Centralized gas supply uses one or more large gas production generators to deliver endothermic gas to multiple heat treatment furnaces through the workshop pipe network. The key points of the design include: calculation of main pipe and branch pipe diameter and pressure drop, independent measurement and regulation of each furnace branch, condensate discharge, backfire prevention and pressure relief, safety shutoff and alarm interlocking. Reasonable centralized air supply can unify the atmosphere quality, reduce the storage of hazardous chemicals, and facilitate centralized monitoring.
- Advantages: Uniform atmosphere quality, reduced methanol storage, easy centralized monitoring and maintenance
- Pipe network design: pipe diameter, pressure drop, slope and drainage
- Each furnace branch requires a flow meter and regulating valve
- Safety: Anti-backfire, pressure relief, shut-off valve, flammable gas alarm
- When new and old furnaces are mixed, it is necessary to balance the pressure of each branch
Why centralize gas supply?
When there are multiple controlled-atmosphere furnaces in the workshop, each furnace may be individually drip-fed with methanol or equipped with a small generator, which will result in:
- Atmosphere quality varies with the status of each furnace;
- Hazardous chemicals such as methanol are stored dispersedly, which puts great pressure on safety and environmental impact assessment;
- Equipment is scattered, making maintenance and data management difficult.
Centralized air supply "centralizes" the atmosphere preparation and delivers it to each furnace like water and electricity. Gauss Control calls this solution a "package protective atmosphere solution" on its fine wire/steel pipe industry page. It includes carrier gas and enriched gas replacement, gas supply pipeline design planning and factory equipment data monitoring. The goal is to reduce hazardous chemical control risks, production costs and shutdown risks.
Key points of pipe network design
1. Pipe diameter and pressure drop
Calculate main pipe and branch pipe diameters based on total flow, pipeline length and allowable pressure drop. The inlet pressure of the terminal furnace must meet the requirements, otherwise the atmosphere of the terminal furnace will be insufficient.
2. Layout and slope
There may be condensed water after the endothermic gas is cooled. The pipeline should have a slope and a drainage device should be installed at a low point to avoid water accumulation affecting the flow and corroding the pipeline.
3. Branch metering and regulation
A flow meter and regulating valve (electric valve if necessary) are installed at the entrance of each furnace to achieve independent adjustment and consumption statistics, which facilitates cost accounting.
4. Materials
Pipe materials and connection methods must be suitable for transporting flammable and toxic gases, and pressure tests and leak detection must be conducted in accordance with specifications.
Safe design
- Generator outlet and key location settings Anti-backfire device；
- Pressure relief and relaxation: Excess gas should be ignited and discharged in a safe location;
- Emergency shut-off valve: Interlocked with fire alarm and furnace failure;
- Combustible gas and CO alarms: Arranged in the pipeline passing area and around the furnace;
- Nitrogen purge interface: Used to replace flammable gas in pipelines before maintenance.
The balance of a mix of old and new furnaces
Furnaces of different types and ages have different requirements for pressure and flow. When designing, you need:
- Check the pressure according to the most unfavorable branch;
- If necessary, install a pressure stabilizing valve in the branch;
- Reserve the expansion interface.
Example
Gauss Control provided 3 160 m³/h RX gas generators and a complete set of gas supply pipeline designs for 30 different types of controlled atmosphere heat treatment equipment for Zhejiang Qiujing Technology Co., Ltd. (which the official website calls one of the largest single heat treatment plants in China). The project has been put into operation and passed acceptance inspection.
Frequently asked questions
After centralized gas supply, can a single furnace still adjust the carbon potential independently?
Can. The carrier gas is centrally supplied, and each furnace still independently controls the carbon potential through enriched gas or diluted air and its own oxygen probe.
Is it okay to have the generator far away from the stove?
Yes, but the longer the distance, the greater the pressure drop and the greater the amount of condensation water. It is necessary to increase the pipe diameter and provide drainage and insulation accordingly.
Is it difficult to retrofit an existing workshop?
The main difficulties lie in the pipeline direction, production shutdown window and safety interlocking. Usually it can be switched in batches, first connect some furnaces for verification and then expand.