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-2- 090109 Rev2

level, the load due to system pressure and the spring load would remain in equilibrium and the valve would

be neither open nor closed. In such circumstances the valve will tend to flutter on the valve seat and may

release a small amount of air but will not be relieving significant pressure from the system. This point is

known as the Warning Pressure, Cracking Pressure or Hissing Pressure. Refer to Figure 1 on the following

page.

If the pressure in the system continues to rise, the load acting on the face of the valve will also rise and will

begin to exceed the load exerted by the spring. When the load due to system pressure exceeds the spring

load, the valve will open and will remain open as long as the system pressure remains sufficient. This point

is known as the Opening Pressure or Set Pressure (also referred to as Rated or Popping Pressure). The

further increase in system pressure will show only relatively minor increases in flow rate. If the system

pressure decreases, the relieving airflow rate will reduce and the valve will start to close. However, the

valve will not fully reseat until some pressure below the Opening Pressure. This pressure is known as the

1.

In practice the valve should be matched to the system to be protected such that the maximum airflow rate of

the valve is never utilized, i.e. the valve should be capable of relieving a sufficient volume flow rate of air

at the opening pressure to ensure that the system pressure drops significantly. If the valve is open and the

system pressure continues to rise above the opening pressure then the valve is relieving less air than is

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TESTER SETUP

IMPORTANT: Perform a functional check of the safety valve by pulling the ring and making sure that

the valve stem freely moves up and down.

IMPORTANT: Close the control valve prior to inserting the test valve. Set the regulator to approximately

30 psig to protect the test valve from being over pressurized.

IMPORTANT: Close the ball valve near the air supply line. Now connect the air supply line to not more

than 120 psig shop air.

Now open the supply line ball valve so the tank fills until the tank gauge reads 120 psig. This should take

When the tank is fully charged insert the test valve and clamp it down securely until the valve base creates

a tight seal with the gasket on the test platform.

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TESTER OPERATION

pression d’un ressort. Afin de protéger la pression d’air dans le système, la pression d’air pèse toujours sur

par le ressort, la soupape s’ouvrira. Si la pression dans le système est maintenue à ce niveau, la force

tendance à produire des battements et libérer une petite quantité d’air mais elle ne relâchera pas une

pression signifiante dans le système. Ce point est connu sous le nom la Pression d’Avertissement ou la

Pression d’Ouverture.

Si la pression du système continue à augmenter, la soupape va continuer à s’ouvrir et relâchera de plus en

plus d’air jusqu'à ce qu’elle soit complètement ouverte. À ce point ci la soupape relâchera près de son taux

de débit d’air maximal, une augmentation additionnelle de la pression aura un effet relativement mineur à

ce qui concerne la hausse du débit d’air. Si la pression du système diminue, le relâchement du débit d’air