What is the structure and operating principle of a stainless steel pressure vessel?

date 2022-06-15

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A pressure tank is actually quite simple: it consists of an outer shell containing an inflatable rubber bladder. Purified water from the water purifier flows into the tank, compressing the bladder and building up pressure. When you turn on the faucet, this pressure forces the water out. So, what is the structure and operating principle of a stainless steel pressure tank?

Stainless steel pressure tank What is its structure and operating principle?

A pressure tank is actually quite simple: it consists of an outer shell and an inflatable rubber bladder inside. Purified water from the water purifier flows into the tank, compressing and expanding the bladder to build up pressure. When you turn on the faucet, this pressure forces the water out. So, what is the structure and operating principle of a stainless steel pressure tank?

Stainless steel pressure tank What is its structure and operating principle?

1. Structure and Operating Principle of the Pressure Tank The pressure tank consists primarily of a valve cover, an inflation port, an air bladder, a carbon steel shell, and flanges. When connected to a water system, it functions mainly as an accumulator. When the system’s water pressure exceeds the nitrogen pressure within the air bladder of the carbon steel tank, the pressurized water is forced into the bladder, compressing the nitrogen inside and reducing its volume while increasing its pressure. This expansion increases the overall water capacity of the system and lowers the system pressure, halting further water inflow until a new equilibrium is established between the system pressure and the nitrogen pressure in the bladder.

2. When the system water pressure falls below the gas pressure inside the expansion tank, the water in the bladder is forced out by the nitrogen pressure between the tank and the bladder, thereby compensating for the system. The system’s water volume decreases and its pressure rises, while the nitrogen volume between the tank and the bladder increases and its pressure drops, until a new equilibrium is reached and the water ceases to be expelled from the bladder back into the system. The pressure tank thus helps regulate fluctuations in system pressure.

3. Thanks to the regulating function of the air bladder, pressure tanks are widely used to control small‑range pressure fluctuations in water systems. In hot‑water heating systems, pressure tanks primarily serve to mitigate pressure swings caused by changes in water temperature, thereby preventing damage to other system control components. When applied to variable‑frequency water supply systems, they can eliminate pressure fluctuations resulting from pump start‑stop cycles, reduce the number of pump startups, and significantly extend the service life of the pumps. In residential building water supply or other water‑supply applications, they can also dampen water hammer effects triggered by valve opening and closing, protecting the entire system from water‑hammer impacts.

Stainless steel pressure tank What types are there?

Type: Gas‑powered and diaphragm‑type.

1. In an air‑filled pressure tank, air is in direct contact with water. Over time, air diminishes due to leakage and dissolution in the water, gradually reducing the volume of water that can be regulated. Consequently, starting the pump becomes increasingly difficult, necessitating periodic air replenishment. Air‑supply methods include using an air compressor, water injection, and timed venting.

2. Diaphragm pressure tanks separate gas from water. The water is contained within a rubber (or plastic) bladder, while the space between the bladder and the tank wall is pre‑charged with an inert gas, typically nitrogen. These tanks eliminate both gas solubility losses and moisture ingress; they can be pressurized once and used over long periods without the need for an air compressor. As a result, capital costs are reduced, the system is simplified, and the range of applications is expanded.

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