Efficient integration of IoT-based micro storages to improve urban drainage performance through advanced control strategies

The smart rain barrel (SRB) consists of a conventional rain barrel with storage volumes between 200 and 500 L, which is extended by a remotely (and centrally) controllable discharge valve. The SRB is capable to release stormwater prior precipitation events by using high-resolution weather forecasts to increase detention capacity. However, as shown in the previous work, a large-scale implementation combined with a simultaneously opening of discharge valves clearly reduce effectiveness. The aim of this work is to systematically investigate different control strategies for wet weather by evaluating their impact on sewer performance. For case study, an Alpine municipality is hypothetically retrofitted with SRBs (total additional storage volume of 181 m3). The results show that combined sewer overflow (CSO) volume and subsequently pollution mass can be reduced between 7 and 67% depending on rain characteristics (e.g., rain pattern, amount of precipitation) and applied control strategy. Effectiveness of the SRBs increases with lower CSO volume, whereas more advanced control strategies based on sewer conditions can clearly improve system's performance compared to simpler control strategies. For higher CSO volume, the SRBs can postpone start of an CSO event which is important for first-flush phenomenon.

Pipe Knocked From Supports by Hydraulic Transient Event

Following what was considered a routine realignment of liquid product lines and tankage at a storage and transfer facility, an incident occurred that resulted in significant movement of a 20-inch pipeline, causing a large section of it to fall from its supports. The event also resulted in the failure of a gasket at a valve flange and loss of containment. The alignment activities and pump startup were investigated for the potential to generate a hydraulic transient capable of generating sufficient force to cause the movement. A transient hydraulic model of the fluid in the piping as it was aligned at the time of the event was generated to assist in determining the cause and to help prevent a similar occurrence in the future. Several scenarios were modeled and are discussed in this paper: 1) pump shutdown from steady flow, 2) pump start up with the discharge valve open, 3) pump startup with the discharge valve closed, and 4) pump start up with a vapor cavity present near a closed valve at the high point in the line. Pipe stress and finite element analysis were used to assess the displaced pipe and to determine if it could be placed back into service. The piping stress analysis indicated that the highest stress in the piping was below the yield stress of the material. Results from a detailed finite element analysis with material nonlinearity confirmed that there was no global plastic strain in the piping due to the event. This left a potential for local plastic strain due to the impact of the pipe against any hard surfaces, and this was addressed with visual examination. In the end, the pipe was lifted back onto the supports, lateral restraints were added at pipe support locations, and procedural changes were implemented to reduce the likelihood of future events.

The Effect of Size and Material of Packing Seal and Pump Flow Rate to Leakage Rate at Stuffing Box of Centrifugal Pump

This research explore on the effect of size and material of packing seal and discharge valve opening to the leakage rate at stuffing box for pump P7301-A. Leak at stuffing box is unavoidable due to gap exists between the pump casing and shaft. Therefore, it is necessary for a suitable sealing system which includes packing size and material to be installed on all pumps for controlling the leakage rate without damaging the pumps. It is also important for operator to know the proper discharge valve opening at which the pump should be operated to get minimum leakage. Experiment was conducted by recording the leakage volume at stuffing box with changes of size (9mm, 10mm and 11mm) and material (graphite, polytetrafluoroethylene (PTFE) and PTFE-Asbestos) of packing seal and discharge valve opening (50%, 75% and 100%) that would determine the pump flow rate. The experiment was executed and analyzed using one factor at a time (OFAT) method whereby the testing of factors conducted one at a time instead of multiple factors simultaneously in determining which setting would lead to the lowest leakage rate without compromising the pump’s healthiness. Feasibility analysis was also conducted on the operating cost focusing on saving in utility bill and maintenance cost that focused on painting and fitting replacement works. Result from experiment and analysis showed that packing seal size and discharge valve opening have effect on leakage rate at stuffing box while material of packing seal is not significant in influencing the leakage rate of this pump. Larger size of packing seal would cause lower leakage rate due to greater obstruction at stuffing box. Leakage rate also declined when the discharge valve was fully opened due to less resistance created at the discharge line had reduced the pressure in the pump casing which led to less leakage at stuffing box. Feasibility analysis showed cost saving of RM5,930.00 on the operating cost and cost saving of RM221,200.00 on the maintenance cost for 10-year operation of 10 pumps can be achieved. Outcome from this study can be utilized to reduce the plant operating cost, maintenance cost, manhours saving and preserve the treated water resources.

