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Connector Sealing Technology

CTIS # 29952

Prepared By John Yurtin

Updated 6-1-2005

Connection Systems Training

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Having a good technical understanding of the expectations and performance of connections can help you properly apply them within the vehicle. Sealing technology should be clearly understood since it is very important to lifetime performance in a vehicle.

This training help you understand sealing and how to apply sealed connections more efficiently.

Excellence

Performance Goal: Do it right the first time, every time

Method: Innovation and continuous improvement

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What is “sealed”?

What causes leakage?

Fluid Dynamics and Capillary Action

Quality Problems

What are the Performance Requirements?

– ISO / SAE / USCAR / IEC

Various Sealing Designations

What is the “real life” expectation?

Resources

What have we Learned?

Contents

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Do we really know what these mean????

The only true definition must be related to a specific set of performance requirements

What Is “Sealed”?

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Watch Example

Breitling – Water Resistant 300 M

– Price $2800

Timex– Water Resistant 50M

– Price $69.95

Look at your watch to see its level of water resistance

As a test, would you place your watch in this beaker of water for the remainder of this session?

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Water can enter a “good” connector or harness in two ways:

1. Fluid Dynamics ( flow from a region of high pressure to one of lower pressure

2. Capillary Action (flow due to close-range molecular forces)

Capillary action is capable of causing far more leakage into a well designed connection or pass-through than fluid dynamics.

Leakage due to quality problems must always be considered.

What Causes Leakage?

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What do customers think?

They need a connector that can withstand some pressure from inside out. With no air bubbles.

Sometimes they require a deeper immersion e.g. 1 M because the pressure is greater.

Think that heating a connector causes great pressure inside…

Think that cooling the connector causes a vacuum to suck water in.

Connector must withstand extreme high pressure spray.

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Heating a connector to 1250 C can result in a 5.1 psi (35.2 kPa) max. internal pressure, (however, this assumes no air can leave the connector, and we know air travels up the core of the wire).

Immersing into room temp water results in

-4 psi (-27.6 kPa) max. [-3.8 psi (26.2 kPa) from cooling (assuming air left the connector), and an additional - .2 psi (1.4 kPa) from 16in. of water pressure],

1P=yh = (62.4 lb/ft3) (3ft) (ft2/144 in2) = 1.3 psi (9 kPa)

It is important to note that if air is free to travel within the core, then even after heating, or cooling the internal pressure equalizes.

Fluid Dynamics(Pressure Differentials)

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From Bernoulli’s equation, it is determined that water hitting a connector at 30 MPH can cause an instantaneous pressure of 13 psi (90 kPa) Since we know that vehicles drive at high speeds through water it is clear that the effect of high pressure spray is significant.

It is common in performance specifications to find a high pressure spray test. It is important to note that if sealing surfaces are shielded from direct spray, then the effect discussed is not relevant.

Fluid Dynamics(Splash and High Pressure Spray)

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Capillary action leakage may be the most common reason for failure in a “good” connection, and can be brought on from temperature changes, vibration and other mechanical and environmental effects.

With capillary action, basically the smaller the gap, the further water can travel and the greater the pressure. (Think of water getting to the top leaves of a tree)

When two smooth surfaces say 40 micro inches come together (like a seal to the housing), the result is approx. 80 micro inches. This can result in gaps of 2 micro inches. Using mathematics, the pressure related to capillary action can reach 83 psi (573 kPa).

Capillary Action

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Theoretically as the gaps between sealing surfaces approach 0, (smoother sealing surfaces and greater interferences) the pressure increases to infinity.

You can relate to this through the earlier example with the watches. How long do you think one of those water resistant watches would last underwater?

Capillary Action

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Quality problems are generally the most common cause of leakage in a “good” connection. These can be from:

Bad sealing surfaces (parting lines, mismatch, surface finish)

Wicking through or between wires

Damaged seals (cut or bunched) or damaged sealing surfaces

Capillary leakage through insert molded or potted interfaces

Improper assembly method

Quality Problems

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Typical Sealing Tests

Temperature / Humidity

Salt Spray / Salt Fog

Pressure / Vacuum

Immersion

Immersion / Flex

High Pressure Spray

It’s important to recognize that the pre-conditioning requirements before these tests, and the subsequent requirements can have a great affect on the final outcome.

