Tank Venting Steam Coil Rupture

I am calculating a vent valve for an atm storage tank (V=2000 m3)

The tank is used to store water solution at around 90 C. (solution boiling point = 120C)  Steam coil is equipped (3.5barg saturate steam)

API2000 doesn't elaborate the steam tube rupture case. Some  adviced to use API520 HX tube rupture case. But I don't think it is a comparable case as tank has quite larger bulk liquid.

In my opinion, it makes more sense to take the coil rupture case as a steam inject heater.   The leaking steam is actually condensed in the liquid. 

Venting capacity should be the volume of condensed steam and condensate from heating coil. 

It would be great if someone in this forum could confirm if the steps i am taking are correct or if there is something i should take into account.

Thank in advance,

I am calculating a vent valve for an atm storage tank (V=2000 m3)

The tank is used to store water solution at around 90 C. (solution boiling point = 120C)  Steam coil is equipped (3.5barg saturate steam)

 

API2000 doesn't elaborate the steam tube rupture case. Some  adviced to use API520 HX tube rupture case. But I don't think it is a comparable case as tank has quite larger bulk liquid.

 

In my opinion, it makes more sense to take the coil rupture case as a steam inject heater.   The leaking steam is actually condensed in the liquid. 

Venting capacity should be the volume of condensed steam and condensate from heating coil. 

 

It would be great if someone in this forum could confirm if the steps i am taking are correct or if there is something i should take into account.

 

rikakose,

Supposing the tank is atmospheric, you could handle the coil tube rupture case by considering an emergency vent with a vent capacity higher than or equal to the maximum steam rate through the coils because the rupture may be happened when the tank is empty or the liquid level is lower than coil level.

 

I am calculating a vent valve for an atm storage tank (V=2000 m3)

The tank is used to store water solution at around 90 C. (solution boiling point = 120C)  Steam coil is equipped (3.5barg saturate steam)

 

API2000 doesn't elaborate the steam tube rupture case. Some  adviced to use API520 HX tube rupture case. But I don't think it is a comparable case as tank has quite larger bulk liquid.

 

In my opinion, it makes more sense to take the coil rupture case as a steam inject heater.   The leaking steam is actually condensed in the liquid. 

Venting capacity should be the volume of condensed steam and condensate from heating coil. 

 

It would be great if someone in this forum could confirm if the steps i am taking are correct or if there is something i should take into account.

 

 

rikakose,

 

Supposing the tank is atmospheric, you could handle the coil tube rupture case by considering an emergency vent with a vent capacity higher than or equal to the maximum steam rate through the coils because the rupture may be happened when the tank is empty or the liquid level is lower than coil level.

 

Thank Fallah, that is a good point. I didn't take the empty tank into account. 

Can some one kindly take some time to verify my calculation regarding to the relief capacity of steam rupture?

I use the general orifice formular. API suggestes to use Crane book which I don't have. 

(The picture link is not allowed)

The fomula I used is the same with wikipedia orifice plate.  

Can I use them?

In some articls, it is suggusted to take C ( flow coefficient) as 1, because the fluid discharges to open/ large area. 

No link to your work, so cannot review..  An orifice calculation should be conservative.  If the vent becomes unreasonably large, you may need to get more rigorous.

You should buy Crane TP410.  In my 38 years, it is the reference I have used the most in process, production, and project roles.  It is reasonable priced.  Maybe your company will pay.

The formula are attached. Hope they are visible now.

1. incompressible vol.

2. compressible mass

For a tube rupture case, should I take C 0.62 or 1? 

Normal operation: 100kg/h steam. Coil size :ID 27.84mm. 

No link to your work, so cannot review..  An orifice calculation should be conservative.  If the vent becomes unreasonably large, you may need to get more rigorous.

 

You should buy Crane TP410.  In my 38 years, it is the reference I have used the most in process, production, and project roles.  It is reasonable priced.  Maybe your company will pay.

Edited by rikakose, 25 October 2017 - 02:08 PM.

When calculate condensate, I assume that condensate passes through the orifice in liquid phase and then flash. 

​By applying these two equations, I got an incredibly large relief flow. 

​Should I just take the normal operation steam flow as relief capacity?

Normally in a coil rupture case one worries about the fluid flow problem (steam flow out the coil rupture) and not the heat transfer problem (steam condenses to condensate).  This is conservative.  Describe the coils.  Tubing or pipe?  Thickness?  Is any corrosion going on (both inside and outside)?  CS, SS or what?

NO, you can't just use the normal operational steam flow as relief.  Anyone could do that.  But, you are an Engineer, right?  You can calculate what will happen.  Of course, if the boiler capacity and steam pipe, fittings, control valve, etc. limits the flow, that can be included.