It looks that the question "1" is deviated from the Compressor design & safety operation guideline. To use the drain valve or safety valve for depressuring the equipment is not a standard procedure, which may cause the damage of these devices due to the improper operation. It's a good idea to verify and confirm the action with Manufacturer before actually doing it.
For the Question "2", you may contact Manufacturer and confirm if the proper EN compliance part is required for item B:2.

Most of these small compressors have a relief valve with a ring. The ring allows one to periodically test the relief valve.

For small compressors like you have shown, it is common to relieve the pressure with either the drain valve or the relief valve. For large compressors, this would be inappropriate and unsafe.

A wide range of materials are available to handle various fluids and operating environments. Common pressure relief valve component materials include brass, plastic, and aluminum. Various grades of stainless steel (such as 303, 304, and 316) are available too. Springs used inside the relief valve are typically made of music wire (carbon steel) or stainless steel.

Brass is suited to most common applications and is usually economical. Aluminum is often specified when weight is a consideration. Plastic is considered when low cost is of primarily concern or a throw away item is required. Stainless Steels are often chosen for use with corrosive fluids, when cleanliness of the fluid is a consideration or when the operating temperatures will be high.

Equally important is the compatibility of the seal material with the fluid and with the operating temperature range. Buna-N is a typical seal material. Optional seals are offered by some manufacturers and these include: Fluorocarbon, EPDM, Silicone, and Perfluoroelastomer.

You should always follow the manufacturers instructions.

Thank you very much for the feedback, and the great information!
much appreciated

I've read this a few times now and am unsure which valve is which and what the difference is.

But neither of those valves should be used to used to depressurise the receiver. That's not their job and you risk damaging them by either using them as control valves to control air releases or just sheer high velocities. Use the main outlet and a hose and proper valve to de pressurise the receiver.

Image A looks like Brass to me.

As Bimr says, read the manual, but I would certainly greatly reduce air pressure before draining water off as it will come out very quickly otherwise and will tend to leave a lot of water in as the air cones down through the water layer.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

Thank you for your feedback.

the product I am receiving is shipped with this type of automatic (8 bar) pressure release valve:


After doing some research, seems all products in this range have an auto pressure release valve with manual release ring:


The supplier said they did not provide the valve with manual release ring because it did not conform to an EN standard.
Now I wonder why the manufacturer did not provide a release valve with ring that complies with the EN standard. -- Surely there must be one that complies

My initial feeling was that not having a manual release would violate safety protocols because:
1) cannot periodically test auto pressure release by pulling the ring
2) cannot release the pressure before opening the tank drainage cock to release any condensation.

> Manual says to just to open the drainage cock, no depressurisation protocol given.

> From what I gather here, the operating pressure is low enough that opening the drainage cock without first releasing the pressure is not high risk.
- The drainage cock is a control valve type so it can be opened gradually.
- I shall inform anyone operating product about necessary precautions before opening the cock to drain (a potentially pressurised) condensation tank.

I don't know enough about small pressure relief valves and EN standards, but I wouldn't be surprised that they don't have a ring on them. My guess is that because some started leaking that people did things to stop it leaking and jammed the valve closed. Keep all the working parts inside the valve and you can't mess with it.

If you think about it though, item 1 is not correct. You are not testing the relief valve - you are just lifting it off its seat. You have no way to test if it is set at the right pressure or not. Relief valve should never go off if the control system works properly. You are much more likely to get leaks and seat damage by repeatedly operating the valve and have it hissing away than if you just left it there.

Item 2 - Again this is a poor use for a relief valve - you really should blow down the receiver using the air line attached to it from the end.

Manual is badly written then.
I disagree about the pressure not being high enough - 135 psi is high enough to cause damage if you allow water to spray out of the drain valve whilst under full pressure.
That drainage valve is not a "control valve" - It looks very much like a quarter turn ball valve which is not designed to be used in throttling mode.

The receiver really should have a separate vent line with an orifice so that you just open it and it blows it down within say 5 or 10 minutes safely.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

LittleInch, it appears that you are not familiar with these low pressure air compressors. However I agree with you that the user should operate the unit in a safe manner.

Here are some portions from the operating manual from another brand with safety warnings. Also a youtube video demonstrating how one person tests the safety relief valve:

Drain air tank daily or after each use.

TO CHECK SAFETY VALVE
Risk of Bursting. If the safety valve does not work properly, over-pressurization may occur, causing air tank rupture or an explosion. Risk from Flying Objects. Always wear certified safety equipment: ANSI Z87.1 eye protection (CAN/CSA Z94.3) with side shields1. Before starting compressor, pull the ring on the safety valve to make sure that the safety valve operates freely. If the valve is stuck or does not operate smoothly, it must be replaced with the same type of valve.

Link

To Drain Tank
Risk of Unsafe Operation. Risk from noise. Air tanks contain high pressure air. Keep face and other body parts away from outlet of drain. Use safety glasses when draining as debris can be kicked up into face. Use ear protection (ANSI S12.6 (S3.19) hearing protection) as air flow noise is loud when draining.
NOTE: All compressed air systems generate condensate that accumulates in any drain point (e.g., tanks, filter, after-coolers, dryers). This condensate contains lubricating oil and/or substances
which may be regulated and must be disposed of in accordance with local, state, and federal laws and regulations.
1. Set the On/Auto/Off lever to "Off" and unplug unit.
2. Turn the regulator knob counter-clockwise to set the outlet pressure to zero.
3. Remove the air tool or accessory.
4. Pull ring on safety valve allowing air to bleed from the tank until tank pressure is approximately 20 psi. Release safety valve ring.
5. Drain water from air tank by opening drain valve (counter-clockwise) on bottom of tank.

The hand levers and rings on safety relief valves are put there on purpose.

• https://files.engineering.com/getfile.aspx?folder=75e1a492-8645-4aaa-8059-3

I have never depressurized an air tank before draining. That would not be at all helpful for assuring fully drainage.

I'm familiar with them, just making the point that what has become custom and practice is not always the right thing to do.

There should be no reason at all why the safety valve should not work and is more likely to fail or get clogged if you use it to flow air and other material through it on a regular basis.

But I accept that is what makes people happy that the relief valve is "working", but it doesn't necessarily make it the best way to design and operate it....

They really should have a separate air bleed vent. IMHO.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

Well then perhaps you should write to the various low-pressure compressors manufacture's and advise them to update their product designs and correct their operating manuals.