SIMULATION OF GASKET LEAKAGE AND CO-RELATION TO DESIGN S e p t e m b e r 2011
TABLE OF CONTENTS Abstract... 3 Abbreviations... 4 Problem Description... 5 Product Construction... 6 Product Assembly... 7 List of various factors affecting the sealing... 8 Solution... 9 Key Learning... 13 Reference... 15 Author Info... 15
Abstract Engineering world has been transforming through its challenges and innovation in Design, Prototyping, Virtual Prototyping and Simulation. It had never been an easy relation between a simulation world and physical testing of products. Particularly when it comes to corelation between water leakage past a sealing gasket and analytical simulation, it had been almost impossible. This white paper brings in a strategic approach in bringing them a relation and making the prediction more reliable. The paper would be explained with a real time product, design strategies in sealing, organized testing approach and systematic co-relation with simulation 3
Abbreviations Sl. No. Acronyms (Page No.) Full form 1 NEMA National Electrical Manufacturers Association 2 UL Underwriters Laboratories 3 IP Ingress Protection 4 PSI Pounds per Square Inch 5 EPDM Ethylene Propylene Diene Monomer Rubber 6 SBR Styrene-Butadiene-Rubber 7 7T 7 View E Touch 8 7K 7 View E Combo 9 DOE Design of Experiments 10 TBD To be decided 4
Problem Description The product requires being qualified for stringent requirement of UL508, UL50, IP65 and NEMA 4X requirements across all variants. Next Generation View is an operator interface product currently in design and development by Rockwell Automation. The product requires being qualified for stringent requirement of UL508, UL50, IP65 and NEMA 4X requirements across all variants. The product is being designed with FDA approved gasket to meet water sealing requirements of NEMA 4X. Water jet testing on the prototypes has resulted in failure, water seeping through the Gasket. This paper would further demonstrate the collaborative effort of Design Team and Analysis Team in establishing a mathematical model of Water seeping failure occurred through physical testing. 5
Product Construction The product comes with a sealing gasket and a clamping device in order to facilitate leak free joint. Next Generation View comprises a user interface monitor being packed in an electronic enclosure. The product is being mounted on to sheet metal or plastic panel in real application. The product comes with a sealing gasket and a clamping device in order to facilitate leak free joint between the Product and the Panel Surface. 6
Product Assembly Since the Cam Clamps are localized, the midpoint between the cam clamps undergoes maximum deformation. Clamping, Gasket compression and Panel deflection As the clamps are clamped all around, the gasket gets compressed to about 50% and creates a sealing. Lowest panel thickness is susceptible to deformation due to clamping load on one side and reaction load of gasket from other side. Since the Cam Clamps are localized, the midpoint between the cam clamps undergoes maximum deformation and in turn resulting in reduced gasket compression at the mid-span. This could possibly create an easy leak point for water. Hence simulating a leak for a given design is almost been impossible to execute. 7
List of various factors affecting the sealing Part Factor Levels Remarks Gasket Cam Clamp Bezel Assembly Gasket Material SBR, Si, Ensulite Design Control Gasket Durometer 41, 42, 43 and 45 Design Control Gasket Thickness 1/4, 3/16, 1/8 Design Control Gasket Width 5mm to 11 mm Design Control Gasket Compression 40% to 55% (solid state 60%) Design Control Type of clamp Span between clamps along a side Span between clamps around the corners Number of clamps in Bezel Distance between gasket and the backup wall Cam Clamp, Screw Clamp 114mm 104mm (linear summation around the corners) 4Nos, 6Nos Touch: 0mm to 1mm / side Combo: 0mm to 50mm / side Design Control (Screw Clamp used only for testing purpose) Design Control (no defined value to start with) Design Control (no defined value) Design Control Design Control (Lesser Distance preferred) Gasket position on Bezel Centered Assembly Control Gasket Though depth in Bezel (Results in exposed surface for water contact) 40% Gasket height (Typ. 1.89mm for 3/16 Gasket), zero depth X Direction: 2.60 Y Direction: 2.45 Design Control (Less exposure preferred) Space beyond the Bezel perimeter Testing Control Panel / NEMA Box Panel material Mild Steel, Polycarbonate and Fiber Glass Standard Testing Conditions Panel Thickness Thickness ranges as per Section 3.5 Standard Clearance between Panel Cut-out and Bezel wall UUT biased to bottom right corner in the cutout Dynamic behavior of the panel due to forced water jet Water pressure variation during test Water jet holding time 1mm to 3mm / side To be centered Dynamic behavior. Ensure rest of the system rigidly clamped 65 GPa Minimize fluctuations 4s / inch Minimize variations Design Control Testing Control Testing Control Testing Control Testing Control 8
Solution Co-Relation Strategy: Co-relation is brought by working with strengths of each of Simulation, Design and Testing World. Co-relation is brought by working with strengths of each of Simulation, Design and Testing World. Each team has attempted to establish the following relationship in below chart. Establishing this on a baseline configuration has helped in making simulation as a reliable method of predicting the water leakage. Co-relation between Water Leakage in Testing and Sealing Pressure: Establishing relation between Water Leakage and Sealing Pressure has been the key in co-relation. This has been established using PSI test on NEMA Gasket held between two parallel plates. Result: Threshold pressure of passing is established to be 11 Psi. 9
Co-relation between Sealing pressure and Gasket Compression: Threshold pressure of passing is established to be 11 Psi. Establishing relation between Sealing Pressure and Gasket Compression became a necessary input for simulation. Gasket Force Vs Defection curve has been generated for various thickness and durometer of gasket. Co-relation between Simulated Gasket compression, Seal Pressure and Experimental results: Based on Designed Geometry and attributes, simulation is being conducted to find the resultant panel deflection, compression and sealing pressure. Accuracy of results was being compared against physical experimentation. Typical simulated results of Panel deflection, Gasket Compression and Sealing Pressure are as below. 10
