Nexen answers your questions
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What happened to Horton Manufacturing Inc.?
What are the requirements for the actuating air?
Is there an optimal air pressure?
How much air must my compressor generate?
How do I connect air to this unit?
Are there points requiring special attention during the mechanical design process?
What should I keep in mind during the mechanical design process?
Are these components CE certified?
What is the difference between red, green, purple or blue paint marks on the friction facings?Why do nexen brakes have a shorter stopping distance while they are slower to react?
Why do Nexen brakes run cooler?
How do I order spare parts for my Horton or Nexen product?
What happened to Horton Manufacturing Inc.?
Till 1999 Horton Inc. had two main activities : Cooling systems for diesel engines and clutches and brakes for industrial motion control. To gain more focus on each of the product groups the owners of the company decided to split the two activities. The people and the manufacturing facility dedicated to industrial motion control products were assigned to a new company which received the name: Nexen group Inc. while the other division became Horton worldwide (www.hortonww.com)
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The name Nexen is based on the Latin word “nexus” which means connection or link. Just as our people and products are essential links to our customers and their products. Additionally the letters “nex” suggest the word “next” appropriate for a company like ours that is moving forward, energized and committed to our customers. Our strengths of the past are the foundation of our future.
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What are the requirements for the actuating air?
Nexen recommends the use of filtered (40µ), lubricated and regulated air (max 8 bar). All seals are lubricated prior to assembly but operating an air engaged or disengaged product with non lubricated air may create o-ring seal wear in cyclic applications or corrosion of the internal parts when the air carries some moisture. Air preparation is critical when operating with non-lubricated air. Filter the air to 5µ and maintain a dew point of 4°C or lower, make sure to select a control valve that operates without lubrication too.
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Is there an optimal air pressure?
All components are designed to hold pressures up to 8 bar, for optimal o-ring and bearing life however it is recommended not to exceed 5.5 bar. The optimal air pressure depends from the application. Elements like reaction time, required torque and available air pressure can influence your choices. As a rule of thumb the pressure should be chosen as low as possible for the task.
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How much air must my compressor generate?
Our components are designed with great care to avoid any air leaks; this means they do not consume air as long as they do not switch status. With every cycle a certain volume of compressed air is consumed, equal to the volume of the air chamber and the air lines between the control valve and the unit. If you multiply the volume of the air chamber, with the number of cycles/minute and multiply this by 7 if you work at 6 bar then you will find the volume of free air (l/min) required.
The torque our components transmit does not depend from the air flow but from the air pressure which means air line diameters can be chosen as small as practical.
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How do I connect air to this unit?
Most Nexen products have a bearing mounted air chamber, which means the air inlet does not rotate with the rest of the unit (no need for rotary air unions and gun drilling of the shafts). These products are supplied with a flexible hose which can cope with the strain created by the bearing drag.
Mount the air connection in the 6 o’clock position (pointing to the floor) whenever possible. This allows draining any moisture that might otherwise get trapped in the air chamber.
On most clutches the air chamber will move axially when the clutch engages, make sure the piping you use is flexible enough to allow these displacements. The friction in the bearings supporting the piston will also create a certain drag. To avoid breaking of the air line we recommend the use of the steel reinforced hoses supplied with the clutch or the use of a fork shaped anti rotation device around the air connector. This device should stop the piston from turning but shall not impede the axial movement of the piston.
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Are there points requiring special attention during the mechanical design process?
Many nexen products are designed for easy friction facing replacement. To take full advantage of this feature one should foresee easy access to the screws and enough clearance to remove the facings or sub-assemblies without having to take the complete unit out of the equipment.
See above paragraph regarding the air line connections
Safety first!
All power transmission products are potentially dangerous and should be guarded and installed in according with applicable regulations. Pictures on this web site show products without guards, only for illustration and clarity purpuses.
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Are these components CE certified?
Nexen pneumatic clutches and brakes are not machines or systems in the sense of the EC machine directive 98/392/EC and therefore do not require the CE marking. For these components Nexen can provide a manufacturer’s declaration in accordance with the EC machine directive 98/37/EC, Appendix IIB
All components that fall under other EC directives ( e.g. EMC) have the CE certification.
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What is the difference between red, green, purple or blue paint marks on the friction facings?
