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Topic: Haldex Pure Air Plus Relief Valve (Read 1429 times) previous topic - next topic

Haldex Pure Air Plus Relief Valve

When FOT services my air dryer they use kit DQ6026. They also install a pressure relief valve part number KN31529. The kit DQ6026 includes a relief valve. Does the Pure Air Plus air dryer use two different relief valves? Thanks,
Larry

Re: Haldex Pure Air Plus Relief Valve

Reply #1 –
Found the answer to my question. FOT service called and told me the kit includes a 175 psi relief valve. But, FOT uses a 200 psi relief valve.
Larry

Re: Haldex Pure Air Plus Relief Valve

Reply #2 –
I wonder why 175psi is not safer than 200psi.  Who would want the air system to go that high before relief.  I understand there is another safety pressure relief on wet tank that is adjustable, which I wonder what it is set for.
It seems that some of our 'old' components could get stressed at 200psi.
BTW, years ago when I took our coach to Foretravel for service, the tech would consistently leave the new brass safety relief valve in the Haldex box along with the plastic cover, metal half-ring and screws, as they were not used.  The techs told me on several occasions that the brass valve does not need to be changed, is hard to reach, has lower quality than what is already installed.  It is probably correct that the relief valve is just only there in case of a run-away compressor and is a fail-safe device, so it never gets any use, so not changing it would be ok.
The irony of this, is that the internal air valve that opens dozens of times on every trip, that we can hear, gets lots of wear, is almost never changed.  But when this internal valve fails, we are down without any air pressure.  The internal valve is part of a the air dryer bottom maintenance kit, which we carry for emergency.

Re: Haldex Pure Air Plus Relief Valve

Reply #3 –
Quote from: Barry & Cindy –
I understand there is another safety pressure relief on wet tank that is adjustable, which I wonder what it is set for.
I believe you will find the safety pressure relief valve on your wet tank is a simple spring-loaded ball type valve, and is set to open at 150 psig.  I think I remember reading somewhere that 150 psi is the maximum pressure allowed in air brake systems by DOT.  Don't quote me on that...

Re: Haldex Pure Air Plus Relief Valve

Reply #4 –
Is there some kind of regulator between the drier and that tanks? What difference would a 200 psi relief valve make if there is a lower pressure relief valve that will vent before the 175 psi valve reaches setting.

Re: Haldex Pure Air Plus Relief Valve

Reply #5 –
Quote from: craneman –
Is there some kind of regulator between the drier and that tanks?  No - just a check valve.

What difference would a 200 psi relief valve make if there is a lower pressure relief valve that will vent before the 175 psi valve reaches setting.  None - it is of no benefit.

Re: Haldex Pure Air Plus Relief Valve

Reply #6 –
Sounds like Foretravel made a design change in a component for no logical reason.Hope it was not just to sell relief valves.When
I changed mine the old one was in so tight I had to put the housing in a vice and drill out.Here's a revealation,when something
has brass threads you do not have to make it cheater pipe tight,the soft threads will seal.

Re: Haldex Pure Air Plus Relief Valve

Reply #7 –
Are we talking about the purge valve on the bottom of the air dryer or some other valve? I think that valve cycles by air in the small line from the D2 governor when the compressor  cuts out. Is that valve also a pressure relief valve if the governor doesn't cut the compressor out or is there another relief valve on the dryer?

Re: Haldex Pure Air Plus Relief Valve

Reply #8 –
John,

Photo below of the AD-9 dryer on my coach.  The pressure relief valve is the brass doohickey at 3:00 o'clock position on dryer base.  I assume there is a similar device on the Pure Air Plus.
 

Re: Haldex Pure Air Plus Relief Valve

Reply #9 –
Pressure relief valve is the one at 3 o clock in the picture. The press relief is a spring loaded mechanical valve opening at pressures well above normal system pressure. The price valve is controlled by the governor it purges the water from the dryer and a bit of air when the governor signals it which is the same time as the unloader stops the compressor from building air. Located at 9 o'clock in the picture it has the heating element so that the water doesn't freeze in it.