Typical simulated results are Panel deflection, Gasket Compression and Sealing Pressure. Tabulation of simulated results and measured deflection: 11
Comparison chart on HCL Simulated results against Measured data at Client lab. Indicating high degree of co-relation. Comparison chart on HCL Simulated results against measured data at Client lab. Indicating high degree of corelation 12
Key Learning After successful correlation of Simulated Sealing Pressure to Comparison Physical leakage chart condition, HCL Simulated simulation results can be against used as tool measured to predict compression, data at Client panel lab. Indicating deflection, high sealing degree pressure of corelation and leakage on any innovative design. Simulating a leakage in Gasket Sealing through FEA is now been accomplished strategically. Following are key summary and recommendations. Design: Sealing pressure (as a result of Gasket Compression and Durometer) and Panel Deflection plays a major role in sealing. Hence achieving uniform sealing pressure all around is the key. All other factors (Gasket material, cross section, Optimized shape, Panel cut-out and clamping) results only marginal improvement. Increasing the number of clamps and reducing the span between the clamps benefitted in sealing with good margin. High Durometer Gaskets (43, 45 durometer) improves sealing pressure, however doesn t benefit as the reaction forces are higher and creates panel deflection. Low Durometer Gaskets (Silicone, Ensulite) reduces deflection, however doesn t provide necessary sealing pressure. Testing: Variations brought in testing had been significant, which needs closer control. Rigid stand for fixing the Test unit, steady flow of water, distance of water jet from test unit, centralized positioning unit over NEMA box enclosure would benefit. Force of water jet on the NEMA enclosure creates dynamic movement on the panel and generating a path for water leakage. Simulation: Simulation helps more in optimizing the Gasket shape, Clamp design, Clamp numbers and Bezel design. After successful correlation of Simulated Sealing Pressure to Physical leakage condition, simulation can be used as tool to predict compression, panel deflection, sealing pressure and leakage on any innovative design. 13
Conclusion Strategic approach and Collaborative efforts between Design, Testing and Simulation Team has resulted in establishing this relation. Strategic approach and Collaborative efforts between Design, Testing and Simulation Team has resulted in establishing this relation. This could help in eliminating any exhaustive efforts of physical testing and cost involved. Hope this technical paper brings in thought of extending Simulation arms to resolve almost impossible Design challenges in Sealing. 14
Reference 1. UL Standard 508 2. UL Standard 50 3. UL Standard 50E Author Info Senthil Kumar P Mechanical Product Design Professional with 10+ years of experience in Design and Development of Electro-Mechanical Devices, Office Automation, Aeronautical Equipments and Automobile products. Santhanaraj Muniraju Mechanical Product Design and Value Engineering Specialist with 15+ years of experience in Design and Development of Automobile, Home appliances and Industrial Products. 15
Hello, I m from HCL s Engineering and R&D Services. We enable technology led organizations to go to market with innovative products & solutions. We partner with our customers in building world class products & creating the associated solution delivery ecosystem to help build market leadership. Right now, 14500+ of us are developing engineering products, solutions and platforms across Aerospace and Defense, Automotive, Consumer Electronics, Industrial Manufacturing, Medical Devices, Networking & Telecom, Office Automation, Semiconductor, Servers & Storage for our customers. For more details contact eootb@hcl.com Follow us on twitter http://twitter.com/hclers and our blog http://ers.hclblogs.com/ Visit our website http://www.hcltech.com/engineering-services/ About HCL About HCL Technologies HCL Technologies is a leading global IT services company, working with clients in the areas that impact and redefine the core of their businesses. Since its inception into the global landscape after its IPO in 1999, HCL focuses on 'transformational outsourcing,' underlined by innovation and value creation, and offers integrated portfolio of services including software-led IT solutions, remote infrastructure management, engineering and R&D services and BPO. HCL leverages its extensive global offshore infrastructure and network of offices in 26 countries to provide holistic, multi-service delivery in key industry verticals including Financial Services, Manufacturing, Consumer Services, Public Services and Healthcare. HCL takes pride in its philosophy of 'Employee First, Customer Second' which empowers our 77,046 transformers to create a real value for the customers. HCL Technologies, along with its subsidiaries, had consolidated revenues of US$ 3.5 billion (Rs. 16,034 crores), as on 30 June 2011 (on LTM basis). For more information, please visit www.hcltech.com About HCL Enterprise HCL is a $6 billion leading global technology and IT enterprise comprising two companies listed in India - HCL Technologies and HCL Infosystems. Founded in 1976, HCL is one of India's original IT garage start-ups. A pioneer of modern computing, HCL is a global transformational enterprise today. Its range of offerings includes product engineering, custom & package applications, BPO, IT infrastructure services, IT hardware, systems integration, and distribution of information and communications technology (ICT) products across a wide range of focused industry verticals. The HCL team consists of over 85,000 professionals of diverse nationalities, who operate from 31 countries including over 500 points of presence in India. HCL has partnerships with several leading global 1000 firms, including leading IT and technology firms. For more information, please visit www.hcl.com