6 replies to this topic

[shekhar dhuri]

Hi,

 

In all my previous projects, SDV (shut down valve) is loacted on the Tank liquid outlet line (which is Pump Suction Line). As per my understadning, this SDV loacation is correct. SDV on the Pump suction line will limit & isolate the Tank inventory mainly during Fire. During Fire, we do need to isolate invetory from rotating parts of the pumps. However I got comment from Seniors to shift this SDV on the Pump discharge to isolate total system (Tank & Pump). 

 

According to me, Typical Cause & Effect of  Tank-Pump System is as follows : 

1. On high - high level, Tank inlet SDV will close

2. On low-low level (or on low-low Pump Suction Pressure) : Pump motor will stop (pump trip)

3. During Fire, Tank oultet SDV will close.  

 

Hence. No additional SDV are required in this tank-pump sys.

 

Please correct me if I am wrong.

 

Regards,

Shekhar Dhuri

Edited by shekhar dhuri, 22 September 2013 - 01:23 AM.

[fallah]

Hi,

 

In addition to SDV closing due to fire case for isolation of a part of the system for depressurizing, it is highly recommended to close that SDV on low low level in suction drum along with simultaneous pump trip. This actions not only protect the pump from dry running, but also keep the inventory inside the drum...

[NAP]

The SDV should always be between pump and the storage. The reason SDV is before pump is because the pump seals are the most weak and prone points for a leak and fire due to spark ignition.

 

If you keep the SDV after pump, you will only isolation the main process from pump+tank but the whole inventory will keep on leaking and feeding the fire causing a much more disastrous situation.

 

Most of the big oil companies' standard dictate the SDV being located between the pump and storage. The SDV being fireproof so that the cables do survive the fire and when an operator hits the shutdown button (which is usually located about 50 ft away from the pump location), the valve closes.

 

The best place to follow is the client standards, not your seniors. If there is no standards, give them the basic safety logic.

[Sharma Varun]

I would also like to add my brief input-

 

Assuming that SDV is provided only for fire purpose, it should be close to the tank.

Also consider that tanks are located in a big dyke areas & pumps are located outside this dyke wall.

[shekhar dhuri]

Hi,

 

Sorry for late response. I am now clear on the location of SDV in the Pump Circuit and  I have placed SDV valve between Tank & Pump in the P&ID.  However Mr. Fallah, I am not clear on 'Closure of SDV on Pump Suction line' during tank LOW LOW Level'.

 

If we are stopping the pump still SDV closure absolutely must ??  I see all my reference projects closing SDV & triping the Pumps on tank low low level. But I am not able understand clearly. Can you Please elaborate ?   

[fallah]

However Mr. Fallah, I am not clear on 'Closure of SDV on Pump Suction line' during tank LOW LOW Level'.

 

If we are stopping the pump still SDV closure absolutely must ??  I see all my reference projects closing SDV & triping the Pumps on tank low low level. But I am not able understand clearly. Can you Please elaborate ?   

 

Hi,

 

In fact, just pumps trip on low low level in suction drum cannot completely prevent loss of drum inventory. Then the best practice would be simultaneous tripping the pumps and closing SDVs on low low level in the drum...

[mansari]

Your understanding is correct. As mentioned by the knowledgeables on this forum, SDV (also called Emergency Block Valve or EBV)is always provided at the outlet of the vessel for fire protection and located as close as possible to the vessel. This valve is normally operated in an emergency situation (fire for instance) through Emergency Shutdown System (ESD).

 

Pump trip on low low level where the signal from the level switch trips the pump is a standard feature to protect the pumps, regardless of the existence of an EBV, however linking the operation of the valve with low low level is a "good to have" feature