Machining – Riggs Machine and Fabricating, Inc.

Tensile testing (aka tension testing)

11/07/2022RMF

We recently got to work with a local steel company to help create samples for the tensile testing of their rolled products. I wanted to look at what the samples were going to be used for once they left the shop.

Tensile Testing measures tensile strength, breaking strength, maximum elongation and reduction in area. There are several variations of these tests, including how the loads are applied across the materials. Below is an example testing unit. The prepared bars are held in the arms and pulled apart.

Universal Tensile Tester — CC BY-SA 4.0 Ganitz

These tests are performed after rolling to ensure uniformity and consistency in the product line.

Other reasons for performing these tests are:

– to find out how well a product will perform

– to see if it meets the client’s standards

– to test a new design

Pallet of Bars to be Cut — A pallet of bars to be cut for testing.

To perform the tests properly, the samples must be prepared for the testing device (tensometer). The ends are wider to be easily held by the device, while the center is cut thinner to allow the deformation and fracture to occur at this point. To help repeatability of testing, the samples must be as similar as possible.

Cutting a Bar for Testing Cutting a Test Bar

The tester will apply an even and consistent force across the sample until it fractures. The elongation that occurs, as well as the amount of force that was necessary to create it, is used in the final calculations.

bar cut for testing

These calculations will help with the following tests:

Yield Strength – The point at which deformation in the part occurs.

Ductility – Percentage of elongation.

Strain Hardening – How much the part hardens with plastic deformation (plastic deformation – a yield point, once passed, is some fraction of the deformation that will be permanent and non-reversible)

Modulus of Elasticity – The point where the material will no longer return to its original length and permanent deformation occurs.

Ultimate Tensile Strength – The maximum stress that the material can withstand while being stretched or pulled before breaking.

thick bar for testing

Thick Bar for Testing - Side Shot

Riggs Machine & Fabricating – Serving industry in KY, OH and WV for over 45 years!

Mill Caps – Handling the Heat and Pressure of the Modern Forge

02/25/2022RMF

As molten billets of steel race through the plant, they are formed into their final shape through a series of ever tightening rolls and presses.

Rolling plates - a hot slab partially finished, Steel Works, Homestead, Pa. - Library of Congress — Rolling plates – a hot slab partially finished, Steel Works, Homestead, Pa. – Library of Congress, Prints & Photographs Division (rep. # LC-USZ62-69674 )

"Rolling Mill with Coil Box" by mouser-nerdbot is licensed under CC BY-NC-ND 2.0 — “Rolling Mill with Coil Box” by mouser-nerdbot is licensed under CC BY-NC-ND 2.0

The stands that hold these forming rolls are under extreme stresses as they progressively squeeze the metals into shape; be it flat sheets, bars, round stock or rails.

Mill Cap - Finished - Front Shot — Mill Cap – Finished – Front Shot

Mill Cap - Finished - Rear Shot — Mill Cap – Finished – Rear Shot

At the top of these stands are the mill caps – holding the components together, absorbing constant shock and vibrations as they maintain pressure on the searing metal as it is is worked beneath it.

The original cap was a cast part. This machined version will be stronger and less susceptible to cracks and weak spots due to the possibility of bad casting. It is also made of a finer grade of metal than the old, worn piece.

On Mill - Ready to Start — On Mill – Ready to Start

Using the drawings, we will CNC a new component from a 22 inch burn-out weighing over 19,000 lbs. (Not many suppliers can provide a single piece of metal that large.) Hooks were welded on the sides so the block could be moved throughout the shop.

Burn Out - Top Shot — Burn Out – Top Shot

Burn Out - Side Shot — Burn Out – Side Shot

These higher quality mill caps will provide a better support system and a more dependable and stable stand. In the long run, they will help provide our client produce a better product and maintain a longer running mill.

Riggs Machine & Fabricating – Serving industry in KY, OH and WV for over 45 years!

Precision Shafts to Get You Running Again!

05/30/201912/17/2021RMF

They say “wheels make the world go round”, but without shafts, nothing would ever move.

A shaft connects a mechanical power source to gears, wheels, turbines, rotors and much more. Shafts can be as simple a basic round bar or as complex as containing exacting bearing fits, keyways, sleeves, grease fittings, snap ring grooves and splines.

Often, the shafts we see have been in service for many years, sometimes running non-stop. Unfortunately when these older shafts break (as shown here), there aren’t drawings available and not a lot of time to get the new shaft machined and the unit running again.

This shaft broke and we got it in 2 sections, still in the housing. After disassembly, we made hand sketches. While the housing was cleaned and checked, we created 3D drawings and then machined a new shaft.

Here is the new shaft ready for inspection. After passing final inspection, the housing was reassembled and the unit was ready for production use.

Finished Shaft – Ready for Unit Assembly

Hopefully a broken shaft won’t take one of your machines, or worse, your facility down. But if it does, Riggs Machine has the experience to get you running again.

Riggs Machine & Fabricating – Serving industry in KY, OH and WV for over 45 years!

Rail Welding Shears

02/01/201904/17/2019RMF

Used when creating a Butt Weld between two sections of train rail, this shear takes a lot of abuse. At the same time, it must follow very tight tolerances to maintain the profile of the rail (especially when a high speed train is running across it).

A butt weld is created in the field using a mobile electric flash-butt welder. The two sections are joined and electricity is applied to the rail ends. The flash-butt welder squeezes the sections together at very high pressure, permanently joining them, but this also creates a seam at the joint with a segment of slag.

Rail w/Hot Slag after Butt Weld
(notice the manual shear in the background)
“Thermite Rail Welding” by PetrS. 2013 licensed under CC

The RAIL WELDING SHEAR is clamped onto the rail and slid along the rail, by the mobile welder, cutting off the hot slag leaving only a small remainder that will be later ground smooth.

