Aug 10, 2012
Liquid gaskets said to outperform traditional materialsBack
Africa|Components|Henkel|Henkel South Africa|Industrial|Loctite|Petroleum|Screen|Systems|Water|Africa|Adhesives Supplier|Chemicals|Manufacturing|Metal|Metal Surfaces|Metal-to-metal Contact|Product|Products|Rubber|Sealed Steel Casing|Silicone Products|Steel|Systems|Water|Anaerobic Technology
© Reuse this
Speciality chemicals and adhesives supplier Henkel South Africa, which is also the manufacturer of the Loctite brand of sealants, maintains that liquid gaskets produce seals that create better results than traditional materials.
To ensure the integrity of a seal between two bolted flanges, it is necessary to have some form of gasket between the mating surfaces that will remain intact and leak-free in often extreme and varying conditions over a prolonged time.
In a test where a sealed steel casing was subjected to torsional stresses, a number of significant differences between various sealing methods were noted, reports Henkel.
In particular, conventional solid gaskets showed leaks after 150 000 cycles, whereas seals made with an anaerobic product con- tinued to show reliability beyond 250 000 cycles.
Further, in the conventional gasket, the tension of the bolt dropped by 25% within just a few thousand cycles.
There are three typical types of gaskets: conventional precut compression gaskets, formed-in-place (FIP) liquid gaskets and cured-in-place (CIP) gaskets.
Although a well-used and traditional method of sealing joints, these gaskets do present some significant and practical disadvantages, says Henkel.
For example, conventional gaskets require an initial compressive load to deform it into the irregularities of the mating surfaces, which, over time, is a major cause of gasket failure.
This occurs when the gasket loses its elastic properties and becomes less resilient. The load on the gasket and relative motion causes a general decrease in the gasket thickness, resulting in a bolt clamp load loss that can cause it to leak.
FIP Liquid Gaskets
Two types of sealants are available for FIP gasketing jobs: anaerobics for rigid joints, such as Loctite 510 and Loctite 518; and special silicone products for applications requiring a flexible seal, such as Loctite 5699.
Further, no retightening of the bolts is required and no allowance is needed for gasket thickness, reports Henkel.
Meanwhile, anaerobic sealants provide high shear strength that stops movement to eliminate bolt loosening and fretting and to increase the assembly’s structural strength.
Anaerobic sealants also allow relaxation of surface finish and flatness tolerances that enable scratches and scored surfaces to be sealed without rectification.
Anaerobic gasket materials only cure in the absence of air when trapped between metal surfaces. This enables it to offer extensive on-part life when exposed to the atmosphere, making multiple application methods possible and reducing the problems associated with the use of volatile or moisture-cured materials on production lines, notes Henkel.
Further, the anaerobic technology enables excess material to be wiped from exterior surfaces or flushed away from interior faces maintaining free, unblocked internal passages and channels.
An advantage of cured anaerobic gaskets is its resistance to petroleum-based fuels, lubricating oils, water-glycol mixtures and most other industrial chemicals.U
nlike precut compression gaskets that are difficult to automatically position on the parts, anaerobic gaskets can be automatically dispensed by robotic dispensers, screen printing or stencil printing systems.
Further, anaerobic gasket products reduce inventory costs, as one container of an anaerobic can be used for flanges of varying sizes and shapes. Precut gaskets can only be used on specific flanges.
They are applied as a fluid in precise beads to one of the surfaces and are cured before use, either by ultraviolet light, heat cure, two-part mix or moisture curing.
Once the bead is cured, an elastomeric material is formed that adheres to the surface. Sealing is achieved through compression of the cured gasket during assembly of the parts.
The advantages of these gaskets include automatic application, serviceability, labour savings, improved quality, reduced inventory and flexible manufacturing.
Meanwhile, Henkel states that flanges, such as pressed steel parts and thin castings with widely spaced bolts, can be considered as flexible, have inconsistent clamp pressure and may move under pressure or dynamic loading.
Sealant manufacturers offer special silicones, formulated to meet all of the requirements of a gasket for flexible joints. Such products provide high elongation to compensate for any micromovement, as well as long-term adhesion to most substrates.
