Hi,

Can i get Firewater pumps p&id for any  plant you are currently working for or worked in before please. 

I want to check the over pressure protection mechanism.

Most systems that I've seen have only pressure safety valve for pump case relief purpose only!! 

 Also if you have any ideas about the philosophy of over pressure protection, please comment with it.

Your contribution and support will be highly appreciated. 

mneemnewiraq2000@gmail

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Original Post

I can't imagine why you'd have overpressure protection on fire pumps. For one thing most of the ones I'm familiar with are centrifugals so that wouldn't apply (overpressure is a positive displacement pump thing) and it may not be an actual electrical device but more likely simply a rupture disc. When it comes to fire pumps the general protection strategy with them is to run to failure unless the failure would cause additional consequences with the assumption that responding to a fire is the greater hazard. For example fire pumps specifically do NOT have overload/overcurrent protection because the goal is to run to failure even if it means burning up the motor. However a short circuit can shut down multiple fire pumps and/or cause other unforseen consequences so short circuit (fuse or magnetic-only circuit breaker) protection is included. Based on the same logic though I have never seen a written standard for fire pumps. I would have to imagine that overpressure protection would be along the same lines...even if we blow the line apart or dump water everywhere and hardly get anything put into action to put out the fire, so overpressure protection wouldn't be included.

PaulEngr posted:

I can't imagine why you'd have overpressure protection on fire pumps. For one thing most of the ones I'm familiar with are centrifugals so that wouldn't apply (overpressure is a positive displacement pump thing) and it may not be an actual electrical device but more likely simply a rupture disc. When it comes to fire pumps the general protection strategy with them is to run to failure unless the failure would cause additional consequences with the assumption that responding to a fire is the greater hazard. For example fire pumps specifically do NOT have overload/overcurrent protection because the goal is to run to failure even if it means burning up the motor. However a short circuit can shut down multiple fire pumps and/or cause other unforseen consequences so short circuit (fuse or magnetic-only circuit breaker) protection is included. Based on the same logic though I have never seen a written standard for fire pumps. I would have to imagine that overpressure protection would be along the same lines...even if we blow the line apart or dump water everywhere and hardly get anything put into action to put out the fire, so overpressure protection wouldn't be included.

PaulEngr, good day!

Actually there are many firewater network damages occurred in the past months due to the high pressure.

The sequence will be like that:

1- due to firewater pressure drop, the main electrical pump will start automatically. And from firewater philosophy, it can be stopped manually only.

2- while the operator investigating the cause of the pump start, this pump will keep the pressure increasing in the firewater network untill the pipe joint fails!

 

And thats why i want to add a control valve to eliminate the overpressure events.

 

Again please if you have any p&id for any firewater system please pass it to me.

Looking for your ideas please.

 

Regards,

 

Mohammed

PaulEngr posted:

Interesting, never noticed before because the title doesn't exactly scream "fire pumps". It also doesn't contain anything resembling a P&ID from a cursory scan, and simply references NFPA 70 (NEC) for electrical installation requirements.

Not sure what you are looking at but my copy, NFPA 20 is titled Standard for the Installation of Stationary Pumps for Fire Protection.

Further, chapter 4 has the following contents

Chapter 4 General Requirements

4.1 Pumps.
4.2 Approval Required.
4.3 Pump Operation.
4.4 Fire Pump Unit Performance.
4.5 Certified Shop Test.
4.6 Liquid Supplies.
4.7 Pumps, Drivers, and Controllers.
4.8 Self-Regulating Variable Speed Fire Pump Units.
4.9 Multistage Multiport Pump.
4.10 Centrifugal Fire Pump Capacities.
4.11 Nameplate.
4.12 Pressure Gauges.
4.13 Circulation Relief Valve.
4.14 Equipment Protection.
4.15 Pipe and Fittings.
4.16 Suction Pipe and Fittings.
4.17 Discharge Pipe and Fittings.
4.18 Valve Supervision.
4.19 Protection of Piping Against Damage Due to Movement.
4.20 Relief Valves for Centrifugal Pumps.
4.21 Pumps Arranged in Series.
4.22 Water Flow Test Devices.
4.23 Steam Power Supply Dependability.
4.24 Shop Tests.
4.25 Pump Shaft Rotation.
4.26 Other Signals.
4.27 Pressure Maintenance (Jockey or Make-Up) Pumps.
4.28 Summary of Centrifugal Fire Pump Data.
4.29 Backflow Preventers and Check Valves.
4.30 Earthquake Protection.
4.31 Packaged Fire Pump Assemblies.
4.32 Pressure Actuated Controller Pressure Sensing Lines.
4.33 Break Tanks.
4.34 Field Acceptance Test of Pump Units.
4.35 Automated Inspection, Testing, and Distance Monitoring of Devices, Meters, and Equipment.

 

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