Hardness testing shall be conducted in places where corrosion protection (resistance) is less critical, as for example on top of supporting rings in the upper quarter of the tank or on an ***inwardly protruding edge*** of the (oil storage tank inspection) manhole shaft

sources:

Securable temporary manhole cover - Patent 715305726 Dec 2006 ... An improved temporary manhole insert for securing a manhole passageway ... with the tab extending inward such that the sealing member provides a resilient .... 21) having one end ***protruding into*** the annular hollow space formed by the spacer elements between the shaft edge and the shaft cover and via ...
www.freepatentsonline.com/7153057.html -

Watertight sealing system with relief valve for manhole having a ...a plate having an outer edge for sealing against the walls of the skirt the plate ..... which a bolt 194 having a shaft 195 with a threaded end 196 is inserted. .... If the skirt 4 has an ***inwardly protruding portion***, the pressing member ...
www.freepatentsonline.com/5743673.html -

Adjustable manhole cover - US Patent 5344253 DescriptionDriving over sunken or ***protruding manhole units results in vehicle damage as ... said top unit having second cavity means adjacent and radially inwardly*** of said ... means 20C to be described hereinafter and has an inner annular edge 24A. ... Inventor: Cuozzo4149816, Metal shaft cover frame. Issued on: 04/17/1979 ...
www.patentstorm.us/patents/5344253/description.html -

[PDF] (12) United States Patent: PDF/Adobe Acrobat - HTML
(20, 21) having one end ***protruding into*** the annular hollow 45 space formed by the spacer elements between the shaft edge and the shaft cover and via which ...
www.invention.net/pdf/7153057.pdf -