Snubber roller covering
Snubber rollers are critical components in continuous surface treatment lines for metal strips and sheets: from pickling to passivation, from pickling lines to coil coating plants. Their task is to guide the metal strip through the plant’s direction changes and into or out of the treatment tanks, maintaining constant tension and a correct wrap angle along the entire path of the line.
The primary function of snubbers is to absorb tension variations, reduce friction at deflection points, and prevent slippage, surface scratching, and strip waviness, especially on thin, glossy, or already surface-treated sheets. Since they often operate immersed in or in direct contact with acidic, alkaline, and high-temperature baths, the roller’s elastomeric coating must guarantee high chemical and thermal resistance over time.
A.Piovan produces its own specific compound in-house for snubber rollers intended for the steel sheet sector, selecting the most suitable formulation based on the type of line and the chemical baths involved. The main technical characteristics are:
- Hardness: typically available from 40 to 70 Shore A, selectable according to strip thickness and line tension.
- Chemical resistance: The compound offers excellent resistance to acids, alkaline solutions, and chemical agents, maintaining its mechanical characteristics unchanged over time.
- Thermal resistance: dimensional and mechanical stability in a continuous operating range up to 120–130°C, with occasional higher peaks.
- Resistance to ozone, UV, and weathering: The compound is highly resistant to ozone and UV aging, a useful characteristic in sections of the line exposed to acidic vapors or an oxidizing atmosphere, where other elastomers tend to crack prematurely.
- Rubber-to-metal adhesion: the coating is vulcanized onto the metal core with a high-tenacity primer, to prevent delamination phenomena under the cyclic dynamic loads typical of continuous high-speed operation on steel sheet lines.
- Surface profile: smooth or slightly grooved surface depending on the application, to promote strip sliding, reduce the adhesion of bath residues or oxide scale, and facilitate drainage of excess liquid.
- Abrasion resistance: compound formulated for a low wear rate even in the presence of sheets with burrs, scale, or rough surfaces, extending the coating’s service life and reducing the frequency of maintenance interventions.
- Anti-static properties (on request): conductive-formulation compounds available for applications requiring the discharge of electrostatic charges generated by the sliding of the metal strip.
A worn, hardened, or chemically degraded snubber roller introduces defects that impact subsequent sheet processing stages:
- Surface marks and scratches: caused by a hardened, cracked, or contaminated coating, which marks the strip during winding.
- Irregular tension and snaking: a roller that is no longer elastic or has become oval-shaped does not correctly absorb tension variations, generating instability in the strip’s path and misalignments.
- Bath contamination: chemical degradation of the coating can release particles into the tank, compromising the uniformity of the subsequent surface treatment.
Periodic replacement of the coating is an integral part of preventive maintenance for a high-efficiency continuous steel sheet treatment line.
A.Piovan Srl has been developing and manufacturing its own elastomeric compounds in-house for over 45 years, ensuring total control over chemical formulation, mechanical characteristics, and vulcanization process quality. This approach allows it to precisely meet the specific needs of each customer, from a single replacement roller to structured supply for pickling, galvanizing, and coil coating lines.
