Recommended torque used to stud bolts carbon steel coated with PTFE.
Stud bolts material
Bolts: ASTM A193 gr B7
Nuts: ASTM A194 gr 2H
Bolt Diameter
Heavy Nuts Size
Torque (N.m) 50 % Yield Stress
3/4”
1.1/4"
215
7/8”
1.7/16”
340
1”
1.5/8”
505
1.1/8”
1.13/16”
730
1.1/4”
2”
1010
1.1/2”
2.3/8”
1770
Optionally, stainless steel stud bolts can be used (however the yield is less than carbon steel).
Stud bolts are used to connect the hose flanges, which are normally made of carbon steel coated with PTFE.
Carbon Steel Stud bolts material.
Bolts: ASTM A193 gr B7
Nuts: ASTM A194 gr 2H
Optionally, stainless steel stud bolts can be used
Stainless Steel Stud bolts material
Bolts: ASTM A193 gr B8M
Nuts: ASTM A194 gr 8M
The most commonly used gaskets are CNAF (compressed Non Asbestos Fiber), or Spiral Wound Gaskets with PTFE filler.
The field hydrostatic test consists of filling the hose string with water, bleeding out any air remaining, and then raising the internal pressure to the Rated Working Pressure (RWP) of the hoses, or the normal operating pressure plus 50%, whichever is greater.
The lifespan of a hose depends on several factors, however, according to Flexomarine's experience, the most demanded hoses, such as First off Buoy and Tanker Rail, usually have a lifespan of approximately 3 years, while a Mainline hose, can reach approximately 5 years.
The used hoses are tested according to OCIMF “Guidelines for the Handling, Storage, Inspection and Testing of Hoses in the Field”, Second Edition – 1995, and basically consists of:
• Visual Inspection
• Hydrostatic Test
• Electrical Continuity Test
• Vacuum Test
The repair of the body of an offshore hose will be performed when only superficial damage has occurred, i.e., a damage that does not affect the primary or the secondary carcass.
The average manufacturing time for a hose, with all its tests, is approximately 10 days.
The hoses should be laid out straight on solid supports, in cool, dry and dark storage conditions.
