The API RP 551 document can be purchased and downloaded from the API website ( www.api.org ) or other online platforms that sell industry standards. You can also check with your organization's library or standards database to see if a copy is available.
I understand you're looking for a regarding API RP 551 (likely a typo for API RP 552 or API RP 551 ? Note: API RP 551 does not exist as a common standard; API RP 552 is "Transmission Systems" and API RP 550 is "Manual on Installation of Refinery Instruments and Control Systems"). api rp 551 pdf