Profile: Bluelimit Surveys Limited offers inspection & testing services to the petro-chemical, oil and gas industries. We use NDT technology in areas, such as construction engineering, petro-chemicals, shipbuilding & repair & public utilities, including the nuclear industry, as well as offshore oil and gas installations. We are accredited to ISO 9002 quality systems. We also offer hardness testing and heat treating surveys. Our hardness surveys can be carried out either in-house or on site. Preheating involves raising the temperature of the parent material to a value above ambient on either side of a joint to be welded. Post weld heat treatment (stress relieving) is used when required by the fabrication specification code and verified by the WPS. It involves raising the temperature of the weld and the heat affected zone uniformly & in a controlled manner. The primary purpose is to reduce residues and internal stresses caused by welding, quench hardening or cold working.