Question

FMEA (Failure Mode and Effect Analysis)

Smelly Gus’s Gas Station sells gasoline. Each non-diesel station carries 87, 89, and 93 octane unleaded gasoline. Customers must prepay for gasoline by inserting a credit card or by prepaying with cash inside the station.

Instructions

Complete a FMEA. Identify the pump’s: function(s), potential failures, potential effects of failures, potential causes of failures, and any possible process controls. Determine Criticality for each potential failure.

Answer 1

Ans 1.  The FMEA or the Failure Modes and Effects Analysis

Every product or process is subject to different types or modes of failure and the potential failures all have consequences or effects.

The FMEA is used to:

· Identify the potential failures and the associated relative risks designed into a product or process

· Prioritize action plans to reduce those potential failures with the highest relative risk

· Track and evaluate the results of the action plans

The Steps to Complete a FMEA:

Step #1: Review and label the Process Steps (using your process map) and the intended function or functions of those steps

Step #2: Consider the Potential Failure Modes for each component and its corresponding function

· A potential failure mode represents any manner in which the component or process step could fail to perform its intended function or functions.

Step #3: Determine the Potential Failure Effects associated with each failure mode. The effect is related directly to the ability of that specific component to perform its intended function

· The effect should be stated in terms meaningful to the product or system performance.

· If the effects are defined in general terms, it will be difficult to identify (and reduce) true potential risks.

Step #4: For each failure mode, determine all the Potential Root Causes

· Use tools classified as Root Cause Analysis tool, as well as the best knowledge and experience of the team.

Step #5: For each cause, identify Current Process Controls. These are tests, procedures or mechanisms that you now have in place to keep failures from reaching the customer

Step #6: Assign a Severity Ranking to each effect that has been identified

· The Severity Ranking is an estimate of how serious an effect would be should it occur.

· To determine the Severity, consider the impact the effect would have on the customer, on downstream  operations, or on the employees operating the process.

· The Severity Ranking is based on a relative scale ranging from 1 to 10.

· A “10” means the effect has a dangerously high severity leading to a hazard without warning.

Step #7: Assign the Occurrence Ranking

· The Occurrence Ranking is based on the likelihood, or frequency, that the cause (or mechanism of failure) will occur.

· Once the cause is known, capture data on the frequency of causes. Sources of data may be scrap and rework reports, customer complaints, and equipment maintenance records.

Step #8: Assign the Detection Rankings

· To assign detection rankings, identify the process or product related controls in place for each failure mode and then assign a detection ranking to each control. Detection rankings evaluate the current process controls in place.

· A control can relate to the failure mode itself, the cause (or mechanism) of failure, or the effects of a failure mode.

· To make evaluating controls even more complex, controls can either prevent a failure mode or cause from occurring or detect a failure mode, cause of failure, or effect of failure after it has occurred.

Step #9: Calculate the Risk Priority Number (RPN)

· The RPN is the Risk Priority Number. The RPN gives us a relative risk ranking. The higher the RPN, the higher the potential risk.

· The RPN is calculated by multiplying the three rankings together. Multiply the Severity ranking times the Occurrence ranking times the Detection ranking.

· Calculate the RPN for each failure mode and effect.

· Prioritize the Risks by Sorting the RPN from Highest Score to Lowest Score. This will help the team determine the most critical inputs and the causes for their failure.

Risk Priority Number (RPN) : An index used in FMEA (Failure Modes and Effects Analysis) to prioritize possible failure conditions, calculated as the product of Severity x Occurrence x Detection Difficulty. If Severity, Probability of Occurrence and Detection difficulty are each evaluated on a 1-10 scale, then the Risk Priority Number can range from 1 to 1000.

Step #10: Develop Action Plan

· Taking action means reducing the RPN. The RPN can be reduced by lowering any of the three rankings (severity, occurrence, or detection) individually or in combination with one another.

Step #11: Who is Responsible

· This is a very important step in Taking Action!

· Be sure to include person(s) responsible and the deadline

Step #12: Take Action

· The Action Plan outlines what steps are needed to implement the solution, who will do them, and when they will be completed.

· Most Action Plans identified during a PFMEA will be of the simple “who, what, & when” category.

· Responsibilities and target completion dates for specific actions to be taken are identified.

Step #13: Recalculate the Resulting RPN

· This step in a PFMEA confirms the action plan had the desired results by calculating the resulting RPN.

· To recalculate the RPN, reassess the severity, occurrence, and detection rankings for the failure modes after the action plan has been completed.

