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Information + Imagination = Design Optimization

Dec. 17, 2013
Demands on MWD tools Part count reduction “Should cost” analyses Divining design consequences Fundamental design changes FEA for operation Regional manufacturing, distribution

“Sensitive, yet tough” is the job description for the hammer-union pressure transmitter used in oil-and-gas well servicing applications like cementing, fracturing and acidizing. These fine-tuned sensors must accurately and repeatably measure the hydraulic and pressure characteristics of drilling fluid in the harsh environments of the secondary, oil-and-gas recovery industry. 

Withstanding mud, corrosion, vibration, humidity, temperature extremes—and the routine shock of hammer blows during installation—the units play a pivotal role in communicating with downhole measurement-while-drilling (MWD) tools to help ensure safety and efficiency in the production environment. The unit’s reliability is critical to the integrity of hammer-wing union fittings used in thousands of energy installations around the globe (see sidebar.)

The world leader in sales of these components is the Viatran business unit of Dynisco, a Roper Industries company, whose model 510 hammer union pressure transmitter has been an industry staple for years. With a number of competitors vying for position as a supplier in the oil-and-gas market, Dynisco decided to review the design of its core product.  Seeking to make the newest model stand out, they launched a redesign project to incorporate functional improvements that customers would respond to, and to increase assembly efficiency and cost-effectiveness.

Begin with Benchmarking

A company-wide philosophy of continuous improvement prompts Dynisco to emphasize design evaluation early in its product development process. Knowing the value of applying Design for Manufacture and Assembly (DFMA) from Boothroyd Dewhurst—with benchmarking, Lean, and Total Cost of Ownership (TCO) methodologies—Viatran engineers joined Dynisco’s Value/Analysis/Value Engineering (VAVE) group to conduct the redesign project. 

The team started with a DFMA-based, competitive benchmarking process. “Evaluating existing Viatran product assemblies alongside competitor offerings helped us glean important design and cost information right from the start in our redesign,” said Matt Miles, DFMA and value engineering manager at Dynisco.

At the core of any DFMA analysis is part-count reduction, Miles noted. “Dynisco has a mantra of ‘part count, part count, part count’,” he said. So to chart every one of those parts, the team disassembled, piece-by-piece, the base parts and adapters of four Viatran units and seven different competing products. This helped them to create a bill of materials for each assembly using the Design for Assembly (DFA) application within DFMA. Each component, as well as its assembly process, was meticulously counted and analyzed, including individual solder joints, wires, and potting (embedment) operations, as well as the major mechanical parts and printed circuit boards within each hammer-union unit.

Knowing the actual geometry of the base part and adapter of each unit gave the group insight to how they were assembled—and provided input for the DFA Index calculations that the team used to compare the assembly efficiencies of their own products versus those of their competitors (Fig. 2.)

“The more parts there are in an assembly, the greater the difficulties or intricacies in the design, and the lower the Index number,” said Miles. “We saw competitors with both lower and higher indexes when compared to our products.  Based on that, we investigated what, in each design, led to a lower or higher index.  That was answered by what feature sets were included, combined with how it was assembled.

“Using this information,” he continued, “we wanted to simplify as much as we could in the refreshed design to help our assemblers.”

Following the DFA analysis stage of the benchmarking, Dynisco’s VAVE group undertook “should cost” analyses for all major machined components from each assembly using the Design for Manufacture (DFM) portion of the DFMA software. Major mechanical components were modeled in 3D CAD to recreate the assemblies and look at the amount of raw material used for the base part, and for the adapter, which houses the electrical connector for each unit. 

Then, the CAD models were analyzed with DFM to determine the cost to machine each part. Combining their DFM cost analyses with CAD models helped the team to understand material usage better, the workpiece size (billet), the manufacturing processes used to machine the parts, and the final weight and cost.

Generating Design Ideas

The benchmarking results generated plenty of ideas for product redesign. “By ranking the attributes we could use the information to avoid previously unknown pitfalls and to guide our new designs,” said Joel Neri, engineering manager at Viatran. As subsequent rounds of design concepts were developed for the new hammer-union unit, now known as Model 511, the VAVE group could provide both DFA and DFM analyses for each proposed assembly by quickly adjusting the DFA and DFM files created during the initial benchmarking process. Creating Pareto charts helped the team dive deeper into the consequences of proposed design changes by identifying “Cost by Subassembly,” “Part Count by Subassembly” and “Part Count by Type.”

This highly collaborative effort generated a number of important design changes. To improve access, the internal diameter of the adapter was increased to accommodate the protective gloves that many workers wear in the field.  To protect the electrical connector from sledgehammer strikes (used by field workers to tighten the Weco nut down onto the hammer union unit on the adapter top), the adapter wall was extended higher and thickened. To address debris collecting in the top of the adapter, the new model has four large window openings and a sloped surface around the connector, providing an easier path to flush out soil, dust, and mud.

And, the most fundamental design change the team came up with adhered to the favorite saying of John Biagioni, vice president/general manager of Viatran, when talking about identifying waste in the business: “eliminate the need.”  The 510 uses six screws to assemble the adapter to the bottom base part.  Each screw uses a teardrop, anti-rotation washer for durability in the heavily vibrating working environment, and each washer is secured with a retaining ring.  A total of 18 fasteners join together just two parts.

“Reducing part count in product assemblies is a core tenet of DFMA,” said Biagioni.  “It consistently provides positive improvements in reliability, quality, and delivery, and it makes products cost-effective and easier to assemble.”