Study of Pulsation Pressures in the Stages of an Electric Submersible Pump at Shut-Off Under Various Speeds of Operation

Background: Electric Submersible Pumps (ESPs) are widely used in agricultural fields, petroleum, and various other industries. These pumps are mostly driven at a constant speed since an A.C. motor is normally used as the drive. However, ESPs can also be operated at various speeds by employing a Variable Frequency Drive (VFD). Several patents have been published in ESP. Normally these pumps are started with the discharge valve at its closed position in order to control the starting current. When the ESP runs at its shut-off position, it will develop a higher head and an increase in fluctuating pressure. In order to evaluate the effects of pressure fluctuation, its characteristics must be investigated. Objective: Experimentally investigate the characteristics of pressure pulsation which are generated at each stage of a multistage ESP during shut-off condition at various speeds. Methods: An ESP with five stages was selected for conducting experiments. A VFD was used for operating the ESP at five speed settings from 80 to 120 % of its rated speed. Piezoresistive transducer was placed at the delivery side of the pump to acquire the signals of unsteady pressure. The pump was operated at closed valve condition at each speed, and unsteady pressure signals due to pressure pulsation were captured. Results: Obtained results have indicated the presence of fundamental frequency pertaining to vane passing frequency and harmonics of higher frequencies. Conclusion: Study of pressure fluctuations at shut-off will help to analyze the failures of ESP due to vibration which occur when the pump runs at closed valve position for a prolonged length of time and stability of these pumps at lower flow rates.

Research on the Diagnosis Method of Reciprocating Compressor Valve Leakage Fault With Vibration Signal

Reciprocating compressor is one of the key machines in chemical and petrochemical industries. The most common failure mode in the compressor is valve leakage. Generally, leakage fault is considered to be of little harm to machines. However, it was found that the serious leakage of the valve would cause abnormal bending vibration of the piston rod and accelerate the formation of fatigue cracks. Most researchers utilized the signal of cylinder dynamic pressure, valve temperature or acoustic emission to diagnose valve leakage fault. However, each of these methods has disadvantages. In this paper, a new method is proposed to diagnose valve leakage fault using vibration signal. The main idea is that the severity of valve leakage can be assessed by analyzing energy of the main frequency band during compression process and the delay of discharge valve opening. Firstly, the vibration signal in the time domain is segmented into several angle-domain signals according to the keyphasor signal. Each of the angle-domain signals corresponds to one cylinder working cycle. Then, the time-frequency analysis is conducted with the Gaussian window, and the main energy frequency band and the compression process are determined. Filtering the signal with a bandpass filter based on the main energy frequency band, and the root-mean-square (RMS) of the filtered signal during compression process is calculated in a crank revolution. Besides, the angle of discharge valve opening is detected. Based on the two indicators, the severity of valve leakage can be estimated. To verify the effectiveness of the method, keyphasor of the flywheel, cylinder dynamic pressure and vibration acceleration of valve are acquired on a double-acting oil-free air compressor under different degrees of suction valve leakage. The experimental results and analysis show that the proposed method can well identify the valve leakage fault, even in the case of weak leakage, and is very effective in quantifying the severity of leakage.

Semi-active noise control for a hermetic digital scroll compressor

Hermetic digital scroll compressor has been widely used as a small-scale organic Rankine cycle application in the heating, ventilation, and air conditioning systems. A clunking noise issue is recently found in an air conditioning outdoor unit, and the main cause of the noise is experimentally identified to be the impact of the scrolls in the compressor unit during the switching process. The semi-active control methods are thus designed to greatly reduce the noise level by using additional valves to adjust the pressure changing rate within the modulation chamber. The response time for the impact of the scrolls can then be controlled by the added valves. The additional release valve with a smaller diameter pipe parallel to the main valve is tested firstly for its performance. Slower flow rate is produced and the pipe can extend the response time and decrease the speed of the impact process by reducing the pressure changing rate. The use of a discharge valve is also tested for controlling the pressure changing rate inside the chamber. The discharge valve with an opposite effect to the release valve is found useful for solving the noise issue. Both noise and vibration results confirm that the impact noise in the frequency range of interest can be reduced by using the proposed semi-active control methods.