REVISIONS. App Thom. App Sud. App PC IG 2014/09/19

Transcription

1 /5 REVISIONS Rev Description Rev n by Sud PC Thom VB LH Clyd r Act Issue Date YYYY/MM/DD Gen. updates to content, format and spec number. Previously FF 204/09/9 IG 204/09/9 N/A N/A N/A N/A N/A N/A 204/09/23 Sud = Sudbury, Ontario, PC = Port Colborne, Thom = Thompson, Manitoba, VB = Voisey s Bay, LH = Long Harbour, Act = Acton, England, Clyd = Clydach, Wales, N/A = Not licable

2 2/5.0 PURPOSE This specification describes the minimum requirements for level measurement. The type of device used for continuous level measurement shall depend on the process conditions, types of vessels, utilities available, and the desired accuracy and reliability. This standard is intended as a general guide. 2.0 APPLICATION This specification, applies at any Vale locations indicated with approval on the cover page, with the following exceptions: 2. EXCEPTIONS None. 3.0 REFERENCE DOCUMENTATION The following documents were used in the development of this document or have instructions and procedures applicable to it. They shall be used in their most recent revision. N/A 4.0 GENERAL Non-contacting level instruments with no moving parts shall be the preferred way of measuring levels. Contact level instruments may be required as backup to the noncontacting instrument, depending on the application. Remote mounted transmitters accessible from ground level, or walkway are preferred. Mercury filled head type level meters shall not be used. 5.0 LEVEL TRANSMITTERS 5. ULTRASONIC Ultrasonic technology shall be used for most level measurement applications where heavy vapours, surface turbulence, foam or dust interference is not a concern. Follow manufacturer installation guidelines with respect to blind zones, sensing distances, beam interferences and environmental conditions to ensure application success.

3 3/5 5.2 GUIDED WAVE OR THROUGH AIR RADAR Radar technology, due to its higher cost, should only be considered when ultrasonic technology cannot be used. Verify the dielectric constant of the liquid to be measured is suitable for the use of radar technology. Guided wave should be used when echoes from tank walls or other obstructions can prevent the proper application of through air radar. 5.3 LASER Laser technology, due to its higher cost, should only be considered when ultrasonic technology cannot be used. The application shall dictate the use of laser as lasers are accurate at long distances and have virtually no beam spread. Care should be taken to prevent dust and dirt deposits on the laser lens by the use of dust tubes and purge air if required. 5.4 PRESSURE May be used for level measurement of clean fluids in vessels or other similar applications which are accessible only from the bottom and where the fluid density does not change. On fluids where deposits can accumulate, a flange connection with diaphragm seals (extended) are preferred. To facilitate maintenance, block and bleed valves should be considered. 5.5 NUCLEAR, CAPACITANCE, CONDUCTANCE, AND OTHERS Other level measurement technologies shall only be considered where none of the preferred technologies listed in previous sections above will work.

4 4/5 6.0 LEVEL GAUGES Gauge glasses may be used for level and interface applications provided the process fluid is nonhazardous and breakage shall not endanger personnel or equipment. Reflex level gauges shall be used on clean services only (i.e. boiler feedwater). On all other services, transparent gauges shall be used, supplied complete with offset cock valves and ball check valves. Mica shields and other protection devices shall be used as required by process conditions. External standpipes may be used on horizontal drums or when special heat treating vertical vessels make the use of multiconnections uneconomical. Standpipes shall be a minimum size of 2 inches. All instruments fitted shall have their own isolating valves. 7.0 LEVEL SWITCHES Where use of a level transmitter is impractical, float ball, conductivity type, vibrating fork and capacitive type level switches are acceptable. Device preference shall be confirmed with plant or mine prior to selection. 8.0 APPENDICES endix A: Revision and Transition Notes endix B: Keywords

5 5/5 endix A: Revision and Transition Notes (Revisions are listed in reverse chronological order with most recent revision at the top. Revision notes describe: what was changed, why it was changed, and the plan to implement the change, including whether changes are retroactive) Revision General updates to content, format and spec number. Previously Rev 5. (was also temporarily numbered SPEC now obsolete) endix B: Keywords