Liquid Haulers Maintenance holds an R stamp certification from The National Board of Boiler and Pressure Vessel Inspectors NBBI), allowing us to repair and alter pressure-retaining items, while providing proper supporting certified documentation.. Frame Repair & Custom Frame Fabrication - Overfill Protection Systems -Tank Steaming -Tank Repair & Custom Tank Fabrication - Braking Systems - Vapor Recovery Systems - P.T.O Systems - Metering Systems & Calibrating We re also state certified to perform annual federal,LP,Vacuum,Petroleum,and DOT cargo tank inspections including: Visual (V) Leakage (K) Internal (I) Pressure (P) Thickness (T) Internal/ External DOT Inspection