pig passage indicator Mechanical/visual pig passage indicators for installation on pipelines, at intermediate pipeline block valve assemblies other launching and receiving ends of pipeline shall be provided separately. The pig signal indicators shall have thread-o-let for fixing on pipeline in field. The pig signal indicator should have the provision of valves isolation for on-line inspection and replacement. Tip of the indicator shall be conical shape. Maximum allowable working pressure shall be 1440/720 psig for high/medium pressure class respectively.