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[Rudra]

Gas holders are used as low pressure storage for gases.
As per my knowledge there are two tanks. In bottom tank water is filled as sealant liquid for gas. The gas enters through a long pipieline portruding above the liquid level. Similarly the gas outlet is from above the liquid level.
Above this tank there is one more inverted tank with top heat is placed, having diameter less than water tank. The top inverted tank is supported on pulley with weights suspeneded equivalent to tank wweight.
Now if outlet flow is higher than inlet, then gas pressure will be less, at that time the top inverted tank will push down into the bottom seal water tank.
If the pressure rises due to higher incoming flow then the tank will be lifted but what is the limit.
If the pressure is high then exactly how this gas holder system work that i dont know.

can anyone help me in understanding the working principle of water seal gas holder.

[Art Montemayor]

Rudra:

What you are studying is one of the simplest, most reliable, and dependable fluid flow regulation devices ever devised – in my opinion. It has no mechanical moving parts, needs no lubrication, needs no calibration, uses available and inert water as its working seal, and employs ever-present and non-failing gravity as its constant counter-driving force. Gas holders have been used for decades and the only reason they have been almost eliminated is not because they failed to operate but rather because of some of their trade-off disadvantages:

• They have a very large foot print. They require a relatively large amount of space and height.
• They are subject to the corrosion that water brings with it and, therefore, need constant monitoring and maintenance.
• In today’s world of liabilities, liberties, and potential terrorism they present a large, easy, and accessible target if they contain combustible or explosive gases such as natural gas.
• In today’s environmentally active social world, they are an eyesore.

The working principle of a gas holder is very simple: it is nothing more than a water seal.

What you have described as a potential over-pressure within the gas holder: “If the pressure rises due to higher incoming flow then the tank will be lifted but what is the limit. If the pressure is high then exactly how this gas holder system work that I don’t know,” is rather simple to explain. All that can happen is that the inherent water seal “breaks” – in other words, the water in the gas holder is pushed out by the higher gas pressure and overflows, allowing the excess gas to vent to the atmosphere. While this may not be desirable, it is automatic and can hardly fail. That’s why all gas holders were thought of as the simplest and most reliable of fail-safe devices ever invented. In fact, some closed storage tanks are kept sealed with an inert gas and a water seal as protection against both pressure and vacuum.

If you make a simple sketch of a gas holder and analyze it from a hydraulic point of view, you will quickly come to the same conclusion as what I have stated above.

I hope this helps you understand it better.