API 653 Exam Chapter 13

API 653 Exam Chapter 13 Introduction to Welding/API RP 577

13.1 Module introduction

The purpose of this chapter is to ensure you can recognize the main welding processes that may be specified by the welding documentation requirements of ASME IX. The API exam will include questions in which you have to assess a Weld Procedure Specification (WPS) and its corresponding Procedure Qualification Record (PQR). As the codes used for API certification are all American you need to get into the habit of using American terminology for the welding processes and the process parameters.

This module will also introduce you to the API RP 577 Welding Inspection and Metallurgy in your code document package. This document has only recently been added to the API examination syllabus. As a Recommended Practice (RP) document, it contains technical descriptions and instruction, rather than truly prescriptive requirements.

13.2 Welding processes

There are four main welding processes that you have to learn about:

  • Shielded metal arc welding (SMAW)
  • Gas tungsten arc welding (GTAW)
  • Gas metal arc welding (GMAW)
  • Submerged arc welding (SAW)

The process(es) that will form the basis of the WPS and PQR questions in the API exam will almost certainly be chosen from these.

The sample WPS and PQR forms given in the non mandatory appendix B of ASME IX (the form layout is not strictly within the API 653 examination syllabus, but we will discuss it later) only contain the information for qualifying these processes.

13.2.1 Shielded metal arc welding (SMAW)

This is the most commonly used technique. There is a wide choice of electrodes, metal and fluxes, allowing application to different welding conditions. The gas shield is evolved from the flux, preventing oxidation of the molten metal pool (Fig. 13.1). An electric arc is then struck between a coated electrode and the workpiece. SMAW is a manual process as the electrode voltage and travel speed are controlled by the welder. It has a constant current characteristic

Figure 13.1 The shielded metal arc welding (SMAW) process
Figure 13.1 The shielded metal arc welding (SMAW) process

13.2.2 Metal inert gas (GMAW)

In this process, electrode metal is fused directly into the molten pool. The electrode is therefore consumed, being fed from a motorized reel down the centre of the welding torch (Fig. 13.2). GMAW is known as a semi-automatic process as the welding electrode voltage is controlled by the machine.

Tungsten inert gas (GTAW)

This uses a similar inert gas shield to GMAW but the tungsten electrode is not consumed. Filler metal is provided from a separate rod fed automatically into the molten pool (Fig. 13.3). GTAW is another manual process as the welding electrode voltage and travel speed are controlled by the welder.

Submerged arc welding (SAW)

In SAW, instead of using shielding gas, the arc and weld zone are completely submerged under a blanket of granulated flux (Fig. 13.4). A continuous wire electrode is fed into the weld. This is a common process for welding structural carbon or carbon–manganese steelwork. It is usually automatic with

Figure 13.2 The gas metal arc welding (GMAW) process
Figure 13.2 The gas metal arc welding (GMAW) process
Figure 13.3 The gas tungsten arc welding (GTAW) process
Figure 13.3 The gas tungsten arc welding (GTAW) process

the welding head being mounted on a traversing machine. Long continuous welds are possible with this technique.

Flux-cored arc welding (FCAW)

FCAW is similar to the GMAW process, but uses a continuous hollow electrode filled with flux, which produces the shielding gas (Fig. 13.5). The advantage of the technique is that it can be used for outdoor welding, as the gas shield is less susceptible to draughts.

13.3 Welding consumables

An important area of the main welding processes is that of weld consumables. We can break these down into the following three main areas:

  • Filler (wires, rods, flux-coated electrodes)
  • Flux (granular fluxes)
  • Gas (shielding, trailing or backing)

There are always questions in the API examination about weld consumables.

Figures 13.6 to 13.11 show basic information about the main welding processes and their consumables.

Figure 13.4 The submerged arc welding (SAW) process
Figure 13.4 The submerged arc welding (SAW) process
Figure 13.5 The flux cored arc welding (FCAW) process
Figure 13.5 The flux cored arc welding (FCAW) process
Figure 13.6 Welding consumables
Figure 13.6 Welding consumables
Figure 13.7 SMAW consumables
Figure 13.7 SMAW consumables
Figure 13.8 SMAW consumables identification
Figure 13.8 SMAW consumables identification
Figure 13.9 GTAW consumables
Figure 13.9 GTAW consumables
Figure 13.10 GMAW consumables
Figure 13.10 GMAW consumables
Figure 13.11 SAW consumables
Figure 13.11 SAW consumables

Now try these two sets of familiarization questions about the welding processes and their consumables.

13.4 Welding process familiarization questions

1.

Q1. API 577 section 5.2
How is fusion obtained using the SMAW process?

 
 
 
 

2.

Q2. API 577 section 5.1
Which of the following is not an arc welding process?

 
 
 
 

3.

Q3. API 577 section 5.3
How is fusion obtained using the GTAW process?

 
 
 
 

4.

Q4. API 577 section 5.3
How is the arc protected from contaminants in GTAW?

 
 
 
 

5.

Q5. API 577 section 5.4
How is fusion obtained using the GMAW process?

 
 
 
 

6.

Q6. API 577 section 5.4
Which of the following are modes of metal transfer in GMAW?

 
 
 
 

7.

Q7. API 577 section 5.6
How is the arc shielded in the SAW process?

 
 
 
 

8.

Q8. API 577 section 5.6
SAW stands for:

 
 
 
 

9.

Q9. API 577 sections 5.3 and 3.7
Which of the following processes can weld autogenously?

 
 
 
 

10.

Q10. API 577 section 5.3.1
Which of the following is a commonly accepted advantage of the GTAW process?

 
 
 
 

11.

13.5 Welding consumables familiarization questions

Q1.
In a SMAW electrode classified as E7018, what does the 70 refer to?

 
 
 
 

12.

Q2.
Which of the following does not produce a layer of slag on the weld metal?

 
 
 
 

13.

Q3.
Which processes use a shielding gas?

 
 
 
 

14.

Q4.
What type of flux is used to weld a low hydrogen application with SAW?

 
 
 
 

15.

Q5.
What shielding gases can be used in GTAW?

 
 
 
 

16.

Q6.
Which process does not use bare wire electrodes?

 
 
 
 

17.

Q7.
Which type of SMAW electrode would be used for low hydrogen applications?

 
 
 
 

18.

Q8.
In an E7018 electrode, what does the 1 refer to?

 
 
 
 

19.

Q9.
Which of the following processes requires filler rods to be added by hand?

 
 
 
 

20.

Q10.
Which of the following processes uses filler supplied on a reel?

 
 
 
 

Click Here To Read Next API 653 Exam Chapter 14 – Welding Qualifications and ASME IX

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