—— A jar maker went through the headquarters’ handbook from cover to cover.

Customers often ask: What material is used for your jar?

If I say carbon steel, the customer frowns; if I say stainless steel, they think it’s too expensive. It seems we’re stuck with having to choose one or the other.

A few days ago, I pored over the product manual from the German headquarters from cover to cover—materials, coatings, top covers, accessories—everything laid out in meticulous detail, with specifications precise down to the micrometer, millivolt, and millibar. By the end, I was left with this realization: this isn’t a matter of choosing one over the other at all; it’s a question of division of labor.

Today, let’s skip the news and talk tech. I’ll translate the contents of the manual into Chinese and lay them out for you to see.

1. According to the original German manufacturer’s manual, there are actually two different methods for making the jar.

(1) Hybrid Structure: Carbon steel for the anaerobic zone, stainless steel for the gas-phase zone.

The manual states: Mixed‑structure anaerobic digesters have been thoroughly validated in the biogas industry. The portion of the vessel that comes into contact with the anaerobic feedstock is made of a material with… KTL /Carbon steel with epoxy coating —— The coating provides protection both during operation and transportation, and it is… “ A durable, cost-effective alternative to stainless steel or enamel tanks. ”。

The gas-phase zone, the upper annular components, and the top cover structure are fabricated from stainless steel, while the external reinforcing profiles are made of hot-dip galvanized steel.

In a nutshell: Use stainless steel where it’s needed, and avoid wasting it elsewhere.

This is not a compromise born of cost-cutting; it involves separately accounting for the corrosion conditions in different zones. The anaerobic zone is immersed in the feedstock and protected by a coating, while the gas-phase zone, exposed to a perennially humid hydrogen sulfide environment, is safeguarded by stainless steel.

(2) All-stainless steel: suitable for food-grade applications and highly corrosive environments.

The other half of the manual covers all-stainless-steel tanks: grades ranging from V2A ( 1.4301  This type) to V4A ( 1.4404 / 1.4571  In such cases, duplex stainless steel can also be used.

Primarily used in the food industry. —— It is used in drinking water treatment, breweries, the beverage industry, dairy processing, and fish processing; it has also been validated in wastewater treatment, biogas production, and the petrochemical industry.

The decision‑making logic is straightforward: if the medium is highly corrosive, hygiene requirements are stringent, or the customer explicitly specifies it, opt for all‑stainless steel; for standard biogas projects, a hybrid structure suffices and is more cost‑effective.

(3) No on-site welding, painting, or forming.

I think this point is the most worth mentioning.

The manual states plainly: the tank module consists of prefabricated steel plates, steel profiles, bolts, sealing materials, and accessories, all fully assembled at the factory and shipped worldwide; on-site, no welding, painting, or forming is required, and installation is carried out by a specialized team.

Why is this important? Because each weld adds another potential leak point and creates an additional surface that must be re‑coated with corrosion protection. Bolted tanks, on the other hand, move both of these tasks back to the factory.

The factory has a pretreatment line, temperature-controlled painting, and quality inspection; the construction site has nothing but wind and dust. That’s the difference.

II. Coating Parameters: The Germans have documented them in great detail.

(1) Resicoat® R4 ES : Single-layer epoxy powder coating

This model is listed separately in the manual, with very practical specifications:

• Single-layer coating, dry film thickness 150–250 μm
• High mechanical strength, meeting high atmospheric corrosion grades. C4 requirements
• Holding water-related certifications (such as ANSI/NSF 61 ), meeting the requirements for biogas stability ( DVGW )
• When used in fermentation tanks, it is suitable for both the liquid and gas phases, particularly well‑suited to operating conditions where the liquid level fluctuates frequently.

“ Frequent level fluctuations ” This sentence is key. The areas where the liquid level fluctuates up and down are precisely where coatings are most prone to blistering and peeling. The manual dares to state this. “ Especially well-suited ” , which indicates that this section has been measured, not just guessed.