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Sealed connectors IPX7The leakage current shall not exceed 50 µA at 48 V applied voltage. Sealed connectors tested shall also fulfill the High Pressure Spray test.

Test points 1 2 3

Electrode

Test sample

100 10

Dimensions in millimetres

A

U

Water Tightness Test

Leakage current is measure between adjacent contacts

This typical immersion test setup is used to detect if water gets into the connector by checking resistance between contacts. (Remember that we aren’t concerned with air getting out of a connector e.g. a pressure test but rather water getting in).

Typical Immersion Test (SAE / ISO / USCAR)

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Test Setup

Position 4

Position 3

Position 2

Position 1Nozzle

90°

30°60°

Reference points(0°, 30°, 60° and 90°)

Test sample

Support

Rotating axis

100 to 150

0°

Typical High Pressure Spray Test (SAE / ISO / USCAR)

IISO 20653 IPX9K

TThe water flowing through the nozzle shall have…

…a temperature of (80 ± 5) °C;

….a flow rate between 14 and 16 l/min;

…a pressure of approximately 8,000 to 10,000 kPa (measured as near as possible to the nozzle aperture).

MMount the samples rotate at (5 ± 1) revolutions per minute, and subject it to the high pressure water jet for 30 s in each of the positions 1 to 4.

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Pressure / Vacuum Test (USCAR)

Pressure / Vacuum Test– 7psi pressure and -7psi vacuum (initial)

– 4psi pressure and -4psi vacuum (after mating and un-mating)

This is a continuous pressure and assumes no air escapes, or gets drawn in, through the wire core.

(*Remember the 5.1 max pressure and 4psi max vacuum that we talked about earlier)

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IP Codes (International Protection)

IP codes are an internationally accepted way to designate environmental sealing performance of a connectors.

Originated by IEC, today IP codes are accepted by most standards organizations.

An example IP code for a connector might be “IPX5”

The following chart explains the code…

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IP Code (Examples IPX5, IP67, IPX9K)First Numeral Second Numeral

First Numeral Second Numeral

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Protection against

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DCS Sealing Codes

Code 0 - Unsealed

Code 1 - Design has limited sealing capability

Code 2 – Mated connection will pass typical salt fog test after conditioning

Code 3 - Mated connection will pass typical salt fog and immersion tests after conditioning

Code 4 – Mated Connection will meet the requirements of SAE/USCAR-2 (Pressure/Vacuum and Immersion)

Code Y – Sealed purchased component (non-Delphi) and sealing capability is undefined.

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Customer Requirements

– Immersion (various liquids), Salt Spray, Salt Fog, High Pressure Spray, Pressure/Vacuum Tests

Real Life Environment

– Location in vehicle, Temperature Extremes, Application

Design

– Sealing surfaces and interferences, Tolerances, Shielding, Materials, Wire-Dress

Considerations

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Mating Devices

– Are the mating devices designed to our standards?

– Is the device itself sealed?

Wire Harness Design

– Can water wick up wire core and get into a connector?

– Does the connector “breathe through the wires?

– How close is the next connection, splice or other termination?

– Is there excessive movement of the wires?

Considerations

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Resources

Sealing Training Presentation – can be used to train the customer as well

“So what’s all this sealing stuff about anyway?” article – good to send to the customer

Pressure Changes In Automotive Connectors tech article. – includes all calculations

Test Specs (CSE Test Center website)

Waterproofing Theory Report – available from J. Yurtin

– very technical report

– Internal use only

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We learned that leakage takes place in two ways...

...capillary action ...and fluid dynamics

Pressure testing should be understood before it is specified, and there are maximum values.

That Customer requirements must be clearly defined and understood

If a system leaks it is likely due to capillary action or a quality problem

What Have We Learned?