API 570 EXAM STUDY GUIDE [MODULE 4 : PART 1] API 576

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API 570 STUDY GUIDE
MODULE 4 : PART 1
API 576 : INSPECTION OF PRESSURE RELIEVING DEVICES

API 576 is the new code introduced in the syllabus of API 570 Piping Inspector Exam. This will come in to effect for the exams from June 2021. API 576, Fourth edition, April 2017 is to be referred.

Though pressure relieving devices are used to protect piping and pressure vessels, this code was not part of the API 570 Piping Inspector Exam but was there in API 510 Pressure vessel Inspector exam.

The integrity of piping system is very much depend on the reliability of the working of pressure relieving devices. There are different methods adopted to relieve pressure in a piping system or we can say that different pressure-relieving devices are available.

Pressure-relieving Device

API 576 definition to the  Pressure relieving Device is as below.

"Pressure-relieving devices protect equipment and personnel by opening at predetermined pressures and preventing the adverse consequences of excessive pressures in process systems and storage vessels."

The other important points are,

  1. These are actuated by inlet static pressure
  2. Designed to open during emergency or abnormal operating conditions
  3. Opens when the internal fluid pressure increases above a specified design value
  4. Can also prevent internal excessive vacuum, if it is designed for vacuum prevention.(Please note that not all pressure-relieving devices can control vacuum)

The pressure-relieving devices are

  1. Pressure-relief valve
  2. Direct-acting pressure-relief Valve
  3. Pilot-operated pressure-relief valve
  4. Rupture Disk Device
  5. Pin-actuated device

The portions to be studied for the exam are,

  1. Section 5 : Causes of Improper Performance
  2. Section 6.1 to 6.3: Related to Inspection and Testing
  3. Section 8 : Pressure-relief valve Visual On-Stream Inspection
  4. Section 10.1 to 10.3 Related to records and reports

Though the above portions are for the exam, please read, Section 3 and Section 4 for an idea of pressure relieving devices including their working principles and area of application. To familiarize these devices, good number of color photos are also given in the code book.

We are not going in detail about the pressure-relieving devices. The details can be availed from Section 4.0 of API 576 code book. 

For better understanding this topic, it is recommended to read and familiarize section 4 of the code book

API 576 : Section 5 : Causes of Improper Performance

11 Reasons are listed as the cause of improper performance of a pressure-relieving device

  1. Corrosion
  2. Damaged seating surfaces
  3. Failed springs
  4. Improper setting and adjustment
  5. Plugging and fouling
  6. Galling
  7. Misapplication of materials
  8. Improper Location, history or application
  9. Improper Handling
  10. Improper differential between operating and set pressures
  11. Improper Inlet/Outlet piping test procedures
From the next part of this series we will go through in detail about the causes of improper performances.


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