Scott 5.5 SCBA

[LFPDLT]

After several years of trying we were finally awarded an AFG grant to purchase SCBA. One of the packs we are considering for evaluation is the Scott 5.5 5500 psi AirPak 75. I would like to hear from anyone who has actually purchased or used these packs, any pros or cons that you have found. Thanks

[nameless]

5500psi is pretty high pressure right? I haven't seen much beyond 4500psi in my little slice of the world. I'd be cautious about filling issues. Will you have to retool your entire fill system to support these? If your mutual aid companies come to a fire or large incident, will they be able to fill them? Sometimes its easier just to get what everyone else has.

[WBFD25]

My department has looked into them. We're awaiting the current AFG announcements to see if we're awarded; if so we'll be purchasing 5.5's in a 45 minute bottle configuration.

They operate at 5500 psi versus the 4500/3500/2216 that are common. Filling won't be a concern as you can put any amount into the bottle up to the rated 5500. Our neighboring agencies all operate 4500 psi, so I'm not concerned in the least. Our fill station at our deparment operates up to 6000 psi, as does our cascade system on our heavy rescue. No concerns there either.

As pointed out, make sure surrounding aid companies can provide filling for the bottles. Not so much in being able to achieve the 5500 rated capacity, but that the thread connections match. There are those new quick-attach bottles which may prove to not be compatable with everyone else. I stuck with threaded bottles for that very reason.

Congrates on the award by the way.

[kuh shise]

There are a number of things in the above forum entrys that give me cause for concern. While the Grade D & E air specifications DO NOT specify minimum dew points, there is a general consensus and specification that states: (Copied from Liberty Mutual Ins. Co.) "The dew point is the temperature at which H2O vapor will start to condense from air. This value depends upon the air's H2O vapor content and pressure. The H2O vapor content of intake air ranges from saturated to very dry. Saturation levels are in the low % range. For example, at 20°C (68°F) air can hold 2.3% H2O vapor (23,100 ppm v/v = 34 mg/L). At 40°C (104°F) this value is 6.8% (68,400 ppm v/v = 51 mg/L). The amount of H2O vapor that gets into SCBA air depends on the intake air level and filter efficiency. SCBA air is required to be dry enough to prevent malfunctions (e.g. air flow blockage) due to internal condensation or icing caused by expansion cooling past regulators. High H2O levels can also inhibit catalysts that convert CO into CO2. CGA G-7.1 does not list an H2O limit for Grade D or E air. However, SCBA air must either have a maximum H2O content of 63 ppm (0.05 mg/l), which corresponds to a -50°F dew point, or an H2O vapor maximum (ppm) resulting in a dew point that is 10°F lower than the coldest temperature expected for SCBA use. Therefore, H2O vapor limits for SCBA air are essentially dependent on the geographic region. CGA dew point limits are not pressure values but refer to "dew point over ice at 1 atm."
Notice that the spec is at one atmosphere, however, when air is compressed the dew point rises. From dew point calculators available on the internet, it is easy to determine that pressure dew points for any amount of moisture in a breathing cylinder at any pressure. The numbers that I am familiar with suggest that a minus 65 deg. F dewpoint, when compressed to 5,500 psi. will then have a dew point around 42 deg. F. This means that if you wear your pack in the cold weather and the cylinder temperature drops below 43 degrees, there will be some liquid water condensing inside the bottle. Not a problem unless that moisture begins to condense in the high pressure regulator stage causing ice to be formed in the regulator. Second problem (long term) could be rusting of the inside of steel cylinders. This might result in contamination (rust dust) entering high pressure regulators and filters as well as rejection of cylinders at the hydro-test inspection.
Another possible problem is with the design of the "Blast Containment" which will need to be able to contain the force of a 5500 psi bottle failure. I have asked our Scott representative about these concerns, but the factory has not given me a formal answer.

[FyredUp]

Even the bottles from NXG2 Scott SCBA have a threaded fitting that they fill through.

[LFPDLT]

Thanks for all the replys so far. Filling the bottles is not a concern, we have a 6000 psi fill station and 4500 is the norm in our area, haven't seen a 2216 bottle in years. As far as the extended scientific reply I will not even pretend to understand what you are talking about, but, I think any of the problems you address would have shown them selves years ago, since the storage tanks on high pressure fill stations store at 6000 psi and are steel tanks. I have not heard of any water vapor or rust problems, also the inside of the scba bottles we would purchase are aluminum, not steel, so there goes the rust concern. Just trying to figure out if this is an idea that never really catches on like the nxg2 bottles, or is 5500 psi going to be the direction future scba will be taking just like 4500 replaced 2216. The thought of a 45 minute bottle the size of our current 30 minute bottles sounds pretty good, but, it seems like a bit of a gamble being the first ones to try it.

[johnsb]

My POC dept is still in the middle of switching over to 4500, as are a lot of rural depts. My full time dept. is heavily invested in 4500's, so I don't see any change there in the near future. I'd expect that only dept's that have to do major upgrades will be going to the 5.5's for now.

[Here and there]

Just from a practical perspective a 5500psi cylinder on a 6000psi compressor is going to require a lot of work on the compressors part. Instead of coasting to 4500 psi, it will be constantly kicking on to top off your cylinders.

More of a pita issue than a real issue, but for the guy who has to fill all the bottles it is something to think about. Also I would be concerned with jumping on the band wagon for new technology unless your department has the resources to make changes in the future or even opt out and go with a full replacement if issues arise. As you seem to be getting these with a grant, I assume that is not the case. Tried and true may be the prudant choice.

