Merkel PRW 1 Double Wiper with Integrated Pressure Relieve Product Information Merkel Hydraulics
Simrit, Your Global Technology Specialist for Seals and Vibration Control Simrit, Your Global Technology Specialist for Seals and Vibration Control offers you a complete service package. A unique range of products and services guarantees you numerous advantages over the competition. Simrit acts as a partner to general industry. Its position as a market leader is achieved through continuous research, development and manufacture. We have the world s widest range of seals and vibration control products, and can offer you solutions based on the demands of state-of-the-art-technology, solutions which set standards. This way we secure competitive advantages for you based on experience all around the world: Simrit has a presence throughout Europe, America and Asia, either directly or through its affiliated companies NOK (Japan) or Freudenberg-NOK (USA). The transfer of knowledge between these markets is incorporated directly into the Simrit service package. With our many Simrit Service Centres and Simrit distribution Partners, we serve and supply more than 100,000 customers worldwide. Our Simrit Partners ensure rapid availability from stock. This means spare parts quickly arrive when and where they are needed. There is a Simrit Partner near you as well. Make the most of Simrit s service package and give yourself a real competitive edge: Constant innovations Uniquely wide range of products Strong product brands Unique materials expertise A wide range of value added services Simrit offers a complete package of products and services, including leading brands such as Simmerring, Merkel, Integral Accumulator, Meillor and ISC O-Ring. Vibration Control Special Sealing Products: Bellows, Diaphragms, Elastomer Composite Parts and Precision Mouldings Lederer Liquid Silicone Products ISC O-Ring Integral Accumulator Merkel Hydraulics / Pneumatics Simmerring 2
Pressure-relieve double wipers make hydraulic cylinders even more reliable and economical The newly developed Merkel PRW 1 double wiper is a key component of modern Merkel rod seal systems in hydraulic cylinders. This innovative step forward with the PRW (Pressure Relieve Wiper) involves the patented pressure relieve function incorporated in the wiper. This reliably prevents pressure build-up between the seal and wiper. There is no longer any need at all for the pressure relieving bore previously required an economical simplification for the manufacture of hydraulic cylinders. The new Merkel PRW 1 double wiper offers greater functional reliability of the sealing system while simultaneously reducing the total costs of the cylinder. The use of the Merkel PRW 1 double wiper can bring about a marked improvement in functional reliability and tightness compared with a solution involving the very popular single-action wipers. The Merkel PRW 1 double wiper is used by well-known manufacturers and has already proved its worth in a whole range of different applications. 3
Merkel PRW 1 double wiper with integrated pressure relieve Today's requirements on hydraulic seals are reliability and a high level of tightness with a simultaneous reduction in costs. Leak-free operation over the entire operating service life is crucial, particularly in the case of rod seal systems. Modern rod seal systems are made up of components that have been specially coordinated to each other. Fig.1: Modern rod seal system with pressure relieve Merkel PRW 1 double wiper, Merkel U-ring LF 300 and guide ring Merkel Guivex SBK Cost reduction thanks to Merkel PRW 1 double wiper The new Merkel PRW 1 double wiper (Pressure Relieve Wiper) with an optimised sealing and wiping effect features an integrated pressure relieve function. It prevents a critical pressure build-up (> 1 MPa) in the space between the wiper and the rod seal. The pressure relieve function has been incorporated in the outer diameter. This means there is no need for a relieving bore between the double wiper and rod seal (Pat. No: German Patent 100 10524). The dynamic sealing lip of the Merkel PRW 1 double wiper reduces the residual oil film of the rod seal, avoiding undesirable wiper leakage. The Merkel PRW 1 double wiper has been developed for housings based on DIN/ISO 6195 type A (detailed information in article list on page 7). Segmented front face provides for pressure relieve Static sealing lip (1) prevents ingress of dirt and water Wiper lip with radius wipes off dirt efficiently while leaving a residual oil film on rod Static sealing edge (2) additional protection from ingress of dirt and water Segmented static sealing lip (3) designed for channelling of liquid provides for pressure relieve Dynamic sealing lip with knife-cut sealing edge excellent tightness low wear Fig. 2: The patented valve function consists of three quasi-static sealing lips, which open at approx. 3 bar, relieve the built-up pressure in the intermediate chamber and then close again immediately afterwards. 4
