the vendor's original instructions or the licensee's initial installation pro- cedures for the grommets. The necessary minimum insulation diameter values

for each grommet size were subsequently provided by EGS Corporation, the sup- plier of the Patel conduit seals. These minimum diameters are also included

in EGS Bulletin 90-1.

This information notice requires no specific action or written response.

If

you have any questions about the information in this notice, please contact one

of the technical contacts listed below or the appropriate NRR project manager.

Charles E. Rossi,lrector

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: T. E. Conlon, RII

(404) 331-5537

N. Merriweather, RII

(404) 331-5577 Attachments:

1. EGS Letter to NRC dated 1/2/90, Enclosing

Product Bulletin 90-1:

Recent Events

Concerning Patel Conduit Seils

- t

2. List of Recently Issued NRC Information Notices

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Attachment 1 IN 90-23

April 4, 1990 January 2, 1990

U.S. Nuclear Regulatory Commission

101 Marietta Street NW

Suite 2900

Atlanta, GA

30323 Attn: Mr. Norman Merriweather

Gentlemen:

In accordance

with our

telephone conversation this morning, we

are

enclosing a copy of EGS Product Bulletin 90-1, "Recent Events Concerning

Patel Conduit Seals, P/N 841206", dated November 7, 1989.

Copies of

the

product bulletin were

sent

to our

utility customers both

by way of

Facsimile and U.S.

Mail.

Subsequently, we

followed

up with personal

telephone calls to each utility's EQ personnel.

The utilities/sites that

have purchased the Patel conduit seal are listed below:

UTILITY

PLANT SITE

Duquesne Light

Carolina Power & Light

Baltimore Gas & Electric

Nebraska Public Power District

Toledo Edison

Omaha Public Power District

Systems Energy Resources, Inc.

Georgia Power Co.

Wisconsin Public Service

Philadelphia Electric

Northern States Power

Consumers Power

Long Island Lighting Co.

Virginia Electric Power Co.

General Public Utilities

Public Service of Colorado

Beaver Valley

Harris/Robinson/Brunswick

Calvert Cliffs

Cooper

Davis Besse

Ft. Calhoun

Grand Gulf

Hatch/Vogtle

Kewaunee

Peach Bottom/Limerick

Monticello

Palisades

Shorehan

Surry

Oyster Creek

Ft. St. Vrain

Please contact us if you need further information.

We would appreciate

the

opportunity

to provide further inputs, especially concerning any notices or

information to be disseminated to the nuclear industry.

Sincerely, Gary J.,El

Productd irector

EGS Corporation 2 150 West Park Loop 2 Suite 301 ? Huntsville, Alabama 35806 = (205) 722-8500 - FAX (205) 722-8533 Knoxville Office c 408 Cedar Bluff Road cSuite 230 2 Knoxville, Tennessee 37923 c (615) 690-6200

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FAX (615) 690-5423

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Attachment 1

IN 90-23

April 4, 1990 MEMORANDUM

TM.

Patel/EGS Customers

FROM'

nary

Elam, Products Director, EGS Corp

SUBJEC1S

DATE.

Product Bulletin 90-1:

Recent Events Concerning Patel

Conduit Seals, P/N 841206

November 7, 1989

i

Grommet Use Rangey

The Patel Conduit Seal was originally supplied starting in 1985.

The

installation instructions were supplied as Patel Drawing A-N-841206-8, Rev. 0 which specified the following:

GRO

MAXIMUM INSULATION DIAMETER (IN.)

GR-12 GR-14 GR-16 GR-18

.170

.150

.135

.120

Implied within these specified maximum diameters is a use range for each

grommet.

Revision E, 3/6/87, of Patel Drawing A-N-841206-8 formally

specified the use range as follows:

GROMMET

NOMINAL USE RANGE:

INSULATION DIAMETER (IN.)

GR-12

.150 - .170

GR-14

.135 - .150

GR-16

.115 - .140

GR-18

.095 - .115 EGS Corporation = 150 West Park Loop , Suite 301 = Huntsville, Alabama 35806 = (205) 722-85002 FAX (205) 722-8533 Knoxville Office 2 408 Cedar Bluff Road:2 Suite 230 = Knoxville, Tennessee 37923 = (615) 690-6200 = FAX (615) 690-5423

Attachment 1

WMORNDUMIN

90-23 MEMORANDUJM

April 4, 1990

November 7, 1989 Page Two

Through discussions this week with one of our customers and the NRC, it

has been brought to our attention that wires with diameters smaller than

those specified have been utilized.

