Temperature Rates 1

[mexven]

Hi i would like to know if anyone knows the temperature rating for a T-S-1000 N-4B-VB jomar valve; i´ve been looking for it on the web and even send a query to their web page and they just can´t gave me a concrete answer about it, so if any one can help me with this i´ll be very gratefull.

 

[gerhardl]

I see your problem. Very often existing valves have unreadable marks or lack proper marking.

If you define the temperature rating as the pressure/temperature ratio given by the valve class, the allowed pressure/temperature curve would be depending on that the valve actually is built after all rules for this class, and certified for this (if certification is necessary for your application).

If the valve is not marked with presure class you should be suspicious.

Usually you can presume that the pressure class markings is referring to the normal pressure/temperature curve for the society responsible for the pressure class issue, and for the given pressure class.

The above is valid for the material (metallic) construction, but is no guarantee that sealings and trim is properly selected to operate properly and not be damaged or leak at your pressures/temperatures. To give working sealings at top allowed material pressure at a given temperature special sealing material considerations or selections mmight be necessary.

Again you should be suspicious if your valve have to operate in upper parts of pressure classes and temperatures.

Thirdly: there is a tendency to 'overrate' valves when the operating conditions show that the valve 'just a tiny bit' for a certain pressure and temperature breaks the allowed pressure/temperature curve.

The reason for this is always cost of going for the next higer and proper pressure class for valves and piping. Please be reminded that the person responsible for breaking the rules also is the responsible if anything goes wrong, if the insurance company will not pay and if persons and property are hurt or damaged.

The valve producer is the only source that can guarantee (from traceable markings on the valve, if any) the data you asks for, and only if there is a guarantee that the valve is not altered, repaired or issued with non standard components and have correct and undamaged sealing and trim.

If they are not able to answer you, you have, if required, to start with full overhaul, inspections and tests.

In this case it could be safer and cheaper in the long run to start with identifying the real operating and safety requirements for your plant and select a new valve suitable for this.

Please also remember that our engineering also consists of the quality assurance aspect: documenting and assuring that the correct valve is installed.

Please excuse me for the long answer, normally the situation is luckily a bit more simple than described, and you are probably already aware of most of the above points, but as I know of cases where one or more of the points above have been overlooked or come up just too late.......