Anhydrous Ammonia Branch Piping

[P1p3r]

I am tasked with connecting a new 16" anhydrous ammonia line to an existing 16" anhydrous ammonia line. My question is... is there a preference for the connection orientation? I've heard that coming off the side or bottom of the pipe is best. Does it really make a difference? Does vapor/liquid phase play a part?

thanks!

 

[GHartmann]

The piping orientation is best set by the layout of the plant and the "from" and "to" destinations.

There may be some consideration if the line is vapor and can "condense" ammonia along the way (avoid pockets etc).

You may want to study the existing installation a bit more to see the current practice in the plant.

 

[P1p3r]

thanks GHartmann... I meant to say that this isn't in a plant, but a ship terminal... we're offloading anhydrous ammonia from the ship to a storage tank about 500 meters away. I've uploaded a diagram of the proposed piping configuration so that you can get a better idea of what I'm doing....

thanks again for your time with this...

 

[GHartmann]

I assume from your reply the line is liquid ammonia from the ship fed into your atmospheric storage tank. There is really no process reason for any particular orientation of the connection. Have the piping engineers / designers route the pipe in the most practical method; the fewer the elbows and turns the better.

Your proposed orientation looks fine.

One other note is that our practice is to use globe vavles for liquid anmmonia (block valves can accumulate liquid ammonia in the bonnet and can create thermal overpressure situations). However, a 16" globe valve is huge and a plug or ball may be acceptable. You will want to find out what the type of existing valves are installed.

You will also want to know if the practice is to use the low temperature A333 CS for when the line is depressured.

I apologize if I have given more information than you needed.

Just out of curiosity: Is this facility at the Port of Tampa?

 

[TD2K]

I also agree that I don't see the need to tie into the 'top' or 'bottom' versus the side if the side makes it easier, less fittings, etc.

Do you need those two valves at the tie-in location or do you have adequate isolation capability at the other ends of the 16" piping network?

That is one big ammonia line.

 

[P1p3r]

All of the information that you've shared is appreciated. I will provide emergency shutdown valves at various places in the line so that the maximum "shut in" is 10,000 gallons. There are overpressure PSV's between each shutdown valve (and, in some cases, 2 PSVs).

I will uses A333 low-temperature carbon steel for the piping... and I had considered globe valves at one point but, as you say, those are a little too expensive. I'll use 4" of urethane insulation for the long run and have a 6" NH3 vapor line parallel to the 16" carrier line... PSV discharge will connect to the vapor line.

It looks to me as if gate valves are installed, but I'll take a closer look. I am mainly curious to know if 90° and 180° turns would create enough pressure drop to cause liquid to condense and, if so, is there a preferred method to handle the liquid.

Thanks for your time and knowledge... yep, it's the Port of Tampa...