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Home / Case Studies / Choosing the Right Solutions for Open Tanks in Electroplating and Metal Treatment
Choosing the Right Solutions for Open Tanks in Electroplating and Metal Treatment
Client
One of the largest players in the aerospace industry in the United States and the world.
Production Process
Gases and fumes are generated during various chemical metal treatment processes such as anodizing, electropolishing, and degreasing (especially when using hot alkaline solutions). Many of these operations involve the use of aggressive acids and alkalis—for example, during metal pickling with hydrochloric or sulfuric acid, surface activation prior to coating, or chemical milling. In printed circuit board (PCB) manufacturing, chemical etching and photoresist processing also release potentially harmful emissions. Additional sources include:
- Phosphating (zinc or iron-based)
- Chromating or passivation
- Electroless plating (nickel, copper, etc.)
- Stripping of coatings or plating layers
- Metal coloring (e.g., black oxide processes)
Problem
Open-surface process tanks used in electrochemical and chemical metal treatment operations—such as electroplating, pickling, anodizing, and etching—generate hazardous fumes that rise from both the vessel surface and treated parts. These fumes often contain corrosive or toxic substances such as hydrochloric acid, nitric acid, or chromic compounds.
Without proper fume capture and ventilation, operators face increased health risks, surrounding equipment suffers accelerated corrosion, and facilities risk violating OSHA and EPA regulations for workplace air quality.
Airborne fumes also tend to rise and disperse rapidly due to thermal lift, hoist movement, and cross-drafts from nearby operations, making localized capture even more difficult. In wide or deep baths, uncontrolled vapors often escape the effective capture zone, compromising overall ventilation efficiency.
Without proper fume capture and ventilation, operators face increased health risks, surrounding equipment suffers accelerated corrosion, and facilities risk violating OSHA and EPA regulations for workplace air quality.
Airborne fumes also tend to rise and disperse rapidly due to thermal lift, hoist movement, and cross-drafts from nearby operations, making localized capture even more difficult. In wide or deep baths, uncontrolled vapors often escape the effective capture zone, compromising overall ventilation efficiency.
Current system component
Several open tanks containing chemical liquids used for metal processing.
Temperature
20-30 °С
Gas/Dust
Gases from electroplating, galvanization, and chemical surface treatment of metals.
Initial Data
Client Communication
Engineer Torch-Air:
I need the following information from you:
- Number and size of the tanks.
- Gas composition from the baths.
- Flow temperature from the vessels.
- Whether you will place the scrubber indoors or outdoors.
Client:
Thank you for your email.
Some information for you to start.
1) Info Sheets
2) Layout and other information
In response to items 3 and 4 of your queries below
-Flow temperature is ambient
-We prefer the scrubber installed indoors at floor level, or about 10 feet above the ground.
Some information for you to start.
1) Info Sheets
2) Layout and other information
In response to items 3 and 4 of your queries below
-Flow temperature is ambient
-We prefer the scrubber installed indoors at floor level, or about 10 feet above the ground.
Engineer Torch-Air:
Please clarify the technical specifications.
I see 8 chemical baths on the LAYOUT.
1. For units No. 2, No. 4, and No. 6, I see umbrellas (hoods). Do you already have these umbrellas? How are they positioned—above, to the side? What are the dimensions of the umbrellas and the diameters of the ducts leading to each umbrella?
2. Do you need exhaust systems for the other baths?
3. I see a common duct; is it already calculated for a specific CFM performance?
So I need to understand the total amount of CFM that will be directed to the scrubber for purification.
For an example, I'm attaching a diagram with options for duct layouts and hood options for the baths.
I see 8 chemical baths on the LAYOUT.
1. For units No. 2, No. 4, and No. 6, I see umbrellas (hoods). Do you already have these umbrellas? How are they positioned—above, to the side? What are the dimensions of the umbrellas and the diameters of the ducts leading to each umbrella?
