Water Tank Manufacture with Flow Control using Forming Gas
December 3, 2020
Automated GTAW Water Tank Manufacture and Gas Wastage
TVC was approached by a company who manufacture Duplex water tanks and use a forming gas for back purging the tanks. As the welding process is automated GTAW, the operation process involves setting up a tank to purge whilst a pre-purged tank is being welded.
Prior to purchasing TVC Oxygen monitoring and flow control equipment, the initial purge was carried out by ensuring that the purge, at a high flow rate, was maintained for a set period of time. The drawback to this method was, however, that the time the tank was on purge could often exceed the nominal time required to fully purge the vessel and, therefore, wasted a large volume of gas.
3-Stage Flow Control Solution
The solution from TVC was to supply a GPM Oxygen monitor with 3-stage flow control. The revised purge procedure using the TVC equipment starts with the operator setting up the tank to be purged and connecting the gas supply which is routed through the GPM 3-stage flow control box. The GPM sampling tube is connected to the tank and, when the ‘Start’ button is pressed, the GPM will start sampling the O2 level and the flow control box starts the purge gas flowing at the high flow rate, in this case about 80 LPM.
Pre-programmed Alarm Levels
The GPM has two alarm levels pre-programmed. These alarms control the Oxygen levels that the flow rates will change at, in this solution the high alarm level is set at 1000 PPM O2 and the low alarm is at 50 PPM. When the O2 level drops below the high alarm level (1000 PPM), the flow control automatically changes over from the high flow level of 80 LPM to the mid-flow level of 15 LPM. As the O2 level continues to drop, once the low-level alarm threshold is reached, the flow control changes to the lowest set flow rate of 5 LPM which is enough to maintain the purge until the operator is ready to transfer the purged tank on to the automated welding lathe.
For every one-minute of high flow purge time saved, the client estimates a saving of £0.36 based on current forming gas costs. Whilst this in itself does not seem a substantial amount of cost-saving, based on saving 10 minutes every hour for an 8-hour working day, for a 5-day working week over a 48-week year the annual cost saving would be £6,912.00. As the savings detailed are for a single welding station, the annual saving for a large-scale factory with multiple production lines could potentially be considerable, especially as the TVC equipment costs would be fully recovered within 21 weeks.
To see if TVC can assist you with your purging, please contact us to discuss your requirements.