Check how to apply for obtaining nbsp;Renewal of Approval for Heat Exchanger Manufacturer . Designated Officer for delivery of Service is Inspecting officer of concern Regional Office. Maximum number of days to get service Delivered is 23 days wide Government Notification no. MISC2017/C.R.66/Lab-9 Dt . 20.06.2017 . Procedure involved for the service nbsp;is Scrutiny of documents, Verification of competency of firm by site visit and issue of approval / renewal letter