It is important to consider the nature of the surfaces involved in a gasketed assembly.
For example, the original substrate used for the component may be metal – but for operational reasons the part has been painted. It is not a metal-to-metal contact that needs to be sealed but rather a metal-to-paint or paint-to-paint configuration.
In those circumstances, an anaerobic that relies on a metal surface in the absence of air to initiate the cure is inappropriate. However, a silicone – even if a rigid joint is involved – is the correct choice.
Edited by: Chanel de Bruyn© Reuse this Comment Guidelines (150 word limit)
Creamer Media Senior Deputy Editor Online
Other Seals, Gaskets and Sealing Mechanisms News
Updated 1 hour 30 minutes ago South Africa slipped one position, from 52 to 53, in the latest world competitiveness ranking, which highlighted power and infrastructure shortfalls, high youth unemployment, as well as inadequate education and technical skills availability as key challenges to the...
Updated 4 hours ago JSE-listed Dipula Income Fund reported that its distributable earnings grew 33.2% in the six months ended February 28, translating into a combined growth of 6.8% in distributions for both A- and B-linked units. The distribution attributable to the A-linked units was...
Updated 4 hours ago JSE-listed Growthpoint Properties’ Kirstenhof Office Park, in Johannesburg, has become the hundredth building in South Africa to achieve a Green Star SA certification from the Green Building Council of South Africa (GBCSA), securing a 5-Star Green Star: Existing...
Recent Research Reports
Steel 2015: A review of South Africa's steel sector (PDF Report)
Creamer Media’s Steel 2015 report provides an overview of the key developments in the global steel industry and particularly of South Africa’s steel sector over the past year, including details of production and consumption, as well as the country's primary carbon...
Projects in Progress 2015 - First Edition (PDF Report)
In fact, this edition of Creamer Media’s Projects in Progress 2015 supplement tracks developments taking place under the Renewable Energy Independent Power Producer Procurement Programme, which has had four bidding rounds. It appears to remain a shining light on the...
Electricity 2015: A review of South Africa's electricity sector (PDF Report)
Creamer Media’s Electricity 2015 report provides an overview of State-owned power utility Eskom and independent power producers, as well as electricity planning, transmission, distribution and the theft thereof, besides other issues.
Construction 2015: A review of South Africa’s construction sector (PDF Report)
Creamer Media’s Construction 2015 Report examines South Africa’s construction industry over the past 12 months. The report provides insight into the business environment; the key participants in the sector; local construction demand; geographic diversification;...
Liquid Fuels 2014 - A review of South Africa's Liquid Fuels sector (PDF Report)
Creamer Media’s Liquid Fuels 2014 Report examines these issues, focusing on the business environment, oil and gas exploration, the country’s feedstock supplies, the development of South Africa’s biofuels industry, fuel pricing, competition in the sector, the...
Water 2014: A review of South Africa's water sector (PDF Report)
Creamer Media’s Water 2014 report considers the aforementioned issues, not only in the South African context, but also in the African and global context, and examines the issues of water and sanitation, water quality and the demand for water, among others.
This Week's Magazine
While economic forecasts for the African continent are most favourable, African airlines may not be able to benefit from the expected growth in the region’s gross domestic product (GDP), International Air Transport Association VP: Africa Raphael Kuuchi has warned....
The Automotive Production and Development Programme (APDP) will need to change substantially post 2020, says Metair Investments South African operations COO Ken Lello. “We must not make tweaks. We have to change. What we are doing is not sustainable.”
Banking group Absa’s forecast is for the rand to end the year at around R13 against the dollar, weakening further to R13.50 by 2016, says Absa sectoral analyst Jacques du Toit. He warns that possible interest rate hikes in the US may see capital being pulled from...
The Dispute Resolution Centre at the Bargaining Council for the Civil Engineering Industry (BCCEI) is now open to handle party-to-party disputes. The BCCEI represents the interests of all level four to nine Construction Industry Development Board companies.
Communications technology firm Ericsson sub-Saharan Africa head Fredrik Jejdling says the company’s commitment to sustainability and corporate responsibility has been integrated into all facets of its operations, which has provided it with sustainable revenue...