The DERA Test Verbiage

/The DERA Test Verbiage
The DERA Test Verbiage 2017-06-28T18:18:03+00:00

The ‘Defence Evaluation and Research Agency


Implemented: December 2000

Subject: the HyPod Hyperbaric Chamber (then branded the “DiveAlive”)

About the ‘Defence Evaluation and Research Agency’[“DERA”]

Normally referred to as ‘DERA’, it was part of the UK’s Ministry of Defence (MoD) until 2001. At that time it was thought to be the UK’s largest science and technology organisation. ‘DERA’ was then divided into two organisations:

  • PDERA’ (meaning “privatised” DERA). This division specilised in ‘short-lived transition bodies’. It later became a commercial public company, QinetiQ Plc.
  • ‘RDERA’ (meaning “retained” in Government) which has now become the Defence Science and Technology Laboratory (‘Dstl’) headquartered at Porton Down and owned by the MoD.

DERA ‘Pressurisation to Destruction’test.

Capable of operating under any likely required pressures.

DERA’s highly accredited and experienced scientific team placed the HyPod in the water pit of their large explosion proof chamber and then forced high pressure air into the HyPod until it failed (exploded). The team were astonished that the HyPod withstood up to 12.6 bar before it failed (that is 13 times atmospheric pressure or 183 pounds per square inch), which was 2.5 times more pressure than the team had thought possible. They had to upgrade their test equipment when the pressure in the HyPod climbed above 5 bar.

Even then the failure occurred at 12.6 bar only because the heavy duty stainless steel lid bulged, resulting in a reduced diameter which dislodged from the neck of the HyPod. (the lid has since been strengthened). The HyPod’s main structure was undamaged and was reusable with a new lid.

Reliability and multi-deployment capability.

The DERA team also oversaw the HyPod being deployed from its carrying bag, pressurised, disassembled and repacked into its carrying bag some 30 times, to prove its robust and dependable qualities.

The DERA Conclusion.

The DERA Deputy Director in charge of the test (Mr Stanley) stated on completion of the test “that there were no extra strengthening requirements needed and that he would be prepared to use the HyPod decompression chamber himself”.

This test was carried out by DERA in 2000, under their strict scientific procedures and protocols and it resulted in the provision of 96 pages of accurate data and test results.

The high pressure which the HyPod withstood before it failed astonished all who oversaw the test. Because their expectations were based on the significant previous experience and knowledge of DERAs research technicians with other collapsible hyperbaric chambers. Therefore the HyPod was not expected to approach anything near a bar pressure in two digits, in fact only 5 bar was the norm with any other system. So based on this previous experience, ‘DERA’ set their electronic gauges to expect a maximum of 5 bar (naturally, ‘DERA’ did have a number of mechanical and digital gauges capable of far higher pressures).

During the initially stages of the test, several hydraulic pumps broke down at approximately 4 to 4.5 bar and technicians had to resort to completing the test using high pressure air, not the standard procedure for conducting such tests.

The recording transducer equipment reached its ‘built in maximum’ of  10 bar after 7.54 minutes of pressurisation. High pressure air delivered at 5000 lbs per square inch, continued to be fed into the HyPod for a further 7.65 minutes, resulting in the failure of the HyPod’s heavy stainless steel Lid at an incredible 12.5 bar as read from the calibration gauge. This failure pressure was some 2.5 times above the maximum thought by DERA to be sustainable !

Even at 12.5 bar, the HyPod remained intact; it was only the Lid that failed. It bulged and significantly reduced in diameter before being dislodged from the neck of the HyPod. Subsequently it was found that a main part of the Lid’s construction differed from the specification required from the lid’s supplier, who had manufactured it in two parts, not just one part as specified. This duplex manufacturing lowered the Lid’s strength and caused it to fail earlier than it should.

In fact, the HyPod’s main structure, the material chamber and its liner were undamaged and, with another pressure lid, the chamber could have been immediately reused as a decompression chamber or hyperbaric stretcher.

The HyPod’s ‘multiple-usage’ Test.

While at DERA it was thought applicable to demonstrate the ruggedness, dependability and ‘ease of deployment & use’ of the HyPod, by assembling, pressurising, depressurising and disassembling multiple times. To this end, firstly a single operative, then two operatives undertook the following procedure fully 30 times: unpack the HyPod, inflate and pressurise to above the required DERA oxygen working pressure. Then deflate, fold and replace the HyPod in its carrying bag. This was witnessed and verified by the DERA Deputy Director

The DERA Conclusion

That the HyPod was a unique product and should be fully deployed in quantities as soon as possible, so that both professional and amateur divers could be assured that a decompression facility was immediately on hand and that they could be then transported to the nearest qualified medical decommission facility without further pain or possibility of permanent injury or death.

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