Housekeeping Projects

According to PMI, a project is a temporary endeavor to create a unique, result or service. This definition does not say that the result or service has to be external customer oriented. A project can be initiated in house to present a better service to the company itself.
Examples:
- A fact finding project to identify waste within the company
- A project to reproduce a product or service that the company takes from 3rd parties. This will result in cost saving and improved lead times.
- A project or initiative to improve internal communication or remove hurdles.
- An in house skill development and training project to improve organizational capabilities.
- A project to change the way of working within the company, e.g. going lean and agile.
- Archiving or documenting best practices and lessons learned from previous projects. 

Although all these projects have in house customers, the big picture is to improve the external customers experience.

Reference
(1).   Project Management Institute. 2017. A Guide to the Project Management Book of Knowledge (PMBOK Guide) – Sixth Edition.