Types of Storage Tank
Types of Storage Tank:- Storage tank is an essential part of process plant because we need to store material weather liquid or gaseous during transportation, production, marketing to ensure continuity. During storage the quality of product must be maintained. Storage tanks are mainly cylindrical in shape having flat bottom and fixed or floating roof.
There are many types of storage tanks available to store different categories of material. Like to store Non-volatile liquid we use Fixed roof, Open roof and Non-pressure storage tank. For Volatile liquid we use Floating roof storage tank. For Gaseous content we use Spherical and Bullet type storage tank.
Non pressure tank
Non pressure tanks are very common for non-volatile liquids like inorganic liquids. These are made of flat metal sheets. In majority case there are in rectangle shape. Flat plates have low strength so we need to provide stiffening. These are simplest type of storage tank.
Fixed roof storage tank
Fixed roof storage tank is another commonly used tank. It has fixed roof. Normally it is welded joints due to which it becomes vapor tight. The vapor generated over the liquid due to temperature difference increase pressure to take care of it relief valve is given over the roof. While removing liquid vacuum is generated to take care of it vent is given on roof which will circulate air in tank.
Floating roof storage tank
- Floating roof storage tank is used while handling extremely volatile liquid. Two types are their 1) External floating roof tank 2) Internal floating roof tank. In these tanks breathing loss, Boiling loss and filling loss is eliminated.
- In external floating roof tank roof is supported on the liquid instead of column or shell. Here very little vapor generation will take place because there is no place for vapor. When frequent filling and emptying of tank is required these tanks are used. Mainly three types of roof are used 1) pan type 2) Pontoon type and 3) double-deck type.
In internal floating roof tanks two roof are available. One is floating on the liquid surface and other is fixed type. It can be either structurally supported or self-supported.
Spherical storage tank
Spherical storage tanks are used when we deal with pressurized gas storage. These tanks can withstand 1 atm to 10 atm pressure. The reason behind spherical shape is that it will provide very less ratio of surface area to volume due to which plate requirement will reduce and automatically cost will reduce than any other shape. Lower S.A. to volume ratio will also help when we need to apply insulation on the surface because we will need less insulation than any other shape.
Spherical shape will require almost half the thickness than classical cylindrical shaped storage tank. Due to these advantages we use spherical storage tanks for high pressure storage.
Horizontal tanks are used when little amount is to be stored. They can be both underground and ground. The length of tank should be six times the diameter. They are equipped with gauges and vents. In underground tanks sacrificial anode is provided to eliminate corrosion of tank.
Most common example of Bullet type tank is gas cylinder at home. They range from 6000 gallons to 30000 gallons. Most common size is 18000 gallons.
So, this is all about types of storage tanks. Different tanks are used based on requirement. Process engineer will decide which tank to use.