What Do the Letters in IP Codes Represent?

Wikipedia has some info here about K ratings. Seems to be a German add-on to the standard.

This site has info about a third digit.

IP code means International Protection and it also mean Ingress of Protection.

IEC 60529 is genereal standard for IP code.

4.1 Arrangement of the IP Code

IP 2 3 C H

Code letters I

(International Protection)

First characteristic numeral I

(numerals O to 6, or letter X)

Second characteristic numeral

(numerals O to 8, or letter X)

Additional letter (optional) 1

(letters A, B, C, D)

Supplementary letter (optional)

(letters H, M, S, W)

Where a characteristic numeral is not required to be specified, it shall be replaced by the

letter "X" ("XX" if both numerals are omitted).

Additional letters and/or supplementary letters may be omitted without replacement.

Where more than one supplementary letter is used, the alphabetic sequence shall apply.

If an enclosure provides different degrees of protection for different intended mounting

arrangements, the relevant degrees of protection shall be indicated by the manufacturer in the

instructions related to the respective mounting arrangements.

Details for the marking of an enclosure are given in clause 10.

4.3

The following examples are to explain the use and arrangement of letters in the IP Code.

Examples for the use of letters in the IP Code

For more comprehensive examples see clause 9.

IP44 - no letters, no options;

I PX5 - omitting first characteristic numeral;

IP2X - omitting second characteristic numeral;

IP20C - using additional letter;

IPXXC - omitting both characteristic numerals, using additional letter;

IPXI c - omitting first characteristic numeral, using additional letter;

IP3XD - omitting second characteristic numeral, using additional letter;

IP23S - using supplementary letter;

IP21 CM - using additional letter and supplementary letter;

IPX5íIPX7 - giving two different. degrees of protection by an enclosure against both water

jets and temporary immersion for "versatile" application.

Thanks for the replies. I searched the threads for info on the letter designations prior to asking the meaning of the added "K's" after the two digit IP ratings (IP6K6K). I was informed the added K's are from the German DIN standards and specify the testing device, conditions,and duration, and water flow, pressure, and temperature. 6K and 9K are different in that 6K specifies water and 9K high pressure steam for the test procedure. Also, the type of vehicle and area to be tested are identified.