Why are injector pipe connections made with flat mating surfaces?

Hi - Can anyone explain why model steam locomotive injectors as drawn by Gordon Chiverton and supplied by Pavier Steam amongst others have flat faced mating surfaces as opposed to the more usual 60 deg conical fitting? Why should it be that standard steam and water connections can be made with conical fittings but not injectors? I sure someone has the answer.

Maybe because of space, flat takes up less room.

All the fittings I make are flat faced; seem to work just fine. As a fellow live steamer once said "with flat facings, you can always stick a teflon washer in to help seal if required"

I was going to suggest that it made them slightly easier to remove to investigate whythey weren't working.

The question was prompted by the statement made by Bill Bailey in his article - "Making of Union Nuts and Nipples" (ME 15/02/1985). End of fourth paragraph, page 189 - after describing his making of coned fittings there appears the statement "Injectors are a different matter"

On injectors that follow the LBSC pattern the steam and delivery cones are fitted from either end, usually with a flat end to the cone and the union butts up against these.

It isn't an issue for the water inlet which is coned.

(Injector for Pamela)

SO that they follow full size practice possibly.

My personal opinion is , that a cone disturbs the flow of steam and water.

You have to make sure that there is no edge and so the streaming water or steam is not changing in its flow from laminar to turbulent.

I have built my own injectors, a design similar to purchased one. The thread was 5/16 32 tpi and I made for test purpose an adaptor to M7 *0,75 mm for older injectors I have. With these adaptors these injectors are not working. Because the thread is not going to the flat of the nozzle and there is from the bore hole a small conical area where the flow is disturbed.

This is my explanation. Correct me if i am wrong.

Werner