ASME PTC 2010 - Intergraph Smart Instrumentation - Reference - Hexagon

Calculate mounting factor:

*L [m]

• Threaded connection:

  

• Other connection types:

  

Calculate Reynolds number:

Calculate Strouhal number:

Calculate natural frequency:

*L [m], B[m,] E[Pag]

1. Calculate average outside diameter:

• Tapered thermowell:

• Other thermowells:

1. Calculate approximate natural frequency:

   

2. Calculate correction factor Hf

• Tapered and straight thermowell:

  

• Stepped thermowell:

  

1. Calculate correction factor Haf:

   

2. Calculate correction factor Has:

   

3. Calculate natural frequency with ideal support:

   

4. Calculate natural frequency of the mounted thermowell:

   

Calculate Vortex shedding frequency

*B[m]

Calculate Scruton number:

*B[m]

Calculate miscellaneous parameters:

*B[m], L[m], E[Pag

1. Parameter Gsp

• Tapered and straight thermowell:

  

• Stepped thermowell

  

1. Parameter Grd (for stepped thermowell only):

   

2. Stress concentration factor:

• Threaded connections:

  

• Other connections:

  

1. Stress concentration factor at support plane (for stepped thermowell only):

   

2. Temperature de-rating factor:

   

Calculate Frequency Limit

• Low density gases: Nsc >2.5 and Tr ,100000

  

• General case: Other values of Nsc and Re

  

Compliance with the frequency limit requirement:

1. Initial evaluation of compliance:

• The thermowell is in compliance with the frequency limit requirement if;
  

  Go to step 10.

• The thermowell is non-compliant with the frequency limit requirement if;
  

  Go to step 10.

1. Evaluate compliance with cyclic stress limit for general case:

• Calculate velocity for in-line resonance:

  1. 

  2. 

  3. 

1. Calculate cyclic drag stress at the root:

   

2. Calculate combined drag and lift stresses:

   

3. Calculate fatigue stress limit:

   

4. Compliance with cyclic stress limit:

• Tapered and straight thermowell:

  • Not compliant with the cyclic stress limit and frequency limit if;

    

    Go to step 10.

  • Complies with the cyclic stress limit if;

    

    Set new frequency limit:

    

    Go to step 9g

• Stepped thermowell:

  • Not compliant with the cyclic stress limit and frequency limit if;

    

    Go to step 10.

  • Case

    Calculate:

    

  • Not compliant with the cyclic stress limit and frequency limit if;

    

    Go to step 10.

  • Complies with the cyclic stress limit if;

    

    Set new frequency limit:

    

    Go to step 9-g.

1. Re-evaluate compliance with the frequency limit requirement if cyclic stress is acceptable:

• The thermowell is in compliance with the frequency limit requirement if;

  

• The thermowell is in non-compliant with the frequency limit requirement if;

  

Compliance with the static stress limit requirement:

*B[m], P[Pag], S[Pag]

1. Calculate radial, tangential, and axial stress due to external pressure:

   

2. Calculate steady-state drag stress at the root:

   

3. Calculate steady-state stress due to the drag force:

   

4. Calculate maximum stress:

   

5. Calculate left-hand side of the Von Mises criteria:

   

6. Calculate right-hand side of the Von Mises criteria:

   

Compliance

• Tapered and straight thermowell:

  • Not compiled with the static stress limit if;

    

  • Complies with the static limit if;

    

• Stepped thermowell:

  • Not compiled with the static stress limit if;

    

  • Case

    Calculate:

    

  • Not compliant with the static stress limit if;
    

  • Complies with the static stress limit if;
    

Compliance with the Dynamic Stress Limit requirement

Calculate parameters:

Calculate drag and lift stresses at the root:

Calculate combined drag and lift stresses:

Calculate fatigue stress limit:

Compliance

• Tapered and straight thermowell

  • Not compliant with the dynamic stress limit if;

  

  • Complies with the dynamic stress limit if;

  

• Stepped thermowell

  • Not compliant with the dynamic stress limit if;

  

  Go to Compliance with the Hydrostatic Pressure Limit requirement section in this topic

• 

  • Calculate:

    

  • Not compliant with the dynamic stress limit if;

    

  • Complies with the dynamic stress limit if;

    

Compliance with the Hydrostatic Pressure Limit requirement

*B[m], P[Pag], S[Pag]

Calculate pressure rating for the shank:

Calculate external pressure rating for the tip:

Calculate pressure rating of the thermowell:

Compliance