Maintenance & Repair
Figure 2 : P & ID extract with valve location . Adapted from https :// www . enggcyclopedia . com / 2011 / 03 / typical-pid-arrangement-heat-exchangers /
2 : Defining activities – This is a list of the tasks required to replace the valve . It also includes estimates of labor , cost , and duration for each of the activities . It is worth mentioning that the MP must possess accurate knowledge of all procedures and regulations that govern the activities – for example OSHA requirements regarding scaffolding , double block and bleed , lockout tagout , etc . 3 : Controlling the activities – Either the PM or someone designed by it needs to inspect the location and assess the quality of the activities being done . Often this includes controlling changes and unexpected situations that arise once the task begins . has frequent meetings with an operation representative , where they discuss not only this task , but others required for the optimum performance of the plant . In one of these meetings , the operation personnel will explain that they cannot wait until the next turnaround to change the valve ; they want to plan a small-duration shutdown to perform the replacement . This could be the result of a need to clean the heat exchanger and to use the opportunity to replace
the valve as well . Once a date for the shutdown is agreed upon , the maintenance planner will put together a list of resources required to execute the replacement . The Maintenance Planner will now move on a two-pronged approach . First , a request for a new valve will be sent to the procurement department , using the same specification as the original valve . The request might include gaskets and bolting , if these items are not readily available . There is always the possibility that the company will have the valve already in stock . In this case , an inspector will be sent to the warehouse to assess if the valve is indeed in condition to be installed ( damage due to improper preservation may have occurred . All materials associated with the task of replacing valve GV-001A are earmarked with the number of the maintenance task , thus preventing them from being used for a different purpose . The second prong is the creation of a list of resources - besides materials – that will be required to the replacement . For this , a field planner goes to the valve location to inspect the site , provide a clear identification of the valve , and list all required resources . For example , the field planner might take a picture of the GV-001A valve ( see Figure 3 ) and later
Milestones
It is worth noting that many of these milestones are associated with estimates of manpower and duration .
Steps for a typical valve replacement
A valve that needs replacement may be anywhere in a plant . In some locations , it may require work at height ( see Figure 1a ); or it may be a light butterfly valve in low-pressure , plastic piping ( see Figure 1b ), which would require no special equipment or procedures for rigging and lifting . The valve that will be used to define the replacement process is a 6 ” # 150 gate valve located upstream a shell and tube heat exchanger ; this valve is identified as GV-001A in the associated P & ID ( See Figure 2 ). When closed , this valve prevents fluid from reaching the heat exchanger HEX-01A during maintenance . A 6 ” # 150 gate valve is fairly representative of the majority of valves found in a refinery . Once operation detects that valve GV-001A needs to be replaced , they log an entry in the maintenance software used by the company . The entry will identify the valve ( tag ) and state the reason why it needs to be replaced ( failure to open , internal leaking , etc .). The maintenance planner
Prior to shutdown
• Confirm date and time of shutdown
• Installation of temporary external lighting ( if necessary )
• Scaffolding erection
• Insulation removal prior to access
• Lifting equipment available on site
• Transport of tools , valve , and other related materials to location
• Assess if crew is trained in all the required procedures ( blind installation and removal , gasket replacement , valve installation , etc .)
• Tagging isolation points and preparing gaskets and blinds for installation
• Tagging of valve to be replaced
During shutdown
• Line flushing
• Isolation of line pressure at the appropriate points
• Work permit for valve replacement
• Inspection of piping surface for damage ( Corrosion under Insulation , for example )
• Disconnection of earthing jumpers ( interruption of electrical continuity )
• Removal of bolting from valve
• Valve removal
• Inspection of flange faces
• New valve installation
• Inspection ( for example , flow diretion and angle from upright position )
• Reconnection of earthing jumpers
• Torquing of valve bolting
• Lubrication of valve stem
• Check packing for tightness ( and correct it if need be )
• Removal of blinds
• Pressure testing complete and documented
• Final inspection
• Site cleaning and old valve removal
After shutdown
• Surface treatment and coating ( if required )
• Coating inspection
• Reinstalation of thermal insulation
• Removal of temporary external lighting
• Scaffolding disassembly and removal
• Final inspection
• Closing of the task on the maintenance software
18 Valve World September 2022 www . valve-world . net