leak test for plant operators - christopher gamblin.pdf

8/11/2019 Leak Test for Plant Operators - Christopher Gamblin.pdf

1/40


2/40

Discussion Scope

LT Method and BLT Techniqueapplication for those employeesthat are not needing certification to

a code and standard.

2


3/40

(d) Examination before shipping. (1) No person may

offer for transportation a tank car containing ahazardous material or a residue of a hazardousmaterial unless that person determines that the tankcar is in proper condition and safe for transportation.

As a minimum, each person offering a tank car fortransportation must perform an external visualinspection that includes:

CFR 173.31 (d)

3


4/40

Divided into three main categories by American

Society of Non-Destructive Testing.Leak Detection,Leak Location,Leak Measurement

Bubble Leak Testing is an example of both LeakDetection, and Leak Location.

Leak Testing Methods

4


5/40

Three common LT techniques for tank car

inspection:Bubble leak testing liquid film (BLT)Chemical Reactivity (CRLT)Pressure change or Pressure Decay

Three Techniques of LT

5


6/40

LT is a form of NDT that uses either a pressurized or

evacuated system to detect the location of leak andpossibly measure the leakage through the leak.

LT when compared to other methods, either surface

(MT, PT) or Volumetric (UT, RT), has a higherdegree of sensitivity to locate the leak or measureleakage.

Leak Testing

6


7/40

Leak;

Physical hole that exists and not the quantity of fluidpassing through.

Leakage:

The flow of fluid through a leak without regard tophysical size of the hole through which flow occurs.

Leak Testing Definitions

Source: ASNT NDT Handbook, 3rd Edition. Volume 1; Leak Testing


8/40

Term leak tight is relative. Nothing is truly leak tight

and different terms should be used.Terms no detectable leakage, no leakage, or zeroleakage truly represent the desired condition beforeshipping a tank car.

Everything leaks, absolute tightness is onlytheoretical in practice. Nothing made by humans cantruly be absolute leak tight.

Leak Tight

8


9/40

Leak Path

9


10/40

LT techniques are measured in leak rates. Thesmaller the leak rate detected, the higher thesensitivity.Examples of minimum detectable leak rates:

Leak Rates/Sensitivity

10

Ultrasonic Leak Detector 10 -1 std cm 3 per second

Bubble Leak 10 -3 std cm 3 per second

Mass Spectrometer detectorprobe

10 -5 std cm 3 per second

Radioactive Isotope 10 -8 std cm 3 per second



11/40

Quantity (mass) of a gas leaking in one second.Volume equal to three dimes stacked vertically.

1 std cm 3 per second

11

10 -2 10 seconds

10 -3 100 seconds

10-5

3 hours10 -8 1 year

10 -12 3000 years



12/40

(Economic) To prevent material loss that interferes

with system operation.

(Safety) Prevent fire, explosion, and environmentalcontamination.

(Reliability) Detect unreliable components, andthose with leakage rates that exceed standards.

Reasons for Leak Testing

12


13/40

LT is an important process to the measure the

reliability of the system under test.

LT can show a fundamental fault of the system.High leakage rates in specific areas may determine:

Gasket improperly alignedValve connections misaligned or improperly threaded

System Reliability

13


14/40

LT is not a direct measurement of continuing system

reliability, only a measurement of the reliability at thetime of testing.

Primary use of LT for railroad tank car industry is to

detect installation errors.

System Reliability

14


15/40

LT sensitivity depends heavily on the skill level andalertness of the LT operator.

LT operators must be trained in the fundamentals ofLT to ensure they are performing a LT correctlyeach time.

Common errors:Operators do not look at test joint for an acceptableperiod of time

not identify all possible leak paths

LT Operator Training

15


16/40

Training plans for LT operator personnel should

include:Disadvantages and advantages of LT methodsIdentify hazards with LTEnhancing testing environments

Techniques for improving inspection skillsFactors affecting LT measurement accuracyProper ways to carry out and conduct LT methods

LT Operator Training

16


17/40

Leak Testing technique must be of proper sensitivity

for scope of test, and also be economical value forthe technique to be desirable for application.

Bubble Leak testing accomplishes both of these

criteria, and represents most of the LT performed inthe RR Tank Car Tank industry.

