Testing F+T traps, how reliable?

Tommi68

I am maintaining a large institutional building with a 2-pipe, vacuum return system, supplied by high pressure steam from a central boiler plant. I have reread Dan's article on testing F+T traps; he says they can only be tested by opening a valve downstream and observing condensate/steam emission? Spirax has conducted a trap audit and passed most, but not all of my F+T traps, using temperature differential and the ultrasonic device. How can I ensure the results are accurate? I have dozens of traps serving as drip legs and end of line. Is the temperature differential test more reliable where I have long cooling loops?

Interestingly, the 1916 steam fitters installed globe valves on the supply side of these traps. What is the intent with having valves upstream of the trap? Was it common practice to drain a steam main? Our mains run in 3, 4, 5 and 7" pipe.

EBEBRATT-Ed

If Sarco did the testing, I would trust what they came up with. The modern testing equipment works well. The old way of using heat sticks, thermometers etc is not as reliable as the modern equipment.

Most large steam plants if they want their traps to work they just replace or rebuild them every 3-5 years or so. The labor it takes to go around and check every single trap is wasted labor.....you get nothing for it it 0 it cost you money. By the time you check them all you could have rebuilt bunches of them. That's just the way it is with commercial steam. And your traps with a vacuum return and high-pressure steam take more of a beating than a typical low-pressure system.

Tommi68

I am finding traps that have not been tested or catalogued for decades. I’d sure like to test them in-house while I search out the problems. 

Tommi68

Any ideas as to why the globe valve would be used for upstream of the filter and trap?

EBEBRATT-Ed

Up stream of the trap you should have a gate valve or ball valve. It's there to service the strainer and the trap. Globe valves are used for throttling and there is no reason to throttle the inlet to a trap.


If you want to build a trap station just find a place, where you can cut in a tee and a valve to get steam to test the traps. On the discharge side you will get water air and flash steam.

The right way is to go around one time and tag all the traps with a # and make a notebook showing the location of the numbered traps and the make/model/pipe size steam pressure etc.

Then you will have the information you need. maybe Sarco has already done this in their report.

You will find it is cheaper in the long run (bad traps waste a lot of steam) to just order the parts and rebuild the traps every few years

Sylvain

EBEBRATT-Ed said:

You will find it is cheaper in the long run (bad traps waste a lot of steam) to just order the parts and rebuild the traps every few years

Indeed
An old trap tested good today may fail tomorrow. While there is a progressive fatigue of the bellows, once it fails, it fails completely.

EBEBRATT-Ed said:

If you want to build a trap station just find a place, where you can cut in a tee and a valve to get steam to test the traps. On the discharge side you will get water air and flash steam.

Wouldn't some length of tube between the valve and the trap be beneficial to have some condensation ?
It also has the benefit of having the dangerous flash steam at some distance from the valve handle.

RPK

I would be interested to see what Sarco’s report looked like. Do they show measured temp difference or thermal images of the traps, or just list pass/fail? Rereading Lost Art of Steam Heating and it is pointing out that there would not be a significant temp difference across an F&T since it will pass condensate at saturated steam temperature. There must be a fairly repeatable temp difference expected if steam trap surveys can use temp difference as a test method.

Tommi68

RPK said:

I would be interested to see what Sarco’s report looked like. Do they show measured temp difference or thermal images of the traps, or just list pass/fail? Rereading Lost Art of Steam Heating and it is pointing out that there would not be a significant temp difference across an F&T since it will pass condensate at saturated steam temperature. There must be a fairly repeatable temp difference expected if steam trap surveys can use temp difference as a test method.

The survey report indicated PASS or FAIL. I observed the testing over 5 days and the only tools used were IR heat gun and an ultrasonic probe. The results were concise and well catalogued. This is our second trap survey since 2020, and from the survey we qualified for a rebate based on projected energy savings.