PVHO Quality Assurance

Subsea Batteries

Subsea Batteries

POWER UNDER PRESSURE Pressure Tolerant Li-Po Batteries for underwater vehicles

The Hydrospace documentation and Quality Assurance program meticulously records all steps in the PVHO design, fabrication and testing processes. Hydrospace meets and exceeds the requirements of ASME PVHO-1 and regularly produces windows for a range of Classification agencies.


For the Fabrication of a PVHO window, Hydrospace requires clients to provide both the engineering drawing and the associated PVHO-1 Form VP2. For Classification requirements, both documents will also require formal Class Approval stamps for final inspection.

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The ASME PVHO Process

For a full overview of the HYDROSPACE Fabrication and Quality Assurance process, click below:


HYDROSPACE ASME PVHO-1 FABRICATION and QA PROCESS – probably this one has link.


Hydrospace provides all other documents and keeps both hard copy and electronic copies of all certifications on file for future reference or if originals are lost.

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Function of PVHO Forms

The design and certification of PVHO acrylic windows is traced through a series of five (5) certificates of conformance, namely PVHO-1 FORMS VP1 thru VP6. The complete fabrication process includes the following step, listed in order of fabrication:


  1. PVHO-1 FORM VP2 – Window Design Certification
    Each New window design must conform to all PVHO-1 engineering requirements.
    PVHO-1 Form VP2 Certifies that the ENGINEERING DESIGN Meets PVHO
    (Class Agency Approval of Engr Drawing & Form VP2 Required for Classification)

  2. PVHO-1 FORM VP3 – Acrylic Material Certification
    All material must meet minimum performance criteria specified in ASME PVHO-1
    PVHO-1 Form VP3 Certifies that the ACRYLIC MATERIAL Meets PVHO
    (Class Agency Surveyor Witness Required for Classification)

  3. PVHO-1 FORM VP4 – Material Testing Certification
    All material must be individually tested for conformance to Minimum PVHO-1 Specifications
    PVHO-1 Form VP4 Certifies the actual MATERIAL PERFORMANCE
    (Class Agency Surveyor Witness Required for Classification)

  4. PVHO-1 FORM VP1 – Fabrication Certification
    Each window must be inspected after fabrication and document conformance to the Engineering Drawing, PVHO FORM VP2 and all PVHO-1 fabrication requirements
    PVHO-1 Form VP1 is the CERTIFICATE of CONFORMANCE for each window.
    (Class Agency Surveyor Witness Required for Classification)

  5. PVHO-1 FORM VP5 – Hydrostatic Pressure Test Certification
    Each window must be Hydrostatically tested in conformance to the window & assembly Drawing, PVHO FORM VP2 and PVHO-1 pressure testing requirements
    PVHO-1 Form VP5 certifies the HYDROSTATIC PRESSURE TEST for each window.
    (Class Agency Surveyor Witness Required for Classification)

  6. PVHO-1 FORM VP6 – Repair Certification
    Any repair to a PVHO window must be fully documented.
    PVHO-1 Form VP6 certifies the REPAIR meets all PVHO-1 requirements.
    (Class Agency Surveyor Witness Required for Classification)

Copies of all these PVHO documents MUST be maintained by the fabricator, user and operator for the life of the window.

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Equivalent PVHO Document

The names of the PVHO forms were changed in 2007. The same forms are used but the naming is different. There are still a lot of PVHO documents on hand that comply with the older convention. The following is a useful cross-reference table between the old and new nomenclature.


Present ASME PVHO-1 Forms
OLD ASME PVHO Enclosures
FORM VP1 Fabrication Cert
FORM VP2 Design Cert
FORM VP3 Material Cert
FORM VP4 Material Testing
FORM VP5 Hydrostatic Test
HRDC QA IMG 93809 1

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