Ans 2.

Pump’s: function(s)

The fuel at the gas station is kept in underground tanks and is pumped up to the surface and into your car by a pump motor. ... As the gas level in your tank rises, the air continues to flow - but when the gas reaches the level of the pipe, the air pressure inside the tube drops.

The gas pump is made up of two components. There's the mechanical component, which actually does the work of pumping the gas into your car. Then there's the computer, which tells the mechanical component what to do and monitors how much gas you've pumped so that it knows what to charge.

The fuel at the gas station is kept in underground tanks and is pumped up to the surface and into your car by a pump motor. When you select the grade of gas you want before you start pumping, the computer tells the blend valve to go to work. The blend valve is responsible for mixing the various types of fuel stored in the fuel tanks to provide the correct blend of gas.

As the right blend of gas is pumped from the underground tanks to your car, it passes through a flow control valve which regulates the speed of the gasoline flow. Information about the fuel passing through the flow control valve is passed on to the computer, which in turn displays the litres (and dollars) you're putting in to your car.

As you know, when your tank is full, the nozzle handle releases, shutting off the flow of gas. This is because there's a small hole near the tip of the nozzle and a small pipe inside that leads back to a shutoff mechanism. This tube constantly sucks in air while you're filling the tank. As the gas level in your tank rises, the air continues to flow - but when the gas reaches the level of the pipe, the air pressure inside the tube drops. The shutoff mechanism in the pump handle senses the change in suction and trips the nozzle off. So…very similar to elves.

We explore the three most common causes of fuel pump failures.

The fuel pump is responsible for delivering fuel from the gas tank to the engine. A seemingly simple task that can easily be compromised when outside issues affect the performance of the pump.

potential failures

The three most common causes of fuel pump failure include:

1. Fuel contamination: Fuel is jeopardized from corrosion, debris and moisture, which can all bring visible contaminants into the tank.

2. Clogged strainers/filters: The aforementioned contaminants eventually clog critical components including strainers, filters and the fuel pump itself. This blockage ultimately impairs the flow of fuel, which may affect the vehicle during acceleration, among other long-term impairments.

3. Electrical issues: Electrical faults are also significant contributors to fuel pump failures. The most common electrical issues are rusted connectors, loose connectors, or melted wiring and connectors. To help identify issues of poor electrical connections, a high quality digital volt/ohm/meter should be used to test for voltage drops and continuity.

potential effects of failures

The three major effects of fuel pump failure include:

1. Hesitation during acceleration: The vehicle’s acceleration is slower than normal or the engine shuts down completely during acceleration. This could mean the fuel pump is struggling to keep up with the increased need for gasoline.

2. Rough idle: A clogged fuel pump prevents the proper amount of gasoline from getting to the engine, which ultimately affects the idle speed.

3. The vehicle isn’t starting: This is cut and dry, but if the vehicle fails to start the fuel pump may be to blame.

If any of these are detected, it’s recommended to inspect the fuel pump to check the status of your vehicle and proactively prevent further issues.

possible process controls

There are a number of different disciplines and workplace specialties in which process control can be used such as:

Engineering

​Software and systems development

​Operations

Quality assurance

​Increase system throughput without additional expenditures

​Increase automation, decrease human intervention

Eliminate rework, scrap, and inefficiencies

​Enhance your capabilities to take on more work

​Boost energy efficiency

· Remote monitoring, control, and management of oil pipelines from the control centre

· Use fibre optics for long-distance transmission of data across the country of installation

· Gigabit redundant ring for high data availability

· Rugged design capable of operating under harsh environmental

Criticality for each potential failure.

- Design method for reliability critical systems is proposed.

- The method identifies similarities in AD and FMECA to improve system reliability.- The method was validated by application to the design of a LNG fuel supply system.

In product design, the initial design stage is being increasingly emphasized because it significantly influences the successive product development and production stages. However, for larger and more complex products, it is very difficult to accurately predict product reliability in the initial design stage. Various design methodologies have been proposed to resolve this issue, but maintaining reliability while exploring design alternatives is yet to be achieved. Therefore, this paper proposes a methodology for conceptual design considering reliability issues that may arise in the successive detailed design stages. The methodology integrates the independency of axiomatic design and the hierarchical structure of failure mode, effects, and criticality analysis (FMECA), which is a technique widely used to analyze product reliability. We applied the proposed methodology to a liquefied natural gas fuel gas supply system to verify its effectiveness in the reliability improvement of the design process.