Bladder Expansion Tank

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Application

An expansion tank is used in a hydronic (heating/cooling) system to accomplish three main tasks: (1) accommodate thermal expansion of the fluid, (2) maintain positive pressure at all points in the system at all times, (3) maintain net positive suction head at the chilled water pump(s).

In addition to perform the 3 tasks, the bladder expansion tanks provide extra benefit of complete separation of fluid from air, which eliminates absorption of air into the system and water logging. It also helps preventing air bound terminal units, excessive corrosion, inefficient balancing and pump cavitation over the life of the system.

Description

The closed bladder expansion tank consists of a cylindrical casing made by carbon steel with a rubber bladder inside. System fluid is connected with the bladder inner chamber via the flange at the casing bottom. The chamber between the casing and bladder is pre-charged with Nitrogen as air cushion. Fluid is contained inside the bladder without contacting casing. The air cushion accommodates the fluid volume changing inside bladder during expansion and contraction as system fluid temperature changes.

The bladder expansion tanks are designed to absorb the expansion forces resulting from the changes in temperature of the heating/cooling fluid in hydronic heating/cooling systems, to maintain the proper system pressurization.

As the system fluid expands, it is forced into the rubber bladder of the pre-pressurized tank to the higher system pressure. The pre-charged air cushion then forces the fluid back from the bladder into the system as it contracts. The rubber bladder is fixed within the casing by flanges at top and/or bottom. It is replaceable easily by removing the flange(s). A pressure gauge is installed on the casing for monitoring working pressure. A charging port is provided on the casing for easier adding air into tank whenever necessary.

Working Principle

Original status:

The bladder is filled with liquid at same pressure as nitrogen inside casing, not deformed.

Contraction status:

Liquid inside bladder is under less pressure when system total liquid volume is less as temperature lower. The bladder is compressed by nitrogen to feed liquid back to system.

Expansion status:

The bladder is expanded when liquid pressure inside is higher than nitrogen, when system total liquid volume is more as temperature higher. The bladder is expanded by liquid and absorb the extra liquid volume from the system.

★However, bladder expansion will be avoided by selecting models with sufficient capacity, even bladder allows deforming at a certain level. Over-expansion is the main reason for bladder broken.

Features

◇ Replaceable rubber bladder.

◇ Pre-pressurized by Nitrogen.

◇ Pressure gauge on casing.

◇ Air charging port on casing.

◇ Complete separation of air from water.

◇ Standard: GB 150-1998 (Steel Pressure Vessels), 2014/68/EU

◇ Permissible operating temperature: 70 °C

◇ Max. permissible system temperature 120 °C

Specification

Model	Total Capacity (L)	Adjustable Capacity (L)	Dimension (mm)
Model	Total Capacity (L)	Adjustable Capacity (L)	Diameter	Total Height	Connection Size
G110	100	54	400	1260	DN50
G350	350	125	600	2000	DN50
G800	800	350	800	2340	DN50
G1300	1300	500	1000	2420	DN50
G2200	2200	750	1200	2800	DN50
G3100	3100	1000	1400	2970	DN50
G4200	4200	1950	1600	3050	DN80
G5500	5500	2120	1800	3170	DN80
G7000	7000	3650	2000	3320	DN80

Detailed Images

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Data sheet: Bladder Expansion Tank

ORDERING INFO

Particular information:

1. Total capacity.

2. Adjustable capacity. If not sure, please provide: total water volume in the system, highest and lowest possible temperature.

3. Working pressure.

★ Selection shall be base on adjustable capacity with sufficient redundant capacity, ensure that bladder won't be expanded (deformed) which is the main reason of broken.

General information for ordering:

1. Quantity of each size.

2. Delivery location, and price term: EXW, FOB, CIF, DDU, DDP, etc.

3. Detailed information of the contact person and buyer's company, which is helpful to prioritize your inquiry with faster response and better price.

SHIPPING

Delivery Options:

Delivery Method	Incoterms Term	Applicable Countries
LCL, FCL by sea	EXW, FOB, CFR, CIF	General for all countries.
Air courier to door	DDU, DDP	General for all countries.
Air cargo to airport	CIF	General for all countries.
Door to door by road	DDP	Cambodia, Laos, Myanmar, Thailand, Vietnam. (keep expanding to more countries)
Door to door by sea	DDU, DDP	Cambodia, Indonesia, Malaysia, New Zealand, Philippines, Singapore, Thailand, United Arab Emirates, United Kingdom, United States. (keep expanding to more countries)

LCL=Less than Container Load.     FCL =Full Container Load
DDU = Delivery Duty Unpaid        DDP = Delivery Duty Paid
The above shipping information is general, and changing from time to time. Confirmation with us is necessary for each order.

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