These shears are precision cut out of Nitronic 60 – a high strength metal known for it’s wear resistance – with a wire EDM machine. The EDM unit cuts parts slower, but with more precision than a waterjet or laser cutter.

The final grooves are added via a CNC and the units are then inspected. A hard-surface weld is added and machined to create a precision cutting edge. The parts are assembled to complete the rail welding shear.

These are ready for the rail and making the travels of passengers and goods go smoother and safer.

This video shows a portable flash-butt welder in use. Notice the Rail Shear clamped on the rail before the unit is lowered on the section.

Riggs Machine & Fabricating – Serving industry in KY, OH and WV for over 45 years!

Welcome Gregg Nichols to the Riggs Team!

01/24/2019RMF

We’d like to welcome Gregg Nichols to our staff. Gregg has a combined 28 years in Industrial Distribution & Manufacturing Operations and Sales.

His prior experience includes 5 years with Perfection Rubber (operations manager and sales), 18 years with MSC / Dolin Supply (team leader and outside sales) and 4 years with American producers (outside and industrial sales)

The business segments he previously focused on included:

Coal
Construction
Chemical
Manufacturing
Petroleum
Power Generation
Steel Production

Gregg’s areas of expertise include:

Hydraulic Hoses, Tubes and Fittings
Metal working – Machining – Hole Making
Material Handling (lifting and rigging)
Pipes, Valves & Fittings
Safety

Gregg has jumped right in and got off to a strong start. His outgoing personality and years of knowledge have been a perfect fit here at Riggs. Call him for a visit to your facility and see why he’s an invaluable asset to our team!

Tapered Tube Plugs – Not as Simple as it Seems

11/20/201804/17/2019RMF

Used during repairs and outages, this simple looking device becomes a necessity. The Tube Plug is hammered or welded into the open section of pipes in boilers and heat exchangers. They plug the end of the pipe to either stop the flow of steam or coolant. If the plug’s seal is not tight the coolant can seep into the material and contaminate it.

What makes this seemingly basic item so important are a few factors. First, its fit must be right. Sure they are tapered, but they must fit without damaging the existing pipe or sliding too far in. Also, the material specifications for Tube Plugs can vary greatly. While some plugs can be made out a carbon steel like 1018, other plugs must match the existing pipe section (i.e. A350 with more carbon content) or even stainless steel, nickle or other metals. If the wrong type of metal is used, it could lead to corrosion, rust, leaks or a possible reaction with existing materials in the system.

Even the machining isn’t always as simple as it may seem. Bar stock in not always available in a size close to what the job requires or the material type needed is only available as plate. In that case, a plug larger than the finished size would be cut from the plate and then turned turn by hand on a lathe. Time consuming, yes, but necessary for a professional fit.

At Riggs Machine & Fabricating, we not only have the experience, but we ask the questions to make sure the job is done right, the first time. Don’t trust those supposed simple jobs to just any shop. Call Riggs first for the dependability and quality your facility demands.

*(Morton, John, 2 Electrolyte Heat Exchanger Tube Bundles in the 8×6 Foot Wind Tunnel, 1975) – http://catalog.archives.gov

Riggs Machine & Fabricating – Serving industry in KY, OH and WV for over 45 years!

Industrial Classroom Training Aids

08/10/201804/17/2019RMF

If you ever wondered where the custom training equipment in industrial classrooms come from, then look no further than Riggs Machine.

At Riggs we can create custom pieces from scratch, like this “oil flinger” demonstration unit. Shown from conception, with 3D renders, to the final unit in the classroom.

And we also often disassemble, create “cut-away” sections, sandblast, paint and reassemble actual pieces of equipment to be used in working classrooms. These units are used for hands-on training before students hit the field. Much better than a video or book based lecture.

Some of these jobs can be more time and labor intensive than actual repairs! But we don’t mind. We’re proud to be part of the team who help educate the next generation who will be keeping our refineries, steel mills and factories running.

Riggs Machine & Fabricating – Serving industry in KY, OH and WV for over 45 years!

Explosion Proof Hatch – Pyrite Ducts

07/27/2018RMF

Here are some newly machined explosion-proof hatches for pyrite ducts.

In preparing coal for energy production, pyrite, a sulfide that contributes to air pollution and acid rain, is removed before burning. The separated pyrite is forced through ducts to waiting hoppers using high pressure fans. These ducts have negative pressure in them. If a chunk of pyrite gets stuck in a hopper then unit has to be shut down and the duct removed from the unit to be cleaned.

Photo by James St. John / CC by
Sphalerite-Pyrite

With the addition of these hatches, if a chunk of pyrite gets stuck in the hopper, it is only a temporary shut down while the hatch is opened and the material is washed out. Once the hatch is sealed, the unit is quickly brought back on-line.

These hatches have also been used as inspection doors on gearboxes, giving quick access to the internals for routine maintenance or adjustments. The locking tab on the hatches also helps keep the unit secure.

A Phonographic Finish!

06/29/201804/17/2019RMF

No, not what is used when a race is too close to call (that’s a photo finish). But a machined finish added to the raised face on a flange to give an extra level of security to prevent leaks and maintain effective seals.

The Phonographic Finish is actually a serrated finish, either concentric or spiral (much like the grooves on a record), that will grip the gasket between pipe sections firmly.

These finishes are typically added on a lathe to specifications set either by the company ordering the flange, the manufacturer or ASME B16.5 guidelines. Below is a render of the completed flange with bolt holes. I would have included a photo of the actual completed unit, but as soon as it was finished, it was rushed to the job site! But that’s why we’re here. Everyone knows who to call when a custom part is needed in a hurry.