where should the spectacle blind be placed ? before valve or after valve?
where should the spectacle blind be placed ? before valve or after valve?
(OP)
In PID, where should I place the spectacle blind, before valve or after valve(flow direction)? I need your advice





RE: where should the spectacle blind be placed ? before valve or after valve?
RE: where should the spectacle blind be placed ? before valve or after valve?
In fact, the spectacle blind is applied for positive isolation purposes; then depending on the conditions it can be put before or after a valve. The main point is that it should be located where would be in line with maintenance procedures and local line/equipment isolation i.e. its application would have minimum impact on the plant operation and leading to minimum loss of inventory...
RE: where should the spectacle blind be placed ? before valve or after valve?
Shut the valve.
Break flange on downstream flange of valve -> CANNOT use a wafer valve for this! ... Note: Breaking this flange is a one-valve isolation - but you have to break the flange to establish a two-point isolation.
Insert spectacle flange, rotate the spectacle, make up the spectacle flange to clamp the spectacle against pressure loss and leakage past the valve.
Write work permit to release work.
RE: where should the spectacle blind be placed ? before valve or after valve?
i.e. if the flow is going into the vessel the blind goes downstream of the valve. If the flow is going out of the vessel the blind goes upstream of the valve. In both cases it's on the vessel side.
Putting the valve closer to the vessel than the blind means you have to isolate everything else in the process piping that feeds into the location to swing the blind.
As a chem eng/metallurgist the first part of any answer I give starts with "It Depends"
RE: where should the spectacle blind be placed ? before valve or after valve?
There might be some exceptions; for example: in the case of a maintenance drain valve even though the flow direction is out of the vessel, the blind should go downstream of the valve.
RE: where should the spectacle blind be placed ? before valve or after valve?
Do You mean You have to empty the complete vessel?
RE: where should the spectacle blind be placed ? before valve or after valve?
As a chem eng/metallurgist the first part of any answer I give starts with "It Depends"
RE: where should the spectacle blind be placed ? before valve or after valve?
RE: where should the spectacle blind be placed ? before valve or after valve?
As a chem eng/metallurgist the first part of any answer I give starts with "It Depends"
RE: where should the spectacle blind be placed ? before valve or after valve?
RE: where should the spectacle blind be placed ? before valve or after valve?
In the PIDs i have seen/reviewed the spectacle blind is placed on the nozzle of the vessel. if there is a spectacle blind for positive isolation somewhere in the PIDs, then depends on the equipment/section/process that you intend to isolate.
regards,
Vlad