Loss of Gas Pressure During TX Shipment

Of course, the first thing you did was notify the manufacturer to discuss this, and what he will do about fixing the problem, right????

Until you get instructions from the manufacturer, nothing said here will encourage you to proceed without a test and recertification by the manufacturer.

If the thing explodes on start-up who will be responsible?

Bite the bullet and fix it properly!!!

TURN OFF CAPS LOCK.

Yes we did inform the mfr. thanks for your good input.

Good job.

If you are facing delivery/commissioning deadlines with penalties, the manufacturer should cover those.

Thanks lyn.

For curiosity sake:

What do you think might have likely occured if the pressure was lost for...say 10 days? I know that is a broad question but if you could give me the short and skinny of it I would appreciate it.

Depends why you lost pressure in the first place and whether TX is a transformer or a liquid cooled high powered RF transmitter.

What is it? transformer or transmitter?

..and also depends on the weather/shipping route/storage environment.

What is the supplier saying?

As I dig further into the receiving of this transformer, it did arrive at the warehouse at 5psi. It shipped from Missouri to Connecticut so there was not a great temperature variance this time of year. The nitrogen bottles arrived turned off for shipping. This was overlooked so after a couple of days this was corrected and the bottles were opened bringing the pressure up to 6psi. It has held since within 2 psi variation.

If it went to zero it was for only a couple of days. So with that being said I feel I want to test the oil for moisture just to be on the safe side.

An ounce prevention is worth a pound of cure.

This test will be done at commissioning too but I don't want to have to wait until the ninth hour to find out that it is in fact wet. Then it skews my startup.

Your thoughts?

Checking the moisture content of the oil is prudent.

I think it will be ok as the transformer case would not be pressure cycling the same as it would when cyclically heated and cooled in operation. When you noticed the low pressure was it just low or really zero where it might have a chance to gulp wet air at night when it cooled down?

Question is, where is the leak? You lost all your pressure in a couple of days. Is that normal? Are there any forklift scars on it? Mashed insulators...?

The 2 psi variation... is that either side of 6psi or has it dropped by 2psi?

Understood Wal.

Oil dielectric (Moisture) test will be performed.

There are no scars or damage to insulators, in fact no damage at all. your comment on pressure being at zero with the possible gulp of air is something that solidifies my initiating tests on the oil.

You bring some good points. I will look into these further. Thanks again for your insight.

Insight? You are too kind. Just musings....

Let us all know how you get along.

Don't just do a dielectric test. That will only tell you if the oil has lost integrity already. It won't help you determine if there is moisture in the oil, which will migrate into the winding paper and degrade the cellulose over time. I recommend having a reputable lab do at least a Karl Fisher test for PPM moisture (ASTM-D-1533), and preferably also do an Interfacial Tension test (ASTM D-971). Those two tests will tell you if you have a moisture problem. They're not expensive, probably less than $50.

If testing reveals moisture you can rent an oil dehydrator to attach to the transformer fill & drain valves. It will circulate the oil through a dessicant bed and dry remove any moisture over a period of days or weeks (depending on the moisture content). You could also bring in a hot oil cleaning rig to dry out the oil quickly, but the dehydrator is much cheaper.

As to what caused the pressure to drop, if you've got a leak you'll be using a noticeable amount of nitrogen now that the bottles are back in service. If the nitrogen usage is normal, I'd suspect it's just temperature differential. I've seen isolated transformers read negative pressure (vacuum) just because the temperature of the unit dropped 15-20 degrees. If the bottles were isolated on a warm day with the transformer in sunlight and the unit is now in a cooler area or indoors without radiant heat from the sun, the oil has likely contracted, allowing the gas headspace to expand and reduce the pressure.

Very good advice. thanks for your input.

Best advice will be "a phone call to the manufacturer" Don't void your warranty.

Understood and agreed.Thanks

another possibility is change in altitude. going lower will change the reading on a sealed gauge. Do you have a sealed gauge? Did the unit go from higher hills to near sea level?

I don't think this is your problem but if you have very low gas usage you should consider it.

Good point. We don't have enough elevation change here in the Midwest to make a difference, so I didn't even think of it!