Using material handling equipment in a galvanizing facility
What are some concerns I should consider when using material handling equipment like chains, wire, fixtures, and safety latches in a galvanizing facility?
Chain and wire are commonly used in a galvanizing facility to load a variety of steel material onto hooks, racks, and cranes. These materials include fabrications, weldments, tanks, boxes, pipes and fittings. Structural steel such as angles, beams, channels, and flat bars are also examples of material handled in a plant. All of these products must be prepared for the galvanizing process by hanging, mounting, or loading on racks, fixtures, or baskets. Depending on the material and a galvanizing facility’s operating practice will determine whether chain or wire are used to load the parts.
The properties of chain and wire, specifically working load limits, are affected by the surface cleaning solutions and the galvanizing kettle temperature. Working load limits are the maximum allowable load that the chain and wire can safely lift. Manufacturers of chain and wire can provide working load limits for these materials at room temperature, but these values at elevated temperatures are typically not available.
To answer the question how much the chain and wire can lift at elevated temperatures, the AGA conducted two studies to determine the reduction in tensile strength when lifting at galvanizing temperature or during the galvanizing process. The AGA investigated different chain materials, wire tying techniques and the effects of the galvanizing process on the working load limits. Based on the results of the study, the breaking strength of chain is reduced by 30% at elevated temperature. Using this information and the chain manufacturers minimum breaking strengths, a safe working load limit can be calculated. In the wire study, the critical factors in determining the working load limit for wires are the high temperature use in the galvanizing kettle, the onetime use of the wire, the deformation of the wire during tying, and the extra step of pulling the knot tight before applying a load to the wire. Since the wire is used only once for lifting loads, the safety factor of ½ of the high temperature breaking strength can be used for the working load limit. Information on the two studies and determining the safe working load limits for chain and wire can be found in the Galvanizing Notes Steel Chain for Hot-Dip Galvanizing and Lifting Wire for Hot-Dip Galvanizing.
After establishing the safe working load limits for chain and wire, another important step is inspection. Wires do not need to be inspected after use since they are only used once and then recycled as scrap materials. However, wires do need to be inspected before use to be sure the correct wire is being used and appropriately tied according to your facility’s wire tying procedure. Wire tying is dependent on human skill level and the knot tightness can affect the safe working load limit. Tighter knots with more bending in the wire allows you to lift more steel per dip. More information on different wire tying techniques and inspection of the wire are discussed in the Galvanizing Note and Galvanizing Guideline on Wire Ties for Overhead Lifting.
OSHA requires chain inspections each day before use and that chains be removed from service when they experience a 14% reduction in chain diameter. The chain can be inspected with a Go/No Go gauge or by measuring the chain diameter using a caliper or micrometer. Chain diameters are then compared to the recommended allowable wear according to ASTM A 413 Specification for Carbon Steel Chain. If the Go/No Go gauge fits onto a link or the chain measurement is below the maximum allowable wear, the chain needs to be removed from service. The Go/No Go gauges are available from chain manufacturers.
A more in depth inspection should also be conducted periodically where each link is examined individually, taking care to expose and examine all surfaces including the inner link surfaces. The inspection of the chain should occur after the zinc has been stripped from the entire chain length. Any signs on the chains of pitting or weld deterioration should be an instant removal of the chain. Detailed information on inspecting the chains are discussed in the Galvanizing Guideline on Chains for Overhead Lifting.
Other lifting devices that are used in the galvanizing plant are fixtures. Fixtures are used to move a variety of steel products through the galvanizing process. The majority of fixtures are designed at the galvanizing facility to accommodate the different shapes, sizes, and weights of steel parts. The variety of work requires fabricating specific equipment to secure the steel product to cranes and hoists in a safe and secure fashion. There is no specification on designing fixtures for use in galvanizing. A Galvanizing Guideline on Fixturing provides information on the use and design of fixtures for overhead lifting in the galvanizing industry.
A question often asked is whether safety latches are required on cranes. Safety latches are used to lock a chain or fixture to the crane. Some OSHA inspectors have claimed the non-use of safety latches creates a hazardous environment. An OSHA interpretation on safety latches refers to the General Duty Clause and how ‘employers need to provide a place of employment free from recognized hazards that can cause or are likely to cause death or serious physical harm to employees.’ In a galvanizing facility, the use of safety latches would create a hazardous environment by unnecessarily exposing employees to the surface cleaning chemicals and molten zinc. A Galvanizing Guideline on Safety Latches was developed to provide an insight into the ASME B30.2 Overhead and Gantry Cranes standard that shows an exemption to the OSHA regulation by stating that safety latches should not be used when the application makes the use impractical or unnecessary. Information on the OSHA interpretation is also provided in the guideline.
By determining proper working load limits, conducting inspections, and taking proper maintenance of material handling equipment can help safeguard from a potential incident at a plant. Keep accurate records of your inspections and take any equipment that does not pass inspection out of service.
© 2019 American Galvanizers Association. The material provided herein has been developed to provide accurate and authoritative information about after-fabrication hot-dip galvanized steel. This material provides general information only and is not intended as a substitute for competent professional examination and verification as to suitability and applicability. The information provided herein is not intended as a representation or warranty on the part of the AGA. Anyone making use of this information assumes all liability arising from such use.