When equipment moves out of service (that is, no longer being actively operated or maintained), it looks to be pretty clear from OSHA's standards (1910.147) as well as a letter of interpretation that in this condition, once the equipment is de-energized and physically disconnected so that there are no longer any hazards present, that safety locks MUST be removed.

https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=INTERPRETATIONS&p_id=25538

Similar issues would exist for instance in bringing equipment into a state of being serviced because for instance at this point it is moving from OSHA 1926 (construction) rules to OSHA 1910 (general industry) rules. 1926 requires tags but not necessarily locks. 1910 requires locks whenever possible (tags only are allowed but only under very limited circumstances).
So...is there any guidance out there as to how to properly move equipment from a state of "out of service" to "in service"?

In a follow up, I found the following letter ofi interpretation which seems to suggest that you either pull the fuses, unwire the fedder, remove the plug, or some other means of disabling power, and hang an "out of service" tag on it. Am I on the right track here?

https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=INTERPRETATIONS&p_id=25516

Pertinent section:

Question (1): Does 29 CFR 1926.417, "Lockout and tagging of circuits," require the use of a lock on deenergized circuits?

Answer: Title 29 CFR 1926 Subpart K addresses electrical safety requirements in construction work. Section 1926.417 ("Lockout and tagging of circuits") states:
[INDENT](a) Controls. Controls that are to be deactivated during the course of work on energized or deenergized equipment or circuits shall be tagged.

(b) Equipment and circuits. Equipment or circuits that are deenergized shall be rendered inoperative and shall have tags attached at all points where such equipment or circuits can be energized. [Emphasis added].[/INDENT]
In promulgating this section, the Agency used the phrase "rendered inoperative," rather than "locked out." This indicates that methods other than lock-out would be permissible[url='http://arcflashforum.brainfiller.com/#footnote1']1[/url] , as long as they rendered the equipment or deenergized circuit inoperative. There are a variety of such methods; two examples are:
[INDENT](1) Removing a fuse or other circuit element for each phase conductor; or

(2) Disconnecting the circuit conductors (including disabling plugs for equipment that is plug-connected).

[/INDENT]