New Mills Pumping Station

[steam guy willy]

Hi Chris, not sure what I will do yet but as it is a presentational project rather than an exhibition piece we shall see ...Thanks for asking ..
Willt

[steam guy willy]

Hi Chris , Was looking at the photos of the numerous valve in the large engine you have photographed and noticed that they looked like what there should be on the engine I am making. This is pumping air and at each end you can see where the 6 individual valves were screwed in. They are now missing and were possibly taken away sometime ago. There is a later monochrome photo with what they looked like , so thanks for the pics

Willy

[crueby]

Hi Willy, those large holes with the fine threads are just like the ones on the water check valves. Probably a very similar valve, but likely with the plate opening inward to hold in the pressure. There must be another set on the outlet pipe?

[steam guy willy]

Hi Chris ,thanks for that and yes these were made in 1898 so I dont know if they used rubber then or if they used rhinoceros hide , ? they did use this for the air pump valves on older beam engines. So ,I have made a drawing of the compressor from what I can see but a bit confused as to why it is square and rectangular  ?? I would have thought that as it used a cylindrical piston that they would not need the whole rectangular pump with all the extra cast iron ?? also the two side covers are bolted on but what is behind them is a mystery ?? I would like to get in and remove them but that is not possible at the moment !! I have been busy at the allotment recently and the summer has now arrived with lots more hours of daylight so spending less time at home in the workshop !!

Willy

[crueby]

Huh. They went to the trouble to make the compressor with square sides and removeable plates on both sides - there must be something else in there, some sort of other valves or passages.  Wonder if you can see anything through the holes where the valves screw in on the end? Borrow a borescope maybe?   

[steam guy willy]

Hi Chris , thanks and this is what I can see through the holes  but can't quite work out what is happening ?? There is also the big spring on the piston rod gland ??

Willy

[Don1966]

 


 
Don

[Charles Lamont]

I suspect what we can see through the holes is just the piston. Do the cylinders perhaps have water jackets for cooling?

[steam guy willy]

Hi All, thanks for the input and yes I have studied the photos and seen that the position of the crankshaft at its furthest away point from the compressor would indicate that the piston is right up against the end cap ...however I was confused by the curved portion of the inside hole that would indicate only half of the hole is admitting the air flow ?? and is part of the casting ?? also there is quite a complex shape around these holes ??,  A stethoscope would be helpful perhaps  and I  dont think there is any cooling water needed in this application ,

Willy

[ddmckee54]

Willy:

I believe that the 6 holes we are looking at in IMG_7345(1), are the holes where the inlet check valves would be installed.  I'm pretty sure that the openings in the top half of both ends of the compressor are for the inlet check valves, as they do share a common manifold.  The pressure manifold is on the bottom maybe?  In IMG_0102 you see what I believe is a condensate drain.  I think that if this cap were removed, you would find 6 exhaust check valves, in a similar pattern as the inlet valves.  There is probably a divider cast into the cap to separate the suction and pressure sides of this end of the compressor.  It looks like this compressor is double ended, so whichever direction you're moving the piston, you are compressing air.

I don't think they would have used rubber or leather for the moving sealing surfaces of the check valves, too much hammering, maybe lapped cast iron and or bronze?

As for half of the inlet area being blocked off, the bronze/copper/whatever ring is probably the bottom sealing ring for the inlet valve cage.  My guess is that the air might have flowed through a hole in the center of the valve cage into the cylinder.  You'd screw the threads in until the cage bottomed out , sealing the cage to the cap.  With this being the suction side, it wouldn't have mattered if the threads leaked a little - it'd just be leaking into the suction side on the intake stroke.

Don

[steam guy willy]

Hi Don yes thanks that sounds reasonable  as there must be a double sided arrangement of the valves to allow the air to pass into the air receivers . through the top pipe with the hand wheel valves . There is also outside of the Bldg this air intake pipe that must be the air intake possibly to  the bottom of the rectangular castings ?? There are  no visible pipe couplings though ? Also there are these circular with hexagonal outsides that looks though the are screwed into the 6 large
holes ?

Willy

[ddmckee54]

Willy:

I would guess that the hex/circular shaped objects you can see in the photo are the visible part of the check valve cages.

I was originally thinking that the 6 openings we could see were on the suction side of the compressor.  If the top valves are on the suction side of the compressor, then the check valve cages would only be exposed to pressurized air from the cylinder during the compression stroke.  I believe that the copper colored rings visible in some of the photos are sealing rings to prevent air-leaks.  You would still get some air leaks around the threads of the valve cages, but only when the compressor was in the intake stroke.   The valve cage will always be at atmospheric pressure or maybe slightly below during the intake stroke, and then the air that would leak around the threads would be leaking into the compressor - not out of it.

If the top manifold is connected to air receiver then I've got it backwards and the top is the pressure side.  If that's the case then they would have had to somehow seal both the inside of the valve cage where it connects to the cylinder side of the cap, and the outside of the cage where it's exposed to the atmospheric pressure.  If they didn't seal both ends of the valve cage, and the middle was pressurized, then they they would have had a constant air-leak of pressurized air.

Don

[steam guy willy]

Hi Don. thanks and there must be another valve somewhere in the system nearer to the output pipe to make everything actually work properly !! as it is double acting there should be something similar to how a slide valve works  ?? but there is no superate
linkage anywhere !! so this crossover valve must be automatic .. I would be good to get a drawing somewhere , thanks again for the input

Willy

[MJM460]

Hi Willy, a compressor needs a valve which allows air into the cylinder, but not out, and a separate valve which allows air out but not in.  On large cylinders there tends to be multiple smaller valves rather than single larger valves to achieve the required flow.

On double acting compressors both types of valve are required on each end.

The valves open and close in response to the pressure difference caused by the piston movement, no operating mechanism is required.  Same as used in a water pump which is similar in many ways but one.

MJM460

[ddmckee54]

Willy:

Like MJM460 said you need both intake and exhaust check valves at each end of the compressor, but they don't need to be cam operated valves. 

The intake check valves, which I believe are the 6 openings that you see on both ends of the compressor, would be set up to allow air to flow into the cylinder on that side of the piston during the intake stroke for that side.  Keep in mind that the compressor is double-ended, so the intake stroke on one side of the piston is the compression stroke on the other side of the piston, and vice-versa.  Once the piston reverses its' direction and goes into the compression stroke for that side, the air pressure in the cylinder would start to build which would force the intake check valves closed.

Once the pressure in the cylinder is high enough, the exhaust check valves would be forced open and the compressed air would be pumped into the air receiver.  The exhaust check valves would probably be similar in design to the intake check valves except they would be set up to only let the air flow out of the cylinder.

I initially thought that the exhaust check valves would have been located on the cylinder side of the cap, directly under the intake check valves.  However that would have meant that to service the exhaust check valves you would have had to tear most of the compressor apart.  An engineer that does something like that does NOT want to meet up with a disgruntled service tech in a dark alley some night.  Now I wondering if maybe the exhaust check valves aren't in the side chests of the compressor.

You don't happen to have any pictures of the compressors with either the side chests open, or the end caps taken off do you?

Don