Steam Joints Extraction Piping

You drew the short straw and have to climb down into the bowels of the low pressure turbine to inspect the steam extraction piping expansion joints. Not a bad  – if your hobby is spelunking. There is only one problem; you can’t inspect what you can’t see.

That cover, along with the end rings, is securely welded down to the piping. It is not removable.

A few facts to ponder while at the dark

The fixed covers are there for a purpose – to protect the bellows in the high velocity of this spent turbine steam. This protection has a trade-off; the bellows can’t be readily inspected visually.

It’s a sure bet that if the expansion joints are older than 20 years, lots of the bellows will have leaking cracks. Those leaks are impacting the turbine’s efficiency.  Get  more info about  Steam joints (also known as ” ข้อต่อสตีม ” in Thai language ) via visiting http://nssteel.co.th/responsive/product.php?catid=34 .

Limited inspection methods

The figure below shows a normal cover arrangement. You should be able to receive a borescope through the gap on one side. The scope will give you some notion of the status of the bellows, but there will still be some difficulty in obtaining a fantastic peek down between the convolutions.

Start looking for indications of cover damage. Often the original designs had lighter covers (and liners) that wouldn’t hold up under the high flow velocities. Those fragments are lodged somewhere down in the condenser. Except this   if you want to know more about valve click at http://nssteel.co.th/  .

Replacement and upgrade options

Also consider upgrading from stainless steel bellows to alloy 625 for improved protection against chloride stress corrosion.

You may conclude that a 20+ year service for the expansion joints is a good run. If you decide to return with the original layout, at least throw in a couple inspection port couplings to improve the view of the bellows with a borescope.