 |
||
| Sulphuric Acid on the WebTM | Technology Manual | DKL Engineering, Inc. |
| ||||||
|
Knowledge for
the Sulphuric Acid Industry Introduction
|
It a design and operating challenge to move molten sulphur around a plant. To keep the sulphur molten and pumpable at the proper viscosity all piping and equipment handling molten sulphur must be heated and insulated. Steam jacketed piping is by far the most common way of conveying molten sulphur throughout the plant. Less common methods are steam or electrical tracing. Jacketed piping is basically a pipe within a pipe. Molten sulphur flows in the central or core pipe while steam flows in the annular space form between the two pipes. Sulphur piping will generally be carbon steel, seamless pipe supply to ASTM A106 Gr. B and/or ASTM A53 Gr. B. Standard sizes of jacketed for molten sulphur are:
Schedule 80 pipe is recommended for pipe sizes 2" and smaller. Schedule 40 pipe is recommended for pipe sizes larger than 2". For on/off service jacketed plug valves are generally used in molten sulphur service. Two acceptable plug valves for this service are manufactured by XOMOX and Durco. Both manufacturers offer partially and fully jacketed valves. Partially jacketed valves provides uniform heat dissipation and is suitable for most applications because of the plug valve configuration and a certain amount of insulating effect of the PTFE sleeve. Fully jacketed valves are for maximum heating or cooling duties without regard to uniform heating of surfaces in contact with the media. For molten sulphur applications, partially jacketed valves are suitable provided insulation is maintained in good condition. The valve body is generally cast steel with a ductile cast iron plug. The plug rotates in a PTFE sleeve that is locked in the body by raised metal lips and grooves surrounding the body parts. Partially jacketed valves are available in sizes from 25 mm to 300 mm (1" to 12") in the 150 lb. rating. 300 lb. rated valves are available from 25 mm to 200 mm (1" to 8") but are generally not required in most acid plant applications. Valves smaller than 80 or 100 mm (3" or 4") are will be wrench operated while larger valves are equipped with a gear operator.
Early piping system used 3 mm (1/8") compressed asbestos gaskets for flanged connections. Many companies no prohibit the use of asbestos so an alternative must be used. Spiral wound gaskets to API Standard 601 made of 304 S.S. and flexible graphite are a good alternative. Steam jumpovers can be hard piped using standard carbon steel pipe fiittings, stainless steel tubing with 'Swagelok' type fittings or flexible hoses. By far the easiest to install and maintain are flexible hose jumpovers. Flexible jumpovers are either annular or helical flexible metal hose constructed of 300 series stainless steel for the hose and outer braid. Flexible jumpovers can also be obtained pre-insulated. Hoses come in standard lengths of 560, 760 and 1220 mm ( 22", 30" and 48"). Diameters of hose are 13, 19 and 25 mm (1/2", 3/4" and 1") diameter. |
|
|
Copyright© 2005-2009 DKL
Engineering, Inc., All Rights Reserved |
