We aim to provide a fully comprehensive heat treatment service to the highest possible standards for a range of gas and electrical techniques and seek inclusion of Site Heat - treatment Services on your approved contractors / suppliers list.
This process involves heating to and holding at a suitable temperature for the material concerned, followed by cooling, usually at a slow or controlled rate. The primary purpose is to soften the material but may also be used to affect other properties or the microstructure. For example other purposed may include machinability, facilitate cold work, modify mechanical properties and relieve stresses. For ferrous alloys, annealing is usually done at temperature above the upper critical limit and can be in the order of 700°C or substantially more. The rate of cooling is normally slow.
As part of the Site Heat - treatment Services Quality System, work instructions/procedures are drawn up to cover all Site Heat - Treatment Services or works operations. The company is pleased to provide such procedural documentation for specific works, on request. There are a number of other engineering services, allied to heat treatment that are offered and which provide technical support and added assurances and are listed below:
- Engineering consultancy services in respect of site and furnace heat treatments for a wide range of welded components.
- Finite element analysis service, thermal and structural, both as support for heat treatment analyses, and more conventional applications.
- Procedural documentation for heat treatment activities.
- Site heat treatment engineering supervision.
- Design and assessment of heat treatment support systems.
- Calibration and maintenance services associated with furnace structures and their associated control instrumentation.
Site Heat - treatment Services offers to its clients the option to hire equipment for weld preheating or post weld heat treatment. All items, which comprise a set of electrical resistance heating equipment, from power source to pad, are available for hire. We would be pleased to discuss your requirement with you, and recommend the most appropriate materials to suit your application.
Heat Treatment Electrical and Gas Method and Equipment(expand)
For bakeout heat treatments Site Heat - treatment Services offers a choice of method by either electrical resistance or high velocity gas techniques - or in some cases, a combination of the two. Both techniques are well proven and accepted throughout the industry. The high velocity gas method lends itself best to the internal heating of large vessels or to the furnace treatment of large components. For more local applications or for vessel sections, it is more likely that an electrical resistance technique would be more suitable. Most of the examples within the Company's experience fall into this category. The fitting of flexible ceramic pad or other heating elements, (rated for safe low voltage operation), to the plate surface, permits automatic zonal control of plate temperature. Accordingly, Site Heat - treatment Services develops a layout and heat treatment procedure designed to meet the requirements of each application. Aspects such as heater type and layout, temperature measurement and control, calibration, safety, insulation method and documentation are addressed within the procedure.
Heat Treatment On Site(expand)
When a heat treatment problem arises, the key to success lies with the ability of the specialist company to respond quickly and efficiently. Prior to any site work, it is vital that clear recommendations provide guidance on the best available technique for the application combined with a competitive approach. For large complex projects, a feasibility study is undertaken by experienced and expert Site Heat - treatment Services personnel to determine the best course of action using the most suitable equipment to provide the desired temperature distribution. Site Heat - treatment Services provides skilled labour and equipment to undertake in situ heat treatments on site. Such heat treatments are usually associated with welding for installation, modification or repairs. It is often localised in nature. Examples of this type of work are the localised heat treatments of pipework butt welds and pressure vessels. A range of standards applies to this work, but the standards below are widely applied. Both electrical resistance and high velocity gas methods are adopted for these on-site activities.
ASME B31.3: 2012
Standard for process piping
ASME B31.1: 2014
Standard for power piping
BS 2633: 1987
Standard for Class I welding of ferritic steel pipework for carrying fluids
BS EN 13480-4:2012+A1: 2013
Metallic industrial piping
Water tube boilers and auxiliary installations
AWS D10.10/D10.10M: 1999, (R 2009)
Recommended practices for local heating of welds in piping and tubing
ASME Code, Section VIII: 2013
Standard for pressure vessel design, fabrication, inspection, testing and certification
BS PD 5500-2012+A3: 2014
Specification for unfired fusion - welded pressure vessels
Welding Research Council Document, WRC 452
Recommended practice for local heating of welds in pressure vessels
Hydrogen Bake - Out(expand)
The hydrogen bake-out process is carried out on plant that has been subject to the uptake of diffusible hydrogen during service. The process is undertaken in advance of any welding operations to reduce the hydrogen content to a safe level prior to the welding operation.
In-House Furnace Heat Treatment(expand)
In-House Furnace Heat Treatment at Site Heat - treatment Services Port Talbot Facility
To supplement the site operations, and to provide a comprehensive service, a heat treatment furnace division has been established at our own premises in Port Talbot. Three furnaces have been established that have been designed for batch heat treatments at temperatures up to 850°C (plus a specialised one which allows temperatures of upto 1050°C) They are utilised on a regular basis for stress relieving, annealing, and normalising of loads. Furnace treatment provides an economic option where an in-situ approach can be avoided. The sizes are as follows:
- Large Furnace: 86 x 63 x 47 Inches / 2184 x 1600 x 1193 mm
- Medium Furnace: 38 x 38 x 54 Inches / 965 x 965 x 1371 mm
- Small Furnace: 25 x 24 x 28 Inches / 635 x 609 x 711 mm
This process involves heating the component to a suitable temperature above the transformation range which can vary with steel composition. The hold period is followed by cooling in still air to a temperature well below the transformation range. This heat treatment generally produces a steel of higher yield and tensile strength than by annealing but with some reduction in ductility.
Preheating For Welding(expand)
Preheat involves heating both sides of a weld joint to a suitable temperature before welding (or thermal cutting) and normally maintaining this temperature throughout the welding operation. Its purpose may be one of several. It may be employed to control the rate of cooling in the HAZ of the weld to reduce hardness, so reducing the risk of cracking or to control the diffusion of hydrogen away from the joint generated from moisture associated with the welding process. Preheating can also be used to limit thermal stresses that may be introduced during welding. For materials of high thermal conductivity such as copper, preheat may be used to compensate for heat losses by conduction away from the joint. The preheat temperature can vary from near ambient to as high as 400°C for alloy steels.
Refractory Dry-Out Or Curing(expand)
Many components, such as pressure vessels, spheres, drums, incinerators and boilers are designed with an internal lining of refractory material in view of service at high temperatures. As-cast sections contain copious amount of moisture. A controlled heating process combined with means for removal of water vapour or steam by forced airflow is generally referred to as a refractory dry-out. Curing may involve higher temperatures.
Solution Heat Treatment(expand)
This involves heating an alloy to a sufficiently high temperature and holding time to cause one or more constituents to enter into solid solution followed by a sufficiently rapid cool to hold these constituents in solution. Austenitic steels are often subject to such treatments at temperatures of 1000°C and higher to prevent a range of problems from reheat cracking to weld decay and stress corrosion.
Residual stresses are built up during the course of a manufacturing process by cold working, grinding or by quenching. Fusion welding also generates residual stresses, as thermal stresses may be introduced by temperature gradients. Technically a part is stressed beyond its elastic limit and plastic flow occurs. The objective of a stress relief heat treatment is to heat the part to a sufficiently high temperature to reduce the residual stresses to an acceptable level. In welding, the term 'Post Weld Heat Treatment' is more widely used, as the purpose of this heat treatment may be to bring about the relief of residual stresses and/or to produce a particular metallurgical structure or material properties.
Post weld heat treatments on ferritic steel welded joints are undertaken at temperatures ranging from 550° to as high at 750°C depending upon the steel type and history.