Blinding is a process which refers to the complete sealing off of a pipe, tower, exchanger, vessel, duct or any other refinery equipment by use of a metal plate which is properly designed so that it is scrammed onto the end of a flanged vessel or pipe or even inserted between two flanges. This is a well-established safety and maintenance process in the gas, oil, onshore and refining industries. It is important to note that the plate covers the bore completely and it has the capacity to endure the maximum that the pipe has without any leak past the plate. Through this process it is a possibility to attain positive flow shut off or rather absolute closure.
During the blinding process a very important document referred to as a blind list always prove to be of value. A blind list is a record listing, which is written, indicating where minds must or have been slot in to specific pieces of equipment which are isolated. Superior to it is the blind book which can be said to be a master book for recording blinding. The contents of the master record book includes description of the blind, the size of the blind, the operator who was in charge of the blinding process, date of removal and the specific specialist that was in charge for the removal, the location of the blind and also the size of the blind. The importance of such records cannot be ignored as they help in the review and keeping progress. Blinds can be casually categorized into two, those that are temporary installed and the permanently installed blinds. The latter refers to blinds that are meant to remain fixed and thus indefinitely in service. The temporarily installed blinds are not to remain in service indefinitely as there removal is known and at a near date.
There are a number of uses of spectacle blind in a refinery located in offshore terminals. It is important to know the maintenance and installation procedures used during management of activities of maintaining the blinds. For instance, it is required that pressure surges are kept in a tight control and a changeover with a relief valve is carries out such as through installation of disc control in a less expensive way it ensures the correct strategy is used that ensures the needs of end users of these blinds are achieved. This ensures their maintenance and prevention of effects such as explosion ort destruction of blinds. It provides the main activities involved during construction of blinds and maintenance activities that are important so that cases of accidents are reduced.
Before the blind list is approved, operations and maintenance supervision will be responsible for identifying the entire blind sites as well as the energy source isolation. During this preliminary but important phase.
There is a number of equipment that facilitates the blinding process. An example of such equipment is a drum whose blinding is achieved by means of a pipe that is connected to the sewer system and can be blinded or subjected to physical disconnection before the issue of entry permits. During the opening process for the drums for hot work services, all lines are expected to be blinded and valve venting should be closed. Equipment used during blinding process is the furnace or a boiler. This is where blinding is done so that the integrity of the tubes is not affected. The routine blinding activities can include repairing the refractory blocks, conducting ultrasonic tests, fuel gas tests and firebox steam. When there is firing of a burner and corresponding fire outage in the refractory system, the tubes are subjected to ultrasonic tests for a specified period of time and the fuel gas lines are subjected to blinding. During the process of operations in the firebox containing common stack with another furnace that is active, it is required that blinding should be provided in the form of isolation of the flue gas that emanates from the tubes.
Equipment that is subjected to blinding is the exchangers where the main blinding activities include ensuring the lines to the tubes or sides of the shells are blinded. It may be necessary to blind an exchanger on either side if there exists a possibility of leakage that can result into leakage of hydrocarbons. Furthermore, it is required that in a case where there is the need to perform a hot work on a line, blinding needs to be performed on the equipment that connects it such as a pump or a furnace so that it is not accessible to the hydrocarbons. When a line contains harmful chemicals, it shall be prepared before being subjected to blinding. In addition, it is required that tanks should be blinded. This is where when there are openings in tanks for entry, a connection of steam lines that connects directly to the tank needs to be blinded in addition, it is required that foam lines connecting tank roofs and other lines of drainage also need to be blinded.
Equipment that needs to be blinded is the pumps in the case where there is the need to perform a hot work and when there is a leakage in the block valves or when there’re is lack of attendance to the functional location of the pump within a period of eight hours.
There are certain precautions that need to be complied with during binding process. For instance, before the commencement of activities, possible sources of gas flare should be identified followed by identification of communications systems that enables communication with employees in the field and any area that can result into leakage of gas into the flare. This will be followed by adjustment of the operations of the units that connects the flare lines so that possible problems are identified and production rates adjusted so that losses are not inflicted on the workers. This should be followed by formation of a work platform that allows proper accessibility. Operation functions should be focused on monitoring the level of progress of the activities so that communications with the affected units is ensured and maintained. While this work will be in progress, a fire watch based on a fire horse line will be used during this testing period. During the installation process, craftsmen involved in installation of the blinds will be provided with protective clothing so that they are protected from flash fires. In case of any deviations, a discussion must take place between the operations manager and the safety supervisor so that the right strategy is used during the installation stage.
During blinding process, there are certain steps that are followed. This ensures blinding process is carried out effectively and the aim of performing efficient functions of pipelines is achieved. The first step during blinding process is the blind list selection process and its identification. Before a blind can be approved, maintenance supervisor will be involved in the activity of identifying any blind and sources of energy isolations. This will be followed by furnishing the maintenance process by means of an approved blind list and a description of blinding locations. The maintenance supervisor then issues the maintenance plan for the system is maintained. The next stage of blinding process is the blind selection stage. This is where the selected flange is in accordance with the piping system into which the installation of the blind takes place. The supervisor the selects the right thickness based on the required pressure and temperature to be sustained by the blind. It is recommended that blinds that have the capacity to sustain temperatures above 700oC should be selected.
The next phase during blinding process is the installation stage. This is where the person in charge of blind installation gets the permit to do so following conducting energy source control in each refinery for each permit process. This will be followed by commencement of installation of the blinds. The blinding process must account for the location o flanges where the nearest flanges are selected during blinding process based on the safety measures to be observed and the nature of the equipment that needs to be isolated. When installation of blinds is complete, contractor craftsman will conduct tests on the master blind for all blinds created. Each blind will be labeled with a red label after it has been installed by the professional in charge of installation. The control room will be tagged with yellow tags in a corresponding manner. When these activities are completed by the craftsmen, there will be a visual investigation of each blind so that installation can be verified. This will be followed by initialization of the master blind list corresponding to each blind that has been created.
The last stage during blind formation is blind removal stage. Upon completing the tasks that require blinds, the supervisor in charge of blind installation obtains the permit that allows him to perform the tasks of removing the blinds. This is followed by the installation of new gaskets, followed by removal of blinds after which is followed by removal of the initial master blind list. Another activity in this stage will be visual inspection of each blind so that they can be removed and initial blind when completed. When the crafts men have completed the operations and blinds have been removed and a master blind has been initiated so that a list that verifies visual inspection is created, operations such as checking if all the blinds have been removed will follow and blind identifiers will be used to identify blind locations. When it has been verified that removal has been implemented in all blinds and blind identifiers have been removed, the operations supervisor performs the tasks of initializing the master blind and declares it complete.
Oil refineries are exposed to a number of harmful conditions that can cause destruction of the piping and delivery systems. The instance of leakage of gases can be of great impact to the affected company and its employees. This has result into the need to sensitize oil manufacturers of the need for binding operations. In this study, an insight has been provided where the main focus has been the stages involved in the design of gassing system so that any individual or organization can participate in the activity.
It is also found that coordination between professionals in the mining sector is of great importance, as a result it ensures an agreement is reached with regards to the maintenance procedures that are more important for oil company operators so that they do not incur high loses as a result of leakage of gasses and liquids from the containers.