Page 9 of catalogue Needle valves of Erhard GmbH & Co. KG

undercut piston. All these features together form an optimum sealing system with minimum wear. The inner shaft seal has also be further improved and an additional sealing element has been added, which contributes to optimisation of the corrosion protection and at the same time additionally helps to prevent stagnant water. Four hard-faced guides – a positive result for longer life By using four wide guide strips, the force of the weight of the piston acts vertically and thanks to the larger

contact surface is also uniformly spread over the guide strips, while, e.g. if only three strips are used, nonuniform attrition and far greater wear occurs. The material used is a bronzealuminium alloy, which has proven its worth for decades in high-pressure Needle valves. Its high hardness properties, assured application thickness of around 3 mm and the extreme wear resistance ensure good anti-friction properties – even for decades long operating periods and no matter what the installation position. The face hardening also further increases corrosion resistance, as the homogeneous material structure does not provide any points for corrosion to attack. Large linear control range – a positive gain for controllability While the usual needle Valves to date frequently have a dead stroke of up to 18 %, the ERHARD RKV Premium needle valve can be precisely controlled from 4 % opening. It therefore enables optimum control of even the smallest quantities without critical annular clearance and a large control range of up to 96 %. The optimised control performance is also assisted by the ERHARD SKG slider crank mechanism, used as a standard, which has an optimally adjusted characteristic torque curve and therefore supplies the suitable torque in every opening angle. A slower closing speed near the “closed” position enables extremely soft closing and eliminates the risk of pressure surges.

In conjunction with the ERHARD SKG slider crank mechanism, the result is a control range of 96 %.

The four hard-faced guides ensure permanently uniform movement of the piston.

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