Correct way to certify hydrostatic testing when it is not 100% (and Sample Size)

#1
I work in the hydraulic hose industry and came across an issue yesterday that has me stumped because our company has been doing it this way for 30 years. We perform hydrostatic testing on our hose assemblies per the requirements of SAE J517. The standard says to test every sample, double the working pressure of the hose and hold pressure for not less than one minute. Our company had interpreted the “test every sample” as to we determine a sample size. We use an AQL of 1.0 by default when a sample size is requested. When testing is done, the paperwork gets turned in for formal test certification to be created. On the test cert we list the specification, pressure, time duration as well as all of the sample represented in the lot, so if the order is for 20 hoses and we only tested 13, we are certifying that all 20 hoses passed testing. Is this misleading? Should we only be certifying to the number of hoses tested?
 
Elsmar Forum Sponsor

Ronen E

Problem Solver
Staff member
Moderator
#2
Yes, it's misleading. Either state that only 13/20 units were tested (I wouldn't recommend it) or state that the lot was tested at an AQL=1.0. Selecting that level of verification means that you (and whoever accepts your shipment, provided that they are aware of this practice) is okay with 1.0% of the units actually failing, in the long run. Please also consider that AQL sampling is not purely statistics/mathematics-based, and it includes an economical component acting behind the scenes.
 

Randy

Super Moderator
#3
Keep it simple and honest "Testing has demonstrated that......." or "Test samples have shown......" and leave it there. It's not a lie and it's not misleading.
 

Ronen E

Problem Solver
Staff member
Moderator
#4
Keep it simple and honest "Testing has demonstrated that......." or "Test samples have shown......" and leave it there. It's not a lie and it's not misleading.
Whether the statement is honest or misleading would depend on what comes instead of your "...............".
Wordsmithing is exactly what makes the difference between real "simple and honest" and misleading. And yes, a statement can be both "not a lie" and misleading.
 

Randy

Super Moderator
#5
Whether the statement is honest or misleading would depend on what comes instead of your "...............".
Wordsmithing is exactly what makes the difference between real "simple and honest" and misleading. And yes, a statement can be both "not a lie" and misleading.
How can either one be misleading? Have not tests been performed? Were the tests done of samples and not the whole? You drive a car everyday made up of parts that have not been 100% tested, fly on airplanes and eat food. OK so they don't use some scientific, gee-whiz, whamo-bamo test protocol and they just grab a line every now and then, test it to whatever pressure they do and it passes... Can we prove it wrong or invalid? Nope.....And like a light bulb the stinking thing can fail at any time
 

Ronen E

Problem Solver
Staff member
Moderator
#6
There's nothing misleading in informing that some of the units have been tested, as long as everyone is on the same page as to the level of testing (i.e. that it's not 100%). It's only misleading if stated in a way that can create an impression factually different from the truth.
 

Mike S.

Happy to be Alive
Trusted Information Resource
#7
This may be a bit off topic, but I'm curious:

You have a lot of 20 hoses. Do you test 13 of those actual hoses, and, if they pass, ship the tested 13 with the untested 7?

Does the test in any way degrade the hose, even if it passes?
 
