TG downstream of cooler for plan 53 B

[CaracasEC]

Hi guys, as per API 682 TG downstream of cooler is not mandatory as phrase "IF SPECIFIED". Based on your experience, is there a benefit installing this TG or just a waste of money..thanks..

 

[flexibox]

Not required providing the heat exchanger is sized correctly you will be fine. Depending on the application most people (90+%) do not have one however some companies do specify them on critical equipment to monitor the seals performance.
What is the application perhaps we can give you a more informed comment.

Cheers

 

[CaracasEC]

Hi Flexibox, thanks for your initial comment. We have an ongoing Ethylene Cracker Plant Project on which a lot of pump will use seal plan 53 B. This will be used on hydrocarbons. For example this pump C4 Hydrogenation Recycle Pump: Product C4 Hydrocarbon (Flammable), Temp 39.4 deg C, Spec Gravity 0.540, Viscosity 0.130 CP, Vapor Pressure 26.41BarA, Seal Chamber Pressure 29.50 Barg Norm/46.40 Barg Max, Seal Config Dual Pressurized Back to Back Cartridge. Thanks....

 

[Airsporter1st]

I agree with Flexibox - most of the time there is not one. The benefit is the comfort factor of knowing that the barrier fluid temperature going into the seal is < 80 degC.

However, for troubleshooting, it is nice to have an indication of both inlet at outlet temps, to ascertain whether there is sufficient flow.

 

[flexibox]

That is a pretty standard application. Personally I wouldn't have one but ensure that the Instalation is good. Use 3/4" dia tubing with sweeping bends not elbows to and from the Heat exchanger. Check the seal drawing so the seal design is self venting and instal high point vents. Put a drain in for maintenance. check the location of any check valves in the plan 53B ensuring they do not create a problem that is make sure the Accummulator can take any barrier fluid expansion due to heat !

Cheers

 

[CaracasEC]

Hi All,
Pls comment on attached seal plan drawings...thnks...

 

[JJPellin]

I would normally specify a temperature gauge downstream of any water cooler on a seal piping plan. API plan 23 is more common for us. With a water cooler, there will eventually be a reduction or loss of cooling. The cooler could lime up on the water side, foul with sediment or gas up. In any case, a single TI on the return line would alert the operators of the loss of cooling. I would much rather replace or de-lime a cooler than have a seal failure. Cleaning the cooler might cost US$500. A seal failure might cost US$10,000. In addition to the cost, a seal failure necessarily carries a risk of product release.

If you have a thermometer, the operators have to have a limit so that they know when to take action and what action to take.


Johnny Pellin

 

[Airsporter1st]

I'm very familiar with this seal and system - having previously worked for the manufacturers.

Aside from the good points made about temperature measurement, just one word of advice:

Make sure that air cannot be injected into the system when filling. This calls for a quick connect arrangement installed on the filling point and fill hose and/or a very robust filling procedure which must be adhered to by the operators.

Air injected into the system when filling will find its way into the loop and from there be centrifuged across the faces causing damage.

 

[CaracasEC]

Para 6.1.2.20 of API 682 Gland plates and/or seal chambers for contacting wet seals shall be designed such that the seal chamber and Piping system is self-venting during start-up and operation thru the piping system. Based on the P&ID the vent is manual since it has a blind flange, would it be necessary that this should be tie in to the flare system?

 

[flexibox]

No the double seal is normally vented to atmosphere but collect barrier fluid in safe collection. Double seal vent systems are not connected to flares.

 

[CaracasEC]

Hi Flexibox thanks, if vented to atmosphere then how should the P&ID be arranged (the blind flange will be remove?)

 

[1gibson]

Waste of money. Use stick on liquid crystal thermometers, or IR temp gun. With an IR gun you can check inlet temp, gland temp, and outlet temp.

A temp gauge on the outlet only tells you that something might not be right. If you take all those temps and look at the data, it should narrow things down.

 

[CaracasEC]

Thanks Mr.Gibson for your great idea...

 

[Airsporter1st]

CaracasEC - You are confusing venting of the seal chamber and associated seal pipework with venting of the seal system.

There is no requirement for a support bsystem for a dual pressurised seal to be self venting.

1Gibson - Both the methods you suggest are OK. Remember though that a) the IR gun must be used properly (i.e. with reference to the measurement spot size vs. distance)and set to the correct emissivity to achieve meaningful results and, b) temperatures taken from the surface of the pipework should typically be increased by around 15 ~ 20 degK to reflect actiual fluid temperature within.

 

[1gibson]

Very true, most methods are "just OK." Any value needs to be interpretted considering all factors. Ambient temp vs fluid temp, distance from measurement to item (seal,cooler)if heat transfer from pipe could be a factor.

I will argue that a differential temp reading is more valuable in this context than knowing exact fluid temp from a single temp gange. The most important information is component temp and relative temperatures; temp rise across seal, temp drop across cooler.

These will indicate any problem with components, or any condition that is different then "normal operation." Really, you are looking for something to be "hotter than usual." With one temp reading, the cause could be high ambient temp, high cooling water temp, high process temp, rub in the seal, or fouling of cooler.

A couple stick on liquid crystal thermometers will tell you who/when/where and reduce the what/how to something that can be answered by anyone with a simple troubleshooting checklist.

You could even stick them on an employee's forehead to see if they need to take a sick day, or in their desk chairs to see if they've spent too much time chatting at the water cooler!

 

[Airsporter1st]

I'm totally with you on the fact that differential temperatures are of more value than absolutes in determining the health of the system - hence my initial comment about ascertainment of sufficient flow.

Personally I am in favour of the liquid crystal thermometers, although when I suggested them to my company in the mid 90's, they did not agree to adopt them. (They were sold in minimum quantities and the bean counters didn't want to make the initial outlay - fools.)

The point I was making in response to your first post was that it is also important to keep an eye on the maximum temperature, since the majority of barrier/buffer fluids will start to degrade above around 80 degC and water tends to lose its lubricity and may flash across the seal faces above the same temperature - so whatever method of skin temperature is utilised, it is important to keep in mind that the actual fluid temperature inside the pipe/tubing will be somewhat greater.