The clarifying design-thought the team came up with? Replace all 18 fasteners by converting the adapter screw directly into the base part. Not only did this innovation eliminate screws, it also eliminated any perception from the field that the six visible mounting screws were a design weakness (they weren’t, as will be shown later.)  (Fig.  3.)

During the redesign, the VAVE group also investigated different materials and manufacturing processes for the new model using DFM.  Based on the design requirements and final geometry, the part was an ideal candidate for investment casting.  By casting the adapter part to “near-net shape,” time-consuming and costly machining processes could be completely eliminated.

For example, the second stage of the benchmarking exercise identified that the workpiece used for machining the 510 adapter is a billet of 304 stainless steel that weighs 4.7 lbs.  After machining, the finished part ready for assembly weighs 1.1 lbs. — which means that 3.6 lbs of stainless steel, 76% of the billet, is being wasted.  Switching to investment casting for the 511 adapter, a 2.9-lb. casting blank is used and only 0.9 lbs. of material is machined away.  Designing with the manufacturing process in mind resulted in significant reductions in both the amount of material used and processing time for the adapter.

DFMA metrics for the entire assembly tell the story well:

•  An improvement in the baseline DFMA index from 7.0 for the 510 assembly, to 9.6 for the 511.

•  Total part count decreased from 102 for the model 510, to 66 for the model 511 (Fig.  4.)

•  Two printed circuit boards were merged into one and solder joints and a snap-fit electrical connector were eliminated.

•  Overall, a total of 36 fasteners were eliminated.

•  A 25% reduction in assembly time was projected.

Meeing Real-World Targets

Now, with their design finalized for the 511, the team needed to find out if the new model would fully meet its performance targets in the real world. They started by creating rapid prototypes of the components’ CAD files using stereolithography (3D printing.)  “This allowed us to touch and feel the parts and mentally walk through the asembly process while having them in hand,” Miles said. The screw-down adapter was the design change that most dramatically reduced assembly time. 

While physically manipulating their prototypes was helpful, the engineers also wanted to quantify the stresses and deformations that would affect the hammer union during actual use. So, they developed finite element analysis (FEA) models from the 511 CAD files to simulate and predict the effects of both normal operating pressures and sledgehammer blows. “Corrosion, vibration, and sledgehammer hits are the hammer union’s enemies,” Miles explained. Baseline FEA analyses were run on the existing design, as well as on the new one. (Fig.  5.) 

“Similar to comparing our benchmarked design against the new one with DFMA analyses, we used the FEA analysis to ensure that the new design would meet, if not exceed, the performance and design criteria of the original,” he said.

“FEA can validate DFMA analysis by showing that you have a strong, robust, cost-effective design,” according to Miles.

“Using DFMA with 3D modeling and FEA really allowed design and development to progress more quickly before ever cutting metal,” Neri added. “This definitely saved a few expensive steps in the process.”

FEA also showed that the screws in the 510 would not fail under typical impact loading in the field, i.e., the adapter would deform first. As noted earlier, there had been a perception from the field that the screws were a weak point; of course, eliminating them in the redesign completely removed that perception. (Fig.  6.)

The Effects of TCO

The early, combined focus of DFMA, Lean, and VAVE on the design of the 511 hammer union was complemented by a Total Cost of Ownership (TCO) initiative that Biagioni implemented at the same time.  TCO analysis begins with the piece-part costs procured from within the supply chain as the TCO model considers where those are purchased—factoring in freight, insurance, duties, and fuel surcharges in shipping from supplier to the business. Finally, additional overhead and risk factors are added into the calculation.

In the case of the 511 project, the team reviewed what TCO would be for a hammer union piece part procured from a supplier in China. They tracked its movement from Shanghai to Dynisco headquarters in Massachusetts, near their welding supplier.  But then there was a switch in suppliers, and no adjustment to the value stream: The part next went to Viatran near Buffalo, NY.  After inspection, the part was put in sets and shipped to a second welding supplier in Syracuse.  Once assembled, the two-piece weldment was shipped to yet another supplier for clean-up and finally back to Viatran for assembly.

The TCO analysis of this exhaustive and expensive value stream showed an additional $22 per hammer union unit in overhead expenses.  To address situations like this, Dynisco has adopted a philosophy of regional manufacturing and distribution.  “In its simplest form, this means build where you sell the product,” said Biagioni. “Regional manufacturing and distribution is currently the quickest way to fulfill demand while minimizing risk.”

Response to demand, wherever it may be, is improved too by incorporating Lean Postponement into designs, to enable the quickest possible reaction to variation.  This involves designing products using as many commercial off-the-shelf (COTS) components as possible, parts that can be made anywhere in the world because they have been right-toleranced.

Postponement was worked into the 511 redesign too. Since customers require many types of electrical connectors, the 510 hammer union offers seven different options.  The same is offered on the 511, but now Viatran has just one casting blank part number into which they can machine the tapped mounting holes and bore for seven different connections. “The same goes for how we stock parts,” said Miles.  “We don’t build up assemblies with the different adapters and connectors; we build them as we need them.  These are the kinds of downstream effects we see from using DFMA strategies.  We had 10 drawings for the 510 adapter.  For the 511 we only have two!”

With the 511 project nearing completion, the team anticipated running future projects in the same way.  “That will be easy now, since we have fundamentally changed our product development process with DFMA, Lean, VAVE, and TCO,” said Miles.  “This 510 hammer union pressure transmitter project provided us with an opportunity to fully explore the power of all these tools and document the results.  We followed our new process to a ‘T’ with the 511, and the results speak for themselves. We’ve learned to design faster, and smarter as well.”    

Lynn Manning is a a science and technology writer in Rhode Island. Contact her at Tel. 401-272-1510