Dinesh Tube India specializes in Shell & Tube heat exchangers both on-site and it works. Shell & Tube heat exchangers are the most common design for many applications. Amardeep Steel Centre provides a wide variety of applications based on the most suitable design and materials to ensure a cost-efficient and reliable solution. The full range provides standardized product lines for an optimal price/quality ratio as well as customized designs for the most demanding duties in oil & gas, power generation, marine, refrigeration and many other industries. There are two main categories of Shell and Tube exchanger:
- Those that are used in the petrochemical industry which tend to be covered by standards from TEMA, Tubular Exchanger Manufacturers Association
- Those that are used in the power industry such as feedwater heaters and power plant condensers.
Figure 1. Shell and tube exchanger.
The shell and tube exchanger consists of four major parts:
- Front Header—this is where the fluid enters the tube side of the exchanger. It is sometimes referred to as the Stationary Header.
- Rear Header—this is where the tube side fluid leaves the exchanger or where it is returned to the front header in exchangers with multiple tube side passes.
- Tube bundle—this comprises of the tubes, tube sheets, baffles and tie rods etc. to hold the bundle together.
- Shell—this contains the tube bundle.
The remainder of this section concentrates on exchangers that are covered by the TEMA Standard.
Shell and tube geometric terminology
Figure 2. Type BEM, CFU and AES exchangers. © 1988 by Tubular Exchanger Manufacturers Association.
Table 1. Shell and tube geometric terminology
|1||Stationary (Front) Head—Channel||20||Slip-on Backing Flange|
|2||Stationary (Front) Head—Bonnet||21||Floating Tubesheet Skirt|
|3||Stationary (Front) Head Flange||22||Floating Tubesheet Skirt|
|4||Channel Cover||23||Packing Box Flange|
|5||Stationary Head Nozzle||24||Packing|
|6||Stationary Tubesheet||25||Packing Follower Ring|
|8||Shell||27||Tie Rods and Spacers|
|9||Shell Cover||28||Transverse Baffles or Support Plates|
|10||Shell Flange—Stationary Head End||29||Impingement Baffle or Plate|
|11||Shell Flange—Rear Head End||30||Longitudinal Baffle|
|12||Shell Nozzle||31||Pass Partition|
|13||Shell Cover Flange||32||Vent Connection|
|14||Expansion Joint||33||Drain Connection|
|15||Floating Tubesheet||34||Instrument Connection|
|16||Floating Head Cover||35||Support Saddle|
|17||Floating Head Flange||36||Lifting Lug|
|18||Floating Head Backing Device||37||Support Bracket|
|19||Split Shear Ring|
The popularity of shell and tube exchangers has resulted in a standard nomenclature being developed for their designation and use by the Tubular Exchanger Manufacturers Association (TEMA). This nomenclature is defined in terms letters and diagrams. The first letter describes the front header type, the second letter the shell type and the third letter the rear header type. Figure 2 shows examples of a BEM, CFU, and AES exchangers while Figure 3 illustrates the full TEMA nomenclature.
Figure 3. TEMA nomenclature. © 1988 by Tubular Exchanger Manufacturers Association.
- Many combinations of front header, shell and rear header can be made. The most common combinations for an E-Type Shell are given in Table 2 but other combinations are also used.
Table 2. Shell and tube geometric terminology
Fixed tube sheet exchangers U-tube exchangers Floating head exchangers AEL AEU AES AEM CEU BES AEN DEU BEL BEM BEN
Essentially there are three main combinations
- Fixed tubesheet exchangers
- U-tube exchangers
- Floating header exchangers
Fixed Tubesheet Exchanger (L, M, and N Type Rear Headers):
In a fixed tube sheet exchanger, the tube sheet is welded to the shell. This results in a simple and economical construction and the tube bores can be cleaned mechanically or chemically. However, the outside surfaces of the tubes are inaccessible except to chemical cleaning.
If large temperature differences exist between the shell and tube materials, it may be necessary to incorporate an expansion bellows in the shell, to eliminate excessive stresses caused by expansion. Such bellows are often a source of weakness and failure in operation. In circumstances where the consequences of failure are particularly grave U-Tube or Floating Header units are normally used.
This is the cheapest of all removable bundle designs but is generally slightly more expensive than a fixed tube sheet design at low pressures.
In a U-Tube exchanger, any of the front header types may be used and the rear header is normally an M-Type. The U-tubes permit unlimited thermal expansion, the tube bundle can be removed for cleaning and small bundle to shell clearances can be achieved. However, since the internal cleaning of the tubes by mechanical means is difficult, it is normal only to use this type where the tube side fluids are clean.
Floating Head Exchanger (P, S, T and W Type Rear Headers)
In this type of exchanger, the tube sheet at the Rear Header end is not welded to the shell but allowed to move or float. The tube sheet at the Front Header (tube side fluid inlet end) is of a larger diameter than the shell and is sealed in a similar manner to that used in the fixed tube sheet design. The tube sheet at the rear header end of the shell is of slightly smaller diameter than the shell, allowing the bundle to be pulled through the shell. The use of a floating head means that thermal expansion can be allowed for and the tube bundle can be removed for cleaning. There are several rear header types that can be used but the S-Type Rear Head is the most popular. A floating head exchanger is suitable for the rigorous duties associated with high temperatures and pressures but is more expensive (typically of the order of 25% for carbon steel construction) than the equivalent fixed tube sheet exchanger.