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Shallow water SeaCircuit Plastic  Pressure Vessels 

Robotic Ocean, LLC introduces 23 diameters of Shallow Water SeaCircuit enclosures whose objective is to reduce the costs of harsh environment enclosures while maintaining the durability and reliability of high quality builds. Lighter and more affordable than our deep water SeaCircuit aluminum housings, these shallow water pressure vessels are made from polyvinyl chloride, a plastic that can be utilized for subsea applications such as junction boxes, electrical instrumentation housings, sensor/battery enclosures, or chemical/biological containment. Due to the varying diameters and wall thicknesses associated with each vessel size, the depth and pressure limitations are not the same for all sizes. Please refer to the table below to get the approved depth and pressure associated with each vessel size.

Intermediate Depth SeaCircuit Plastic  Pressure Vessels (Heavy Wall)

The SeaCircuit product line offers the following advantages 








 Standard SeaCircuit housing assemblies are available immediately for online purchase, however vessel customizations can be accomplished by emailing us at or go to our CUSTOMIZE A PRESSURE VESSEL webpage. Most assemblies require additional features and accessories such as electrical connectors, vent plugs, ported hole patterns, carrying handles, acrylic windows, or internal/external PCB brackets. Hole patterns for your endcaps can be handled by sending us the precise information required to meet your needs. Please email us for other more specific concerns, questions, or information.

This product exceeds all NEMA and IP67 / IP68 / IP69k ratings and is designed for full immersion for indefinite periods at the rated depth. SeaCircuit enclosures are in compliance with engineering standards ASTM-D1785 and ASTM-D2665. Although a safety factor was applied to obtain the theoretical pressures and depth ratings, please note that dimensional tolerances based on these engineering standards will slightly affect actual ratings. All pressures ratings based on compression yield strength. A variety of material combinations is available to suit the diverse needs of our customers. Besides polyvinyl chloride, clear acrylic (Perspex/Plexiglas), 6061 aluminum (aluminium) are also available materials by which all components can be made, however if different materials are combined depth and pressure ratings may be affected. Please see our website for the latest materials to be standardized and become a part of the SeaCircuit family of products.


Use the following part numbering system to order/identify SeaCircuit housings:

The part numbering system is designed to concisely provide all the information necessary to fabricate the housing assemblies prior to any customization. In addition to this part number, you may provide the details of your customizations to clarify and expedite your order. From gure 2, the value of L is the total length of the unit from a top endcap fiber to bottom endcap fiber. Housing lengths are typically de fined by their packing length (PL). This is the usable length of a pressure vessel in inches which is continuous and without axial curvature. Use decimal values if necessary. For metric, append a `M' to the value.

Dimension `E' is known as the `endcap lip' and shall be no less than .275". If you prefer to provide total length (L) rather than packing length, we can provide the associated packing length (PL). Many endcap con gurations are quite common, thus Robotic Ocean has produced the endcap
con guration table of common endcap styles/features which can be selected via the part numbering system. If you do not see your desired feature listed in the table, it can be produced by contacting us with your endcap needs.

An example of using this part numbering system for a size 16 shallow water SeaCircuit pressure vessel with a packing length of 36.5" using a single O-ring seal whose endcaps are made from PVCin the con guration as one at endcap and one domed endcap shall be 16.00-PVC-36.5-A-PVC-M-PVC. Terms from the Endcap Con guration Table and this document shall be de ned. A DOMED ENDCAP refers to an of the shelf cap end which ultimately becomes glued (either by you or by the factory). SINGLE and DOUBLE SEAL endcaps are at endcaps that contain single or dual radial O-rings, respectively. A PLAIN endcap is at, provides a watertight seal and has no other features. An endcap RETAINING FEATURE secures the endcap to the shell without screws. The RETAINING LINE is a plastic cord which is inserted into the retaining feature. This is an alternative to having ENDCAP FASTENERS, the traditional method of securing endcaps by using machine screws anchored to the shell. When possible, fasteners are typically longer than normal in order to serve as both jack screw and endcap fastener. JACK SCREWS aid in removing at endcaps from their shell. As the jack screw is turned, it gently lifts up on the endcap pushing it away from the shell. Multiple jack screw holes are drilled in order to lift the endcap equally from multiple locations. VENT SCREWS allow the enclosure's pressure to equalize when installing/removing endcaps. A PERMANENTLY SEALED endcap is a domed endcap which is chemically fused to the shell.

It is imperative that when ordering a pressure vessel that an understanding of ENDCAP FASTENERS and JACK SCREWS is clear. Endcap fasteners pull the endcap down via the metal insert embedded in the shell wall, as depicted in the gure below. This prevents the endcap from moving. Jack screws, as shown in the next gure, gently raise the endcap move upward because of the gripping action of the jack screw on the metal insert embedded in the endcap. This process is used to aid in the removal of endcaps. Be sure to remove the vent screw or vent plug prior to using jack screws to prevent damage to the pressure vessel assembly. Multiple jack screw locations are typically used to lift different sides of the endcap. For all speci ed shallow water SeaCircuit ratings, an assumed temperature of 70F (21C) is used to compute ratings. Please note that mechanical properties such as yield strength do change with temperature. These standardized pressure vessels are a good step toward efficiency and optimal pricing, but we know it may not ful ll all of your pressure vessel needs. Just let us know your constraints for the shell and each endcap (including connectors, size, and pressure/depth), and we will produce your vessel with your precise constraints. Please refer to our deep water aluminum SeaCircuit product line for deeper ocean applications. At Robotic Ocean, LLC, our design is to lower costs for users of our products while optimizing ease of ordering, and time to the consumer. Please visit for the latest information pertaining to low cost water-tight enclosures. Designed and assembled in USA.

Testing and Verification of  Pressure Vessels

   Although mechanical data is readily available for metals this is not always the case with plastics so we use our own method for obtaining Young’s modulus or stiffness of the plastics we use. This allows us to take account of changes when the material is wet and when it is warm. Initial validation of the pressure vessel is performed by monitoring the external pressure after a nitrogen backfill. To prove that a housing can withstand a rated pressure we perform hydrostatic tests. This involves applying water pressure to the external surfaces of the housing in a pressure vessel. The pressure rating of the all 23 standardized sizes is available in the table above. It is important to prove the margin of safety, or how much pressure can be applied in excess of the working pressure before the housing material deforms. This can only be done with a test to destruction causing the housing permanent damage. A photograph of the pressure vessels after destruction testing is shown below.

Pressure testing Robotic Ocean intermediate depth SeaCircuit plastic pressure vessels (Heavy Wall)  

at deepsea power and light 

Note: Pressure vessels after a destructive test