CHAPTER 8 MODELING OF WIRELESS SENSOR NETWORKS FOR LPG PLANT MONITORING USING CUCKOO SEARCH

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1 93 CHAPTER 8 MODELING OF WIRELESS SENSOR NETWORKS FOR LPG PLANT MONITORING USING CUCKOO SEARCH 8.1 INTRODUCTION Wireless Sensor Network is a significant field across the globe for monitoring the proper utilization of resources including water, oil refineries, petrochemical plants, natural gas, etc (Jawhar et al 2008). As oil and gas are highly hazardous, maintaining the economic progress of a country depends on aiding of these resources and facilities. The increase in demand of energy efficiency in oil and gas industry paves way for the development and investment in Wireless Sensor Network technologies. There are numerous technologies to monitor the resource exploration, production and transportation. Network services like localization, tracking, data aggregation and energy-efficient multihop routing are used for monitoring the resources with appropriate control mechanism. Considering the above characteristics and prominent features of monitoring, a mesh model is developed to monitor the effective functioning of Liquefied Petroleum Gas (LPG) Plant. LPG is an eco-friendly fuel and hazardous chemical which may result in mass destruction if not handled with care and safety. There are many safety precautions to be followed in a LPG bottling plant and they are nonnegotiable. The manual effort alone cannot support in practicing the safety operations, in addition to aid manual work, some sophisticated and automated systems are essential to preclude accidents. Hence in this research the use of

2 94 WSN technology is investigated to monitor LPG plant. Mesh topology is considered and the performance of the network is analyzed by ZigBee and Wireless Hart protocol. 8.2 LIQUIFIED PETROLEUM GAS PLANT OPERATION LPG bottling plant is a plant where LPG is filled into cylinders for storage and distribution through various LPG distributors. The schematic setup of a LPG plant is described in Figure 8.1. The plant consists of various units as Bullet storage unit, Pump and compressor unit, Bottling unit, Reposition and Dispatch unit, and Maintenance and Control unit (Chandra 2009). The plant has the facility to receive bulk LPG by Tank trucks of various capacities e.g. 7MT, 18MT etc (or) pipeline from a reliable source such as refinery and other LPG Bottling Plant. The LPG is transferred to bullets laid in the plant by means of hoses and pipelines. LPG will be stored in bullets at a pressure of 5 7 bar and ambient temperature conditions. Figure 8.1 Schematic View of LPG Bottling Plant

3 95 Then the LPG is channelized to cylinders by means of pipelines positioned inside the plant. The primary operation in a bottling plant is associated with proper filling of LPG cylinders. The sequence of activities for bottling include receipt of cylinders, visual inspection and segregation, cylinder filling, tare weight marking, tightness test etc. Once the cylinders are received, it is thoroughly checked under two classifications namely new cylinders from manufacturers and old cylinders from customers. All new cylinders received should be supported by Test Certificate for ISI (Indian Standards Institute) inspection and approval from CCE (Chief Controller of Explosives) before they are put into use. Based on the visual inspection the cylinders are segregated as under filled, leaky/defective, spurious, etc. Indepth examination of each and every cylinder is performed and appropriate remarks are put on the relevant transfer documents. The liquid LPG at a differential pressure of 8 bar is filled into the cylinders. Then the cylinders are verified for correct weight to prevent underfilling and over-filling. The corrections are carried out if required. The selfclosing valve is checked for leakage and any other defects. Then the cylinders are immersed in test bath of water, to identify bung leak or body leak and if leaky cylinders are identified it is evacuated and scrapped immediately. The good cylinders are sealed and stored in the repository unit. Then the cylinders are dispatched on the basis of requirements to the needy areas. The overall control of the plant is monitored from the control room. Any obstruction in these activities will shackle the entire operation of the plant. 8.3 NEED FOR PLANT MONITORING Monitoring resource plants relies first and foremost on sensory data information about its surroundings as well as about its internal working. This sensory data represent the next evolutionary development step in plant