Nexen offers a variety of friction materials; this means the torque of Nexen products can be tailored to the application needs.
Each material has a specific friction coefficient. The higher this friction coefficient, the higher the torque your unit will produce but also the higher the wear on the disc and the friction lining. Lower friction coefficients will reduce the wear in a very significant way and will also reduce the noise levels.
Our catalogues and web site only post the static torque of the component fitted with standard facings (unless otherwise specified) to calculate the torque of the other versions please see the graph and the table below.
|
| Torque* | WHEN | WHY |
| Standard | 100 % | All round, cyclic stopping | Best compromise torque ↔ wear |
| Hico | 140 % | E-stop, Holding, Maximal torque | High torque in a small package. Disc and facing wear will be higher! |
| Loco | 60 % | Continuous slip, soft stop, tension control | Low noise, low disc and facing wear |
| Ultra Loco | 32 % | Low speed or high precision tension control | Hardly no “stick-slip” at low speed, or to improve the cooling capacity/torque ratio |
* Static torque expressed in % of the values published in our catalogues, dynamic torque is 85% of static torque (dashed lines)
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Brake squeal is caused by resonance in the mechanical components of the brake. Elements that increase the noise are: a high friction coefficient and high hardness of the friction material, the own frequency of the disc, the absence of dampening in the brake structure, low speed.
All nexen brakes are designed to be silent, special attention went to the mechanical dampening. That is one of the reasons why nexen uses cast iron discs, the cushioning of the air in the piston as well as the rubber material of the o-rings have a positive effect as well.
Friction materials are made from organic resins filled with fibers and elements that will increase or reduce the friction coefficient. If the brake is used at high temperatures but low contact pressures there will not be enough wear to regenerate the contact surface and glazing may occur. A glazed friction material will have a much higher tendency to produce brake squeal. The best remedy is to replace the friction material by a material with a lower friction coefficient, this will require higher contact pressures for the same performance and the friction reducing additives usually have a positive effect on glazing as well.
If you wish to avoid the “bang” when the brake is applied you may remove the return springs and reduce the air flow towards the brake. This might increase the brake drag when the brake is released.
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Why do Nexen brakes have a shorter stopping distance while they are slower to react?
It is true that compared to an electromechanical brake the air controlled units have an extra delay before the torque starts to build up, caused by the reaction time of the valve and the physical process of inflating or deflating. The reaction time however is not the only element that determines the total stopping distance. The deceleration rate is the critical element and this is determined by the available dynamic torque. The torque build-up is literally “explosive” and nexen brakes often offer more than twice the dynamic torque of it’s competitors which means the stopping distance is less than half.
To improve the reaction time of an air actuated brake, make sure to use a fast valve with enough air flow, but also keep the air lines short and with a minimum of elbows. The supply pressure should be close to 6 bars.
For spring applied brakes we recommend the use of a quick exhaust valve mounted on the air inlet of the brake.
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Why do nexen brakes run cooler?
Do you remember the riddle of the bath tub with the running tap and the drain? How long will it take till the tub flows over?
Well we have increased the capacity of the tub and increased the drain rate. No wonder the level in the tub stays lower: Nexen brakes have ventilated cast iron discs, these discs can absorb more heat than the thin steel discs of electromagnetic brakes. The cooling fins and the open architecture of our units result in a much higher heat transfer rate.
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How do I order spare parts for my Horton or Nexen product?
Each nexen (formerly Horton) component is uniquely identified by a 6-digit Part Number (e.g. P/N 950150) This P/N defines, model, size and all options like bore size, friction material and surface finish. If you supply this 6-digit P/N you are certain to receive the exact replacement part.
Most nexen products can be completely rebuilt. Nexen offers kits containing wear parts: facing kits (containing friction facings and their mounting screws) or repair kits (containing bearings, o-rings, springs and maintenance instructions). Most of the time these kits contain all the parts you need to give your unit a new life. All other parts like discs or housings are available as individual parts as well.
At the back of our repair and installation manuals you will find a parts list with an exploded view of the product like shown below. 
Please provide the P/N of the complete unit (e.g. 800100) and the item numbers you require (e.g. item 13 and item 18) your nexen partner will then convert these into nexen Part Numbers.
Maintenance manuals can be downloaded on the www.nexengroup.com website.
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