Leak Testing

Question 1

Which of the following systems or components would require the greatest precautions and special considerations when preparing for a leak test?

A. Piping and pressure vessels

B. Refrigeration piping

C. Vacuum chambers

D. Sintered material components

Answer 1

1) - D

Question 2

Pressure change leak testing is dependent on three variables. A change to any of these three will have a direct effect on at least one of the other two variables. These three variables are:

A. pressure, volume, and pumping speed.

B. pressure, volume, and temperature.

C. volume, temperature, and ambient atmospheric pressure.

D. temperature, pumping speed, and fluid viscosity.

Answer 2

2) - B

Question 3

Which of the following is an LT technique?

A. Static

B. Gaseous diffusion

C. Dynamic

D. Detector probe

Answer 3

3) - D

Question 4

Which of the following LT techniques can reliably quantify a leak ≤1.0 × 10–7 atm cc/sec in a normal industrial environment?

A. Bubble leak testing

B. Pressure change leak testing

C. Mass spectrometer leak testing

D. Liquid penetrant testing

Answer 4

4) - C

Question 5

Establishing differential pressure between the test object and the environment is an essential element in which of the following NDT methods?

A. X-ray diffraction

B. Leak testing

C. Neutron radiography

D. Electromagnetic testing

Answer 5

5) - B

Question 6

Which of the following best describes the LT technique in which the interior of the test object is continuously evacuated during the test, a tracer gas is applied to the exterior, and a leak detector is connected to the vacuum system?

A. Static leak test

B. Helium leak test

C. Dynamic leak test

D. Halogen leak test

Answer 6

6) - C

Question 7

Assuming no significant leakage in a constant-volume system, if the temperature increases during a pressure-drop leak test, the pressure in the system will:

A. increase.

B. remain the same.

C. decrease.

D. first decrease, then increase to its former level.

Answer 7

7) - A

Question 8

If the sensitivity of a halogen leak detector remains constant throughout a test, and the pretest and posttest calibrations are acceptable, which conclusion can be made?

A. No leaks smaller than a certain size have gone undetected.

B. Total leakage rate is less than a certain amount.

C. Instrument and procedure capable of detecting leakage of a certain size.

D. Detection only upstream of tracer gas.

Answer 8

8) - C

Question 9

All leak detection techniques are dependent upon:

A. barometric pressure.

B. oxygen content.

C. other gases in mass spectrometer.

D. establishing differential pressure.

Answer 9

9) - D

Question 10

Outgassing is defined as:

A. release of gas from materials in a vacuum.

B. proportional to gas temperature.

C. viscosity of pressurizing gas.

D. drop in test pressure due to leakage.

Answer 10

10) - A

Question 11

Essential information for pressure change leak test:

A. Helium concentration, leak response, background

B. Barometric pressure, start/stop time, temperature

C. Temperature, elapsed time, volume, pressure

D. Mean free path, viscosity, pressure differential

Answer 11

11) - C

Question 12

Easiest way to increase sensitivity:

A. Change instrumentation.

B. Turn down thermostat.

C. Use environmental chamber.

D. Increase test time.

Answer 12

12) - D

Question 13

Using 50% helium instead of 100% will:

A. increase

B. decrease

C. produce no change

D. invalidate

Answer 13

13) - B

Question 14

Variable NOT recorded in vacuum decay test:

A. Pressure

B. Volume

C. Temperature

D. Elapsed time

Answer 14

14) - C

Question 15

Final calibration 40% greater than preliminary:

A. Nothing

B. Recalibrate and repeat

C. Increase duration

D. Increase helium concentration

Answer 15

15) - B

Question 16

Most important safety precaution:

A. Remove flammables

B. Calibrate detector

C. Stand clear, PPE

D. Secondary containment

Answer 16

16) - C

Question 17

Best technique for low‑pressure fluid vessels:

A. Bubble leak testing

B. Helium vacuum mode

C. Pressure change testing

D. Mass spectrometer

Answer 17

17) - A

Question 18

Fine leaks in hermetic components:

A. Helium mass spectrometer

B. Bubble immersion

C. Halogen diode

D. Pressure gauge monitoring

Answer 18

18) - A