General Informations

1. In checking the quality of weld, what are the pros and cons of various

non-destructive weld inspection methods i.e. ultrasonic test, radiographic inspection
and magnetic particle flaw detection test?
Currently, there are three common non-destructive testing of weld, namely radiographic
inspection, ultrasonic testing and magnetic flaw detection test.
The method of radiographic approach was used commonly in the past until the arrival of
ultrasonic inspection technique. The major difference between the two is that ultrasonic
testing detects very narrow flaws which can hardly be detected by radiographic method.
Moreover, it is very sensitive to gross discontinuities. Tiny defects, which characterize
welding problems, are normally not revealed by radiographic inspection.
Moreover, ultrasonic inspection possesses the advantages that it can accurately and
precisely locate a defect as well as figure out its depth, location and angle of inclination.
In the past, it was expensive to adopt ultrasonic means for inspection. Nowadays, the rates
for both inspection methods are comparable. Most importantly, the x-ray and gamma ray
used in radiographs are radioactive and pose potential safety hazard to testing technicians
on site. Reference is made to Paul G. Jonas and Dennis L. Scharosch.
Magnetic flaw detection test can only be used for checking flaws in any metallic objects.
This method is commonly used for inspecting surface cracks and slightly sub-surface
cracks. However, surface and sub-surface cracks can be readily detected by radiographs
and ultrasonic inspection.

2. Is the procurement of third party insurance necessary to be incorporated in
contract for construction works?
The purpose of third party insurance is to protect contractors from bankruptcy in case there
are severe accidents happened to the third party due to the construction work. Therefore, in
government contracts, contractors are requested contractually to procure third party
insurance from the commencement of contract until the end of Maintenance Period. If
contractors have the financial capability to handle the claims due to accidents to third party,
the client is not bound to include this requirement in the contract.

3. What is the difference between sureties and security?

In construction contracts, if a contractor fails to perform the works, the employer would
suffer from severe financial loss and therefore some forms of protection has to be
established in the contract.
For surety bond, the contractor obtains a guarantee from a third party i.e. a bank or an
insurance company, which in return for a fee, agrees to undertake the financial
responsibility for the performance of contractor’s obligations. This third party will pay to
the employer in case there is a contractor’s default.
For security, a sum of money is deposited in the employer’s account and upon satisfactory
fulfillment of contractor’s obligations, the sum will be repaid to the contractor