×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Are you an
Engineering professional?
Join Eng-Tips Forums!
• Talk With Other Members
• Be Notified Of Responses
• Keyword Search
Favorite Forums
• Automated Signatures
• Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

#### Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

# Failure Rates2

## Failure Rates

(OP)
Does anyone have recent updated failure rates for ESD type ball valves, solenoid valves and quick exhaust valve ?

This is equired to be included in a fault tree analysis to determine valve PFD.

Thanks,

### RE: Failure Rates

Contact the manufacturers of the devices.  They MUST have this information.

### RE: Failure Rates

2
The original poster might want to contact the Reliability Analysis Center (http://rac.alionscience.com) and see about getting a copy of their publication NPRD-95 "Nonelectronic Parts Data".

For the last poster (mooimooi), you may find MIL-HDBK-338, "Electronic Reliability Design Handbook" helpful.  In chapter five of the handbook, it derives the exponential form of the reliability function assuming the hazard rate equals the failure rate and that the failure rate is constant (these assumptions are not always valid but are often used for simplistic, first-cut analysis).  The hazard rate is defined in terms of

h(t) = (-1/R(t))*(dR(t)/dt)

and so from linear ordinary differential equations theory one can solve this to get R(t) = exp(-h(t)*t) = exp(-lambda*t) if h(t) = lambda = constant.  Note that for very small values of lambda the Taylor series expansion of the exponential function exp(x) = 1+x+(x^2)/2!+(x^3)/3!+... can be used to approximate the probability of failure, which is F(t) = 1-R(t) as simply lambda, given the above assumptions.  You get that by 1-exp(-x)=x-(x^2)/2!+(x^3)/3-... and all the second-order and higher terms vanish for very small values of x (for our application, "x" is lambda).

Anyway, you can get MIL-HDBK-338 in .pdf format from
http://assist.daps.dla.mil/quicksearch/
and though it is a huge document (4.7Mb, over 1000 pages) it is definitely worth skimming through to identify directly applicable parts.

Good luck,

-MC
ps. You might want to check my math.  I'm submitting this at 1am while riding out an episode of insomnia.

#### Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

#### Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

#### Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a partâ€™s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

# Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

• Talk To Other Members
• Notification Of Responses To Questions
• Favorite Forums One Click Access
• Keyword Search Of All Posts, And More...

Register now while it's still free!