Impulse Tubing

[borrise]

To all have an experience in plant operation.

Please give some explanation on this matter.

How the slope in impulse line tubing affect the measurement? Does making the slope greater than the min requirement
have any affect in the measurement, response or error?

Thanks

[carl_e]

I haven't heard of too much slope being a problem for the 3 decades I've been around process instruments. For 8 decades, DP transmitters have been piped below a steam line with a vertical impulse tube/pipe. You can't get any greater slope than vertical.

Impulse tube problems occur in gas measurement when solids or gas condensate collect at the lowest elevation. Or in liquid measurement when vapor/air collects at a high elevation point. As long as there's drip/drop leg to collect the liquid/crud in the gas lin and a vent to vent the vapor/air in a liquid line, then you'll be OK.

TuV NEL recommends an 8% slope.

[carl_e]

I haven't heard of too much slope being a problem for the 3 decades I've been around process instruments. For 8 decades, DP transmitters have been piped below a steam line with a vertical impulse tube/pipe. You can't get any greater slope than vertical.

Impulse tube problems occur in gas measurement when solids or gas condensate collect at the lowest elevation. Or in liquid measurement when vapor/air collects at a high elevation point. As long as there's drip/drop leg to collect the liquid/crud in the gas lin and a vent to vent the vapor/air in a liquid line, then you'll be OK.

TuV NEL recommends an 8% slope.

[Hix]

As is recommended in API RP-551 2007, you do need slope depending of the service the impulse line will work. For Gas/Steam Service you need the instrument above the tapping point, therefore it should be slope up at least 1" per ft long. This will allow any condensation to easily return to the service line. As for liquids is the oposite, you will need slope down at least 1" per ft long, as this will allow any air bubbles to return to the service line. Keep in mind that is recommended that the impulse lines to be max. 20 ft long, but the engineering department, depending on the field conditions, might change this.

[borrise]

Thanks for the answers guys.

I have another question for impulse line slope.
What will happens if you don't put any slope on impulse line as per standard spec.
How does the slope affect the occurrence of maintenance of such instrument?