EMKA 1100 program of Swing Handles is under continuous development

The EMKA 1100 program of Swing Handles is under continuous development to meet the needs of specialist panel builders in the UK. This widely configurable range provides a structured set of key options, a small number of fixing hole formats and is designed to facilitate the interchange of most application components between different models, e.g. rod systems, cams, cylinders and key options, to suit the needs of equipment manufacturers and installers.

1100 program handles have also now been developed for operation as part of EMKA's innovative electronic lock system. In addition we have recently seen the introduction of the 1154 type as a vandal-resistant handle in both die-cast and stainless steel. Both with the handles recessed into the cabinet for additional security.

The 1100 series has been developed over many decades to give a broad coverage of customer needs - based initially on "the right sized handle to suit the door". There are now five visually different groupings to suit varying cabinet styles.

Swing Handles were originally designed by EMKA for improved safety, looks and ergonomics, recently progress has been with a focus even more on safety, by further reducing the front protrusion when closed - such that now only a total 9mm is normal.

Long term evolution of this dynamic product range has encouraged the production of many specialist variants, e.g. push button, non-keyed, padlockables, combination locks, electronic lock and now more than 16 different cylinder variants - as well as the ability to accept other manufacturers cylinders, a requirement often found where large national users need to meet specific security policies or for national/international organisations who wish to standardise their security arrangements.

Naturally customised developments incorporate the standard modules wherever possible, e.g. by use of standard components in a special body to meet unusual design criteria, thus enabling customers to use differentiated body styles to provide brand recognition, customer logos and corporate colours for mouldings or paint finishes.

Present designs of 1100 Swing Handles utilise PUR polyurethane injected foam gasket for enhanced sealing and longevity - it also greatly aids speed of installation.

For further information, e-mail: emka@emka.co.uk or view website: www.emka.co.uk to download  the EMKA product catalogue.   Refer to page 94

New Parker hoses increase profitability in industrial applications

Parker Hannifin, the global leader in motion and control technologies, has launched three new hydraulic hoses, developed to minimise maintenance and increase profitability across a wide range of industrial applications. These are the PowerLift 477, the ideal hose for crane and lifting equipment, the RemoFlex 412, a pilot line hose with an increased working pressure of 12.0 MPa, and the Push-Lok Plus 801, the new low pressure hose with a higher working pressure and an extended colour range.

The new Parker PowerLift 477 medium pressure hose has been specifically developed for the crane and lifting equipment market, where increased working pressure and restricted space are the driving factors for hydraulic hose technology. The Parker PowerLift features two steel wire braids, and offers a combination of higher working pressure, smaller outside diameter based on compact hose construction, tight bending radius and light weight. In addition, the nitrile inner tube offers increased chemical resistance to bio oil and the outer cover is resistant to abrasion, providing longer service life and reduced overall equipment costs.

The RemoFlex 412 is a highly flexible pilot line hose for an increased constant working pressure of 12.0 MPa and meets the requirements of modern hydraulic control systems mainly used in mobile applications. The hose combines an abrasion and ozone resistant cover with a small outside diameter and excellent fluid compatibility through a nitrile inner tube. The RemoFlex 412 is ideal for many industrial sectors, especially in space restricted mobile construction equipment.
           
The Push-Lok Plus 801 is a new low pressure hose from Parker with a higher working pressure and extended colour range. The hose features Parker's Push-Lok® self-grip system, which makes assembly easy and fast with no need for tools or clamps; as a result, assembly time and stock levels can be noticeably reduced. The hose is available in seven colours to simplify identification, production processes, control of maintenance intervals and stock planning. The long service life of the Push-Lok hose, in combination with its continuously high performance, have made it the market leader in the low pressure market. Push-Lok fittings are available worldwide and are made to DIN, BSP, SAE, JIC and ORFS in steel, brass and stainless steel.

For more information, view website: http://www.parker.com or its investor information website: http://www.phstock.com

New bearing surface coating
and ceramic rolling elements reduce
premature bearing failure in large electric motors

A new surface coating for rolling element bearings has been developed by Schaeffler that insulates the bearings from damage caused by the passage of electrical current in large AC or DC motors.

Schaeffler's Isotect® A coating is an insulating layer for rolling element bearings that can be applied to the outer or inner ring external surfaces. Alternatively, depending on the application, the bearings can be assembled with ceramic rolling elements.