Our experience with the Patel Conduit

Seal indicates that a slightly undersized wire will not degrade the sealing

function.

For instance, Specimen P-1 in Report PEI-TR-841203-12, Rev. A

utilized a GR-16 grommet with wires ranging from .110 to .115 diameter

(.005 below the use range).

The insulation diameter of all wires to be sealed should be measured or

otherwise verified prior to the selection of the grommet size.

The grommet

part numbers (GR-12, GR-14, etc.) do not necessarily correspond with wire

gauge, i.e., a 16 AWG wire may require the use of a GR-18 grommet.

If

further help is required, consult with EGS Products personnel at 205/722-

8500.

In the near future, EGS intends to investigate and possibly extend the

grommet use range.

Loosening of Union Nuts:

At the same utility, the torque on the conduit seal union nuts was verified.

One of ninety conduit seals was found to have a significantly loose union

nut.

In approximately

half of the ninety

seals, the nut moved

approximately 1/4 inch when 50 ft.-lb. torque was applied.

This does not

indicate a degraded seal.

As a precaution, at a convenient time, we

recommend

that all conduit

seal

users

verify

the torque

on

a

representative sample of installed conduit seals.

To verify torque, attempt

to tighten the union nut first at a 40 ft-lb. wrench setting, then at a 50 ft.-

lb. setting.

If the nut doesn't move, it can be concluded that the 50 ft.-lb.

torque is intact.

Be sure to hold the 2 housing halves with pipe wrenches

so as not to disturb or over-torque other joints or electrical device

housings which may be connected to the conduit seal.

gA,,gIa/n.

AMADAWNCID

P Fj.ObMOGF

MEMORANDUM

November 7, 1989

Page TIhree

Attachment 1

IN 90-23

April 4, 1990 Conclusion

We do not believe these conditions are a serious concern in that some

slight variation in wire diameters and union nut torque should not degrade

the sealing function.

All users should be aware of conduit seal use ranges

and torque requirements.

If there is reason to believe that use ranges and

torques are not consistent with our installation procedures, we recommend

a review of your installation procedures and installed configurations.

We

encourage you to seek our inputs.

We are in the process of revising the

conduit seal installation procedure drawing, A-N-841206-8, to include

specific instructions to measure wire diameters.

The drawing will be

forwarded soon.

This bulletin was prepared as a service to our customers

to provide accurate information concerning the conduit seal.

Should you

have further questions, please contact Gary Elam or Johnny Jenkins at

205/722-8500.

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Attachment 2

IN 90-23

April 4, 1990 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information

Date of

Notice No.

Subject

Issuance

Issued to

90-22

90-21

90-20

90-19

90-18

90-17

89-59, Supp. 2

90-16

Unanticipated Equipment

Actuations Following

Restoration of Power

to Rosemount Transmitter

Trip Units

Potential Failure of Motor-

Operated Butterfly Valves

to Operate Because Valve

Seat Friction was Under- estimated

Personnel Injuries Resulting

from Improper Operation of

Radwaste Incinerators

Potential Loss of Effective

Volume for Containment

Recirculation Spray at

PWR Facilities

Potential Problems with

Crosby Safety Relief Valves

Used on Diesel Generator

Air Start Receiver Tanks

Weight and Center of

Gravity Discrepancies

for Copes-Vulcan Valves

Suppliers of Potentially

Misrepresented Fasteners

Compliance with New

Decommissioning Rule

3/23/90

3/22/90

3/22/90

3/14/90

3/9/90

3/8/90

3/7/90

3/7/90

All holders of OLs

or CPs for nuclear

power reactors.

All holders of OLs

or CPs for nuclear

power reactors.

All NRC licensees

who process or

incinerate radio- active waste.

All holders of OLs

or CPs for PWRs.

All holders of OLs

or CPs for nuclear

power reactors.

All holders of OLs

or CPs for nuclear

power reactors.

All holders of OLs

or CPs for nuclear

power reactors.

All materials licensees.

OL = Operating License

CP = Construction Permit