Hiro Nisha Systems PVT LTD has awarded iFluids Engineering to conduct a study in modelling about pulsation and vibration control subjected to stripped sour water transfer pumps and piping network.
In IOCL Gujarat Refinery, the stripped Sour water from Washing water surge drum is drained and pumped out using a washing water pump through a 2” pipeline.
The stripped Sour water is transferred from Washing water surge drum to washing water pump. The discharge of washing water pumps is connected with a 2” pipeline and the discharge of the pump is connected to the tie in point.
The goal of the pulsation study is to evaluate the pressure variations and forces at various system sites within the network of stripped sour water, as well as to verify that the pressure pulsations are within the permissible limits determined in accordance with API 674 Design Approach 1.
Here, Pulsation Study was required to be carried out for an network operating at a pressure range of 2.8 kg/cm2 to 21.4 kg/cm2.
For this network (high pressure) the Fluid planned to be studied is Stripped Sour Water.
A Typical Pulsation study was conducted as per the following steps:
- Step 1: 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).
- Step 2: Software-based system modelling.
- Step 3: Provide the necessary information on the pump, the piping system, and all other system components.
- Step 4: Provide the flow, pressure, and fluid characteristic data.
- Step 5: Run the model using the software’s static and transient functions.
- Step 6: Analyze the output values and visual outcomes.
- Step 7: System design and operation optimization (till the pulsating effect is accomplished as minimally as possible).
- Step 8: Create a detailed report for the client that includes an evaluation of the design and changes made to address any problems.
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.
- 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.
- A scenario is developed to simulate the pump running at the desired speed for constant RPM.
THE FOLLOWING OUTPUT GRAPHS WERE OBTAINED AT THE END OF THE ANALYSIS
- Steady State Analysis with Dampener
- Steady State Analysis without Dampener
- Transient State Analysis with Dampener
- Transient State Analysis without Dampener
RESULTS
Without dampener, magnitude of vibrations recorded are severely increased. According to software results, maximum peak to peak pressure limit has been exceeded. Results confirm that the installation of dampeners is mandatory on reciprocating pumps. The force results also provide that the Maximum forces are at 0.153 and 0.253 kN.