When you’re tightening a nut onto a bolt, did you ever step back and think — that it is only the last turn that makes a difference and the other turns are just wasted motion?

Welcome to thinking “Lean,” a management process that is focused on eliminating all waste in manufacturing a product or providing a service. And as a contractor you’re actually doing both — and given the competitive environment you should be interested in eliminating all waste in your operations as it affects your costs, the bottom line and your sustainability.

This article will introduce Lean concepts while thinking about something typically overlooked in most horizontal directional drilling (HDD) contractors’ operations: the design and performance of their bentonite mixing equipment. Why focus on something considered routine? Because a world-class Lean organization is focused on continuous improvement and no process or equipment is considered too small to examine.

Thinking Lean is based on: 1.) proactively designing processes to avoid waste; 2.) implementing repeatable processes with low variability and high quality; and 3.) continuous discovery and elimination of wastes while operating.

Let’s look at these in the reverse order; there exists seven original wastes that you should be looking to eliminate during operation.

Waiting: Is your drill rig waiting on your mud mixer? This could be because the mixer’s cycle time is too long or because your mixer has a lower operating availability (percentage uptime).

Overproduction: Do you have to pre-mix mud and utilize storage tanks to meet rig pump input requirements during a job sequence (e.g. pullback)?

Motion: Is the hopper of the mixer placed where operators can efficiently and safely load dry product?
Defects: Does your mud mixer filter out typical foreign objects (e.g. pieces of bags, leaves, etc.) and provide fully hydrated bentonite slurry for maximizing drilling components life and in bore performance?
Transportation: Are you transporting backup equipment, spare parts, extra dry product or too large a mixer to jobsites?  

Inventory: Does your mixer have a 100 percent yield? A 5 to 10 percent gain in mixer yield affects other aforementioned wastes and over a short period of time could cost you more than the mixer.

Over Processing: Is your mixer providing 100 percent yield in the shortest possible time or does it need to run for long periods of time — burning energy, increasing your environmental footprint and/or causing delays in other processes?

It is also easy to see how many of these items can impact multiple areas of waste.

For example, if you need to pre-mix mud and utilize storage tanks, you are probably incurring wasted motion and activities as the footprint of your jobsite grows and your operating team needs to work around the extra equipment. Often Lean-thinking organizations perform a spaghetti diagram that maps their people’s movement over time on a jobsite. It is amazing what reducing the complexity of a site and/or efficient placement of equipment can do to reduce the amount of motion used on a job.

Another example that is impacting contractors operating in environmentally-controlled municipalities and regions is the cascading affects of wastes — whereby needing to generate a larger volume of drilling mud, increases drilling waste volume, that leads to a significantly higher volume of waste that needs to be properly treated and disposed of — that drives up costs and associated transport and disposal liabilities.

Next, let’s look at providing for robust and smooth operations. A concept used by Lean organizations is “Takt time.” Takt time measures the maximum time per unit to complete a task, process or product. Takt time analysis was developed to remove bottlenecks that would halt production or cause waste elsewhere (idle machinery, idle people, etc.).

In the case of a mud mixer, it is critical that the Takt time of the mixer is less than that of the drill rig as overall performance in HDD is typically linked to operating uptime and rate of performance of the drill rig. An additional benefit of a Takt time analysis is that it typically leads a team into a “value stream mapping” exercise whereby all flow of materials and information required to complete a process working step or sequence of working steps is analyzed to eliminate wastes. A critical consideration to implementing matched Takt times is equipment reliability, so in the context of a mud mixer, consideration and tracking of equipment cycle-time, operating uptime and maintenance, repair, and overhaul (MRO) needs are of critical importance as an HDD contractor does not want their drill rig sitting idle while waiting for support equipment.

Lastly, proactively designing processes to avoid waste, is a critical step in developing a sustainable Lean contracting business. It means that a contractor and all operating staff identify and design best practices. It should become routine practice that everyone view their work as a process and that they continuously examine those processes for eliminating waste using Lean principles. It is also critical that managers and leaders understand the difference between performance and practices as the sustainable businesses will be the ones with solid practices that can be executed robustly by properly trained staff.

Therefore, a mud mixer should be selected with features and advantages that enable a team to develop mixing processes that robustly mix drilling mud without a specialist. So, let’s take a look at some mixer features that might lead to advantages and Lean benefits that you might have overlooked.

  • The mixer should have multiple shear points (as shown in the diagram on pg. 46) as each shear point enhances hydration and opening of the bentonite platelets and therefore reduces the cycle time needed.
  • The hopper should be designed to prevent bridging of the dry bentonite when being filled so as to not choke off dry product flow, and it should terminate in a large opening at the entry of the mixing chamber to enable the generated vacuum to draw in product even when damp or wet.
  • A trash pump should be used, as it provides for greater handling of heavy muds, will provide greater life, better handle recycled slurries and additives including those designed to prevent loss of circulation as a trash pump has greater internal clearances and is designed to encounter foreign objects.
  • The mixer should contain well placed jetting features to eliminate dead spots in the tank and be able to mix while jetting to provide optimal full volume continuous batch mixing.

Overall, consider the total cost of ownership and operation not just the purchase price — as a good practice whenever you’re looking at support equipment, it is usually best to select whatever makes the drill perform better.

Roger Woods is president of Surface to Surface, which is based in Petrolia, Ontario, Canada. Scott Gray, Ph.D. is senior engineer with BDO-Dunwoody, in Sarnia, Ontario, Canada.

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