21st Century At Mannings

A progressive engineering company, which started out in general engineering work, is now one of the world leaders in heat treatment, environmental protection and electronic data processing systems.

Mannings Thermal & Environmental Engineers of Southport, UK has its roots in the early 1950s, which is also when Ron Manning, who is now Chairman and Managing Director, joined the family business. At the time their main work was on steel fabrication and engineering service projects. The company’s first diversion into a specialist field came a few years later when a research and development programme was undertaken into heat treatment processes and equipment. Over the years the technology has advanced considerably to meet the requirements of the modern manufacturing industry. By continual product development and investment Manning now manufacture a wide range of heat treatment products and have specialist expertise available, which is in demand worldwide. A recent expansion in their furnace heat treatment division took place by the acquisition of Excel Heat, which has also provided them with a design, production and service base in the West Midlands.

In the 1980s Mannings established close links with an environmental company and were able to add an advanced design of air filters to their product range and the Mannings Environmental Division was established. The environmental business has rapidly developed and is now a well-known and respected name in environmental testing, odour abatement, ventilation and other specialist areas.

Data Collection and processing activities developed from Mannings extensive use of computerised control and data logging and this has led the company into new and interesting markets where Mannings have gained international recognition.

Heat Treatment

Although heat treatment is simply a process of heating and cooling, the underlying changes which are included in materials under different conditions are much more complex.

For this reason equipment and techniques are often developed for individual application and Mannings make the proud boast that they can solve any heat treatment problem.

Although blacksmith have used heat in the manufacturing of iron implements for many centuries modern processes are very much more sophisticated.

Electric Surface Heating Equipment

Mannings are probably best known for the range of equipment, which they manufacture for sale and hire for on-site heat treatment processes. Power sources, mobile transformers and temperature controllers are available as well as self-contained heat treatment centres, fully automatic programmers and temperature recorders. A wide variety of heating elements are also produced such as flexible ceramic pad heaters, finger elements, tank track heaters, channel heaters, pipe butt clamp-on heaters and braided heaters.

Heat treatment units have been designed for a sub-sea operation and Mannings also supply cables, connectors, thermocouples, insulation and all the necessary accessories required for all the electric surface heating projects. The complete range in shown in a comprehensive catalogue available in different languages and all equipment can be purchased on-line from the web site.

Nuclear Industry Heat Treatment

One of the largest and most complex contracts for the supply of electric surface heating equipment was for BNFL’s Sizewell A Power Station. The whole project involved removing and replacing a large circumferential weld on three of the four boilers associated with the second Magnox Reactor and most of the equipment used for the heat treatment process was provided by Mannings.

The preheating and postweld heat treatment of each boiler was a critical part of the project and this was carried out by Didcot Heat Treatment Ltd of Abingdon who allocated a total of 84 engineers for the operation. Over 12,000 ceramic pad heaters were supplied and these were arranged to suit the contours of the shell and to fit around obstructions on the surface, such as tubes and nozzles. Mannings also supplied over 100 heat treatment centres, as well as special recorders and other equipment, including over 200 miles of cable.

More than 800 temperature-measuring thermocouples were fixed to each weld and a computerised monitoring system was used to show, instantaneously, the individual and average weld temperatures. Detailed computer printouts were produced and the temperature of every segment was adjusted to maintain the profile required. The operation needed an enormous amount of electrical power and ten 11 KVA transformers were required for the task.

Aircraft Maintenance

In the aircraft industry it is necessary to repair any small flaws in engine casings and expertly stress relieve by heat treatment before engines can be allowed back into service. In an industry, which demands the highest technical standards, this stress relieving process must be carried out under carefully controlled and monitored conditions.

For this reason GE Aircraft Engine Services Ltd of Nantgarw, Cardiff installed Mannings purpose built electric heat treatment centre which can stress relieve several very small areas of metal components simultaneously at high temperatures in confined spaces. The maximum temperature, which can be achieved, is 1000°C and the heated zone can be kept to a minimum size. Before being awarded the contract, Mannings carried out a study of the technical requirements and prepared a report of their recommendation.

The heat treatment unit is housed in a portable, skid mounted steel cabinet. It has a separate programmer for each of twelve independent heating zones and is fitted with all the necessary monitoring instrument, indicators and alarms. Two chart recorders with selectable channels allow a permanent record of up to 48 separate temperatures to be obtained from sensing elements fixed to the work piece. A feature of the system is the array of heating elements provided with the unit. These are critical to the stress relieving process since they direct energy to the location where it is required. The elements are marked with the engine repair type so that similar heat treatments can be easily replicated.