I think where Kuh Shise is going is the potential for new air quality standards. The current requirements are designed around 4500 psi, down the road it is possible D grade air will not be good enouugh for the 5500 psi cylinders. Is your department in a position to replace a compressor (compressors)? At $30-40K each that is a serious issue to consider.

[IronsMan53]

The 5.5 may not catch on. There are other options out there in development such as the very low profile packs that the IAFF is spearheading.

The 45 minute 5.5 cylinder may be smaller than the 4.5 version but it is only less than one pound lighter. Also, if you happen to have a cascade without a compressor Scott recognizes that you reduce the number of cylinders you are able to fill from that cascade by approximately 40% for the 5.5 version due to the higher cylinder pressure. So instead of filling, say, 10 cylinders you could only fill 6. This makes sense since if you operate from a 6000 psi cascade you only have 500 psi of room instead of 1500 psi.

Also this tells me that if you do have a cascade with a compressor then the compressor will have to run more. Is that really something you want to do? In my experience, our compressors are the weak links in the chain. They require regular maintenance and are very expensive to repair.

[Skojo]

Along these same lines, does someone manufacture something larger than a 6000 psi fill station? If so, can someone provide some names/recommendations?

Also, is it worth looking into fill stations that are greater than 6000 psi?

Skojo

[Lewiston2FF]

Thanks for all the replys so far. Filling the bottles is not a concern, we have a 6000 psi fill station and 4500 is the norm in our area, haven't seen a 2216 bottle in years. As far as the extended scientific reply I will not even pretend to understand what you are talking about, but, I think any of the problems you address would have shown them selves years ago, since the storage tanks on high pressure fill stations store at 6000 psi and are steel tanks. I have not heard of any water vapor or rust problems, also the inside of the scba bottles we would purchase are aluminum, not steel, so there goes the rust concern. Just trying to figure out if this is an idea that never really catches on like the nxg2 bottles, or is 5500 psi going to be the direction future scba will be taking just like 4500 replaced 2216. The thought of a 45 minute bottle the size of our current 30 minute bottles sounds pretty good, but, it seems like a bit of a gamble being the first ones to try it.

Basically what the extended scientific reply is saying is that by increasing the pressure in the cylinder by 1000psi you may be causing water condensation issues that could become a problem when operating in low temperature conditions. As the pressure of the air rises so does the dew point (temperature at which water will begin to condense out of the air) so what may work for you at 4500psi in your area may become a problem at 5500psi. With the cylinder valve at the bottom of the cylinder it would be possible to collect water in the high pressure line and cause the high pressure regulator to freeze up. Obviously this would be very bad. You might want to talk to your fill station manufacturer or maintenance guy to see what might be needed to fill the 5500psi cylinders.

[firepundit]

[QUOTE=Lewiston2FF;1352962 With the cylinder valve at the bottom of the cylinder it would be possible to collect water in the high pressure line and cause the high pressure regulator to freeze up. Obviously this would be very bad. You might want to talk to your fill station manufacturer or maintenance guy to see what might be needed to fill the 5500psi cylinders.[/QUOTE]

All of the cylinder valves I have seen on SCBA cylinders have a tube that protrudes into the cylinder to prevent just such an event.

No problems with the rest of the post.

[kuh shise]

Firepundit is correct about the "dip tube" extending into the cylinder to prevent direct introduction of either condensate or particles. The real problem will occur with condensed micro droplets (fog) in suspension. When this dispersion passes through the first stage regulator, the expanding fluid (air + water) will pull heat out of the valve and surrounding materials. Any heat in the up-stream side of the valve assembly will migrate toward the low stream (colder) side of the valve. This drop in temperature will allow the fog to condense on the valve and valve body as the air passes through the valve. I am not certain of the amount of moisture that could be condensed and frozen to the valve, before the bottle pressure drops suffiently to again completely vaporize the moisture, but this needs to be determined and a positive answer provided by the manufacturer. Another problem might be the condensate coming in contact with the bimetalic connection (stainless valve body and aluminum cylinder liner). In a previous post a mention that "The Poster" had never seen any problems with high pressure cascade bottles. This is precisely how I became aware of the condensate problem. We found micro rusting on the inside of our cascade and aerial bottles at the standard hydro test. Since we have an automatic moisture & CO monitor, I began questioning as to how this might have happened. (no test records of anything above -68 F for the life of the system) All I am saying is, before jumping into a new system, I would require the manufacturer to address these concerns.

[firepundit]

I have a feeling this model will go the way of the AirPak III. That was a 3000 PSI unit with the old chest mounted regulator and breathing tube back in the 1980's I believe, might have been late 19070's but I don't think so. The only ones I ever saw were offered to my in trade. They stayed with the department.

[Lewiston2FF]

All of the cylinder valves I have seen on SCBA cylinders have a tube that protrudes into the cylinder to prevent just such an event.

No problems with the rest of the post.

You know, I knew that too. Not sure why I put that. I'm going to chalk it up to a bad brain moment.

[ryebread]

We have been using the 5.5 in Denver for about 5 months. No issues yet. If you are interested, I can connect you with one of our guys.

[LFPDLT]

Thanks ryebread, I sent you a PM.

[firefighter8054]

My last Dept had the 5.5 4500psi paks I really liked them they felt comfortable and light weight scott would be my choice if i was buying for my Dept.

[firepundit]

My last Dept had the 5.5 4500psi paks I really liked them they felt comfortable and light weight scott would be my choice if i was buying for my Dept.

OK.

But, what if you had to pay for it, and the associated costs, personally?

[firefighter8054]

oh heck no not out of my pocket lol