In this topic we will discuss the operation of Thermodynamic Steam Traps (also known as TD traps in the industry) and will provide some quick hints on how to test this type of traps and ensure they are operating properly.
This type of traps has a moving disk, simply when condensate is present it lifts the disk and the trap allows condensate to pass through. When all the condensate is out steam will reach the trap and due to the disk design it will pass through the disk and create some pressure on the top of the disk forcing it to close. Now the trap will close and no fluid will pass through.
While the trap is closed, steam will start to condense upstream the trap, causing condensate to accumulate. After a few minutes (this time will vary depending on operating factors), the steam that was pressurizing the disk will condense too and condensate from upstream the trap will push the disk again and pass through the trap.
From this you can tell that the way this type of traps operate is ON/OFF operation. It is not continuous. This makes testing TD traps fairly easy as the following:
How to Test Thermodynamic Steam Trap
1- If the trap is discharging intermittently, that is an indicator the trap is operating properly.
2- If there is no discharge coming out of trap and the line it is connected to has steam flowing, that means the trap is failed closed. Sometimes the strainer or valve upstream the trap could be clogged.
3- If there is live steam coming out of trap all the time, that means the trap is failed open.
These traps are fairly easy to repair as you can get a disk repair kits from most manufacturers as disks tend to wear after so many cycles. With most manufacturers, you will be able to replace the disk while the trap is inline by removing the top cap only. Here comes the benefits of having isolation valves upstream and downstream the trap to allow you to work safely on the trap.
Where to use Thermodynamic Steam Traps
1- One of the most common use of TD traps is for main steam drip line.
2- For tracing lines. TD traps can handle cold temperature.
3- For high pressure applications, for example where steam pressure is above 300psi. TD traps can handle higher pressures.
4- For super heated steam applications.
Where NOT to use Thermodynamic Steam Traps
1- On main steam header in the boiler room.
2- On all types of heat exchangers.
3- On process equipment where loads vary and immediate condensate removal is required.
4- On moisture separators (also known as steam separators).
5- On low pressure systems operating at 15psi (1 bar) or lower. TD traps will not operate on any low pressure system. Many manufacturers recommend minimum 30psi (2 bar) of upstream pressure for the trap to operate properly.
Below is a short video showing a TD steam trap with an open end operating normally. You can contact us with any questions about TD traps using the form below.