CSWIP NDT WELDING

STRIP CLADDING SUBMERGED ARC STRIP CLADDING ELECTROSLAG STRIP CLADDING

strip cladding

INTRODUCTION TO STRIP CLADDING

Cladding is a welding process in which a material with desired properties is deposited on the surface of a base material. The common C/Mn or low alloyed inexpensive base metal has mainly a load carrying function. The deposited sophisticated material imparts surface properties such as corrosion resistance, wear resistance, etc., to the substrate.
To the manufacturer of pressure vessels, surfacing techniques are getting more and more important. Components reach sizes such that their fabrication calls upon the use of clad materials.
There are different processes to obtain a clad material :
– clad plates produced by rolling which are mostly only available in standardised dimensions and grades
– explosion clad plates
– clad plates made by welding
Among all the welding processes submerged arc and electroslag strip cladding offer maximum deposition rate, better bead characteristics and trouble free operation using unsophisticated welding equipment. Strip cladding is also a very flexible process covering a very wide range of applicable materials.
The fact that in general it is used to clad finish shaped components eliminates the eventual problems arising with cold or hot forming.
The principle of strip cladding was developed about 70 years ago (the first patent was granted in the USA around 1920) but in Europe the process retained detailed attention when the nuclear industry started (late 1950’s).
The nuclear power industry needed a method whereby thick- wall pressure vessels could be given a corrosion resistant inner surface.
Several modifications of submerged-arc welding with strip have been developed mainly with a view to further increase surfacing capacity.
In the first part of this paper the SUBMERGED ARC STRIP CLADDING process will be discussed, in the second part the ELECTROSLAG STRIP CLADDING technique will be described. The influence of the working parameters will be given and the main advantages and limitations will be listed.

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RADIATION SAFETY QUESTION ANSWERS NDT CSWIP COURSE

Keywords for this article are RADIATION SAFETY QUESTION ANSWERS NDT CSWIP COURSE. radiation protection materials. radiation safety officer. radiation hazards and protection.

RADIATION SAFETY QUESTION ANSWERS NDT CSWIP COURSE

Several isotopes of elements such as hydrogen and carbon exist in nature. The isotopes of any given element differ only in terms of:
  • the number of protons in the nucleus
  • the number of alpha particles in the nucleus
  • the number of neutrons in the nucleus
  • chemical properties
The difference between x-rays and gamma rays of equal photon energy is:
  • the wavelength of the gamma rays is shorter
  • x-rays originate from an x-ray tube whilst gamma rays originate from a radioactive material
  • the gamma rays are more hazardous to health
  • the gamma rays have a higher velocity than the x-rays
If an ytterbium 169 has a half life of 32 days and the original source activity is 5 Ci, what will the source activity be 96 days later?
  • 5 Ci
  • 25 Ci
  • 625 Ci
  • 3125 Ci
The type of radiation that has a quality factor of 20 is:
  • gamma radiation
  • beta particles
  • alpha particles
  • x-radiation

 

When a radiation incident occurs, such as a gamma ray source becoming jammed in the delivery tube the most sensible way to proceed is to:

 

  • monitor the area until the safety officer arrives
  • after first of all securing the situation – if possible covering the source with bags of lead shot, adjusting safety barriers etc – make a plan of the actions that will be needed to make the source safe
  • bury the equipment under several meters of earth
  • call the fire brigade

 

Which isotope has a half life of 5.3 years?

 

  • cobalt 59
  • cobalt 60
  • cobalt 62
  • cobalt 70
Exposure to ionising radiation can have “genetic effects”. Such effects are best described as:
  • those which can appear in the offspring of the person exposed to radiation
  • effects such as headaches and diarrhoea which occur soon after an acute exposure to ionising radiation
  • effects such as cancer which may not appear in the subject until some years after exposure to ionising radiation
  • none of the above

 

The law that can be stated as: is called:
  • the Bunsen Roscoe reciprocity law
  • the inverse square law
  • the build-up law
  • Hooke’s law

 

The proportion of scattered radiation increases as:
  • the photon energy of the primary beam decreases
  • the photon energy of the primary beam increases
  • the intensity of the primary radiation decreases
  • the intensity of the primary radiation increases

 

Gamma ray equipment including wind-outs and projection tubes should be checked for leakage of fissile material on a regular basis; records of such checks should be maintained on file. The type of radiation monitor that is usually used for such checks is a:
  • Geiger counter
  • scintillation counter
  • proportional counter
  • ionisation chamber
An alpha particle is sometimes referred to as:
  • an electron
  • a helium nucleus
  • a proton
  • an electron – positron pair

 

Under the ionising radiation regulations the category of persons which has an annual dose limitation of 20 mSv is:
  • trainees
  • classified persons
  • radiation protection advisers
  • the general public
One important factor concerning the warning signals used when performing radiography on site is that:
  • a combination of audible and visible signals should be used
  • audible and visible signals should be used both before and during exposure
  • the warning signal signifying “radiation exposure imminent” and the warning signal signifying “radiation exposure in progress” should be different
  • an audible warning of at least 120 decibels is required prior to exposure

 

If the dose rate at 10 m from a source of radiation is 20 mSv/h the distance from the source at which the dose rate falls to 7.5 mSv/h will be:
  • 4 m
  • 3 m
  • 9 m
  • 8 m

 

The term used to describe a large dose of ionising radiation received in a relatively short period is:
  • an acute exposure
  • a somatic exposure
  • a genetic exposure
  • a brief exposure

 

One advantage of the Geiger Muller tube is that:
  • its volume is relatively small. This makes it useful for locating leakage paths in radiation bay shielding.
  • it operates at a low electrical voltage. Typically 12 V.
  • it can distinguish between high energy and low energy x-rays
  • it is exceptionally sensitive to alpha radiation
The device used in gamma radiography to restrict the size of the radiation beam, thus improving safety and reducing scatter problems is called a:
  • focusing cup
  • collimator
  • mask
  • diaphragm
A source of cosmic radiation is:
  • the sun
  • the earth
  • iridium 192
  • californium 257
Devices which record total radiation dose over a period include TLD badges, film badges and:
  • scintillation counters
  • electronic integrating personal dosimeters
  • Geiger counters
  • both (b) and (c)
In order to obtain a reading of radiation dose from a TLD badge the badge must be:
  • heated
  • exposed to UV-A radiation
  • placed in a powerful magnetic field
  • placed in a high voltage electric field
Concerning the emission of gamma rays which of the following is true?
  • All radioisotopes are gamma emitters
  • Some radioisotopes emit gamma rays and no other type of ionising radiation
  • Some radioisotopes emit gamma as a by-product of alpha or beta emission
  • Gamma rays are emitted only by man-made radioisotopes

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