Pulsation Analysis Study for API 674 Design Approach 1: Vibration Control for Sour Water Pumps at IOCL Gujarat Refinery
iFluids Engineering has been engaged by Hiro Nisha Systems Pvt. Ltd to conduct a Pulsation and Vibration Analysis for the stripped sour water transfer pumps and the associated piping network at IOCL Gujarat Refinery. This study aims to evaluate pressure pulsations, identify potential pressure variations across system sites, and ensure that pressure levels are within permissible limits as per API 674 Design Approach 1 standards.
Project Overview
- The stripped sour water from the Washing Water Surge Drum at IOCL Gujarat Refinery is drained and pumped through a 2” pipeline using a Washing Water Pump.
- The water flows from the surge drum to the pump, then from the pump discharge to the tie-in point through the 2” pipeline.
- The goal of this Pulsation Analysis is to examine the entire network, which operates under a high-pressure range of 2.8 kg/cm² to 21.4 kg/cm².
- The fluid under study, Stripped Sour Water, requires a thorough evaluation to determine pressure pulsation levels and system stability across the pipeline
What is Pulsation?
Pulsation generally occurs when a liquid’s motive force is generated by a reciprocating or peristaltic positive displacement pump, and is most commonly caused by the acceleration and decelerations of the pumped fluid. This uncontrolled energy appears as pressure spikes and usually leads to damaged seals, gauges, diaphragms, valves and piping joints. The visual manifestation of pulsation is vibration.
Pulsation Analysis Procedure
A Typical Pulsation study was conducted as per the following steps:
- System Research: Research the system at hand to identify potential pulsation sites (during the design stage) or gather the necessary information regarding pulsation sites (in an existing system).
- System Modelling: Software-based system modelling.
- System Information Provision: Provide the necessary information on the pump, the piping system, and all other system components.
- Flow, Pressure, and Fluid Data Input: Provide the flow, pressure, and fluid characteristic data.
- Model Execution: Run the model using the software’s static and transient functions.
- Data Analysis: Analyze the output values and visual outcomes.
- Design Optimization: System design and operation optimization (till the pulsating effect is accomplished as minimally as possible).
- Reporting: Create a detailed report for the client that includes an evaluation of the design and changes made to address any problems.
Standard Procedures for PD Pump Pulsation Analysis
The following are the standard procedures for pulsation analysis in PD pump systems:
- Creation of the model: Definition of pipeline and process equipment during model construction. A Steady State run is performed in order to check whether the system is defined correctly.
- Determination of network Natural frequencies. The system is shocked with a brief pulse (rapid increase in flow rate) to identify the excitation frequencies.
- Excitation Frequency Graph Generation: Generation of the Excitation frequency graph and selection of Natural frequencies for further analysis. For a defined frequency, the PFA module calculates the PD pump speed (RPM) that will excite the chosen frequencies. These frequencies are commonly referred to as ‘worst-case’ pump speed because they match up with the harmonic frequency of the system and cause the most vibrations when operating at that frequency. However, as the PD pumps run at constant speed of 134 RPM, that speed and the corresponding harmonic frequency, if applicable, will be considered for evaluation of pulsation level.
- Scenario Development: A scenario is developed to simulate the pump running at the desired speed for constant RPM.
Output Analysis and Key Results
Four distinct output graphs were generated from the Pulsation Analysis:
- Steady State Analysis with Dampener
- Steady State Analysis without Dampener
- Transient State Analysis with Dampener
- Transient State Analysis without Dampener
The findings highlight that without a dampener, vibration levels are significantly high, with peak-to-peak pressure limits exceeding the safe threshold. The results confirm that installing dampeners on reciprocating pumps is crucial to control pulsations and mitigate forces. The maximum recorded forces were 0.153 kN and 0.253 kN, reinforcing the importance of dampener installation to reduce these force levels.
Conclusion
The Pulsation Analysis Study conducted for Hiro Nisha Systems Pvt. Ltd at IOCL Gujarat Refinery demonstrates the critical need for dampeners to maintain safe vibration levels and pressure within the pipeline network. By following API 674 guidelines and integrating vibration control measures, the stripped sour water system is safeguarded against excessive pulsation, ensuring long-term operational reliability and safety.