4 96 as follows (LPG specifications 2012); 1. The level of LPG stored in the bullets as well as bottled in the cylinders should not exceed 85% of its capacity to ensure thermal expansion and safety norm as pressure should not raise above 11 bar. 2. The gas flow from the outlet of the reservoir bullet should not exceed 40 Gallons/minute. 3. The temperature of the plant should be ambient and should not exceed 410 degree Celsius. 4. LPG has an explosive range of 1.8% to 9.5% volume of gas in air. This is considerably narrower than other common gaseous fuels. LPG liquid is lighter than water while LPG vapor is heavier than air. This gives an indication of hazard of LPG vapor accumulated in low lying area in the eventuality of the leakage or spillage. If these constraints are violated, then the infrastructure of the plant will be ruined. Small amount of gas leakage seems to be a minor issue but eventually it leads to fire blaze and explosions if unattended. The lack of basic safety features will ultimately cause loss of life and destruction to property. Therefore continuous monitoring is pivotal for a crucial infrastructure which causes financial losses to the industry. There are number of technologies to monitor and protect the resource plants. Most of the technologies are specifically designed to detect, locate and report pipeline leakages as pipeline gement plan. The solutions rely on the availability of a wired or fiber optic network to transfer the information to the base station. The wired networks are usually

5 97 connected to regular sensor devices that measure specific attributes such as flow rate, pressure, temperature, etc. There are a number of problems using wired networks with regular sensors for plant monitoring. Mohamed and Jawhar (2008) states that if there is any damage for any part of the wires of the network, the whole pipeline monitoring system will be compromised. It is easy for unauthorized people to disable the monitoring system by cutting the network wires. Different types of information are reported through the network. Some of this information is considered more important to be delivered to the control station than others. For example information reporting a fire is more important than information about pressure measurement. In addition, Duplicate and unwanted information can be transferred on the network causing significant delay for other more important information. This is due to the lack of quality of Service (QoS) support in these existing networks. Jawhar et al (2007) explains the advent of technology in computing and electronics pioneered the wired networks by Wireless Sensor Networks with its immediate physical environment allows each sensor to provide localized measurements and detailed information. The ability to communicate not only allows sensor data and control information to be communicated across the network of nodes, but nodes to cooperate in performing more complex tasks such as statistical sampling, data aggregation, system health and status monitoring. In this research work, the pipeline monitoring is revised and extended for LPG plant application considering overall functioning of the plant. A reliable sensor network model is developed with Cluster based routing methodology for resilient network communication. Sensor nodes are placed in and around various units of the

6 98 plant. The nodes at each unit are clustered by cuckoo search algorithm. The sensed information is transmitted to the base station by wireless HART protocol. Various test conditions are considered and the performance of the plant is evaluated to meet the real time scenario. 8.4 DESIGN OF CUCKOO BASED HART PROTOCOL The developed mesh network model aims to implement an energy efficient plant in leakage detection and monitoring of events. The LPG plant system comprises of uniform distribution for sensor placement. The sensor nodes are deployed in and around the five major units in the plant namely, Tanker Unloading Section; Bullet storage unit; Pump and compressor unit; Bottling unit; and Reposition and Dispatch unit. Ten numbers of sensors are placed around each unit. To avoid redundancy and to provide collaborative data processing, clustered architecture is employed. The cuckoo search algorithm is applied for cluster formation. As detailed in chapter six of section 6.3.1, the cluster formation is carried out by considering node eccentricity, distance constraints and energy level of the nodes. The energy function (8.1) is related to the minimization of energy and maximization of lifetime of the nodes. n 1 f ( df i) 100* di (8.1) i 1 The dynamic clustering architecture helps to suppress redundant data and offers consistency in cluster formation. After the clusters are formed, the Cluster Heads (CHs) fuse or aggregate the information before forwarding it to the base station. The transmission of data to the base station or control room is carried out by HART protocol.

7 Wireless HART Highway Addressable Remote Transducer (HART) communication protocol is established for process monitoring and control in industrial automation. The protocol developed in The wired HART devices have certain constraints like cost, unreliable data delivery to the end user. So the wired HART technologies are modified to the next level of implementation. i.e., Wireless HART. The sophisticated communication protocol was developed in 2007 to provide simple, cost-effective and reliable way to deploy new points of measurement and control without the wiring costs. It is designed for wireless sensing and actuation, where wired sensing is prone to hazards. Hart Foundation (2011) states that the Wireless HART standard supports multiple messaging modes including one-way publishing of process and control values, spontaneous notification by exception, ad-hoc request/response, and auto-segmented block transfers of large data sets. As per the requirements, these capabilities allow communications to be tailored and aids in power reduction and overhead. Wireless HART operates with IEEE compliant radio model and uses Time Division Multiple Access (TDMA) and channel hopping to communicate between devices. The communication protocol differs from MAC in Time-synchronized Mesh structure employing Direct Sequence Spread Spectrum. The frequency management is done as per packet basis and the communication protocol operates in 2.4 GHz. The three main components of HART network are wireless field devices, network manager and gateways. Each device in the mesh network can serve as a router for messages from other devices. Thus it helps in inter communication within the devices to increase the scalability of the network (Leander et al 2011).