2. Do you need exhaust systems for the other baths?
3. I see a common duct; is it already calculated for a specific CFM performance?
So I need to understand the total amount of CFM that will be directed to the scrubber for purification.
For an example, I'm attaching a diagram with options for duct layouts and hood options for the baths.
Diagram
Client:
1. Hoods are not installed on all units. The parts that are to be cleaned/dip treated are mounted on a jig. the jig (with parts) lowered to the baths using an overhead crane.
Any hood over the tanks will interfere with the loading/handling of the jig with the parts in process.
2. According to the process owners-only three chemical baths (2,4,6) need to be vented because of the odor emanating from them. The rinse baths do not need exhaust systems.
3. The common duct is drawn for representation purposes only. The total CFM of the exhaust system (and other engineering) will be determined by the vendor.
Nothing fancy — just show a typical chemical bath on your sketch with the two side unit options and indicate the airflow direction. I’ll review this with the process owners to finalize the best approach.
Any hood over the tanks will interfere with the loading/handling of the jig with the parts in process.
2. According to the process owners-only three chemical baths (2,4,6) need to be vented because of the odor emanating from them. The rinse baths do not need exhaust systems.
3. The common duct is drawn for representation purposes only. The total CFM of the exhaust system (and other engineering) will be determined by the vendor.
Nothing fancy — just show a typical chemical bath on your sketch with the two side unit options and indicate the airflow direction. I’ll review this with the process owners to finalize the best approach.
Engineer Torch-Air:
The width of the tanks is 48 inches, which makes it difficult to effectively use a TOP hood from one side alone; we recommend installing TOP units if the bath width is less than 30 inches, as the suction force significantly drops beyond this distance. To ventilate these vessels, we can offer several placement options:
- Install hoods on both sides.
- Install hoods on one flank with a push-pull air extraction setup on the opposite flank.
- A single-slot hood at the bottom provides ventilation of the bath surface but offers minimal airflow for parts once removed.
- A vertical extraction device with multiple slots, ensuring ventilation for drying parts but needing a stronger vent setup. The height should be at least as deep as the bath to properly ventilate the parts.
1.1 Single-slot hoods on both sides – 6 × 1300 = 7800 CFM
1.2 Vertical hoods placements on both sides 6 × 2600 = 15600 CFM
1.3 Single-slot air extraction units on one side of the baths require 3 × 1300 = 3900 CFM. A forced airflow system on the opposite side of the tanks requires an extra 100 CFM for all three units. This push-pull setup necessitates a high-pressure fan to ensure effective extraction.
1.4 Vertical hoods on one side of the tanks require 3 × 2600 = 7 800 CFM. A forced vent system opposite the tanks requires an additional 100 CFM for all three baths. This forced airflow requires a high-pressure fan for the push-pull system.
Engineer Torch-Air:
To choose the appropriate venting option for your tank based on vapor intensity and gas lift:
Additionally, a Tornado-type wet scrubber will be needed to treat emissions collected by the exhaust units. It can be equipped with a demister, which captures droplets and vapors directly near the vessels. Captured substances can also be drained back into the vessel or into the drainage setup. Such a hood can have an additional system for periodic washing of the demister. Washing can be performed either with a fresh solution or with clean water, depending on the nature of the solution and the client's preference. In this case, an additional scrubber will not be required.
- Opt for option 1.1 if the tank is used intensively but vapor rise remains moderate.This configuration ensures efficient vapor capture, even when vertical lift is minimal but emission levels remain high.
- Select option 1.2 when the tank operates under high load and vapors rise significantly—typically due to high vapor pressure or fast evaporation rates.
- Use option 1.3 if the vapor intensity from the vessel is low and the gas lift is not significant. This setup is suitable for low-emission scenarios where vapors remain close to the surface.
- Option 1.4 – Suitable when vapor emissions are low, but the gases rise to a greater height due to thermal lift or agitation.
