Low pressure alarms in pipelines

[Hierro]

How to determine low pressure value settings in pipelines ?

Say for instance, that the design pressure of a pipeline is 1100 psig, and the normal operating pressure is 850 psig. At what pressure should I set a low & low-low pressure alarm that'd warn me of an irregular condition ?

Thanks.

 

[TD2K]

One thing you need to consider is what is the lower end of the operating pressure range? You don't want to have a lot of false alarms, especially if they result in pipeline isolation valves closing.

Also, what type of upsets are you trying to detect? If it's a pipeline leak, pressure switches will detect relatively 'large' leaks. You can get a feel for what size leaks by doing some hydraulic calculations.

 

[kbander]

If you create an alarm, you have to determine:

1. If anyone is going to do anything if it alarms. If the only action is to acknowledge the alarm, then the alarm shouldn't exist.

2. If an alarm is required, what should the priority be? Hopefully your company has a standard for setting Emergency, High, Medium and Low priority alarms (i.e. Emergency = right now!, High = within a couple of minutes, Medium = during your next round, Low = sometime during your shift...something of this sort)

3. Don't add an alarm if some other alarm gives you the same information. You don't want to add to alarm flooding problems. If this alarm is the only way of telling that your pump has shutdown, then great. If you have other reliable ways of telling, then the alarm might not be required.


Just a few thoughts.


Regards,


Bob

 

[bhwtam]

It all depends on your system requirement and what you are going to protect.

You may consider using 95% and 90% of your lower-bound pressure value as a factor for setting. Of course, you need to double check and make sure that it is OK with your system.

 

[Hierro]

Think I got it...

I ll have the pumps shut down when 15% of the lowest normal operating pressure (LNOP) is reached.

I ll have an alarm setting in our control room @ 5% of the LNOP .... just to be aware !

Thank U all.