BSP inconsistency

[Richard Lindsay]

Hi folks,

I’m trying to understand why 2 items advertised as 5/8 bsp are not the same size?

So I have a draft beer system at home and bought a beer keg coupler with threads advertised as male 5/8 bsp(p). In order to attach the beer line to the coupler, I bought an adapter which was advertised as female 5/8 bsp.

When I measure these the male thread is 20.5mm and the female 21.5mm and therefore don’t join

Any ideas?

Thanks for your time

 

[oilhead]

You may have two different variations of BSP. The male is described as BSP(p) which is parallel . Your female is probably BSP(t), or taper. You may still be able to mate them, with ptfe or a sealer, depending on the pressures involved.

 

[just pumps]

Hi folks,

I’m trying to understand why 2 items advertised as 5/8 bsp are not the same size?

So I have a draft beer system at home and bought a beer keg coupler with threads advertised as male 5/8 bsp(p). In order to attach the beer line to the coupler, I bought an adapter which was advertised as female 5/8 bsp.

When I measure these the male thread is 20.5mm and the female 21.5mm and therefore don’t join

Any ideas?

Thanks for your time

How are you measuring inside the female connector.

 

[MeldrewsMate]

You may have two different variations of BSP. The male is described as BSP(p) which is parallel . Your female is probably BSP(t), or taper. You may still be able to mate them, with ptfe or a sealer, depending on the pressures involved.

I don't think it is at all common to find a female tapered thread.
And I have to say that 5/8" bsp is not a size I'm familiar with either; 3/8", 1/2", 3/4" yes.

 

[MeldrewsMate]

Could it be that you bought a 3/4"bsp female coupling by mistake?

 

[oilhead]

Black iron or zinc plated BSP fittings are almost always taper threads. Brass is normally parallel. 5/8" BSP is not a common size, but imported equipment often features weird sizes, and American gear uses NPT, which is very close to BSP but has different pitch profiles.

 

[JohnD]

If your connectors are plastic (you didn't say) I doubt they are tapered.

When I measure these the male thread is 20.5mm and the female 21.5mm and therefore don’t join

A small male will easily fit into a slightly roomy female.

On parallel thread connectors, the seal is not performed by the thread, but by the rubber or fibre washer.