Thread starter Similar threads Forum Replies Date
K AS9100 - 7.3 - Are these black and white questions with specific correct answers AS9100, IAQG 9100, Nadcap and related Aerospace Standards and Requirements 1
R What is the correct way to refer to NIST? Calibration Frequency (Interval) 4
T Correct MSA study for an automated camera system which makes attribute inspection Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 1
M NANDO codes of products - These are not the GMDN codes, correct? EU Medical Device Regulations 4
K The correct way of doing a 2 Sample T test Reliability Analysis - Predictions, Testing and Standards 7
B PED 2014/68/EU - Is this Traceability audit finding correct? Other ISO and International Standards and European Regulations 4
K Assigning the Correct Procedures Applicable to Job Titles General Auditing Discussions 15
JoshuaFroud How important is using the "correct" GMDN? Other Medical Device Regulations World-Wide 5
M Specifications Aerospace - Who is responsible for providing the correct specification(s) AS9100, IAQG 9100, Nadcap and related Aerospace Standards and Requirements 14
supadrai OEM Changing the name of the manufacturer - length of process? Is 1-3 months correct? Other Medical Device Regulations World-Wide 0
J How long should I have to correct an audit finding? VDA Standards - Germany's Automotive Standards 7
E SPC for Dummies - The correct meaning of all the graphs Statistical Analysis Tools, Techniques and SPC 3
C UDI Label Verification - How do we ensure the barcode is correct and prove it? 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 4
N Correct reading for analog pressure gauge ISO 17025 related Discussions 2
J How to measure process quality? Is DPPM the correct metric? Capability, Accuracy and Stability - Processes, Machines, etc. 5
P The correct way to do a Linearity and Stability Study on a Critical Dimension Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 8
L Choosing the correct Distribution for Acceptance Sampling Inspection, Prints (Drawings), Testing, Sampling and Related Topics 19
A Safety Shoes & Temporary Workers - Is it correct to reuse again or not? Occupational Health & Safety Management Standards 11
S Definition MTBF and MCBF Correct Definitions Definitions, Acronyms, Abbreviations and Interpretations Listed Alphabetically 5
T What is the correct UMDNS Code for Tracheostomy Tube? Other Medical Device Regulations World-Wide 2
E Correct Statistical Test comparing 2 Groups Statistical Analysis Tools, Techniques and SPC 14
N What is the easiest way to verify we have the correct customer supplied materials? Misc. Quality Assurance and Business Systems Related Topics 5
D The correct way to analyze Skewed Data using Minitab Using Minitab Software 3
C Rolling the correct M8 1.25 Pin Thread Manufacturing and Related Processes 2
E Database search is correct to capture medical device ISO 13485:2016 - Medical Device Quality Management Systems 2
S Choosing the correct Elisa Test Food Safety - ISO 22000, HACCP (21 CFR 120) 1
J TS 16949 - Which definition of Automotive is correct? IATF 16949 - Automotive Quality Systems Standard 3
L Correct Sample Size for Attribute Gage R&R (Good / Bad parts) Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 12
R Correct Cable Ports After Work and Weekend Discussion Topics 2
S Is it gramatically correct to say Singapore people or Singaporeans ? Coffee Break and Water Cooler Discussions 12
H Determining the Correct Sample Size when AQL points to two Sample Sizes AQL - Acceptable Quality Level 7
J How IAQG plans to ensure that correct PEAR level determination is done by Auditors? AS9100, IAQG 9100, Nadcap and related Aerospace Standards and Requirements 8
K AS9102 Form 3 for Assemblies - Verification that the Assembly is Correct AS9100, IAQG 9100, Nadcap and related Aerospace Standards and Requirements 3
J MSA Emergency - PV%=100(PV/TOL)in American? And that is correct? Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 13
F Can you tell me if this table is correct? Gage R&R Problems Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 12
T Is the following flow for Training Needs Analysis correct? Training - Internal, External, Online and Distance Learning 6
M Calculating Cp and Cpk - Is my calculation correct? Capability, Accuracy and Stability - Processes, Machines, etc. 7
J Are my Cpk and Cp Calculations Correct? Capability, Accuracy and Stability - Processes, Machines, etc. 4
D What is the correct Working Standard for Digital Micrometer? General Measurement Device and Calibration Topics 21
T Correct use of NPT (National Pipe Thread) Thread Gages General Measurement Device and Calibration Topics 15
R First Pass Yield - Am I doing correct the First Pass Yield Metric Quality Tools, Improvement and Analysis 2
C Correct Tool for Gage R&R - Assay Dilutions Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 2
B How to Correct Bad Employee Performance-Attendance and/or Tardiness Quality Manager and Management Related Issues 84
R How to determine the correct Sample Frequency for SPC Features Statistical Analysis Tools, Techniques and SPC 66
Q Latest ISO 9001:2008 Rev. E - Correct? ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 5
bobdoering The CORRECT steps to implement an SPC chart Imported Legacy Blogs 16
E Orthographic Projection - Which view is correct? Coffee Break and Water Cooler Discussions 4
M Calculating correct Cpk - Getting different answers Capability, Accuracy and Stability - Processes, Machines, etc. 3
P Is Blaming Operators for Nonconformances correct? Quality Manager and Management Related Issues 62
arios If the estimates are correct Mexico could win a future Soccer World Cup Funny Stuff - Jokes and Humour 19
Similar threads


















































Top Bottom