Seal Plan 52

[10815L]

Hi all,
I would like to know about a pressure guage range if a pump is developing 12 and 26 barg pressure.
In my refinery, we are facing problem seal pot high pressure alarm and when asked from operator, he is replying Pressure is zero. our maintenance team installed a pressure guage with range of 0 to 40 barg.
I need your assistance with reference for correct local pressure guage range.
Thanks
10815L

 

[flexibox]

have you checked the calibration of the Pressure transmitter or switch?

 

[gr2vessels]

The 0-40 bar range seems suitable for the mentioned 12-26 bar operating pressure. Ideally, you operating pressure should be within the middle 66-75% of the gauge range, which is correct in your case. Don't try to tighten the range, you risk unstable reading at low end and the top end of the gauge. A much larger range might not register large movements on the scale.
Cheers,
gr2vvessels

 

[JJPellin]

You did not provide enough information to give a proper reply. So, I will make some assumptions. First, the seal pot does not normally operate at pump discharge pressure. It probably operates at a very low pressure of some flare system. If the seal were to fail catastrophically, the seal pot would probably still not see pump discharge pressure. Depending on the configuration of the pump, it may see suction pressure or it may see some pressure between suction and discharge.

The pressure gauge needs to be appropriate for the maximum pressure which it may see. If your flare runs at 0.2 barg and the pump suction pressure is 5 barg, then a 40 barg gauges is not appropriate. An appropriate gauge might have a full scale of 5 barg or perhaps 10 barg. Keep in mind, you not need to have the maximum pressure in the center of the gauge range. You only need to be able to distinguish a leaking seal from a seal that is not leaking. And, of course, you do not want the gauge to fail from overpressure in the event of a seal failure.

If you want a better reply, you need to provide your flare pressure, suction pressure, discharge pressure and pump configuration.


Johnny Pellin

 

[10815L]

Hi JJPeliin,
I'm not talking about one pump, here is many pumps in my refinery. Flare pressure is even less than 0.2 barg.
The acutal problem is, seal pot high pressure alarm is coming frenquently and set value is 0.5barg for pressure switch and pressure is on pressure guage always not readable may be due to high range.
I want to know about the standards for pressure guage specification.
Thanks
10815L

 

[Pumpsonly]

What is the scale division of your 40 Bar gauge and the size? If it is a 4 inch gauge, you will hardly see any difference between 0 and 0.5 bar reading if the gauge is 3-4 feet from the eye.

 

[JJPellin]

As I already noted, for this service, I would select a gauge with a full scale approximately equal to the highest pressure you would expect to see. This value depends on the suction pressures of the pumps, the discharge pressures of the pumps and the configurations of the pumps. Since you seem to have multiple pumps somehow sharing a common system, you would also need to examine the P&ID for the entire system. You have not provided any of this information. So, the best we can do is guess. And I don’t like to guess. Thus, I cannot help you.

Johnny Pellin

 

[gyaneshwarp]

Plan 52 is non pressurised plan. The Pot pressure in normal condition is approximately flare pressure.

Switch setting is generally at 0.7 bar pressure.

In view of this I would recommend that whatever is maximum stuffing box pressure, if a pressure gauge is selected for that range should be sufficient.

Even in the case of total seal failure buffer fluid pressure will not be even nearer to stuffing box pressure.