Bubble leak testing or vacuum box testing is an integral part of a tank inspection process as recommended by API and other international standards to establish the condition of a tank bottom plate weld or shell to bottom plate weld.
The latest edition to Silverwing’s vacuum box range is the V750 which has been completely redesigned with the operator and API 650 / 653 inspection standards in mind.
The design incorporates a 750 mm weld inspection length, extremely rugged body, calibrated vacuum gauge and vacuum relief valve, internal LED’s to ensure correct visibility along the test weld and a new two stage seal designed to maximise efficiency and reduce operator fatigue.
Vacuum gauge and relief valve
The V750 has an industrial vacuum gauge rated to 30 in Hg as well as a calibrated vacuum relief valve. The use of a calibrated vacuum relief valve ensures the correct vacuum is generated as recommended by international standards. The advantage of the relief valve is once the required vacuum has been generated (20 or 10 inch Hg) the relief valve opens and maintains the required vacuum preventing too great a vacuum being generated which can damage the vacuum box and cause injury to the operator.
Electric pump or compressor driven
The vacuum is generated by the use of an electric vacuum pump or by use of an Air Vacuum Generator (AVG) and external compressor. Inspection companies tend to use the electric pump with the vacuum boxes due to its greater flexibility while construction companies tend to use the AVG based systems.
High and low pressure models
The vacuum boxes are rated to either 20 inch Hg (10psi/0,7bar) which are recommended for in-services tanks or 10 inch Hg (5psi/0.37bar) which are recommended for new build tanks.
The V750 vacuum box is supplied with an industrial 63 mm face glycerine filled pressure gauge rated to 30 in Hg as required by ASME V Article 10 – Bubble Test Vacuum Box Technique. Along with the vacuum gauge is a vacuum relief valve which prevents the box from drawing too great a vacuum which could damage the box.
The optional built in LED lights provide the recommended light intensity along the weld under test as recommended by API 650.
The LED lights can be switch on and off with a simple push button eliminating the need for the operator to move their standard halogen lights as they move round the tank.