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Ingress Protection of Servo Motors

Sealing is an important design tool used to prolong the life of motors against harsh environments containing dust or liquid contaminants. There are arguably an unlimited number of applications for servo motors and each comes with its own environmental challenges.

Sealing can be compromised or degraded by incorrect applications, harsh conditions or conditions not covered by the design intent.  Even long operating periods under normal conditions will degrade sealing.

Designs are developed with general operating conditions in mind, but the ultimate qualification of the IP rating is very structured.  The design engineer must design to pass these specific conditions.

The protection levels and test conditions are clearly specified in international standards.  The latest editions are:

  • Drives – IEC 60529 2.2 Edition, August 2013, Degrees of protection provided by enclosures (IP code)
  • Motors – EN 60034-5 4.1 Ed, Nov 2006, Rotating electrical machines Part 5:  Degrees of protection provided by the integral design of rotating electrical machines (IP code) - Classification

Discussion Points

  • Kollmorgen products are designed with operating conditions in mind that are similar to the conditions defined in the standards but, the ultimate rating is qualified based on testing at a static, nonoperating, condition.  Ingress protection will vary depending upon operating conditions.  Customers will often expect to get the same protection when operating under any condition, so they need to understand the failure modes during operation.
  • An IP rating at one level does not imply that the design meets the requirements of “lower” levels of protection.  I.E.  IP67 does not automatically mean we meet IP65 or IP66.
  • The liquid (second number) ratings are based on protection against water at temperatures defined by test specifications.  This is typically at room temperature except for IP69K which is 80◦C.  Other liquids and environmental conditions must be evaluated for material compatibility.

How sealing fails

  • Incompatibility between seal and environment (materials, temperatures, viscosities) can compromise or degrade the seal leading to leakage.
  • Liquids sitting (pooling) on the lip of the seal when the internal temperature or pressure of the motor or actuator drops will allow the vacuum action created by decreasing temperatures and pressures inside the motor to pull contamination past the seal.
  • Similarly, washing down a hot motor can result in the same cooling / vacuum conditions that pull moisture into the motor.
  • If exposure is longer than normal test times the capillary action under or through components like bearing sleeves, seal sleeves and ecap potting holes have been ingress points.
  • Spiral “microgrooves” created during shaft machining can “pump” liquids under the seal lip.  Plunge grinding of the sealing surface is ideal.
  • The shaft surface in contact with seal wears at a higher rate than expected.  This can be caused by lack of lubrication, if needed, and solid contaminants that get under the seal lip and erode the shaft surface.  Hardened shaft surfaces are ideal.
  • Motors with shaft seals mounted to oil filled gearboxes may leak oil past the seal when oil pressure builds during operation and/or temperature changes.
  • Seals simply wear out over time.
  • Damage during installation:  Nicks and scratches caused by tools and sharp edges of shaft can result in seals leaking “out of the box”.  Using proper, well maintained tools is important.  Polished, smoothed and/or chamfered shaft transitions that the seal must pass over can prevent this.  Kollmorgen takes every effort to prevent this from a design and manufacturing standpoint.

Protection Ratings Summary

First Characteristic – Protection against 1) access to hazardous parts, 2) ingress of solid foreign objects

Level Object size protected against Effective Against
0   No protection against contact and ingress of objects
1 >50 mm Any large surface of the body, such as the back of a hand, but no protection against deliberate contact with a body part
2 >12.5 mm Fingers or similar objects
3 >2.5mm Tools, thick wires, etc.
4 >1mm Most wires, screws, etc.
5 Dust protected Ingress of dust is not entirely prevented, but it must not enter in enough quantity to interfere with the satisfactory operation of the equipment; complete protection against contact
6 Dust tight No ingress of dust; complete protection against contact

Second Characteristic - Indicates the level or protection provided against access to hazardous parts and the ingress of water.

Level Protected Against Testing for Details
0 Not protected    
1 Dripping water Dripping water (vertically falling drops) shall have no harmful effect.

Test duration: 10 minutes

Water equivalent to 1mm rainfall per minute
2 Dripping water when tilted up to 15° Vertically dripping water shall have no harmful effect when the enclosure is tilted at an angle up to 15° from its normal position.

Test duration: 10 minutes

Water equivalent to 3mm rainfall per minute
3 Spraying water Water falling as a spray at any angle up to 60° from the vertical shall have no harmful effect.

Test duration: 5 minutes

Water volume: 0.7 liters per minute

Pressure: 80–100 kN/m²
4 Splashing water Water splashing against the enclosure from any direction shall have no harmful effect.

