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Bridging Pit Gauge - Standard

Part No.: N88-09

Bridging Pit Gauge - Standard

Price: $750.00
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Bridging Pit Gauge System

The Bridging Pit Gauge System allows the Corrosion Inspector to Span over or Cantilever into Large Areas of Weight Loss Corrosion, to obtain accurate and consistent measurements, or cross sections, of Pit Depth. As conditions dictate, the operator can simply use the Main Blade or can assemble the Bridging Pit Gauge up to an over all length of 28" (725mm).

The contact Surfaces (Blades) of the Bridging Pit Gauge are fitted with an exclusive Knife Edge, so they can be used on Flat, ID (Convex), and OD (Concave) Surfaces, where a flat or notched contact surface can introduces error on Convex Surfaces. Like our Standard Pit Gauges, the Knife Edge gives the operator a clear view of the contact point, and the area being inspected.

With the addition of the optional Magnetic Hold Downs, the operator uses their width to quickly align the Bridging Pit Gauge System to a curved surface. This leaves his hands free to scan through very large areas of weight loss corrosion. This holds true when the Bridge Elements have been assembled with a slight contour on an irregular surface.

Pit Gauge
N88-9Main Blade, Imperial Dial Indicator, Connector Blade, 2-Extender Tees, End Blade, Slider Blade, Hardware, Extra Contact Point, and Carrying Case.
Main BladeN88-9-1Center and End Dial Indicator Mounting Positions, Cutaway Nose for next to welds. 5.5" (144mm) long.
Connector BladeN88-9-2Joins Tee Sections to increase length. 3.5" (90mm) long.
End BladeN88-9-3Mounts on end of Tee for extra contact. 1.5" (38mm) long.
Slider BladeN88-9-4Extra Point of Contact and doubles as an End Blade in Spanning Configuration. 1.5" (38mm) long.
Extender TeeN88-9-5Extends effective length of all models. 12" (305mm) long (Longer Tees are optional).
Hold Downs
N88-9-61 required for each Tee Section used. 15/8" (41mm) long.
Fastener KitN88-9-7Fasteners, Allen Key, Nylon Thumb Screws, Contact Point.
Carrying CaseN88-9-8Hard Sided Plastic Carrying Case for entire kit.


All Bridge type Blades (Main, Extender, End,&Slider) have two distinct sides, that are differentiated by the transverse mounting holes. On one side there is a clearance hole, while on the opposite side the hole is threaded ). When assembling, start the fasteners on the Thread Clearance Side of the Blades, so the fasteners can be properly tightened against the Extender Tee's. Do not tighten fasteners if an Extender Tee is not within the Slot area of a Blade.

When assembling the unit, press firmly (as illustrated) on the Extender T, and the Blade you are attaching it to, while tightening the 10-24x" Button Head Machine Screws with the 1/8" Allen Key. When assembled in this fashion, the overall length of the unit should have a straightness of approximately 0.015". When more accuracy is required, assemble the unit on a flatsurface.If the surface of the workpiece has an irregular surface (slight curve, distinctbend or hills and valleys), simply assemble the Bridging Bar, but do nottighten the fasteners. This will leave the Bridge loose and free to match thecontour of the workpiece. When the operator has contoured the assembledBridge, all the fasteners can be tightened. The operator should be mindfulthat this contouring assembly will be fine at a given point, however it will needto be checked when the Bridging Bar is repositioned.

Magnetic Hold Downs

Magnetic Hold Downs are intended for Scanning with a Bridging Pit Gauge, however they can be used on any of the Jr. Bridging Pit Gauge Group, with a diminished range of motion. Magnetic Hold Downs also provide the inspector with increased mobility, as he is not required to support the Bridging Pit Gauge. The following are instructions for the use, and using, the Magnetic Hold Down Blocks.

Magnetic Hold Down Blocks are designed to easily slide on the Extender Tee's, and are best put in place prior to assembly. With the Bridge assembled, and placed on the workpiece, the entire Bridging Pit Gauge can travel over a distance of about 9" (290mm). Longitudinal or position measurements of the Bridging Pit Gauge are taken off the Scales (imperial and metric divisions) that are fastened to the top of the Extender Tees.

Each Magnetic Hold Down is equipped with 2 (two) "-20 UNC Nylon Thumb Screws. The Thumb Screws have two purposes, firstly to retain or capture the Magnetic Hold Down onto the Extender Tee. The second use of the Nylon Thumb Screws is to set the tension or to lock the Magnetic Hold Downs. As an example, if the Bridging Pit Gauge is being used vertically, the operator will want the tension set higher, to keep the unit from sliding. If the Bridging Pit Gauge is being used on a highly irregular surface, the operator will want the Nylon Thumb Screws set very loose, to allow the Blades to more easily slide over the workpiece.

When setting a Bridge to a Convex surface, such as the OD of a Pipe, or a Concave surface, such as the ID of a Vessel, the Magnetic Hold Downs are used to align the entire assembly. The operator will see this when he attempts to rock the Magnetic Hold Downs from Side to Side. If the unit rocks, the Magnetic Hold Downs are not on the same Longitudinal Axis and must be realigned. When the rocking stops, the operator knows the Bridge is aligned, however, most formed surfaces (pipe, vessels, and tanks) are irregular, so rocking may not be eliminated but must be kept to a minimum to increase measurement accuracy.

When preparing for a Scan, the Magnetic Hold Downs should be placed at the correct longitudinal position along the Extender Tee. When general evaluation is being done, and the operator is not recording measurements, place the Magnetic Hold Downs in the Middle of the Tee, to allow movement of the Bridge in both directions. When the operator is going to record measurements, for Plotting a Cross-Section, place the Magnetic Hold Downs at the end position of the scan, then move the bridge to the starting position. The operator takes a reference reading, between a magnetic Hold Down and the Scale on the Tee, before starting the longitudinal movement.

Shipping Weight:   2.00 lbs
Manufacturer:   Western Instruments
Manufacturer Part No.:   N88-09
Part No.:   N88-09

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