Temperature Measurement on LNG lines 1

[kieran14]

I am looking for information on the installation details of an RTD surface mount pad to measure temperature on crogenic lines. As the gas is liquid the obvious choice would be on the bottom of the pipe but someone has told me there could be the possibility of condensation running down the pipe therefore mounting on the side would be better, can anyone advise?

 

[invalauble]

Typically when mounting RTDs on pipe surfaces, you don't want to mount on the very top or very bottom. Very top is bad because the pipe could be only partially full. Very bottom is bad indeed becauase of condensation, rain, etc. Common practice is to mount the RTD firmly with a stainless-steel strap-clamp at 4:30 or 7:30. That way the condensation would drip off the bottom of the pipe but you'd still be measuring the liquid-filled portion of the pipe. The best way to measure temp, though, is to install a thermowell and insert your RTD or thermocouple into the flow path.

 

[Yordif]

There are also some companies using fiber optic cable as a sensor for temperature detection on the LNG lines. The cable itself is run along the line and acts as a detector. Several kilometers are possible for run lenght.One company I know of is Sensa, a division of Schlumberger. I think they have some relevant information on their website

 

[IRstuff]

What exactly is the purpose of your sensor?

Are you wanting to measure the temperature of the LNG, or what?

The temperature of the outside of the pipe may have little to do with the actual temperature of the LNG

TTFN

 

[kieran14]

The sesnor is a 'cheap & nasty' way of measuring the temperature of the LNG. When the Cryogenic lines on an LNG terminal are not being used they have to be constantly cooled so that they don't expand and contract every time they are used (i.e. every time an LNG ship exports LNG to the terminal) otherwise they would eventually fail due to fatigue. The lines are cooled by continually by pumping a samll amount of LNG around the plant so that the LNG lines are kept at cryogenic temperatures.

A thermowell is the best way to do it but since these 'cooldown' monitoring temp sensors need to be installed every 50 metres you can imagine the cost!

The fiber optic method is quite costly and difficult to install as most of these LNG lines come pre-insulated before they are even installed.

The information on the orientation of the sensors was useful i.e. 4:30 or 7:30.

Thnaks,

Kieran

 

[nedwardous]

Keiran, is this LNG line at the Isle of Grain LNG import terminal?