May I ask if the breather valve of an internal floating roof tank can be removed?
Thread Content
Each of the nitrogen outlets of the three methanol floating roof storage tanks in our facility is equipped with a breather valve, while the nitrogen inlet to these tanks is controlled by a self-acting control valve. Now, it is intended to switch to using a pneumatic valve to control the nitrogen inlet; the breather valves on the three storage tanks will be removed, and the nitrogen outlets of these three tanks will be connected together to a single buffer tank, with the outlet of this buffer tank being controlled by a pneumatic valve. May I ask everyone, is that possible? If it’s not possible, please tell me why. Thank you! This post was last edited by nnza on 2008-12-16 19:25]
This design should work fine, but how is your pneumatic valve controlled? What if the control fails? Could that cause the storage tank to deflate? That’s a problem. Generally speaking, simplicity leads to reliability; it’s not true that the more complex the equipment, the better it is
Personally, I think it shouldn’t be canceled – don’t storage tanks also have vent valves? Automatic control is usually implemented during the design phase, but it’s possible that such automatic control could fail. Similarly, I think a storage tank should also be provided; I’m not sure if my answer is correct!
The roof of finished oil floating roof storage tanks usually only has a flame arrester, without a vent valve. Could it be applied to methanol? Experts, please provide an answer.
I haven’t seen such a design yet, but the idea put forward by the original poster is good and feasible. The nitrogen outlets of the three storage tanks can all be connected to one buffer tank; I would add a breather valve to this buffer tank for overall control. This reduces the number of times the tanks undergo breathing processes, thereby protecting the oil tanks. This method is effective in reducing breathing losses in oil tanks – this is discussed in works by Huang Chunfang, published by Sinopec Press in 2003 and 2005. It’s a shame that design firms don’t make use of this approach very often.
The key question is: are there any drawbacks to the combination of your existing vent valve and self-acting control valve? If nitrogen is used solely for pressure maintenance, then there are basically no issues with your new approach (of course, it’s necessary to consider the possibility of negative pressure occurring). Pneumatic control valves require more maintenance compared to self-acting control valves
Of course not. A breathing valve is an essential accessory for oil tanks; even if a storage tank uses nitrogen sealing, a breathing valve is still necessary.
Replacing the breathing valve with a pressure control valve poses significant risks. If there are problems with the control valve and the liquid level changes greatly, it could lead to accidents.
A vent valve is essential; if methanol liquid is being stored, a vent valve is usually used in combination with a flame arrester, and this is very important. I am also working on projects of this kind.
Personally, I think it can be canceled. The working principle of a breathing valve is to control the air pressure at the top of the tank, preventing pressure instability in the tank. The system mentioned by the original poster can effectively solve this problem, so there is no need to set it up. Of course, the cost is relatively higher, but for media that cannot be vented, recovery devices must be installed.
Thank you very much for your answers. Since the nitrogen consumption due to the breathing valve cannot be recovered, using a buffer system can appropriately reduce nitrogen consumption. Of course, this nitrogen consumption is extremely low; the main purpose is to demonstrate whether it is feasible to use a buffer system. Personally, I think it is feasible, as a buffer system can fully fulfill the function of a breathing valve.