The equation for HG is:

Code:
HG = W – H

W = ABASTR * ( AM + AB ) / 2.0
H  = PI / 4 * G * G * PEQ


       W       - FLANGE DESIGN BOLT LOAD
       H       - TOTAL HYDROSTATIC END FORCE

       ABASTR  - ALLOWABLE BOLT STRESS AT AMBIENT TEMPERATURE
       AM      - LARGER OF AM1 AND AM2
       AB      - CURRENT TOTAL BOLT AREA
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Regards,
Richard Ay - Consultant