Iain, can you please repost the pics of your electric driven booster? Sounds extremely interesting.
I don't think I can.
The post together with the photos and some additional forum members comments were all taken down by what I can only assume was a moderator. I have had no explanation of why or who or the reason. So have assumed that the photos and explanation performance details were not in keeping with the forums moderators terms and requirements of things and products you as recreational divers need to know or of products that are outside of the recreational scuba general sports equipment range of products and brand names.
I have no intention of arguing the position and if this type of equipment is deemed not suitable for sports diving use fine by me. I will not be suppling any more photos drawings or detailed specifications to this post unless informed otherwise.
Yes 6 lt/min is extremely low but for me it does not matter at, the compressor may run all night long.
I should say in addition and purely from a position of safety so not to offend any of the moderation terms
set by the removal of my original post but from purely a safety position IMHO no compressor gas booster used by recreational divers especially one compressing high pressure oxygen should be run unattended all night long in a residential building or home property.
Although the compressor I detailed in question is fitted with 3 interstage relief valves for each of the three stages together with a thermal motor overload cut out safety switch and an automatic cut out pressure switch to shut down the pump when full pressure is achieved as standard for the build spec.
However if the compressor was to be used in a domestic household setting and especially if being used unattended overnight in say outside or in a yard /compond or separate building I would suggest in addition a remote temperature device or RTD to be fitted at a point just after the final 3rd stage discharge valve (hot side)
From the design calculation mathematics each of the 3 stages create a temperature rise together with the pressure and if you ignore the cooling effect for the moment and work off the highest calculated static gas temperature created at the discharge side of the valves as the gas carries over up unto the next stage of compassion you get the following:
1. Assuming a gas temperature of 37.778
°C (100
°F ) at the approach inlet side
2. Assuming an ambient air temperature of say the same 37.778
°C (100
°F )
3. Calculated without considering any interstage cooling and at a zero cooling effect position
Then taking the 3 stage design at say 160 RPM and a compression stroke length of 12mm
with an inlet pressure of 1.72 bar ( 25.0 psi) the compressor will develop a flow at the required high pressure of 517.97 L/hr ( 18.29 SCFH) or 8.63 L/min ( 0.30 SCFM) just a little better than the 6 L/min you originally quoted but due to my original reducing of the inlet pressure to a mid point range between the allowable zero inlet pressure to the maximum 1.72 bar inlet pressure in order to achieve any gas scavenging requirements or application.
The compression ratio's for compressing dry Oxygen are also a considered calculation and are as follows:
1st Stage compression ratio is CR 3.29:1 and is under the maximum 5:1 ratio for oxygen
2nd Stage CR 3.6:1 (Again well under the industry maximum of 5:1 CR for compressing Oxygen )
3rd stage CR 2.59:1 (Again also well under the industry recommended maximum of 5:1 )
Please Note and consider well that the lowest compression ratio of 2.59:1 is also by competent engineering design also at the highest compressive design load of 155 Bar G (2250 psi) with a conservative margin of safety included.
Further the gas temperature generated is also a safety requirement and a major consideration for any purchase of equipment used for the compression of Air Gas or Oxygen using a compressor and or booster. These considerations are a factor sadly omitted from you as recreational divers in favour of imported scubee sports brands and models. While you remain ignorant of the risks and required considerations before purchase
Again consider also that the design calculation are at a maximum ambient air temperature of a tropical Island and not the UK England of 37.778
°C (100
°F ) together with an inlet gas temperature also of the same 37.778
°C The generated temperature that the booster will create before the finned tube cooling will be in the worse of possible conditions and will be as follows:
1st Stage 230.63
°C (447.14
°F )
2nd Stage 187.28
°C (369.11
°F )
3rd Stage 158.16
°C (316.69
°F )
Further after each stage and before the next stage the cooling coils will reduce the generated temperature down to what is called the approach temperature and this will be within 6 degrees over the surrounding ambient air temperature or inlet gas temperature whichever is the greater.
Again notice by proper engineering design and to achieve the highest possible safety design factor the highest temperature has been pushed to the lowest pressure even in the hottest of climatic conditions for safety.
Knowledge is power and faith moves mountains. But keeping a purchaser and the recreational scuba diver end users ignorant of proper engineering design detail options and features together with the required safety considerations is necessary only in a sports product industry to
make the biggest margins of profit for the cheapest of imported junk price and to ensure the continuation of you the purchaser in ignorance as it's cash cow.
