What are the standard performance over-design margins?
There are no standard margins for heat transfer (or thermal duty), surface area and pressure drop. Overdesign factors are stream and/or application dependent and may vary from 0 and 10%, unless other project specific values are specified.
Are distributor areas included in calculation of the heat transfer surface area?
Distributor areas are normally not included.
Should filters be installed to prevent plugging?
To avoid most plugging issues, filters must be installed on all streams. For more information, see Section 8.2.2.1 of the ALPEMA Standards.
How can plate-fin heat exchangers be cleaned on site?
Cleaning procedures depend on the nature of the fouling or plugging. For more information, see Section 8.2.
What is the lifetime of a plate-fin heat exchanger?
Under steady-state conditions the lifetime of a plate-fin heat exchanger is comparable to that of other heat exchange equipment types. Well operated plate-fin heat exchangers installed over 40 years ago are still in operation. Refer to Section 8 for recommended good practice.
How can plate-fin heat exchangers be repaired on site? Are there standard repair procedures?
Repair procedures depend on the type of damage. Seal welding of leakages or blocking of damaged passages may apply. It is recommended that any repair be carried out only by the manufacturer or a recognised specialist repair team. For more information, see Section 4.12.
What are recommended maintenance intervals and procedures?
Normally no routine maintenance should be required; see Section 4.10 of the ALPEMA Standards.
What are the allowable nozzle loads?
The associated piping can impose forces and moments on the heat exchanger nozzles. See Section 5.12.2.4 of the ALPEMA Standards for nozzle loadings.
Why were the allowable nozzle loads increased in the 3rd edition of the Standards?
Loads were increased to bring them in line with industrial practice.
What are the limits for temperature differences?
Temperature differences and thermal stresses are associated, and these stresses must remain within the acceptable limits. See Sections 4.9.1, 5.8 and 8.1.3 (item 6) of the ALPEMA Standards for guidance.
What mercury concentrations can be handled?
Plate-fin heat exchanger systems should not be operated in environments where mercury concentrations are greater than 0.1 micrograms/Nm3. Above this limit, mercury guard beds should be installed and mercury tolerant features should be considered in the design of the exchanger. See Section 8.3.2 for guidance.
Can plate-fin heat exchangers be used in water service?
Yes, provided freezing is avoided and other considerations, such as pH values between 4.5 and 8.5, are followed. See Section 8.3.1 for additional guidance.
What amount of input data is required with an inquiry?
Generally the process conditions are required as shown on Fig.7-3 (lines 2-25) and Fig.7-4 (download here). A preferred alternative to tabulated physical properties and temperatures is to provide a process simulation data file.
Is there a recommended filter mesh size?
A mesh size of 177 microns (80 Tyler) is recommended for most applications. See Section 8.2.2.1 for more information.
Are fouling factors used in BAHX design?
Because clean fluids are processed, fouling factors are not used unless specified by the customer. See Section 8.2.1.
What is a 'cold box'?
The term cold box is used to describe a carbon steel casing which houses cryogenic equipment. See Section 9.2.
What is the minimum temperature approach (pinch point) for a BAHX?
A good guideline is 1 to 3 °C depending upon the application. Minimum temperature approaches even lower than 1 °C are possible in a few applications.
How are BAHXs thermally insulated?
By either filling a casing (cold box) with perlite or using slab insulation. Both types of insulation are installed on site.