September 2019

Spiral Wound Gasket Manufacturers

Sep 30, 2019

Spiral Wound Gasket Manufacturers and Suppliers are your best resource for understanding the selection process.  When choosing a gasket material recovery and compression set should be important considerations. That’s because joints flex and move under changing temperature and pressure. If the gasket material can’t adapt to a varying distance between flanges the joint is certain to leak.

Rather than rely on the inherent material properties, spiral-wound gaskets seal by acting like a spring, expanding and contracting to fill the space available. Spiral-wound gaskets aren’t the solution to every gasketing problem, but for flanged joints, and especially those in petrochemical industries, they can be an excellent solution.

Spiral-wound gasket construction

Spiral-wound gaskets are made from a flat metal strip coiled into a shape rather like a clock spring. Interleaved with the steel is a good sealing material like PTFE or graphite. The metal is given a bend as these are coiled so that in profile it has a ‘U’ or ‘V’ form.

This profile gives the gasket its excellent recovery. Imagine the flange faces pressing against the legs of the ‘V’: closing the gap compresses this shape while opening it lets the ‘V’ spread further apart. In this way, the gasket stays in contact with each flange and maintains a good seal.

Most spiral-wound gaskets have a solid metal outer ring. This prevents over-tightening which would damage the gasket. Some also have an inner ring to protect against chemical attack or high pressure.

When to use a spiral-wound gasket

Spiral-wound gaskets excel in flange applications that see big swings in temperature and pressure. (The kind of environment that makes bolts lengthen and clamping pressure drop.) In addition, when the non-metallic element is PTFE or graphite these gaskets provide excellent resistance to chemical attack. This is why spiral-wound gaskets are the gasket of choice in refinery and related petrochemical applications.

Spiral Wound Gasket Manufacturers and Suppliers

It takes specialized equipment to manufacture spiral-wound gaskets. The leading producers are Flexitallic and Garlock. At Hennig we stock gaskets from both, and if you need something non-standard we can get that for you too. If you have an application you think needs a spiral-wound gasket, call or email and we’ll be happy to help.

Spiral Wound Gaskets
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NEMA vs IP Rating

Sep 16, 2019

NEMA and IP ratings are two systems that define the levels of safety and environmental protection provided by an enclosure. The enclosures themselves are usually fabricated from steel or durable plastic, but they need an opening for assembly or access to the equipment inside. That opening is sealed with a gasket, which is key to how the enclosure is rated.

NEMA vs IP Rating:  Different standards, same goal

NEMA ratings define enclosure protection in terms of the environment. IP ratings, (the system used in Europe and elsewhere,) define ingress protection (hence “IP”) in terms of solid objects and liquids. These systems overlap and the most widely used ratings are as follows:

  • NEMA 2 (Indoor use, protects against vertical drops) – broadly equivalent to IP11
  • NEMA 3 (Outdoor use, protects against rain and snow) – comparable to IP54
  • NEMA 4 (Protection against hose-directed water) – IP50
  • NEMA 6 (Temporary immersion at limited depth) – IP67

Gasket Implications

The two factors to consider are the cutting method and material. A gasket cut from strip has joins, and that creates potential leak paths. A gasket cut by die, laser or waterjet has no such joins and so provides better protection.

The gasket material must be compressible to seal completely all around the opening. (Hinges and clamps sometimes create gaps that vary widely.) If the enclosure will be opened frequently the material should also resist taking a compression set. Cellular gasket materials are a popular choice, but a closed-cell structure is essential to prevent water penetration.

When selecting any gasket material, it’s important to consider the environment. Those used outdoors could suffer UV exposure and wide temperature swings. Gaskets used near high voltage electrical equipment need good ozone resistance. Flammability may also be a concern.

NEMA an IP Rated Gasket Material

Closed-cell silicone foam is often used for enclosure gaskets due to its low compression set and wide temperature range. EPDM can be a cost-effective alternative and has good UV resistance, but depending on the environment and protection needed there may be other options. To explore the range of gasket materials appropriate to your application, speak with a Hennig Gasket product specialist.

FAQs
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UV Resistant Rubber Sheet

Sep 02, 2019

You’ve probably seen dried up and cracked nitrile and neoprene gaskets. Chances are, you’ve replaced a few too! In many cases the culprit is ozone. Here we’ll explain what ozone is, how it forms and what processes/activities expose gasket materials to ozone. Then we’ll suggest materials to use if you have an ozone problem which includes UV resistant rubber sheet.

An oxygen compound

Ozone is just oxygen atoms bound together in groups of three. Its chemical symbol is O3. In nature, ozone exists only in the stratosphere, a layer of the atmosphere five to thirty miles up. However, it can be produced artificially at ground level, and those are the processes that break down nitrile and neoprene gasket materials.

Oxygen atoms react readily with other elements. That’s why iron rusts and aluminum oxidizes. O3 is even more reactive than regular O2, so oxidizes materials even faster. When it contacts gasket materials like nitrile rubber (Buna-N,) natural rubber and neoprene it changes how their polymers are crosslinked. This hardens the material, which then cracks under load.

Ozone-producing processes

Ozone forms in the presence of ultraviolet (UV) light and electrical sparks. Both can break the bonds between oxygen and itself and other elements to free up individual atoms. These quickly recombine as O3.

UV light is widely used for purification and disinfection. Many city water systems use UV purification and UV disinfection is widespread in the medical sector. Ozone is a natural byproduct and itself is used for purification.

Electrical sparks are common around brushed electric motors, especially those using high voltages. High voltage switchgear is another source of ozone.

UV Resistant Rubber Sheet

When choosing a gasket material for an ozone-producing environment stay away from nitrile rubber and neoprene. Instead, consider silicone and EPDM materials. These are available with similar properties to nitrile and neoprene but are less susceptible to oxidation. Other good choices are PTFE and Viton/FKM.

Talk to the UV resistant rubber sheet materials specialists

If you think ozone could be an issue in a gasket application, talk to our specialists. They’ll help you select an EDPM, silicone or other ozone-resistant material suitable for your application.

Applications, EPDM Gaskets, Silicone Gaskets
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