Before beginning any wellhead flange disassembly it pays to consider the following safety questions:
- Could the connection still contain some pressure?
- Could the assembly still contain toxic or dangerous fluid or gas?
- Does the flange connection retain a load?
Use diligence in taking precautions against the dangers revealed by these questions.
Procedure
Always wear eye protection and gloves.
Before starting to loosen flange nuts and bolts, check that the assembly contains no pressure. Always assume that if you can’t see inside the assembly, it may contain pressure, or hazardous or toxic contaminants. If you determine that a risk of retained pressure exists, it will pay to wrap the flanges around the gap between flanges with a safety device adequate to deflect any ejection of this possible pressurized liquid or gas.* If you cannot obtain a specialized flange wrapping device, wrapping the gap between flanges with several layers of duct tape will provide some protection from ejected liquids. Always work with adequate ventilation and air circulation. 1
To help avoid problems sometimes encountered when taking flanged joints apart, use the reverse of the procedure commonly used to assemble and secure them.
- Loosen nuts and bolts in the same sequence used to tighten them .
- Partially loosen every nut first, all around the flange.
- Only after the above step, slightly back-off the loosened nuts on the bolts, leaving a small space between the nut and the back of the flange. Do not remove the nuts.
- With the nuts and bolts apparently loosened, attempt to move the flanges in relation to one another to confirm that any seal has broken and no pressure remains. Watch for and remain cautious about any non-pressurized liquids or gases that may escape and could pose a danger.
- If the above step has revealed the connection has broken and no contaminants exist, remove all bolts and nuts to separate the flanges.
- Handle any parts that you intend to reuse with care.
If difficulty occurs during the process of removing the nuts and bolts for flange disassembly, you may want to consider using:
- A nut splitter.
- Commercial penetrating solution on the nuts and bolts.
- Application of heat to the nut to expand and loosen the nut (Always discard any heated nut, and the bolt with it).
- A nut welded to the end of any stud bolt tapped into a flange, to provide a head on the stud to allow you to better grip it and unscrew and remove the stud bolt from it’s tapped hole (As a last measure on stubborn tapped in studs, you may also saw off tapped in stud bolts and drill out the remainder from the tapped hole. You will need to determine the original tap drill size used to drill the tapped hole at the time of the original manufacturing, and use that drill size. Exercise extreme care to drill the exact center of the sawed off stud to avoid damaging the tapped hole in the equipment. Tip: Do not use a flame cutting torch to cut off any tapped in stud bolt, as this may harden the stud and make it very difficult to drill).
| * | Operators may find Flange Wraps, or Flange Safety Spray Shields, by an internet search for these items. |
| 1 | Words in bold italic indicate they have subjective meaning and persons using this information must use experience to improve the reliability of their judgement when the meaning of these words can have impact on performance. |
