Explosionproof Electric Unit Heating Systems for Offshore Rigs
- F.S. Epstein (Industrial Engineering and Equipment Co.) | A.K. Arekapudi (Industrial Engineering and Equipment Co.)
- Document ID
- Society of Petroleum Engineers
- European Petroleum Conference, 22-25 October, London, United Kingdom
- Publication Date
- Document Type
- Conference Paper
- 1984. Society of Petroleum Engineers
- 5.2.1 Phase Behavior and PVT Measurements, 1.6.5 Drilling Time Analysis, 4.2.3 Materials and Corrosion, 4.1.2 Separation and Treating, 6.3.3 Operational Safety, 4.1.5 Processing Equipment, 1.6 Drilling Operations
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|SPE Non-Member Price:||USD 28.00|
We have developed an explosionproof electric unit heater system to operate in ambient temperatures down to -30F. (-34C.) [-70F. (-57C.) with modification]. The self-contained system includes a blower, heating elements, controls and provisions for focusing the warm airstream on provisions for focusing the warm airstream on personnel up to 20 feet (6.1 meters) away. personnel up to 20 feet (6.1 meters) away. Ratings up to 91 KW (310,000 BTU/HR) will provide air temperature rises as high as 164F. provide air temperature rises as high as 164F. (91C.).
Comfort heating on the deck of a rig operating in arctic and subarctic climates presents a unique set of engineering challenges. Traditionally steam unit heaters, consisting of a steam coil and explosionproof blower mounted in a cabinet, have been used. However, this requires a source of steam, usually a separate boiler, to feed the unit heaters. Both the boiler and the lines running to the heaters are high maintenance items, especially in harsh environments where they tend to freeze up. If insulation is not properly replaced after repair, freezeup will properly replaced after repair, freezeup will soon reoccur.
To avoid the problems associated with a steam system, we were asked to develop an electric explosionproof unit heater system for use on a large semi-submersible rig that was placed in service early last year. The design was to meet the following criteria:
1. Safe operation in a methane gas atmosphere and prompt, safe shutdown when hydrogen sulfide is detected.
2. Resistance to salt spray corrosion.
3. Qualification to U.S. Coast Guard requirements which involves approval by either the Underwriters Laboratories or Factory Mutual Laboratories.
4. Airflow of at least 2000 standard cubic feet of air per minute (944 dM3/S).
5. A capacity of 91 KW (310,000 BTU/HR) at 575 volts, 3 phase, which produces an air temperature rise of 148F. (82C.).
6. Suitablility for operation in an ambient temperature of -30F. (-34C.).
7. Focusing the airstream to achieve 50F. (28C.) minimum temperature rise 20 feet (6.1 meters) away from the unit outlet.
8. Rotation of the entire unit in a horizontal plane to any one of eight positions, and/or tilting it at 15, 30 or 45 to the horizontal.
9. Individually replaceable heating elements.
10. A protecive housing around the entire assembly to reduce the chances of accidental damage.
To operate safely in an environment containing combustible gases, electrical equipment must satisfy two basic conditions:
First, any electric device that might produce a spark, such as a magnetic contactor, fuse or disconnect switch, must be housed in an explosion proof enclosure that will contain an explosion without rupturing. (The British term "flameproof" is equivalent to the U.S. term "explosionproof.") Cast aluminum enclosures are commonly available for such service. To gain access to the electrical components, these enclosures are normally furnished with bolted covers. The mating surfaces of the cover and box are machined flat to within 250 micro inches (635 micro centimeters) and must be at least 3/4 inch (1.91 centimeters) wide so that the flame resulting from an internal explosion will be cooled before it reaches the outside atmosphere.
|File Size||1 MB||Number of Pages||10|