Furnace Heat Treatment

Mannings have designed and manufactured standard and specialised furnaces for numerous heat treatment processes and custom-built furnaces for many advanced applications where heat treatment is carried out under controlled conditions. Heavy firebrick refractory linings have been placed with low thermal mass insulation and heating is usually by gas, oil or electricity. By the use of fully automatic furnace control systems it is possible to achieve very accurate temperature control and fuel savings of up to 47% are experienced with modern furnace compared to the traditional firebrick designs. Mannings also offer ‘self build’ furnace and ovens, which are economical solutions for customers who have their own technical and assembly capabilities. As part of a self build package Mannings supply manufacturing and assembly drawings as well as the main components and the necessary installation, maintenance and operating instructions.

Furnaces are manufactured in a variety of configurations to suit the particular situations such as Roller Hearth, Roller Cover, Top Hat, Bogie Hearth, Multiple Hearth and many more. In addition special furnaces are continually being developed to suit modern heat treatment applications, for example those providing controlled atmospheres.

Mannings also operate a 50 tonne heat treatment furnace at their factory in Southport, which is probably one of the largest in the country.

HYDRAULICS INDUSTRY

A high efficiency furnace supplied by Mannings to the Midlothian works of MacTaggart Scott & Co Ltd is an example of how modern high efficiency design and controlled temperature uniformity can lead to energy savings and production improvements.

The furnace, which is fired by natural gas, was designed to produce temperature uniformity within very tight limits, so that a variety of metal components could be stress relieved to a high standard, in the minimum amount of time.

MacTaggart Scott & Co Ltd is known all over the world as designers, manufacturers and installers of hydraulic machinery. Their range includes winches and motors for the mining industry as specialised marine hydraulic equipment. Before the installation of the new heat treatment furnace, it was necessary to subcontract stress relieving of critical components.

The furnace is a Roller Cover type, which was installed into an existing production line. The furnace base and one of the end walls are permanently fixed in position. However the furnace cover is mobile so that it can be moved to allow clear access for loading the parts to be heat treated, and unloading the finished items. The cover is mounted on rails, which ensures accurate positioning and powered movement is by means of an electric drive motor.

Loads of up to five tonnes can be treated and the heat source is from two, low-level nozzle mix gas burners arranged to fire in parallel. These burners are modulated in response to the signal from a plc in the control panel to achieve the desire set temperature. This temperature is extensively monitored by sensing devices to ensure maximum efficiency.

Electric Furnace

Advances in electric furnace technology have dramatically reduced running cost and modern designs provide a quiet and cool working environment and have a relatively short payback time. As a result, many foundries are now installing their own heat treatment facilities, which enables them to have better control over their output and to reduce production cost. Balfour Beatty Rail Engineering Ltd, Midland Foundry based in Nottingham, installed an Excel Heat electric furnace, which has enabled them to carry out their own heat treatment of cast components and reduce cost at the same time. The furnace incorporates the latest development in thermal insulation and control systems to meet demanding technical requirements of this application.

Excel Heat have been manufacturing electric furnaces for almost 30 years and is a Division of Mannings Thermal and Environmental Engineers who are one of the UK's leading heat treatment specialist companies.

For further information please contact Mike Kealy, Excel Heat, Oak Street, Quarry Bank, Brierley Hill, West Midlands, DY5 2JQ. Telephone: 01384 560713 Fax: 01384 411742 E. mail mike@excel-heat.com

The new in-house facility in used to carry out stress relieving and annealing and allows direct control over quality and delivery time. As well as this, the added flexibility makes it possible to quickly and economically reschedule production, if required, to meet urgent demands.

The furnace has a sheet steel casing, which is internally lined with ceramic fibre to save energy and minimise weight. The electric heating elements are arranged in four groups and their support are manufactured from sintered aluminium. To minimise the heat treatment cycle time and reduce running costs the furnace is fitted with two fans. A re-circulation fan provides convection, which assists rapid and uniform heat distribution, and a separate cooling fan comes into operation, under controlled conditions, during the later part of the heat treatment cycle.

The components to be heat-treated are placed on the furnace base, positioned directly on the shop floor. To allow all-round access to the base, the entire furnace can be raised up, guided by steel posts so that the components can be easily loaded and unloaded. The furnace control panel incorporates programmable logic and the required cycle is automatically followed and monitored once it has been selected by the operator. A facility has been included in the control panel design, which will delay the automatic start up of the furnace, if required, until the low tariff electricity period begins.

