Pneumatic Relief Valves

Hi!
I have a question about point 8.8. of the rules:

A certified pressure relief device [PRD] must be installed in each part of the pneumatics system where
a different operating pressure is used (operating pressures separated by a pressure regulating device).

That means, if i have three different working pressures for example:
i use full pressure for main cylinder, 2 bar for retracting main cylinder (for saving gas) and 7 bar for a short stroke pushing device on the backside of the robot (to push the robots frontside down during acceleration). In this case, i need 3 pressure relief valves according to the rules! Normally a 3 way pressure regulator have in fact a built in relief valve to prevent a higher pressure than adjusted in the secondary (working) line. Is this kind of valve legally valid as a relief valve ?
Obviously i´m talking only about the low pressure circuits.

BTW: a big thank you to all organizers and moderators for this great new forum!!

Helmut

The rules all work together... so:

8.8. A certified pressure relief device [PRD] must be installed in each part of the pneumatics system where a different operating pressure is used (operating pressures separated by a pressure regulating device).
8.8.1 PRD(s) must have a rating of 1000 psi (68 bar) or 110% of the pneumatic component with the lowest €˜maximum working pressure€™ rating protected by that particular PRD, whichever is the lower.
8.8.2 Pneumatic systems employing pressures less than 50 psi or systems employing air compressors that have a maximum output pressure lower than the pneumatics component with the lowest €˜maximum working pressure€™ do not require a PRD.

2 Bar would not require a PRD as you can run up to 50psi (3.5 Bar) without a PRD.

The PRD need only be rated at 110% of your components rating, not your actual working pressure.
In other words, regardless of your actual running pressure, the PRD is rated for your components to protect them.

As you have stated, the low pressure circuit is already protected by an integral PRD in the regulator, usually set to 200psi.

Basically, although you are running 3 different pressures, you are only using 2 different ratings of components. And therefore only require 2 PRD.

Kane Aston
http://www.makerobotics.comhttp://www.makerobotics.com/

Thanks!
as far i understand now, i need only one relief valve for the main low pressure circuit although i provide some subsystems from this point with additional regulators at diffferent pressures, if the rating of the used components is equal or higher than the main supply pressure. Is this correct ?

Helmut

In most cases the regulator,to provide low pressure in a system has its own presure relive valve.So most people using low pressure systems are safe on that acount.(if they didnt fiddle with it)
Combined with the commercialy available 1000psi PRD with a 1/4 bsp tread,most regulators can be modified with that, just replace the bottleside clock for this PRD.

Now for the pure Full pressure users this commercial PRD is not difficult to be fitted in the system,anywhere between the bottle and the first valve in the system is more than adequate.Nothing more that a T adaptor.

Another ,and more interesting question.How are the technicals going to test this PRDs?

Mario
my question wasn´t is it adequate? (designing, construction and repair of adequate hydraulic and pneumatic circuits is my occupation) rather the question is is the circuit according to the rules?

How are the technicals going to test this PRDs?
in theory this should be easy: a certified PRD have a lead seal and and is adjusted to the certified pressure. In practice, this point will be a little bit tricky.......

Helmut, that you dont have any trouble with making a safe system is already known to me, and that wasnt my point.
Just commenting that in most dual systems this PRD point is mostely adressed to, on the exception of customized things.

I myself have equiped several robots with custom PRDs,or these were completey selfbuild(copies in better material)or adapted bought ones, Non came with a lead seal.

Now my main Q, as in robot wars many people are pushing the limits of the stuff, and in some cases invent new things to do wath they want,How are the technicals going to check if all complies tot the FEA rules.

In Robot Wars I never had any pressure check on the PRDs, and these arent cheap components when bought.So why fit them, the take space, weight and money.. and nobody bothered?

Also, Im somewhat the main CO2 man in the Netherlands and Belgium,and I want to know... does anyone has an idea to check everything works like it should...Some of the roboteers can build good stuff, but this leaves open the possibility of mistakes or wrong messurements.

mario
i test and adjust my relief valves, pressure switches and my custom made stuff in the workshop normally with a enerpac hand pump (and AFAIK, you too), works up to 1500 bar with normal hlp 32. works easy, properly and safe, needs no heavy aditional equipment, but cleaning after test can be a problem on a event.
the annoying word in the rules is certified.
In austria and germany a certified PRD is 2 times more expensive than the equivalent normal valve (same brand and type, but pre-adjusted and sealed).
in all the rules (RW, BB, FRA) i´m still missing the nominal flow of the PRD at relief pressure. Theoretically I can use a certified NS 0.1 mm PRD, witch is useless in some cases of overpressure.

quote:

N.B. The PRD(s) dictate the maximum pressure available in that part of the pneumatics system. The
PRD(s) must have a flow rate capacity that exceeds the maximum flow rate that can be expected under
€˜over pressure€™ conditions.
This may cause problems. If I do understand this correctly, if Im using a FP setup with buffer tanks, I have to use PRD with a higher flow rate than the one between buffer tank and ram...?
This is close to impossible.

Holger

ups, haven´t read this remark in the rules...
holger, IMO you need only 1 PRV with sufficient flow rate in the FP circuit on the primary (supply) side, not between buffer and ram. Your huge Niedozka- Valve will do the job easily :)

quote:

huge*lol* Compared to the gas bottles outlet diameter - agreed. Hope this is how its meant to be.