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SPC Assumptions

SPC Assumptions

Introduction

Statistical Process Controls (SPC) is a suite of methods that can be employed to control a manufacturing or assembly process. It has a wide range of potential applications ranging from consumer products to defense. It can be employed at the lowest element of component manufacturing or an assembly operation.

This article discusses the assumptions necessary to understand SPC.

Fundamental Assumptions

  • The process is stable and in control.
  • The data are independent of each other.
  • The data of each subgroup are identically distributed.
  • Real valued data are approximately normally distributed and counting data may be approximated by the normal distribution.
  • A measurement can occur in only one subgroup, i.e., sampling without replacement.

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Is a Task a Deliverable?

Is a Task a Deliverable?

Tasks (or action items) are a fundamental building block of an ongoing work-effort or project schedule.  While we tend to think of completed actions as deliverables, a project schedule can also be considered a project deliverable….and the value of well-written task (within the schedule or otherwise) is often overlooked.

Generally, a task begins with a verb (some action to be performed) to achieve a milestone or outcome to some desired level of completion.  (Recall a previous related article where we discussed the “definition of done”.)

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Was BP’s Catastrophe in the Gulf a Defining Moment for the Oil Industry?

Was BP’s Catastrophe in the Gulf a Defining Moment for the Oil Industry?

Guest Post by Geary Sikich (first posted on CERM ® RISK INSIGHTS – reposted here with permission)

1. Introduction

The BP Deepwater Horizon catastrophe cast a shadow on the oil industry and its senior executives.  Has the industry learned its lessons or will it be forced to repeat the same mistakes over and over again? Oil company executives and board members should have seen the Deepwater Horizon event is as a wake-up call for the industry. [Read more…]

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Pump Life Extension — The Impeller

Pump Life Extension — The Impeller

A spinning pump impeller provides the means to draw incoming product through the pump, energise it, and then force it out under pressure. The impeller coverts the electrical energy from the motor into hydraulic energy of the liquid. It does this by taking the liquid into the center of the impeller and flinging it outward at high speed. To efficiently continue to do this the impeller must remain in the same condition as it was when first installed. If the impeller deteriorates the conversion from electrical to hydraulic energy becomes inefficient. Power is wasted, flow and pressure fall and the pump cannot do its designed duty. [Read more…]

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Your organization sucks at reliability if (#2) … it loves firefighters so much it forgets to hate fires.

Before you go on, please have a look at British comedian John Oliver’s video on infrastructure – https://www.youtube.com/watch?v=Wpzvaqypav8.

OK, if you are reading this and still haven’t watched the video … please go back and try again. You can do it.

If you haven’t watched the video by now, then I concede defeat. In short, the video is a humorous take on the state of US infrastructure. Particularly bridges. Bridges have been collapsing with alarming frequency in recent years. And after much political wrangling there is still no plan to pay for fixing crumbling columns, spans and struts. It is not as if the federal and state governments don’t know how bad things are (again … watch the video).

Oliver proposes a perhaps novel reason for all of this. [Read more…]

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Common and Special Causes of Variation

Common and Special Causes of Variation

Introduction

Quality Costs for manufacturing or services can be categorized as prevention and appraisal costs, and internal and external failure costs. Control occur in prevention and appraisal activities, both of which rely on data. However, when data is collected, it shows variation. One must understand variation to know how to react.

Dr. Deming indicated that 94% of variation is from common causes and about 6% is from special causes. So what are the common and special causes of variation?
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Entering a New Market Gone Wrong

Entering a New Market Gone Wrong

Guest Post by John Ayers (first posted on CERM ® RISK INSIGHTS – reposted here with permission)

This risk story includes risk at the enterprise level, the program/project level, and the product level.  From the enterprise level risk, it was a little naïve on my company’s part to think they could go from zero not having manufactured any sonobuoys previously) to full up production the first time around without investing the time and finances to go up the learning curve prior to making the bid.  From the program/product level risk viewpoint, the baseline plan did not include sufficient component and subassembly trial builds and testing before finalizing the concept, preliminary design and final design. [Read more…]

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Equipment Criticality

Equipment Criticality

How do you decide what level and type of maintenance to use on an individual item of plant and its sub-assemblies? Not all equipment is equally important to your business. Some are critical to production and without them the process stops. Others are important and will eventually affect production if they cannot be returned to service in time. While other items of plant are not important at all and can fail and not affect production for a very long time. [Read more…]

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Your organization sucks at reliability if (#1) … it could be on ‘that’ Fatboy Slim album cover.

Your organization sucks at reliability if (#1) … it could be on ‘that’ Fatboy Slim album cover.

Alright … this needs a lot of context. English electronic music artist ‘Fatboy Slim’ released his ‘You’ve come a Long Way, Baby’ album in 1998. Its cover art was a photograph of an attendee at the 1983 ‘Fat People’s Festival’ in Danville, Virginia. And perhaps due to its ‘heritage,’ the album’s cover was changed to an image of a bookshelf for North American listeners. But the rest of the world got to bask in its magnificence.

So what is particular about this photograph? The subject is a larger than average human (as you would expect noting where it was taken). And he is wearing a shirt emblazoned:

I’m #1 so why try harder?

I am not writing this as a commentary on human value versus instinctive stereotypes. Far from it. There are plenty of people who are ‘better than all others at something’ that do not have sleek chiseled physiques. [Read more…]

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How To Create An Environment of Innovation

How To Create An Environment of Innovation

I found myself seated next to a corporate executive in a recent flight out of Atlanta, while I was attempting to read a book, he was yammering away on his cell phone about quarterly results and the need for a reduction in head count.  Hearing this, my hopes of becoming engrossed in a good book was now over. Now I’m just upset at how some folks seem to make life changing decisions with such little regard or emotion. [Read more…]