IMCA publishes acrylic plastic viewports guidance
Publications - February 16, 2012
Acrylic plastic viewports in diving systems have been in satisfactory use for a number of years. However, the development of testing them by polarised light showed that there are various misconceptions about them.
The International Marine Contractors Association (IMCA) has just released updated guidance on the topic. An initial guidance note which sought to correct these misconceptions was initially prepared as AODC 030 in 1986 following advice from Det Norske Veritas (DNV). Now a revised document has been produced by IMCA through the Safety, Medical, Technical & Training Committee of its Diving Division Management Committee as part of its planned phased review of AODC guidance notes, which are then issued as IMCA guidance.
“Acrylic viewports are used in many pressurised systems under a variety of conditions world-wide and this document has been produced to provide general guidance,” explains IMCA’s Technical Director, Jane Bugler. “It includes additional guidance on deterioration compared to its predecessor, and identifies a reference document which perfectly complements it.
“That document is the ASME ‘Safety Standard for Pressure Vessels for Human Occupancy: In-Service PVHO Acrylic Windows Guidelines, PVHO-2: 2003’ which provides technical criteria and guidelines for the in-service inspection, care, repair or replacement, testing and recertification of pressure vessels for human occupancy (PVHO) acrylic windows.”
The IMCA document comes to five specific conclusions:
• Acrylic plastic viewports should be properly certified and marked prior to use.
• It is generally agreed that they should be replaced after 10 years of service (PVHO-2: 2003 provides additional guidance when determining the length of service.
• Examination of an acrylic plastic viewport by polarised light after the viewport has been in service is of very limited use, as all such viewports will show evidence of inbuilt stress.
• The use of polarised light to check that acrylic plastic viewports are correctly mounted and evenly pre-stressed is not a simple matter and should not be used as a principal test
• When mounting an acrylic plastic viewport, it is critical, especially when installing new ports in old pressure vessels, to check that the housing is the correct dimension and that the viewport and any sealing gaskets or O-rings are properly seated and of the correct size. A torque wrench should be used to correctly tension fixings diametrically to the manufacturer’s specification when replacing retainers.
IMCA’s new publication IMCA D 047 is available for free downloading from the IMCA website at www.imca-int.com with additional printed copies available to members at £2.50 and non-members at £5.00 (plus 20% for delivery outside Europe).
More articles from this category
- Divex secures contract for saturation diving system
Equipment & Technology - August 22, 2014
- Tidewater reports results for lastest quarter
Company News - August 21, 2014
- Chellsea takes delivery of newbuild PSV
Vessel & ROV News - August 20, 2014
- Sea Surfer joins Deep Sea Supply fleet
Vessel & ROV News - August 19, 2014
- Siem Giant enters service offshore Brazil
Vessel & ROV News - August 18, 2014
- OSBIT secures Well Ops LARS deal
Equipment & Technology - August 15, 2014
- Strategic Marine appoints Business Development Manager
Company News - August 14, 2014
- UTEC StarNet extends partnership with Sky Futures to North America
Company News - August 13, 2014
- EMGS sticks with Boa Galatea
Contracts, Tenders and Rates - August 12, 2014
- UK "has billions of barrels of oil" - but extracting it is more and more costly
News - August 11, 2014
- Fugro teams with WFS Technologies for wireless ROV integration
Vessel & ROV News - August 8, 2014
- DOF awarded contract offshore Brazil
Contracts, Tenders and Rates - August 8, 2014
- Sinopacific secures first contract in Mexican market
Yard News - August 8, 2014
- Summer publishing schedule
News - August 8, 2014
- SMD to supply Sistac with work-class ROV
Vessel & ROV News - August 7, 2014