pipe questionnaire.docx

Q.

What is the purpose of hydrogen bake-out? When should hydrogen bake-out should ideally be carried out? Which international code provides a reference to hydrogen bakeout?

A.

Purpose is to allow hydrogen to diffuse from the weld and thus mitigate the potential for hydrogen assisted cracking, which is more likely to occur in alloy steels where martensite is formed during cooling. Hydrogen (as H20) is more prevalent in flux coated/cored electrodes and submerged arc fluxes. Hydrogen is dissociated through the arc into hydrogen and oxygen and thus transferred into the weld. Hydrogen bake-out should be carried out immediately after weld completion to avoid delayed cracking. If low hydrogen welding consumables are used, hydrogen bake-out is not necessary till Grade P22. Referencing code for hydrogen bake-out is AWS D10.10

Q.

For carrying out PQR testing as per AWS D1.1, shall PQR be qualified with destructive testing or with Non-destructive testing and destructive testing both?

A.

Both non-destructive and destructive testing need to be carried out to qualify PQR, as per clause 4.9.2.1 of AWS D1.1 2015.

Q.

A333 Gr 6 material has been procured for a project for which construction code has been specified as ASME B31.3. Supplier has provided absorbed energy values for impact test in MTC. a) What is the criteria for acceptance of impact test as per ASTM and ASME B31.3? b) What should be impact test temperature? c) Should the material be accepted?

A.

a) Acceptance criteria as per ASTM is absorbed energy impact values whereas fir ASME B31.3, the criteria is lateral expansion values. b) Impact test temperature shall be as per ASTM, since material falls under the purview of ASTM and ASME B31.3 also approves material procurement as per ASTM. c) Yes, material can be accepted provided all provisions of ASTM are met.

Q.

As per ASME B31.3, if stresses produced during hydrotest exceed yield stress of a material, what shall be the re-calculated hydrotest pressure?

A.

As per 345.4.2 clause c , the lower of 1.5 times the design pressure and pressure limited by yield strength of material.

Q.

In a certain PQR for SMAW, the electrodes used for all passes were of AWS classification E7018 and corresponding WPS also showed filler material as E 7018. Manufacturer now proposes to use E7015 instead of E 7018? Is requalification of PQR required?

A. Q.

Why Carbon percentage cannot be detected by X ray fluorescence method?

Q.

A welded part is to be radiographed and is 1” thick with 1/8” reinforcement. What ASTM wire set IQI shall be used on radiographs if a source side technique is used?

Q.

What will happen if UT thickness readings are taken on a base material whose temperature is above 90 degree Celsius? a)Thickness readings will be lower b) Thickness readings will not change c) Thickness readings will be higher

Q.

What are the requirements for PED job?

Q.

Explain step by step process for executing ASME section I code job?

Q.

Can pre-heating be used in lieu of Post weld heat treatment for repairs, alteration and weld metal build-up?

A.

Yes, as per API 570 8.2.2.1

Q.

What is the WRC diagram? What is it used for?

A.

WRC is the welding research council 1992 diagram established for calculating the nickel and chromium equivalent of the weld metal in question. It is also known as the Schaeffler diagram. The drawback of this method is that chemical composition of weld should be known prior to calculation.

Q.

What should be the ferrite number for austenitic SS material?

A.

Austenitic SS material has practically non-existent ferrite content.

Q.

What method of hardness testing for PQR is mandated by NACE MR0103 for PQR testing?

A.

Vickers hardness Test.

Q.

Welder qualification test has been carried out as per ASME sec IX in austenite SS material. Is the same welder qualified to weld CS material? IS the same welder qualified to weld duplex SS material?

A.

No welder cannot weld CS material due to deletion of backing which is an essential variable. Since P number of Duplex SS is P10H, welder can weld duplex SS.

Q.

As a quality engineer, what precautions other than safety shall be taken during hydrotest of piping assembly?

Q.

What are the requirements during PQR testing when impact test is an essential variable?

Q.

What is the difference between SS 304, SS 316L and SS321?

Q.

What type of heat treatment shall be carried out on SS321H pipe?

A.

Stabilizing heat treatment

Q.

What is simulating heat treatment?

Q.

What is the standard followed for thermocouple placement for local heat treatment?

Q.

What is geometrical unsharpness? What is the formula for calculating geometric unsharpness?

A.

Ug = f * t/d Where: f = X-ray generator focal spot size t = the thickness of the material d = distance from x-ray source to front surface of material/object

Q.

What is dead zone in ultrasonic testing?

A.

In ultrasonic testing, the interval following the initial pulse where the transducer ring down prevents detection or interpretation of reflected energy (echoes). In contact ultrasonic testing, the area just below the the surface of a test object that can not be inspected because of the transducer is still ringing down and not yet ready to receive signals.

Q.

What is snell’s law?

A.

Snell’s law is a formula used to describe the relationship between the angles of incidence and refraction, when referring to light or other waves passing through a boundary between two different isotropic media, such as water, glass, or air.

i is the angle of incidence and r is the angle of refraction. This constant value is called the refractive index of the second medium with respect to the first. Q.

What are the essential variables in SMAW welding as per WPS?

Q.

Concentric reducer is used in pump suction (Yes / No) Explain.

A.

No. Air pockets may form if concentric reducer is used at pump suction, which results in cavitation and cause damage to pump. To avoid this problem, Eccentric Reducer with flat side up (FSU) is used in Pump Suction.

Q.

What are the common welding defects? What are the common reasons for porosity?

A.

Lack of penetration, Lack of fusion, Undercut, Slag inclusion, Porosity, Crack, Faulty weld size & profile, Distortion. The presence of gas pores in a weld caused by entrapment of gas during solidification is termed as porosity. The pores are in the form of small spherical cavities either clustered locally or scattered throughout the weld deposit. Sometimes entrapped gas give rise to a single large cavity called blowholes.

Cause : A.

Chemically imperfect welding consumables, for example, deficient in deoxidiser.

B.

Faulty composition of base material or electrode, for example, high sulphur content.

C.

Presence of Oil, grease, moisture and mill scale on the weld surface.

Q.

D.

Excessive moisture in the electrode coating or submerged- arc flux.

E.

Inadequate gas shielding or impure gas in gas – shielded process.

F.

Low welding current or too long an arc.

G.

Quick – freezing of weld deposit.

What is the depth of penetration in steel by cobalt – 60, Iridium – 192

A.

A.

Cobalt -

160

:

9 inch

C.

Iridium -

192

:

3 inch

Q.

What is the relation between exposure time & film distance?

A.

The exposure time (T) is directly proportional to the square of the focus to film distances (D). The equation is expressed as: T1 = D12 T2 D22

Q.

How the Radiographic films are classified?

A.

The Radiographic films are classified as:A.

Class

-

I

:

Highest contrast, lowest speed.

B.

Class

-

II

:

High contrast, Low Speed.

C.

Class

-

III

:

Medium contrast, Medium Speed.

D.

Class

-

IV

:

Low contrast, High Speed.

Q. What ASME code is to be followed for edge preparation? Q. What is contamination of stainless steel? What is meant by sensitization of stainless steel?