API 675 over view

Quick Reference Guide for API 675 3rd Edition

1. API 675 3 rd Edition Over view(Positive Displacement Pumps Controlled Volume) Mahendra Prabhu S Senior engineer - mechanical

2. Scope Reciprocating and Controlled volume pumps Hydraulic diaphragm or packed plunger design Rotary Positive displacement pumps are not included Diaphragm Pumps that use direct mechanical actuation are excluded

3. Terms and Definitions Acceleration Pressure – Anticipated System Acceleration Pressure The estimated Pressure Change due to changes in velocity in the piping system. It is an important factor in the application of reciprocating pumps because of the pulsating nature of the flow in the pump suction line, in addition to NPSHr , Vapor pressure and pressure required to overcome suction line losses. Controlled volume pump A reciprocating Pump in which precise volume control is provided by varying effective stroke length. These pumps are also known as proportioning, chemical injection, dosing or metering pumps.

4. Cont.…. Diaphragm Pump A pump designed such that the process fluid is isolated from the plunger by means of a hydraulically actuated flat or shaped diaphragm. Displacement Volume displaced per stroke. Displacement depends only on the physical dimensions of the pumping element. Net Positive Inlet Pressure (NPIP) Minimum instantaneous pressure determined at the datum elevation (Under side of the pump mounting plate) during pressure pulsations, Minus the vapor pressure of the fluid at the maximum operating temperature and at any specified operating point.

5. Cont.…. NPIPA - Net Positive Inlet Pressure Available determined by the Purchaser from NPSHA and system design data including the acceleration losses. NPIPR – Net Positive Inlet Pressure Required determined by vendor including the acceleration losses. Packed Plunger pump (or) Packed Piston Pump – The Process Fluid is in direct contact with the Plunger. Volumetric efficiency - Ratio of the pump rated point flow to the total theoretical displacement per unit time.

6. Pump Designations (Liquid End)

7. CONT.

8. Pump Designations (Drive End Pumps)

9. CONT.

10. Design Equipment shall be able to run at maximum rated input speed and relief valve setting conditions simultaneously. The pump flow rate shall be adjustable over specified range of turndown ratio. Rated capacity shall be at least 110% of Maximum capacity specified. The steady state flow accuracy shall be with in plus or minus 1%. The Flow repeatability shall be with in Plus or Minus 3% at rated flow and specified turn down ratio. Deviation from linearity shall not exceed Plus or Minus 3% of rated flow at specified turn down ratio.

11. CONT. Suction and Discharge Check valves seats or cartridges shall field replaceable. If specified double check valves shall be furnished. Double diaphragm designs shall be provided with tapped hole connected to conductivity probe in hydraulic type or Pressure type detector in dry design for detecting diaphragm failure detection. Diaphragm pumps shall have an integral , adjustable hydraulic relief valve to prevent failure of drive mechanism from excess discharge pressure. The relief valve setting pressure shall be 10% or 175 kPa (25 psi) above the rated discharge pressure.

12. CONT. Packed Plunger pumps requires external relief valves at purchaser piping. Gears used in pump assembly shall be metal. Service factor shall be 1.5 AGMA 6022 or AGMA 6013.

13. Capacity Adjustment Changing the actual or effective stroke length or stroking speed. Pump shall be capable of accepting manual or automatic stroke control Device used to change the capacity shall have visual indicator. Visual indicator shall have % of effective stroke length indication. Manual control shall be provided with positive locking device to retain capacity setting.

14. Driver - Motors Motor power requirements less than 1 hp , motor specification shall be agreed between Vendor and purchaser. Motor power above 1 hp – IEEE 841. The motor rating shall be at least 110% of the maximum power required. The motor rating shall be suitable for 100% of PLV accumulation pressure. PLV- Pressure Limiting valve.

15. Pressure Limiting Valves -PLV Positive displacement pumps shall be provided with pressure limiting valves or other protective devices. PLV shall meet the requirements specified in API 520 or API 526.

16. Pulsation Suppression Devices Pulsation suppression devices are located in Suction and / or discharge. Three types of suppression devices are as follows. Volume bottles without internals. Pulsation dampeners using gas filled chamber isolated from pumped fluid by piston or elastomeric diaphragm. Pulsation filters or attenuators and other proprietary designs based on acoustic suppression techniques.

17. Testing Hydro stating test pressure shall be minimum 1.5 times MAWP But not less than 150 kPa or 20 psi. Performance testing Flow repeatability and linearity tests are specified they shall run by using 100%, 75%, 50%, 25% and 10% of rated capacity in descending and ascending order. Adjustable stroke length and adjustable speed tests are contected independently.

18. Test tolerances

19. Annex Annex A- Data Sheets Annex B - Materials Annex C – Inspector Check List Annex D – Controlled Volume Pumps vendor drawing and data requirements. Annex E- NPSH vs NPIP Annex F- Pulsation and Vibration control techniques

20. Annex E- Net positive Suction Head (NPSH) Vs Net Positive inlet Pressure (NPIP)

21. CONT.

22. Annex F- Pulsation and Vibration control techniques The analysis described in this section will not be accurate if any of the following conditions apply. Liquid velocity > 0.3 m/s and < 3m/s. Liquid temperature is high ,cavitation is expected. The service has a critical hazard condition. Analysis approach 1 – Analytical study Analysis approach 2 – Acoustical Simulation Approach 3 – Peak to peak pulsation levels Approach 4 – Pulsation induced shaking forces

23. Maximum Allowable Pulsation Levels

24. Inlet Pressure vs Liquid vapor pressure