Test duration: 5 minutes

Water volume: 10 liters per minute

Pressure: 80–100 kN/m²
5 Water jets Water projected by a nozzle (6.3mm) against enclosure from any direction shall have no harmful effects.

Test duration: 3 minutes minimum

Water volume: 12.5 liters per minute

Pressure: 30 kN/m² at distance of 3m
6 Powerful water jets Water projected in powerful jets (12.5mm nozzle) against the enclosure from any direction shall have no harmful effects.

Test duration: at least 3 minutes

Water volume: 100 liters per minute

Pressure: 100 kN/m² at distance of 3m
7 Immersion up to 1 m Ingress of water in harmful quantity shall not be possible when the enclosure is immersed in water under defined conditions of pressure and time (up to 1 m of submersion).

Test duration: 30 minutes

Immersion at depth of 1m
8 Immersion beyond 1 m The equipment is suitable for continuous immersion in water under conditions which shall be specified by the manufacturer. Normally, this will mean that the equipment is hermetically sealed. However, with certain types of equipment, it can mean that water can enter but only in such a manner that it produces no harmful effects.

Test duration: continuous immersion in water

Depth specified by manufacturer
9K Powerful high temperature water jets

Protected against close-range high pressure, high temperature spray downs.

Smaller specimens rotate slowly on a turntable, from 4 specific angles. Larger specimens are mounted upright, no turntable required, and are tested freehand for at least 3 minutes at distance of 0.15–0.2 m.

There are specific requirements for the nozzle used for the testing.

This test is identified as IPx9 in IEC 60529

Test duration: 30 seconds in each of 4 angles (2 minutes total)

Water volume: 14–16 liters per minute

Pressure: 8–10 MPa (80–100 bar) at distance of 0.10–0.15 m

 Water temperature: 80 °C

Kollmorgen Products that offer Ingress Protection

Not Rated Frameless - KBM, TBM, RBE, DDL, Flying lead motors (no electrical protection)
IP20 Drives and Electronics
AKM…P or M (Molex connectors on cable)
IP40 VLM (no seal)
CTP, CTM Stepper (no seal)
Powermax II® Stepper - P2, M2 (no seal)
Stepper T2, H2, E2, MH, MX (no seal)
"Sealed" DS Series Precision Tables (Stainless seal strip, Nitrile based magnet strip)
IP44 R Series Actuators (Fluorosilicone seal strip)
“Water Tight” R2A Series Actuator (Silicon sealant added to all external seams)
IP54  AKM (no seal, rotatable or straight connectors)
AKM2G (no seal)
EC Actuators (Polyurethane wiper seal)
N Series Actuators (Polyurethane wiper seal)
IP56 RGM
IP64 C, CH09, 13…1xx5 (Hollow shaft, sealed option)
IP65 AKM2G…V (Viton® spring lip, wet); AKM2G…T (Mineral filled PTFE, dry envir)
AKM (PTFE Seal, Rotatable connectors or cable, see Selection Guide)
Goldline® B, BE, M, ME, BH, MH
R Series Servo Motor
EC Actuators (Polyurethane Protective Boot + venting)
N Series Actuators (Polyurethane Protective Boot + venting)
C, CH…2,3xx5 (Solid shaft, sealed option)
DDR (Buna-N, Viton®, and Turcon® T25 seals) O-ring groove on mounting face for optional protection.  O-ring to be provided by customer.
Powerpac® K3, N3, K4, N4, H3, E3 Stepper (with shaft seal)
H4, E4 Stepper (with connector and shaft seal option)
PMA Servo Motor (standard TENV)
R Series Servo Motor (standard TENV)
S Series Servo Motor (standard TENV)
IP67 AKM (PTFE Seal, straight connectors, see Selection Guide)
AKM…0W, Washdown (PTFE seal); AKM…0F, Food Grade (PTFE FDA seal)
Goldline® (…S option, Viton® Seal)
EKM (Viton® shaft seal, MIL style connectors)
DDR (Buna-N, Viton®, and Turcon® T25 seals) O-ring groove on mounting face for optional protection.  O-ring to be provided by customer.
PMA Servo Motor (optional washdown duty, seal option)
IP68, Submersible Goldline® S Series (20,000 ft, pressure compensated) The only one specifically design to operate at this rating
IP69K AKMH (Water-tight cable exit, Mineral filled PTFE shaft seal, EPDM O-ring Flange Sealing)

Viton is a registered trademark of The Chemours Company.
Turcon is a registered trademark of Trelleborg.

 

Last update: 4 April 2019