The invention relates to an apparatus (1) for the applying of and removal by suction of operating fluids onto rolling stock (2) and off rolling stock (2) in the inlet (4) of cold rolling systems (6) and comprises at least one spray device (7) arranged above or below a rolling stock transport line (8), wherein at least one operating fluid can be placed by the spray device (7) onto a surface of the rolling stock (2) or onto a surface of a working roll (9) which makes contact with the rolling stock (2), and to at least one suction removal device (10) which can be arranged above or below the rolling stock transport line (8) and on the same side of the rolling stock transport line (8) as the spray device (7), wherein the suction removal device (10) acts in the vicinity of the surface of the rolling stock (2) or of the working roll (9). The spray device (7) and the suction removal device (10) are attached onto a common component frame (12) and therefore form a compact unit (14.1; 14.2).

Provided is an apparatus of removing foreign substances from a hot-rolled steel strip, including a reverse direction injection unit provided to inject high-pressure water in the reverse direction of a moving direction of the strip toward the strip moving to the entrance of the winder by the side guide, wherein the reverse direction injection unit includes a plurality of upper reverse direction injection nozzles arranged along a width direction of the strip to inject high-pressure water to an upper surface of the strip, and the plurality of upper reverse direction injection nozzles is arranged such that an interval of the upper reverse direction injection nozzles located in a central area along the above arrangement direction is narrower than an interval of the upper reverse direction injection nozzles located in both edge areas.

Methods for detecting an amount of a rust removing agent in a sample are disclosed, the methods using a colored reagent complex formed from a reaction of a transition metal salt and a salicylate salt or acid, or a derivative thereof. A method includes making a test sample solution comprising the sample and the colored reagent complex, evaluating the visible color and/or absorption value of the test sample solution, and comparing the visible color and/or absorption value of the test sample solution to the visible color and/or absorption value of a reference solution containing a known amount of rust removing agent.