Functional reliability The attainment of the seal wear limit and malfunctions of the rod seal are indicated via the wiper pressure relieve. The system also remains functional in this state. The Merkel PRW 1 double wiper is not pressed out. Resulting damage to the hydraulic system is avoided. Ingress of dirt The ingress of dirt via the housing is reliably prevented by the static sealing lip on the front face and the static sealing edge of the Merkel PRW 1 double wiper. The optimised wiper lip ensures that soiling is always removed while leaving the lubricating film on the rod (mean particle ingress according to ISO 4406: 1987 13/5). This means that the Merkel PRW 1 double wiper far exceeds the requirements on the degree of purity as specified by ISO 4406 for high-performance servo systems and high pressure systems (Fig.3) and (Fig.4). Drive Piston rod: Piston rod Ø: Speed: Hydraulic fluid: Pressure in cylinder: Test dust: Dust supply: Light source Measuring cell Contaminated oil Q = constant 25 ml/min Oil supply Intermediate flange Dust atmosphere Photocell Cylinder chamber Rigid shaft R a 0.2 µm 50 mm 0.45 m/s HLP 32 50 bar ISO MTD of PTI 5 g/h Fig.3: Basic diagram for dirt ingress test rig Metering flume Meter Type of hydraulic system Particle > x/ml Sensitive control systems, laboratory, aerospace industry High-performance servo systems, high pressure systems High-quality and reliable systems, gen. mechanical engineering Medium pressure range, general mechanical engineering and vehicles Low pressure range, general heavy plant engineering, vehicles To particle sensor Particle size Fig.4: Functional principle of an automatic particle sensor Wiper under examination Measured results for a specified time interval Degree of purity ISO 4406: 1987 11 / 8 14 / 11 16 / 13 18 / 14 19 / 15 Fig. 5: Recommendations for degrees of purity (source: Mahle Filterfibel) 5
Technical properties and behaviour Possible applications with various hydraulic media Medium/Temperature Material 94 AU 925 Hydraulic oils, HL, HLP 30 C to + 110 C HFA/HFB liquids + 5 C to + 50 C HFC liquids 30 C to + 40 C HFD liquids Water + 5 C to + 40 C HETG (rape seed oil) 30 C to + 60 C HEES (synthetic ester) 30 C to + 60 C HEPG (glycol) 30 C to + 40 C Mineral greases 30 C to + 110 C Merkel PRW 1 double wiper made of low-temperature polyurethane (92 AU 21100) for use under extremely cold conditions on demand Surface quality R max R a Running surface * * Bottom of groove < 6,3 µm < 1,6 µm Side of groove < 15,0 µm < 3,0 µm * The surface roughness of the running surface should be related to the sealing component used! Tolerance recommendation Nominal d D D1 16 100 H 10 H 10 6
Merkel PRW 1 double wiper Housing based on DIN/ISO 6195 type A Article list Surface corresponds to bottom of groove rounded and burr-free d D D 2 L 1 L 2 R(1) R(2) H 3 Profile Article No. 22 30 28 4 6 0.3 0.2 7 4 49012374 25 33 31 4 6 0.3 0.2 7 4 49012375 28 36 34 4 6 0.3 0.2 7 4 528538 30 38 36 4 6 0.3 0.2 7 4 530000 32 40 38 4 6 0.3 0.2 7 4 531403 35 43 41 4 6 0.3 0.2 7 4 531022 36 44 42 4 6 0.3 0.2 7 4 531411 37 45 43 4 6 0.3 0.2 7 4 49012106 38 46 44 4 6 0.3 0.2 7 4 49005191 40 48 46 4 6 0.3 0.2 7 4 531116 45 53 51 4 6 0.3 0.2 7 4 531412 48 58 56 4 6 0.3 0.2 9 5 526679 50 58 56 4 6 0.3 0.2 7 4 528607 55 63 61 4 6 0.3 0.2 7 4 528815 70 80 77 6.3 8.3 0.3 0.2 9 5 49022349 77 87 84 6.3 8.3 0.3 0.2 9 5 49005392 80 90 87 6.3 8.3 0.3 0.2 9 5 49005193 85 95 92 6.3 8.3 0.3 0.2 9 5 49005391 92 102 99 6.3 8.3 0.3 0.2 9 5 49005192 7
Product Information Merkel Hydraulics Simrit, Your Global Technology Specialist for Seals and Vibration Control Simrit Services Your Benefits Constant innovations Technological edge Uniquely wide range of products All from one source Strong product brands Specialised technological expertise Unique materials expertise Longer unit service life A wide range of value added services Competitive advantages, efficiency and lower costs e. g. Merkel PRW 1 Double Wiper with Integrated Pressure Relieve Your Benefits Excellent tightness Improved functional reliability Overall reduction in costs Vibration Control Special Sealing Products: Bellows, Diaphragms, Elastomer Composite Parts and Precision Mouldings Lederer Liquid Silicone Products ISC O-Ring Integral Accumulator Merkel Hydraulics / Pneumatics Simmerring Headquarters Europe Freudenberg Simrit KG 69465 Weinheim, Germany Phone: +49 (0) 18 05-74 6748 Fax: +49 (0) 18 03-74 6748 e-mail: info@simrit.de www.simrit.com 20 GB 012 2.0 0205 Br. ABT