Bubble Leak Testing

17


18/40

Three techniques classified by the how the liquid

used for detection is applied:

Liquid ImmersionLiquid FilmFoam application

Bubble Leak Testing

18Source: ASNT NDT Handbook, 3rd Edition. Volume 1; Leak Testing


19/40


20/40

BLT allows observer to distinguish real leaks from

virtual leaks.

Virtual Leaks are those in which trapped gases areescaped during a test and are observed.

Safe to apply BLT with proper inert gases, andtesting liquids, in combustible areas.

BLT Advantages



21/40

When performing BLT, or any LT technique beyond

its limitations, it renders the test inaccurate and theresults dangerously false.

LT

BLT Limitations

21


22/40


23/40

Importance of cleaning test surface

Cleaning a tank car connection prior to performing aLT should include as a guideline:

Remove by safe means any sings of rust, grease,

oxide films, or other visible surface contaminants.

BLT Limitations Surface Cleaning

23


24/40

Non-technical applications of LT can cause ordinary

soap and water combination to be used.

While economical, these testing solutions diminishthe sensitivity of the test, possibly causing them to

be lower than 10 1 std cm 3 per second .

Example: Dishwashing soap and water

Commercial vs HomemadeBLT Solutions

24


25/40

Limitations of Common Soap for BLT

Soaps form sticky, gummy deposits that can clogleaks. Bath tub ringSoaps are alkaline; pH values of 10.5 to 11.5. Cancause severe corrosion to Aluminum Alloys.

Soaps contain chlorides and borates. These cancause stress corrosion cracking on stainless steels ortitanium alloys. Many valves are SS or 22 Ti.




26/40

Commercial BLT solutions are favorable over soapand water when compared:

Have pH between 6-8Do not form deposits when mixed with hard waterViscosity allows low surface tension, allows BLTsolution to spread over surfaceStabilized solutions are resistant to bacteria andmaintain sensitivity over long periods of time

Allow BLT solution to dry to a clean stateTemperature range -30F to over 150F




27/40


27


28/40


28


29/40


29


30/40

First and foremost, safety is key in working withloaded tank cars or any pressurized vessel.

Along with tank car shipping location safetystandards, LT safety briefings should include thesetopics:

Working with pressurized vesselsHazards with going on top of, or below tank car.

Process Steps for BLT

30


31/40

Clean areas of interest to BLT. Remove dirt, slag,

rust, or any foreign debris.

Consideration of the cleaning chemical must betaken in consideration for compatibility with BLT

solution.


31


32/40

Create pressure differential. Creating a highpressure side, and lower pressure side will startleakage to flow.

General guidelines state that a minimum of 15 psig

(210 kpa) be used as a starting pressure.




33/40

Temperature should be checked prior to applyingthe BLT solution.

Use IR or contact thermometers. Must be betweentemp limits of BLT solution.


33


34/40

Apply BLT solution.

Flow solution over test area, not creating bubbles inthe processDo not brush or spray unless LT solution is designedfor such application!

Gently flowing solution over area will allow completecoverage. Care should be taken to observe thesolution as it is applied.


34


35/40

Allow BLT solution to Dwell on the test area for aspecific amount of time.

Usual Dwell times are 5min -10min

After Dwell time has elapsed, inspect area for

bubble formation


35


36/40

Inspection should be done in a adequateenvironment to get the best results for the test.Improve the environment to increase the sensitivityof the test:

Increase lighting

Better position to keep view angle at 0-15If possible, improve temperature, wind, humidityUse BLT solutions that have higher visibility


36


37/40

Test joint must show no bubble formation to beconsidered to pass the leak test

BLT will show bubbles collapsing and reforming toindicate a leak

Inspection

37


38/40

LT procedure should be written by an ASNT Level III

Allows for uniform application by all LT operatorsSpecifies the minimum requirements for conductinga test

A procedure should list all aspects of the LT that are

essential to be metCan provide reasonable certainty that a specificsensitivity is being met

LT Procedure

38


39/40

Procedures should include:

Cleaning requirementsLT solutionTemperature limitsTest Pressure

Acceptable leak rates (Acceptance Criteria)Reporting of a leakCleaning practice

LT Procedures



40/40

CONTACT INFO

Christopher Gamblin:Watco Compliance Services, LLC

EMAIL: [email protected]:713-703-5123

THANK YOU!

leak test for plant operators - christopher gamblin.pdf

Documents