NON-TRACER GAS METHODS TO EVALUATE ISOLATION DAMPER LEAKAGE Peter Lagus, Ph.D., CIH Lagus Applied Technology, Inc Joe Bendyk Exelon Limerick Station NHUG

NON-TRACER GAS METHODS TO EVALUATE ISOLATION DAMPER

LEAKAGE

Peter Lagus, Ph.D., CIHLagus Applied Technology, Inc

Joe BendykExelon Limerick Station

NHUGChicago, Illinois

July 2008

LAGUS APPLIED TECHNOLOGY, INCORPORATED

ALTERNATIVE TEST(S) FOR

ISOLATION DAMPER LEAKAGE

For reconnaissance test we want “simple” go/no-go test

Want less expensive and less procedurally intensive test than a tracer gas test

Ideally, test to be performed by plant personnel For reconnaissance test, need not have the precision

and accuracy needed during inleakage testing.


CRH ISOLATION DAMPERS


Occur singly or in pairs within a given ventilation train Provide isolation from unfiltered or normal OS Air

intakes Provide isolation of CREVS from adjacent (non-

safety) systems Can contribute significant unfiltered inleakage

MAJOR TYPES OF

CRH ISOLATION DAMPERS

Butterfly Parallel Blade Opposed Blade Expandable Bladder


DAMPER LEAK RATES

Bubble-tight damper spec (ANSI N510) implies 0.011 SCFM allowable leakage

A 0.01 inch opening between two flat 24 inch damper blades will leak roughly 3-4 SCFM with a 5 in. w.g. differential pressure



Damper

Qleak

DAMPER PAIR LEAKAGE TESTDamper

Interval Volume, V

DAMPER PAIR LEAKAGE TEST

Close both dampers and use volume between them as a test chamber

Methods based on ANSI N510– Direct Flow Rate Measurement– Pressure Decay Measurement

Caveat: Testing both dampers simultaneously may INOP the CREVS/CRE. – Depends on system design and plant specs


DIRECT FLOW RATE MEASUREMENT

Provide measured flow rate at appropriate (low) delivery pressure (usually the System Design dP)

Flow for 10 minutes Record flow rate every 30 seconds Compute average flow rate. Required components

– Compressed air source– Delivery regulator– Low pressure (pancake) regulator– Flow Meter


PRESSURE DECAY METHOD

LAGUS APPLIED TECHNOLOGY, INCORPORATED LAGUS APPLIED TECHNOLOGY, INCORPORATED

Pressurize volume to 1.25x System Design Pressure Measure pressure decay at 1 minute intervals for 15 min (or

until pressure decays to 75% of design value) Measure gas temperature in volume at beginning and end VERY Sensitive to Temperature Changes

– 1 Deg F dT can cause approx 10% change in calculated flow!! Calculate leakage rate Required components

– Compressed air source– Temperature sensor– Pressure sensor

» Absolute pressure readings are better» Pressure readings should be corrected for barometric drift

LEAK RATE CALCULATION

Qav=Average Leak Rate (SCFM)

Pi,Pf=Initial and Final Pressures (lb/ft2)

Ti,Tf=Initial and Final temperatures (Deg R)

RA=Gas Constant 53.35 ft-lb/(lb Deg R) dt = time interval (min)


(0.075)dtR

V

T

P

T

PQ

Af

f

i

iAVG


LEAK RATE vs TIME for PRESSURE DECAY TEST (10 in. wg to 2 in. wg)(Interval Volume in Parenthesis)

0.01

0.10

1.00

10.00

0 2 4 6 8 10 12 14 16 18 20

DECAY TIME (min)

LE

AK

RA

TE

(S

CF

M)

(100 Cu Ft)

(50 Cu Ft)

(75 Cu Ft)

(25 Cu Ft)

(10 Cu Ft)

WHAT ABOUT A SINGLE ISOLATION DAMPER?

Previous tests use two dampers to create test volume– Works great if neither damper leaks

If either damper leaks then need a method to measure flow across each separately

Infrequently isolation can be provided by a single damper– Very rare

Test can be qualitative or semi-quantitative test– Use simple test gear– No major intrusion into ductwork/damper area– Short duration test(s)


SINGLE DAMPER LEAKAGE TESTS

Source and Receptor Tests– Use smoke, aerosol, visible light as source– Use appropriate sensing equipment/element

Traverse Tests– Use flow through damper opening to detect leak– Measure flow directly or measure another characteristic of

the flow

Feeler Gauge along Sealing Surfaces– Need access– May affect dP conditions


CAVEATS

No warranty implied or expressed Some of the following test techniques/test equipment

have not been used in the nuclear industry Some of these test techniques/test equipment are

used in other industries to find leakage sites Other test equipment may be more useful or usable

than the equipment shown in the following Theoretically all of the following test techniques

should be capable of finding a leaking damper



(SOURCE & RECEPTOR TESTS)

Smoke Generator plus Borescope (+ light source) DOP Generator plus Light Scattering Photometer Light Source plus Photometer



DAMPER

Qleak

SINGLE DAMPER LEAKAGE TEST

SOURCE

SAMPLE




LIGHT SOURCE FOR GE BORESCOPE


SMOKE GENERATOR FOR DAMPER TEST



AEROSOL GENERATORS


LASKIN NOZZLE AEROSOL GENERATOR

LAGUS APPLIED TECHNOLOGY, INCORPORATED LAGUS APPLIED TECHNOLOGY, INCORPORATED

VISIBLE LIGHT PHOTOMETER


LED LIGHT SOURCE


(TRAVERSE TESTS)

Ultrasonic Probe– At 5 in. w.g. differential across at a 24 inch long by 0.01

inch crack the flow velocity is several thousand FPM– Probe is “tuned” for air leak frequencies

Hot Wire Anemometer Flow Traverse– MUST hold anemometer probe perfectly still!!– Measurement uncertainty is large, but because of the high

sensitivity the measurement shows which damper(s) leaks



ULTRA SONIC PROBE IN USE


ULTRA SONIC PROBE

HOT WIRE TRAVERSE

Measure flow at several traverse points Any indication of flow indicates a leak if the probe is

stationary Probe MUST be stationary

– Use Vent Lok with Thermocouple fitting to clamp the probe

Hot Wire anemometer exhibits sensitivity as low as 5 FPM.– In a 1 ft2 duct this is 5 CFM!



HOT WIRE TRAVERSE TEST

DUCT

VENT LOK WITH SWAGE THERMOCOUPLE FITTING


HOT WIRE ANEMOMETERS

RECOMMENDATIONS

If possible, test dampers pair-wise– Careful NOT to INOP System

If leakage is unacceptable, then use single damper tests to find out which one (or both) is leaking

Single damper tests need not be quantitative since a leak indication is all you are looking for– If you find a “leaker” you gotta bite the bullet and fix it.

Email Joe Bendyk ([email protected]) at Limerick--ask about borescope and smoke test

Email Kevin Fleming ([email protected])--ask for details about DOP + L. S. Photometer test


Documents

NON-TRACER GAS METHODS TO EVALUATE ISOLATION DAMPER LEAKAGE Peter Lagus, Ph.D., CIH Lagus Applied Technology, Inc Joe Bendyk Exelon Limerick Station NHUG