8 100 The main advantage of employing Time-synchronized Mesh prototype is to avoid Radio Frequency Interference from other wireless systems such as Wi-Fi networks and cordless phones, RF noise from machinery, physical obstruction of radio paths between devices, multipath effects between sources and receivers, and node losses due to depleted battery supplies and environmentally unfriendly operating conditions (Wagner 2010). The time synchronization among the nodes helps to maintain the information among the nodes by self-made acknowledgement and reception of packets in respective time slots. Clear channel assess tests are available and blacklisting avoids the frequently used channels Algorithm for Plant Monitoring The proposed protocol design is detailed as follows, 1. Initialize the number of nodes, cuckoo nests, eggs in nests, number of cuckoo, step size, location of base station, location of nodes, and energy of nodes. 2. Establish the network, by deploying the nodes around the units. 3. Perform cuckoo search by choosing a node at random from every unit. 4. Check whether the energy function of node is greater than the threshold? 5. If yes, rank the solution as cluster head; else update the solution. 6. Cluster head broadcasts advertisement to abandon nests in the unit. 7. The Worse nodes join the cluster head as cluster members.

9 Nodes sense information. 9. CH creates TDMA schedule for each node to transmit the sensed data. 10. CH receives data from members. a) Normal Functioning Yes /No b) Area of Detection pipelines/ Bullet/ storage/filling/ Tanker unloading c) Type of Fault Leak/ Increase in flow/ thermal expansion/ Fire d) Level of Leakage 11. CH aggregates the data. 12. CH sends signal to actuates the alarm if a) = Transmit the data to the base station using Wireless HART mechanism. 14. Switch on fire water engine if c) = Trip the equipments and halt the plant within 3 minutes. 8.5 EXPERIMENTAL RESULTS AND DISCUSSION The proposed Cuckoo clustering with HART protocol is analyzed by experimental results in order to indicate the quality of decisions the cuckoo search makes on clustering of nodes and efficient data communication to the base station by HART mechanism. The network is developed by analyzing the graph routing algorithm proposed by Liao and Ge (2010) for wireless mesh networks. The network model is simulated using MATLAB. The schematic view of LPG Plant of SHV energy private limited is given in Figure The simulated view of the plant is given in Figure 8.3.

10 102 Figure 8.2 Topographical view of LPG Plant The transmission energy of the nodes is set as watt. The receiving energy of nodes is set as watt. The energy spent in active state of the nodes is set as watt. The number of nodes is chosen as 50.The energy spent in the sleep state of the nodes is set as 0.15 micro watt. The initial energy of the nodes is set as 1000 Joules. The sensor nodes are allowed to sense the data every 5 seconds and the cluster heads are allowed to transmit the data to the sink every 1 minute. The long interval helps in reduction in energy consumption. In Table 8.1, the energy consumption of the plant for the two different architectures is analyzed. It is found that the energy consumption of the Cuckoo Based Hart Protocol exhibits nearly ten times less when compared to ZigBee Protocol.

11 y position (metre) x position (metre) Figure 8.3 Simulated view of LPG Plant Simulation time(s) Table 8.1 Energy consumption ZigBee Architecture Energy consumption (J) Wireless HART Architecture Energy consumption (J)

12 Energy consumption (joules) HART ZigBee simulation time 9seconds) Figure 8.4 Energy consumption of the network The energy consumption of 50 nodes for 1000 seconds is depicted in Figure 8.4. It is inferred that the ZigBee and HART architecture has almost similar energy consumption. Due to the variation in the timeslot in the MAC, the energy consumption in HART is lesser compared to ZigBee Protocol. The HART protocol can be varied as per the applications to achieve desirable results. 8.6 CONCLUSION The Cuckoo Based HART Protocol is developed to achieve energy efficient Wireless Sensor Network by utilizing multimodal objective

13 105 functions. Cuckoo search is applied for cluster head selection and formation of clusters among the Sensor nodes. The proposed protocol is compared with the standard ZigBee protocol. The simulation results exhibits that the proposed protocol produces comparable results mainly due to optimal search process in cluster formation and allocation of appropriate paths in transmission of sensed data. The developed optimal algorithm reduces complexity in chain formation and the test case conditions are verified. The results are obtained by running more number of simulations. The plant modeled with 50 nodes deployed at various units around the plant and the different stages of leakage are analyzed.