This is an excellent high quality video showing Air Diver performing underwater clamp installation. The waterdepth is about 14 m ( 46 ft). I believe the video was taken using[abbr title=”Remotely Operated Vehicle”]ROV[/abbr]. (ROV umbilical – 03:08). It is possible to perform double operation Diving & ROV as long as in accordance with all the safety requirement. I’ll share these requirement in future post.
From the video we can observe the following:[unordered_list style=”bullet”]
- Newly installed riser clamp ( [abbr title=”Water Depth”]WD[/abbr] ~ 14m)
- Subsea Riser Clamp No. 1 from [abbr title=”Mean Sea Level”]MSL [/abbr](Refer to the mark no. 1 on the riser clamp door)
- Seen no anode on the clamp. Assumed there is a metal contact between horizontal jacket brace & riser clamp.
- The bolt & nuts are impact tighten.
- Messenger line to supply divers with all required tools & equipment.
- Diving in tropical water. Diver wears denim diving suit.
- The that i’m not sure is the yellow structure shown in 03:39
What is Riser Clamp?
It is a Structure which is intended to keep the riser in place. There are various type, size and design of riser clamp.
- Hanger Clamp (Load Bearing Clamp) : a clamp design to handle the vertical loading which capable to takes the weight of the entire riser + horizontal restraint. The clamp allowed the riser to slide axially.
- Sliding or Guide Clamp : The clamp installed below after the load bearing clamp towards seabed. It provide horizontal restraint but again allow the riser to move/slide axially (typically 5mm anulus gap between riser & neoprene pad installed on internal surface of riser clamp shell.
- Client specifications / Contractual requirement.
- Riser Clamps design & drawings – To ensure the right clamps installed at the right position.
- Approved Riser Clamps installation procedure. Typically its a subsection of Riser Installation Procedure. The riser clamp installation procedure will become standalone if the installation is performed by different vessel which install the riser. Normally a small DPDSV or small barge. This approach is more economic if there is a lot of riser clamps need to be installed in a year programme/contract. In this case most of the time, the final tightening will also performed by this small DSV. The main work barge will only tighten the load bearing clamp.
- Riser clamp installation Action List. This is a small field document but a very important piece of info. its a suit to site type of document but in line with all the above document. I’ll share sample of riser clamp action list in future post.
- As built report (document/visual) signed/withness by client.
Ok Offshoreman, need to stop here. been a long time i’m not writing. Please come back or comment this post. I might miss an important notes. Or maybe someone expert from subsea division may add notes to this post … Spasiva!
Offshore Riser Installation (Source Flickr)