Additionally, a Tornado-type wet scrubber will be needed to treat emissions collected by the exhaust units. It can be equipped with a demister, which captures droplets and vapors directly near the vessels. Captured substances can also be drained back into the vessel or into the drainage setup. Such a hood can have an additional system for periodic washing of the demister. Washing can be performed either with a fresh solution or with clean water, depending on the nature of the solution and the client's preference. In this case, an additional scrubber will not be required.
Engineer Torch-Air:
This option is applied when the client prefers to avoid an additional wet scrubber for vapor neutralization from the baths or when its installation is not technically possible.
Additionally, the installation of an exhaust fan is required.
Please choose the suitable option and we will propose the appropriate scrubber.
Comments from the client are needed concerning the materials and compositions for producing the vent units and the full system. Based on the compositions attached, I can suggest the following materials:
TANK 1 - polypropylene, PVC are suitable
TANK 4 - PVC, PVDF
TANK 6 - PP, PVC but I am not sure
It turns out that PVC is suitable for everything together. However, please confirm, as it is unclear what ultimately enters the ventilation and in what amounts.
Additionally, the installation of an exhaust fan is required.
Please choose the suitable option and we will propose the appropriate scrubber.
Comments from the client are needed concerning the materials and compositions for producing the vent units and the full system. Based on the compositions attached, I can suggest the following materials:
TANK 1 - polypropylene, PVC are suitable
TANK 4 - PVC, PVDF
TANK 6 - PP, PVC but I am not sure
It turns out that PVC is suitable for everything together. However, please confirm, as it is unclear what ultimately enters the ventilation and in what amounts.
Proposed Solutions
As a result of extended correspondence and a series of calls with the client, a mutually agreed-upon solution was reached.
The client decided that an exhaust setup is required for three tanks using a push-pull configuration — meaning that air is blown in from one side and extracted from the other. Two of the tanks do not have built-in exhaust units, so they need to be manufactured, while one vessel has its own integrated exhaust system, to which we will connect the ductwork.
The client decided that an exhaust setup is required for three tanks using a push-pull configuration — meaning that air is blown in from one side and extracted from the other. Two of the tanks do not have built-in exhaust units, so they need to be manufactured, while one vessel has its own integrated exhaust system, to which we will connect the ductwork.
Additionally, to ensure air purification, a wet scrubber will be required — we have also proposed supplying this unit.
Characteristics | Information |
Volume (cfm) Scrubbing column pressure loss Maximum vacuum on the body | 3 900 CFM Max pressure drop - 6 in.w. 5 000 Pa |
Weight | 2500 lbs |
Temperature range | From 40 to 170 ˚F |
Column and Tank | HDPE |
Pipes | HDPE |
Valves | HDPE |
MATERIALS of column internals | Packing – Polypropylene Mist eliminator – Polypropylene Nozzles – Polypropylene |
Bolts, nuts, washers | AISI 304 |
Mounting brackets | AISI 304 |
Pump | 3HP, 208-240/460, 3 ph, polypropylene/CPVC |
Sump Capacity | 200 gal |
Gas cleaning efficiency | For particles 5 um 99,9% depending on the gas and the solution used for irrigation and the air flow temperature. For water soluble gases up to 99.9%. For acid fumes up to 99.9%. |
Gas concentration at the scrubber inlet | 2000 ppm |
Dust cleaning efficiency for dust 0.01 µm and up | no more 99.99% depending on the irrigation solution density: as the irrigation increases, the catching efficiency increases as well |
The efficiency of the scrubber in its standard configuration (example) | HCl-NaOH - 99.5% HF-H2O - 99.5% NH3-H2O - 99.9% Cl2-NaOH - 98% |
Best Baghouses for Pharmaceutical Powder Particles
We always perform precise calculations and offer expert assistance in selecting the optimal dust collection or gas cleaning systems, typically completing this process within 1 to 2 days
Head of Engineering,
Vladimir Nikulin
Vladimir Nikulin
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