August 2015

Preparing Flanges for New Gaskets

Preparation is everything they say, and that’s certainly true for flanged pipe connections. As flanges are brought together and the bolts tightened, the flange gasket compresses and flows into surface irregularities. If those are too severe for the gasket material to fill, the joint will leak. Here’s some advice on flange preparation.

Step 1: Inspection

Examine both flange faces carefully for damage like cracks, dings, burrs and radial scoring. Scoring is the worst problem as this will almost certainly create a leak path. Also check for alignment and verify that the faces are flat and parallel. (It’s possible for flanges to warp if the bolts are tightened in the wrong sequence.) Some softer gaskets will tolerate flanges being slightly out of parallel, but this does depend on the material being used.

Also check bolts, nuts and washers for signs of damage or corrosion. If in doubt as to fitness for purpose, opt to replace.

Step 2: Clean the Mating Faces

It’s common for traces of the old gasket to remain on the flange surfaces. These can be removed with a wire brush or scraper. However, to avoid damaging the flange face, this must be made from a softer material. Brass is usually a good choice. Always brush in a circumferential direction and not radially.

Step 3: Preparation

Inspect the new gasket for damage and ensure that it’s the correct size for the joint. Don’t use any kind of sealant on the gasket or sealing faces unless specifically advised to do so by the gasket manufacturer.

Proper torque tightness is essential to deform the gasket and seal the joint. If there’s excessive friction bolts will seem to be at their torque limit when they’re not, resulting in leaks. This can be avoided by lubricating the threads and under the heads of the bolts. (Ensure the lubricant is compatible with expected service conditions.)

Do it once

Inspection and cleaning may seem time-consuming, but doing a job once is better than having to fix a leak. That’s why thorough preparation of flange surfaces is so important.  Contact Hennig Gasket & Seals for custom manufacturing of flange gaskets to your exact specifications.

Food Grade Gasket Manufacturing

Food grade non-metallic gaskets are made from materials approved by the FDA for repeated and demanding contact with edible products. They must withstand high pressures, have a wide temperature tolerance and be extremely resistant oils, acids and chemicals without degrading or becoming susceptible to bacteria formation—for the obvious reason that food-grade gaskets and seals must not impact food quality or safety whatsoever. FDA-approved food-grade non-metallic gaskets are also used in pharmaceutical and cosmetics manufacturing for the same reason.

There are several materials that we can use to fulfill food grade non-metallic gasket orders:  

White Nitrile (Buna-N)—Commonly used in food processing because it remains durable and flexible when cycling between temperatures of -31°F to +230°F. It is highly resistant to petroleum, mineral and vegetable oils, acids and a wide range of aromatic hydrocarbons.

White Neoprene—Works well in food-processing and packaging environments, as well as pharmaceutical, commercial kitchens, cosmetics plants and grocery store applications with a temperature tolerance of -20°F to +180°F.

Red or White FDA Silicone—Have a temperature tolerance between -94°F to +392°F and are often used in everything from food processing to laboratory and surgical applications because of its low volatility and durability. Resists oils and acids well.

EPDM—Food-grade EPDM has a temperature tolerance of  -20°F to +230°F. It’s smooth, resists abrasion, is color-stable, non-marking and odor-free; for these reasons, it has earned the additional approval of the USDA for poultry and meat processing.

PTFE—As one of the most chemically-resistant plastics available, FDA-compliant PTFE is extremely common in food and beverage processing, cosmetics and pharmaceutical manufacturing. It also has an outstanding temperature tolerance of -328°F to +500°F.

Gylon®—This is a specific brand of PTFE with a 450°F to +500°F . It is extremely chemical and temperature resistant with reduced creep relaxation qualities.

While all of these materials (and a few others not listed here) are FDA-compliant, not all of them are suitable to all food, cosmetics or pharmaceutical production processes. Please contact Hennig Gasket and Seals, Inc. at 1-800-747-7661 and we can discuss which food-grade, non-metallic gasket material would be best for your needs.