(2) Powder Coating Systems: Single-layer to Three-layer

In addition to that specialized coating, the manual also outlines a complete powder-coating solution:

• Coating structures are available in single-layer, double-layer, and triple-layer options.
• Thickness range 60–250 μm
• Tolerance pH 3–11
• Pore detection voltage 90–1100 V
• The coating raw materials are sourced from leading global paint suppliers.

pH 3–11 This range essentially encompasses the typical operating conditions of biogas slurry, organic acids, food‑processing slurries, and industrial wastewater. The higher the pore‑detecting voltage, the greater the coating’s density. —— This is a testing method, not marketing jargon.

(3) 25 How did this figure for the year come about?

We communicate externally that carbon steel tank bodies are equipped with an epoxy coating, with a design life of… 25 Year. Some people think this is just a slogan.

In fact, it is underpinned by several hard‑and‑fast parameters: substrate pretreatment, coating type, dry film thickness, corrosion grade, and inspection standards. For each of these, the manual provides corresponding numerical values.

We present the parameters in writing so that customers can verify them, rather than relying on our verbal explanations.

III. The top cover is not just placed on arbitrarily.

The manual lists several types of top covers; choose according to your intended use:

• Unpressurized lightweight top
• Heavy-load top —— The top must be equipped with a mixer, or it may be subjected to heavy loads.
• Airtight Pressure-Resistant Top —— Can be achieved 90 mbar Overpressure, -5 mbar Negative pressure
• Self-supporting or supported, slope 0°–20°
• Any type of steel will do—stainless steel or coated steel.
• Aluminum geodesic dome ( Geodesic Dome )

The covering plan has also been provided: a double‑membrane gas holder for gas storage; coverings of glass‑reinforced plastic (GRP) and membrane structures to block odors and mitigate environmental impacts.

Choosing the top cover essentially comes down to three considerations: whether personnel and equipment will be allowed on it, whether it needs to be pressure‑tight and sealed, and what the local wind and snow loads are. Once these three factors are clearly defined, the model is naturally determined.

IV. Accessories: Whether a jar is easy to use depends half on its accessories.

The appendix list in the manual is very comprehensive:

• Flanges, pipes, and various types of fittings
• Ladders: straight ladders, spiral ladders, and tank wall ladders, equipped with guardrails and fall protection.
• Platform: Circular corridor, maintenance platform, walkway, and bridge
• Agitators: Central‑type, Side‑mounted, Submersible
• Insulation layer and outer shell of the tank
• Valves, tank heating, and measuring devices

These items may seem insignificant, but during on-site commissioning, missing even a single flange could mean waiting an entire month. That’s why the more detailed the list of accessories is when providing a quote, the smoother things will be down the line.

V. Schumann Says a Few Words

After finishing this manual, my strongest impression is that Germans don’t really write technical documentation… “ High quality ”“ Industry-leading ” For this kind of term, just write “micrometer,” write… pH , write voltage, write millibar.

40 Years of experience in manufacturing jars, worldwide. 4000  Multiple units, with over two million cubic meters of fermentation capacity installed in the past five years. —— Behind these figures, it’s really just the result of these parameters being painstakingly accumulated, one by one.

We wouldn’t dare claim that every single one of our products outperforms the competition. But one thing is certain: for every specification listed in our manual, we’re confident enough to let our customers bring their instruments in to verify it themselves.

During the inspection visit by the Korean customer, they used an ultrasonic thickness gauge to take measurements point by point, and after finishing, they said… “ Consistent with the drawings. ” Back then, I figured: only if the parameters are laid out clearly would I dare let others test them.

VI. Quick Reference Table of Technical Parameters (Recommended to Save)

Table 1 Main Technical Parameters of Schumann Bolt‑Assembled Tanks (Diameter According to the German Headquarters Manual)

Note: The above information reflects the official position as stated in the German headquarters’ handbook and on the company’s website. For specific projects, the contract’s technical specifications and the confirmed drawings shall prevail.

100~15,000 m³ ｜One image per can, German-style design

Jack Li | +86 15993026132

Henan Shuman Tank Equipment Co., Ltd.