In the past, bearings used in large AC or DC motors with only a few pairs of poles were prone to damage from the passage of electrical current. Today, due to the increasing use of frequency converters, this potential danger is growing. Around 3 per cent of all electrical machines manufactured worldwide are controlled by a frequency converter. This figure is expected to rise to 10 per cent over the next couple of years.

Isotect® A acts like a resistor and capacitor connected in parallel. With DC voltage and low frequency AC voltage, the choice depends on the ohmic resistance of the bearing. With higher frequency AC voltage, which is often found in frequency converters, it depends on the capacitive reactance of the bearing. To ensure good insulation, the ohmic resistance should be high and the capacitance should be as low as possible.

Depending on the operating temperature, Isotect® A has a high resistance ranging from several Ohm up to 10Gohm. To allow for the capacitive resistance of bearings used with a frequency converter, Schaeffler has selected not only the appropriate material for the insulating layer, but also the most suitable layer thickness, which both play a key role in ensuring optimum protection.

As capacitance is derived from the surface area of the protective layer and its thickness, the coating is applied to either the inner or outer ring external surfaces, depending on the application. If operating conditions require even higher protection, Schaeffler offers rolling element bearings assembled with ceramic rolling elements across most of its bearing range.

Types of bearing damage
There are typically two types of bearing damage caused by the passage of electrical current: 'fluting' and 'welding beads' (or craters).

Fluting is relatively easy to identify and runs transverse to the raceway. The washboard appearance of the resulting pattern represents the final stage of the destruction of the raceway in a bearing exposed to the passage of electrical current. Fluting can be caused by either a continuous flow of electrical current, EDM (electro-discharge machining) or high frequency electrical current.

Welding beads or craters represent the early onset of raceway destruction and the initial stages of fluting. Identifying craters and welding beads requires detailed examination of the structural changes that have taken place in the bearing rolling surfaces. This is greatly simplified by the use of a scanning electron microscope.

Current-related bearing raceway damage is typically caused by 'classic bearing current', in other words, the asymmetrical distribution of magnetic flux in mains-operated AC or DC machines, as well as to converter-induced bearing current (which occurs in the form of circular current, EDM current and rotor earth current).

Classic and converter-induced bearing current can severely damage the raceway structure and the lubricating grease, either through continuous current flow or in the form of voltage flashover and discharge. Capacitive bearing current found in converter operation is considered as harmless.

In electrical terms, a bearing can be thought of as simply a connection between resistance and capacitance of the lubricant. When the elasto-hydrodynamic (EHD) condition (i.e. the complete separation of the rolling elements by the lubricant) is achieved during operation, the bearing behaviour is capacitive. In this case, the lubricant acts as an isolator, preventing the passage of electrical currents up to a specific threshold value.

However, under conditions of mixed or boundary friction, the electrical behaviour of the bearing changes and is considered as an ohmic resistor. Here, the lubricant does not completely separate the rolling elements, resulting in roughness peaks and metal-to-metal contact. This can cause a continuous flow of electrical current through the bearing. During such periods of contact, the rolling elements fuse with the rolling surfaces for a short time and immediately break apart again due to the dynamics of the bearing. During this process, extremely fine metal particles are torn away from the bearing raceway and the rolling element surfaces, mixing with and contaminating the lubricant. These metallic particles are then rolled into the raceway, forming a new layer that does not have the same hardness as the original surface. The problem is exacerbated by system-related vibration and fluting.

Discharge flashes
Even though a protective lubricant layer may prevent a continuous flow of current through the rolling elements, converter operation can cause electrical discharges that penetrate the lubricant film. These 'discharge flashes' blast fine metal particles out of the rolling surfaces, producing 'craters' with welding beads. The resulting metallic particles add to lubricant contamination. When the number of metal particles reaches a certain level, new contacts and bridges can be formed in the contact zones. Therefore, the process takes the same course as continuous current flow, resulting in fluting.

Experience gained by Schaeffler using its own and independent research has established that current densities of less than 0.1 A/mm² do not represent a danger to bearings. However, current densities at or above 1 A/mm²often lead to eventual raceway damage.

Not every bearing in an electrical machine will need to be fitted with one that has current insulating properties. With mains-operated machines, it is often sufficient to replace only one bearing with a current-insulated bearing in order to avoid possible current damage. However, when frequency converters are used, it is normally necessary to fit current-insulated bearings in several bearing locations. For further information, e-mail: info.uk@schaeffler.com    Refer to page 99