Open Gap HiLo Tool

The Open Gap HiLo Tool is designed to measure the internal HiLo geometry of two pipes that are aligned for open gap welding.

Key features

  • Measures the fit-up between two pipes

  • Two blades measure the internal HiLo through a gap between the pipes

  • Magnetic base makes it easy to use

  • Uses highly accurate dial gauge

  • Calibration/verification stand

  • Has become the industry standard tool

  • Traceable measurements


A client approached us for a tool that would improve on the only HiLo tool that was available at the time which was very inaccurate and unreliable. The pipes to be checked have a bevel and are brought together with a small 2 - 3 mm gap. This allows the probes to go through the gap and measure the fit-up between two pipes is within the desired specification. As the requirement was often for a fit-up of better than 0.5 mm for steel catenary risers this required a tool that would be accurate to better than 0.05 mm. Over a number of iterations we arrived at the tool that we sell today. Early versions were hand held devices but our customers almost always prefer a magnetic base. These devices have become universally used around the world by all the major pipelay companies or welders. The importance of getting pipes to match up accurately is to ensure a good weld and to avoid any stress concentrations due to the mismatch between the pipes. For critical fatigue sensitive pipes, the HiLo measured confirms the fit-up predictions from the OMS SmartFit process and provides the last check before the pipe is welded. The pipe may be checked again for HiLo post weld by OMS’s weld inspection technology.


Unlike our Closed Gap HiLo Tool this tool was required to have two small blades with a hook on each end. To operate the tool first it is placed on the pipe and the magnetic clamp is activated. Next the blades are moved by rotating a thumb screw to get the blades directly above the joint between the two pipes. The dial gauge is then pushed downwards into the pipe against the force of a spring to the point at which the two blades go through the gap between the pipes. The tool will have previously have been set such that the dial gauge registers zero when the blades are of equal length. The dial gauge is then rotated through 90 degrees and the two hooks are then able to touch the inside of the pipe as the pressure on the dial gauge is released. Any mismatch in the blades can be read from the dial gauge as a positive or negative number. The process is repeated as many times as the procedure requires to provide a suitable spot check of the HiLo mismatch between the two pipes.


The Open Gap HiLo Tool is designed to measure the internal HiLo geometry of two pipes that are aligned for open gap welding. The use of standard digital gauges means that the tool will be familiar to pipe inspectors and is simple to use. All tools are sent out calibrated and a yearly calibration and repair service is provided.