Steam Trap Basics: Types, Sizing & Selection
In this section, we discuss the following topics regarding steam trap:
What is a Steam Trap and the different types
A Steam Trap is an automatic valve which holds back steam and only opens to discharge condensate from steam lines. This is important because steam must be kept dry. Wet steam will cause the temperature of the steam to fall and this will affect the critical processes. It can also damage steam equipment such as reducing valves and safety valves. Presence of condensate can also cause water hammer.
As a best practice, steam traps are installed:
- Along steam lines to remove condensate
- Before the steam entry into the process equipment to ensure dry steam
- After the process equipment to remove the condensate which has been formed.
Thermodynamic
Compact design
Cost effective
Thermostatic
Adjustable discharge temperature
Energy saving
Ball Float
Continuous discharge without holdback
Large capacities available, can handle high pressures
Inverted Bucket
Good for applications where condensate must be removed immediately
Wide range of condensate loads
Sizing & Selection
| Pressure | Best Choice | Second Choice | |
| Steam Mains | < 1,6 MPa | TB9 | GC1, D, S, ES |
| < 2,1 MPa | TB7 | GC1, S | |
| < 6,4 MPa | TB51, TB52 | S61, S62, ESH | |
| < 19,6 MPa | TB71, TB72, TB81, TB82 | ||
| Tracing | Steam Tracer Lines | TB | D |
| Tank Heating | TB | D, ES, S | |
| Copper Tracing (Instrument Tracing) | TB1N | DC1 | |
| Process Equipment | Heater | G, S, ER | S |
| Heat Exchanger | G | ES, ER | |
| Vaporizer | G | ES, S | |
| Distiller | D | ES, S | |
| Sterilizer | D | ES, G, S | |
| Cylinder Dryer | ES, ER | ||
| Band Dryer | G | ES, ER, D | |
| Multi-Platen Presses | G | ES, D, S | |
| Vulcanizer | D | S, ES | |
| Tyre Presses | D | S, ES | |
| Autoclaves | D | G, ES | |
| Laundry Equipment | Dryer | G | ES, D, S |
| Tumbler | G | ES, D, S | |
| Presses | D | S, ES | |
| Steam Mannequins | D | ES, S | |
| Steam Iron | SL3 | SD1 | |
| Steam Mangles | D, G | ES, S | |
| Food Processing Equipment | Process Boiling Pans | G | ES, D |
| Hot Tables | D, G | ES | |
| Drying Platens | D, G | ES | |
| Jacketes Boiling Pans | D | G, ES, S | |
| Tilting Pans | ES | D | |
| Brewing Pans | G | ES, D | |
| Evaporator | G | ES, ER | |
| Retorts | G | ES, ER | |
| Heating & Air Conditioning | Steam Radiator | W | D |
| Unit Heaters | G | ES | |
| Convectors | W | D, ES | |
| Radiant Panels | W | D, ES | |
| Air Heater | D | ES,G | |
| Air Humidifiers | ES, G | D, S | |
| Heating Coils | D, ES | G, S | |
| Air Conditioning Units | ES, G | D | |
| Calorifiers | G, ES | D |
Sizing
The purpose of sizing is to ensure that the discharge capacity can meet the requirements. First of all the steam flow rate must be known. After applying a safety factor of around 2 to 3 times, the required capacity of the steam trap is known.
Based on the differential pressure (difference inlet and outlet pressure of the steam trap), the maximum capacity of the selected steam trap can be known. The maximum capacity of the steam trap must be higher than the required capacity.
Where should I install a steam trap?
Ideally, a steam trap should be installed every 30m to 50m of steam piping. Steam traps should be installed at the lowest point. Not only is this better for good discharge of condensate, it also facilitates the maintenance of the steam traps.
Avoid group trapping if possible. Always use individual trapping.
Maintenance through Steam Trap Survey
An efficient trap wastes less energy. In addition, it also maintains clean and dry steam.
Under the proper conditions, a steam trap is expected to last around 3 – 5 years. However it can fail prematurely due to:
- Pipe debris such as pipe rust
- Steam cuts especially at high pressures
- Improper orientation during installation
If a failed steam trap is not replaced, it could lead to issues like water hammer or the process cannot achieve the required temperature.
Leaking Traps
The most common issue is leakage of the steam trap. When this happens steam can be seen to be flashing from the steam trap. There could also be small leaks which can only be detected using an ultrasonic vibration detector or thermal imaging.
Besides being a health hazard, even a small leak could potentially lead to thousands of dollars in energy loss over time. For example, if we take a thermodynamic steam trap at 3 bar steam, the financial loss per year due to leaking steam could look like this:
These calculations are for one small steam trap. In a large refinery, the number of steam traps could number in the thousands. The financial loss due to leakage of steam has a huge impact on costs and the environment.
Plugged / Choked Traps
The trap may fail to discharge condensate properly as the orifice could be choked. Dirt, pipe scale, rust, packing and joint material or debris can cause these blockages. When this happens, the user may observe that the temperature cannot achieve process requirements. In serious cases, the condensate collects at the bottom of the pipe which can result in waterhammer.
Steam Trap Inspection Survey
Techmatic performs scheduled steam trap survey to check all the steam traps periodically and ensure that all traps are in proper working conditions. We use the ultrasonic vibration, thermal imaging and stethoscope methods to check for leaks. Based on this data, the steam loss can be calculated using a software.
If found to be faulty, the trap can be replaced or serviced.