Technical Support for Boiler Operations.
Here you will find technical information for tube Installation, Rolling and Removal operations.
On a weekly basis we will endeavor to add helpful information within this page.
Choosing the Right Tube Expander for the Job.
Assessment of the task.
- Tube Material
- Tube OD.
- Tube Wall Thickness (BWG)
- Tube Sheet thickness
- Any Obstructions - Water box or channel plate, Tube projections etc.
Calculating the Rolled Inside Diameter.
- Rule of Thumb: the harder the material, less wall reduction
- Percentage wall reduction guides:
- Copper or Cupro-Nickel - 8% to 10%.
- Steel, Carbon Steel and Admiralty Brass - 7% - 8%.
- Stainless Steel, Titanium - 4% - 5%.
- 3003 or 4004 Aluminum - 5% Maximum.
- 6061T Aluminum - 10% to 12%.
Chart of Birmingham Wire Gauges used in the sizing of tube.
Duty Cycles and Ratings
When using an arc welding machine, it is crucial to understand
what its duty cycle is as it will help you preserve the life and
quality of the machine. When purchasing a MIG welder it will
have a specification on the packaging or in the manual called
the duty cycle. This refers to the amount of welding that can be
achieved in a given amount of time. The reason this
specification is important is it informs the user of how long
the MIG welder can work at its optimum level.
Duty cycle refers to the amount of time a welder will weld in a given time frame at given amperage. The duty cycle is a rating that indicates how long a welding machine can be used at its maximum output current without damaging it. Duty cycle is based on a ten-minute time period. A welding machine with a 60% duty cycle can be used at its maximum rated output current for six out of every ten minutes. The welding machine may overheat if the duty cycle is exceeded. At lower current settings, the duty cycle may be increased and the power source used for a longer period of time.
As an example, a welder with a 20% duty cycle means it can be used for 2 minutes out of 10 at a given amperage setting, and then it must cool down. A welder with a 50% duty cycle can be used for 5 minutes out of 10 at a given amperage. These are just guidelines, and each unit might run more or less at different levels. Most spec sheets will show how the duty cycle will scale from high to low settings. Most equipment is rated at 2/3 to 3/4 of its maximum output. When you are using less amps the duty cycle goes up, more amperage it goes down.
It is important to note that duty cycle becomes inaccurate when being measured over a different time period, especially a longer one. One welder might have a duty cycle of 50% at 200 amps, and this means it can run for 5 minutes out of 10 before it has to be shut down to cool off. It does not mean that the same welder can be run for 30 minutes out of an hour at 200 amps, even though 30 minutes is 50% of an hour just like 5 minutes is 50% of 10 minutes. Duty cycle must be consistently measured in a 10 minute time frame.
Ambient temperature and humidity can have some effect on the duty cycle. A machine will sense its temperature via a thermocouple, and will shut down when it exceeds its duty cycle, coming back on line when it has cooled. To improve or maintain duty cycle, run the machine at minimum amps required for the job, keep the fan area clean, and have the inside of the machine cleaned by a repair center or by yourself, making sure to unplug the power cord occasionally. In the event that the duty cycle is exceeded and the breaker is tripped, allow the MIG welder to cool down for at least 15 minutes. A rated duty cycle on any MIG welding machine is there to protect you and your welder from any long-lasting damage.