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Last Updated: 2020.6

(Fixed, Floating, and U-Tube)

The conditions grid is a repository for tubesheet design cases. Values entered here will overrule values entered on previous tabs. For example, if shell pressure on this tab is 15 PSI and shell pressure on the shell tab is 50 PSI, 15 PSI will be used in the calculations; however, a value entered on the conditions grid will not change the value on any other tab.

The values entered on this tab default based on settings from other tabs. If temperatures, pressures, or materials are changed on the other tabs, the values on this tab will update even if they were manually changedonly reflect those changes for new rows that are added. If the values on this grid are manually changed, they will remain the same until a change on another tab or a manual adjustment occurs.not be updated by changes to the other tabs. 

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Shell Pressure: The shell side internal design pressure for Design Cases. This may be an operating pressure for the other cases (e.g., Operating, Startup, Shutdown, etc)thermal cases.

Shell Vacuum: The shell side external design pressure for Design Cases. This may be an operating external pressure for the other thermal cases (e.g., Operating, Startup, Shutdown, etc).

Shell TsT_s: The shell material maximum mean metal design temperature for Design Cases. This may be an operating temperature for the other thermal cases (e.g., Operating, Startup, Shutdown, etc).Shell Tsm.  This temperature is used to determine the shell material properties for the row under consideration, with the exception of the alpha values.  It is conservative to use a higher value here and this will typically match the design temperature for the shell side, though the operating temp may be used in the thermal cases as mentioned.

Shell T_sm: The mean shell temperature along the shell length as expected during the case under consideration (e.g., Operating, Startup, Shutdown, etc). It is generally not conservative to substitute the shell design temperature for TsmT_sm as a higher delta between T_sm and T_tm is what is considered conservative.

Shell TsT'_s: The metal temperature of the shell at the tubesheet as rim as expected during the case under consideration (e.g., Operating, Startup, Shutdown, etc). It is usually not conservative to substitute the shell design temperature for TsT'_s. This value is only required for radial differential thermal expansion calculations.

Tube Pressure: The tube side internal design pressure for Design Cases. This may be an operating pressure for the other thermal cases (e.g., Operating, Startup, Shutdown, etc).

Tube Vacuum: The tube side external design pressure for Design Cases. This may be an operating external pressure for pressure for the other thermal cases (e.g., Operating, Startup, Shutdown, etc).

Tube TtT_t: The tube material maximum mean metal design temperature for Design Cases. This may be an operating temperature for the other thermal cases (e.g., Operating, Startup, Shutdown, etc).Tube Ttm.  This temperature is used to determine the tube and channel material properties for the row under consideration, with the exception of the alpha values and the tube values @ T_ts.  It is conservative to use a higher value here and this will typically match the design temperature for the tube side, though the operating temp may be used in some cases as mentioned.

Tube T_tm: The mean tube temperature along the tube length as expected during the case under consideration (e.g., Operating, Startup, Shutdown, etc); this considers the entire tube bundle. It is generally not conservative to substitute the tube design temperature for TtmT_tm as a higher delta between T_sm and T_tm is what is considered conservative.

(TcT')_c: The metal temperature of the channel at the tubesheet rim as expected during the case under consideration (e.g., Operating, Startup, Shutdown, etc). It is generally not conservative to substitute the channel design temperature for TcT'_c. This value is only required for radial differential thermal expansion calculations.

(T'): The metal temperature of the tubesheet at the rim as expected during the case under consideration (e.g., Operating, Startup, Shutdown, etc). It is usually not conservative to substitute the tubesheet design temperature for T'.  This value is only required for radial differential thermal expansion calculations.

Stress: The material allowable stress. When a 3.5:1 safety factor is specified in the vessel screen, this value comes from Section II, Part D (Table 1A for Ferrous Materials, Table 1B for Non-Ferrous Materials, and Table 3 for Bolting). If a 4:1 safety factor is specified, this value is calculated based on the ultimate strength from Table U in Section II, Part D; furthermore, the value is limited to the values listed in the allowable stress tables for yield and creep governed cases. In cases where the temperature exceeds the highest temperature entry for this material’s stress line, the value will be zero. Shell Stress and Shell Band Stress are based on TsT_s. Tube Stress is based on TtT_t. Tube Stress @ Tts T_ts is based on TtsT_ts. Stationary Channel Stress and Floating Channel Stress are based on TcT_c. Tubesheet Stress is based on TtsT_ts.

Yield: The material yield strength based on Section II, Part D, Table Y-1. In cases where the temperature exceeds the highest temperature entry for this material’s yield line, the value will be zero. There are several materials that do not have clear matches in these tables. When a clear match cannot be found by the software’s assignment criteria, the software will calculate the yield strength using the external pressure chart and the method described in UG-28(c)(2) Step 3. This is more common with non-ferrous materials. If no match is found and the software cannot perform the described calculation, this value will be zero. Shell Yield and Shell Band Yield are based on TsT_s. Tube Yield is based on TtT_t. Tube Yield @ Tts T_ts is based on Tts T_ts. Stationary Channel Yield and Floating Channel Yield are based on TcT_c. Tubesheet Yield is based on TtsT_ts.

Modulus: The material modulus of elasticity based on the TM tables from Section II, Part D. The value shown here is based on the applicable TM table. In cases where the temperature exceeds the highest temperature entry for this material’s TM table, the value will be zero. There are several materials that do not have clear matches in these tables. When a clear match cannot be found by the software’s assignment criteria, the software will instead retrieve the modulus of elasticity from the external pressure chart assigned to the material. If this attempt also fails, then the value will be zero. This is more common with non-ferrous materials. Shell Modulus and Shell Band Modulus are based on TsT_s. Tube Modulus is based on TtT_t. Tube Modulus @ Tts is based onTtsT_ts. Stationary Channel Modulus and Floating Channel Modulus are based on TcT_c. Tubesheet Modulus is based on TtsT_ts.

Alpha: The material mean coefficient of thermal expansion based on the TE tables from Section II, Part D; column B is used in those tables. There are several materials that do not have clear matches in these tables. When a clear match cannot be found by the software’s assignment criteria, this value will be zero. Shell Alpha_s,m and Shell Band Alpha_s,m1 are based on TsmT_sm. Shell Alpha s’ ' s is based on Ts’T'_s. Tube Alpha s_t,m is based on TtmT_tm. Stationary Channel Alpha C’ '_c and Floating Channel Alpha C’ '_c are based on Tc’T'_c. Tubesheet Alpha’ is based on T’.

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