EPS vs. Acid Pickling Operations Cost Comparison

In this analysis of operational costs of an EPS and a hydrochloric acid pickling line, the primary bases for comparison are the 4-tank acid pickling line versus the 2 Cell EPS line described in the EPS vs. Acid Capital Cost Comparison. We have detailed item-by-item breakdown of operating costs for these two systems. In addition, we have average total operations costs from other push-pull acid pickling lines in North America. These lines process low carbon strip averaging between 2.5 and 3.5mm (0.10″ and 0.138″) thick.  The owners tell us that when these lines are running well their operating costs are between $14 and $16/ton (based on current energy costs), therefore, we’re using $15/ton as the average variable cost for acid pickling of low carbon strip of this thickness range.

The comparable variable cost for EPS pickling of that material is $12/ton, roughly 20% less than the acid pickling. The analysis below examines the main components of variable operating costs to show how EPS and acid pickling compare. For further insight on EPS Cell costs data, use the EPS Operations Cost Calculator.

4 Tank Acid Pickling Line

2-Cell EPS Coil Line

Energy Cost

Energy is the EPS Line’s largest component of operating cost. This all-electric system uses powerful Slurry Turbine motors, coolant pumps and terminal equipment motors. The 2 Cell EPS Coil Line’s electric cost is $4.00/ton (33% of the $12/ton total), based on our $.08/Kw-hr rate ($.0692/Kw-hr was USA average industrial electric rate in 2018).

The 4 tank acid pickling line uses both fossil fuel and electricity. Natural gas heats the acid and electricity powers the terminal equipment and the many pumps required. USA natural gas prices have been stable and low recently, keeping energy cost for the acid pickling line a low $3.75/ton – 25% of the $15/ton total variable cost.

At 150 hp each, Slurry Turbine motors consume ample electricity.

Labor Cost

Labor can be the highest variable cost component of an acid pickling line. It runs low carbon fast, which entails lots of material handling. Plus, the line is so long that threading, station controls and overall line supervision requires multiple operators.  Acid picklers we surveyed use 6 to 8 production staff per shift, averaging $4.60/ton.

By contrast, EPS has achieved a level of automation that just 2 workers per shift are needed. Line thread and speed control are fully automated so operators spend the most time with material handling (the very short line length makes this practical). As a result, EPS direct labor costs amount to $1.80/ton, based on a $30/hr rate.

The complete operations staff of a 2 Cell EPS Coil Line.

Production Supplies

Production supplies for acid pickling are acid, additives, water, filtration supplies and oil. We don’t count banding, paper and items that do not directly contribute to pickling. Costs vary due to how acid regeneration is handled and some transportation aspects, but the picklers we surveyed averaged $2.80/ton.

EPS production supplies are steel grit, additive, makeup water and filter media. The $/ton cost of these changes surprisingly little with strip thickness and number of Cells in the line. For this average low carbon scenario, they come to $3.80/ton; however, that assumes the use of a scalebreaker, which lowers cost by 20%. That is why EPS Coil Lines we specify always include a scalebreaker. 

EPS’ LG50 angular steel grit is delivered in these 2-ton sacks.

Maintenance/Repairs

This final component of acid pickling variable cost is . . . well, highly variable. It depends on maintenance practices, the build and age of the line and capacity utilization. Items included are repair parts, weekly and major outage repair services and terminal equipment upkeep (roll regrinds, bearing replacements). The average cost for acid picklers we surveyed came to $3.85/ton.

We have detailed data on EPS wear parts life  (turbine blades, nozzles, valves, etc.) and maintenance costs.  In fact, the greatest variation in this category for an EPS line is the upkeep of the roller leveler.  We calculate total EPS Coil Line maintenance and repair costs for this low carbon scenario to be $2.70/ton.

EPS Slurry Turbine blades are an example of a wear part.

Summary of Operations Cost Comparison

For pickling of low carbon coils in the range 2.5 – 3.5 mm (0.10″ – 0.138″), relevant acid pickling and EPS variable operating costs are roughly allocated as follows:

EPS vs. ACID PICKLING - OPERATION COSTS
Acid PicklingEPS Pickling
Energy$3.75/ton$4.00/ton
Labor$4.60/ton$1.80/ton
Production Supplies$2.80/ton$3.80/ton
Maintenance/Repairs$3.85/ton$2.70/ton
TOTAL$15.00/ton$12.00/ton

We must caution that these costs are representative estimates. Local market conditions will strongly influence energy costs and labor rates. In addition, we obtained acid pickling cost data from just a few picklers and there is much variation in their data, hence the need to use averages.

The good news is EPS is competitive with acid pickling for the scenario where acid pickling’s costs are lowest. If you introduce high carbon, alloy steels and AHSS into the mix, the EPS operations cost advantage grows  because an acid pickling line’s output drops dramatically for these grades, while the EPS line speed decreases only modestly (see details). To evaluate this effect more fully, we encourage you to use the EPS Operations Cost Calculator; however, please note that the Cost Calculator models only the EPS CELL operating costs, rather than the costs of the entire EPS Coil Line including terminal equipment. 

In addition, while acid pickling is mature technology, EPS is new and continues to improve, driving its operations costs even lower. In fact, we are testing developments in the Production Supplies and Maintenance/Repairs cost categories that we are hopeful will eventually drop EPS variable operating costs to below $10/ton.