Field Instrument Support Details Technical Requirements

1. PURPOSE

1.1       This engineering standard defines requirements for the location and design of field instrument mounting stands and racks.

 

2. SCOPE

2.1      This standard applies to all field packages.

 

3. RELATED DOCUMENTS

3.1      Air Products Engineering Documents

 

INSTD-001   Standard Instrument Support Details

 

4. GENERAL

 

4.1       “Field instruments” (as used in this engineering standard) include transmitters, switches, controllers, indicators, and transducers. They do not include in-line instruments mounted directly in the piping or equipment.

 

4.2      The selection of instrument stands or racks shall be made from the INSTD-001 series details.

If a special stand or rack is required, the designer shall use these details as a “GO-BY.”

 

4.3       Items such as instrument mounting type, 2″ pipe, and surface shall be identified on the instrument specification.

 

 

5. INSTRUMENT LOCATION

 

5.1       All field instruments shall be located as close as possible to their respective process connections. Multiple instruments shall be combined on a single stand if the process connections are located within 6 m (20 ft) of each other.

 

5.2       All field instruments mounted on or near the cold box shall not interfere with the cold box maintenance, removable panels, or field piping and shall be mounted at a serviceable location.

 

5.3      All field instruments mounted near cryogenic or process piping shall maintain a minimum of

300 mm (12 in) clearance to allow for possible insulation.

 

5.4       Field instrument stands and racks may not be mounted in walkways or areas where serviceability of equipment is required.

 

4PS51005A, Rev. 1, Page 2 of 2

 

5.5       Indicating instruments which require routine monitoring by an operator shall have a centerline elevation between 900 mm (3 ft) and 1350 mm (4 ft 6 in) above grade or platforms.

 

5.6       Instrument locations are determined by the designer unless specific locations are noted on the flowsheet.

 

 

6. INSTRUMENT STANDS AND RACKS

 

6.1       Whenever possible, all individually or multiple mounted instruments shall maintain a center line elevation of 1350 mm (4 ft 6 in) above finished grade or operating platforms. A maximum of four instruments may be mounted on a 50 mm DN (2 in NPS) pipe stand. When five or

more instruments are mounted together, a rack is required.

 

6.2       Whenever possible, instrument stands or racks shall be permanently attached to structural steel or equipment foundations. In the absence of suitable steel or foundations, the

installation of separate concrete pads or piers to support instrument stands shall be employed only if no other acceptable support is available.

 

 

7. VIBRATION CONSIDERATIONS

 

7.1       Particular care shall be exercised when instruments are installed in the vicinity of reciprocating compressors. Piping, structural steel support piping, intercoolers, suction and discharge bottles may not be used to support instrument stands. For compressors larger than 250 hp,

instrument stands shall not be located on the compressor foundation or skid.