An additional feature of the new furnace is the capability to carry out the heat treatment process in an inert atmosphere. This prevents cast iron components from scaling during treatment and avoids the necessity of shot blasting every piece once it comes out of the furnace. To achieve this, nitrogen can be fed to the furnace chamber at a controlled rate and at different points in the treatment cycle to exclude the possibility of air entering the furnace and prevent oxidisation.

Site Heat Treatment And Refractory Curing

When it is not possible to use a conventional furnace to carry out the heat treatment on a large site built vessels the answer is to turn the vessel itself into a huge furnace by thermally insulating the outside and to use the internal fired technique. Gas-fired burners can achieve this and Mannings have developed a Portable Gas Fired High Velocity Combustion Unit, which is specially designed for on-site heat treatment and refractory curing. When it is not possible to use a conventional furnace to carry out the heat treatment on a large site built vessels the answer is to turn the vessel itself into a huge furnace by thermally insulating the outside and to use the internal fired technique.

Gas-fired burners can achieve this and Mannings have developed a Portable Gas Fired High Velocity Combustion Unit, which is specially designed for on-site heat treatment and refractory curing. On many of these applications it is necessary to ensure high volume low temperature conditions at the start of an operational cycle. The combustion unit can achieve this since it can produce a stream of heated air and combustion gasses at high velocity to promote turbulence and give good convective heat transfer. Because of the extremely high turndown capability of the burner, it is possible to keep the airflow constant over a wide range and regulate the heat output by simply adjusting the fuel consumption.

Giant Pressure Vessels

These burners were used when Mannings successfully completed the post weld heat treatment of two giant steel pressure vessels, which were probably the largest ever, built in the Middle East.

The vessels were identical 19 metre diameter spheres used for strong liquefied propane at the Abu Dhabi National Oil Companies LPG Blending Facilities at Ruwais. Each sphere weighs approximately 500 tonnes and has a shell thickness of over 50mm.

To achieve the correct post weld heat treatment on each vessel the temperature of the whole sphere had to be raised gradually to 620°C and held at this temperature for a set period of time before being cooled at a specific rate.

During this heat treatment cycle it was essential that temperature uniformity was maintained over all areas of the entire construction within set limits.

Al Khaja Pimex awarded Mannings the contract who are a specialist heat treatment company based in Dubai and who were responsible for the entire job of Preheating and Post Weld Treatment. Al Khaja Pimex connected over 60 thermocouples at intervals around the sphere surface so the temperature could be carefully monitored and recorded. Mineral wool insulation was then applied to the outside to surround the shell and this was firmly secured in place.

All of the temporary service were put in place such as orange, scaffolding, lighting and power and two of Mannings specialist combustion engineers then carried out the final preparation before commencing the heat treatment process which took three days to complete on each sphere. The gas used to fire the burners, had to be delivered to the site by tankers and approximately 28 tonnes of fuel gas was required on the project.

Ian Adamson who is Mannings International Sales Manager said to be able to raise over 50 tonnes of steel to a temperature of 620°C and keep it uniformity to within 15° is an excellent achievement and the successful completion of this contract is a credit to all concern”.

Induction Heating

The latest technology, which Mannings can now offer, is induction heating. They use a method, which applies patented technology for the rapid removal of large turbine bolt, and this has significantly reduced maintenance downtime for power generation specialists.

The new process uses low voltage electromagnetic induction heating to apply heat where it is needed, to cause bolt expansion. As a result, all of the bolts on a typical HP turbine can be loosened and tightened within a ten-hour shift, which reduces expensive down time.

The new induction heating system uses a water-cooled wand, which is inserted inside the bolt itself. A variable frequency power supply is then applied to produce heat, which causes expansion between the threaded areas and allows the securing nuts to be removed by hand or by normal hand tools. In this way intense heat is directed into a small space in a short amount of time.

An important additional feature of the water-cooled wand is that, once the operation is complete the wand is cooled and can be removed safely. Steve Smith, who is in charge of induction heating at Mannings said, because the power requirement is substantially less for the overall process than the traditional high output cartridge heater, unnecessary heat transfer to other parts of the machinery is minimal.

Energy Savings Of The Future

Methods of saving energy in manufacturing processes are continually being sought as companies strive to reduce costs. Mannings have discovered that cost savings are often accompanied by faster production rate. This is because improved methods of heat distribution and control can lead to faster heat transfer and reduced energy consumption.

Even although the basic principles of heat treatments have bee applied for over 3000 years there is still considerable scope for technological advances in this essential process.