What are the NDE Required for heavy wall Stainless Steel Pipe after Full welding?

The NDE requirements can be done as per  "Muhammad Usman Asghar Rana" . Apart from the NDE requirements mentioned by him we can also want to perform Ferite number Test and PMI to confim the ferrite number and metal composition after welding.

• The only methods for demagnetization that I have seen work include heat treatment and magnetic induction. Heat treatment can be performed with electric resistance coils or an oxy-fuel torch, heating
• the pipe to a dull cherry red and holding it at that temperature for several minutes, then allowing to cool to ambient over a long period of time. The other method is usually effective and much
• simpler and does not affect the metallurgical integrity of the pipe as heat input can. This method includes taking the positive welding lead and coiling it around the pipe near the joint to be welded.
• Several coils should be made tight to the pipe and each other, then induce current through the lead by welding for a few minutes on a piece of scrap or something just to allow current flow through the
• coiled welding cable. You are essentially turning the pipe into a big electromagnet by doing this. If it doesn't work the first time, try reversing the direction that the lead is coiled around the pipe and induce currrent flow again. More often than not, this will demagnetize the pipe enough so that the weld can be made. (Uncoil the leads from around the pipe before making the pipe weld)

Having mentioned stainless steel as material of pipe, depending upon diameter and thickness UT Scaning, UT gauging can be applied 

LPI for surface and must be do UT and RT for volumatric test of heavy wall thickness

Introduction to Detection and evaluation of flaws tubular products   WROUGHT TUBULAR PRODUCTS are nondestructively inspected chiefly by eddy current techniques (including the magnetic flux leakage technique) and by ultrasonic techniques.
In general, the eddy current and magnetic flux leakage techniques are applied to products not exceeding1020 mm (40 in.) in diameter or19 mm ( in.) in wall thickness.
On the other hand, ultrasonic inspection is used on tubes ranging from3.2 to2030 mm ( to80 in.) in diameter and from0.25 to64 mm (0.01 to2 in.) in wall thickness.
However, there are many exceptions, and the range of special techniques and applications associated with each inspection method is large.
Most welded and seamless tubular products arenondestructively inspected by the manufacturer at the mill.
The many uses to which steel tubular products have been applied form a basis for classifying steel tubular products; for example, the terms casing, tube, and pipe are assigned on the basis of usage, as in water-well casing, oil-well tubing, and drill pipe.
A second classification is based on methods of manufacture.
Accordingly, all steel tubular products can be classified as either welded or seamless.
A third classification applicable to special shapes can be considered subordinate to both of the general classifications above.
The major applications of the nondestructive inspection of tubular products are: · Detection and evaluation of flaws · Sorting of mixed stock · Measurement of dimensions · Comparative measurement of specific physical and mechanical properties Of these, the primary application is the detection and evaluation of flaws.
Sorting is often an auxiliary application employed for grade or size verification and can be based on chemical composition, dimensions, physical and mechanical properties, or other significant variables.
A difficulty encountered in sorting arises when variables of little or no interest affect instrument indications to a greater degree than do the variables of interest.
Several applications involving the measurement of dimensions and physical properties are described in this article.
Others, such as the measurement of coating thickness and the non contact measurement of wall thickness and variations in diameter, require highly specialized instrumentation.
Additional information on the inspection of pipe and pipelines, including the examination of field-welded girth welds, is available in the articles "Weldments, Brazed Assemblies, and Soldered Joints" and "Boilers and Pressure Vessels".
  NDE detection methods Visual (surface) Replica (surface) Liquid penetrant (surface) Magnetic particle (surface and subsurface) Eddy current Microwave Ultrasonic Radiography X-ray computed tomography Neutron radiography Thermography Optical holography Speckle metrology Digital image enhancement (surface The many uses to which steel tubular products as defect that went to detected in Pipeline Inspection Remote visual inspection using a robotic crawler.
Radiography of weld joints.
The part is placed between the radiation source and a piece of film. 
The part will stop some of the radiation. 
Thicker and denser area will stop more of the radiation.
The film darkness (density) will vary with the amount of radiation reaching the film through the test object      

Mr Osama Abdalla answered thoroughly and coverd all NDT Methods.
As per my openion in such a case i.e heavy wall stainles steel pipe after full welding (thickness not mention) inspector must know the thickness of the part being inspectd through NDT Methods.
However, one can perform Ultrasonic inspection to find out presence of flaw in welding.
       

it will depend on the typr of the Joint, in case the joint is a T joint with fillet weld then an MPI test will be suitable.

in case the joint is a full penetration T joint or Butt Joint, UT or RT will be suitable.