Page 223 - Know and Understand Centrifugal Pumps

Know and Understand Centrifugal Pumps

Common O-ring compounds used in mechanical seals
There are many rubber compounds used in industry as O-ring
secondary seals. Some elastomeric compounds are only found in one or
two sealing applications in one industry. We have listed the following
four compounds, which find broad popularity in almost any production
plant.
1. Fluorocarbon (VitonB) is a rubber compound that is compatible
(meaning it resists without degradation) with most petroleum based
liquids and gases (propane, gasoline, crude oil), some acids and
other chemicals. It is used extensively in the petroleum refining and
petrochemical industry. Its temperature range is good from -15" F
to +400" F. (-25" C to +205" C).
2. Perfluorocarbon (KalrezB, Parofluofl, ChemrazB) is a rubber
compound compatible with most organic and inorganic liquids and
gases and aggressive chemicals. This material finds popularity in
chemical processing and pharmaceutical plants, and wherever the
temperature of the application demands. Its service range is from
about -20" F to +500" F. (-30" C to +260" C).

3. Nitrile (Buna-N) is a rubber compound popular in most
household plumbing applications. It's a basic plumbers O-ring seal,
and handles most household liquids and chemicals. Because
industry pumps so much water, this elastomer may be the single
most popular O-ring secondary seal in the world. Its service range is
from -30" F to +250° F (-34" C. to +120 C).
4. Ethylene Propylene (EP, EPDM) is an O-ring rubber compound
that is compatible with most water-based chemicals. It is good with
caustic soda, detergents, water treatment chemicals, steam, and
wastewater and with food processes like milk, beer, and soups. EP
rubber compound is petroleum based and for this reason it should
never come into contact with petroleum based chemicals.
It will dissolve. Its service range is from -70" F to +300° F (-57" C
to +150° C).

How many different O-rings to heat some water?
Let's consider an industrial boiler. You may need at least three of these
previous mentioned O-rings just to prevent leaks and drips in a simple
hydronic or steam boiler. Raw water comes into the boiler room with
pipes, gauges, valves and instrumentation. All these fittings would
probably use Nitrile rubber O-ring seals to give long-term leak free
service.
Next, the raw water must be treated before it can be pumped into the
boiler. Treating the boiler water does three things. First it controls the