Valves Suitable seat
Factors to consider when selecting an elastomer for a butterfly valve seat Butterfly valves are a very common type of valve found in many
applications. They are relatively compact, simple, easy to maintain and come in a multitude of materials. Selection of the housing, disc and shaft is straightforward in most applications. However, selection of the seal or seat material in valves with elastomer seals is probably the most difficult and important decision in specifying a valve. There are several things to keep in mind as you select an elastomer for a butterfly valve seat. The major factors to consider are temperature, pressure, chemical compatibility, agency approvals, wear and cost. First, it is important to remember that the user is the application expert and the manufacturer, or his representative, is the expert on what seal or seat options are available. The manufacturer should have resources and experience to help you make a decision, but will only know as much about your process as you tell him.
One of the most basic process application parameters is temperature. The temperature information should include the minimum and maximum continuous process temperatures as well as the ambient temperature around the valve as it operates. Short duration high temperature conditions (which could occur at startup or other times) should be identified for consideration by the valve manufacturer.
Elastomers are not good conductors of heat and can typically resist temperatures well above normal operating limits for short periods of time. The position of the valve disc during these short duration temperature events is important as well. A valve seat with the disc in the open position is not highly stressed and much less likely to fail than a seat on closed valve seeing the temperature spike. The valve manufacturer’s application engineering staff should be able to use the temperature information provided by the user to determine which seat or seal material is suitable.
This seat was used at temperatures in excess of recommended. It has been permanently moulded into a solid shape, and the disc is no longer able to move freely.
www.solidsandbulk.co.uk November 2010 • Solids & Bulk Handling 43
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60