Firewater pumping systems

In the third e.vample, the line terminates at 53%. This means DO NOT run this pump at less than 53% of the BEP. 53% of 4500 gpm is 2385 gpm. Because this is a firewater pump and because firemen need to throttle the nozzles on their fire hoses, then we need to install a pressure relief valve on this system with a discharge bypass line so that the pump dumps the restricted water (less than 2400 gpm) back into the suction tank or lake. If not, this firewater pump is likely to suffer bearing failure during an emergency. 

Several catastrophic fire incidents in the petroleum industry have been the result of the facility firewater pumps being directly affected by the initial effects of the incident. The cause of these impacts has been mainly due to the siting of the fire pumps in vulnerable locations without adequate protection measures from the probable incident and the unavailability or provision of other backup water sources. A single point failure analysis of firewater distribution systems is an effective analysis that can be performed to identify where design deficiencies may exist. For all high risk locations, fire water supplies should be available from several remotely located sources that are totally independent of each and utility systems which are required for support. 

Small capacity pumps commonly referred to as "jockey" pumps are provided on a firewater system to compensate for small leakages and incidental usage without the main pump(s) startup. They are set to start 0.70 to 1.05 kg/sq. cm. (10 to 15 psi) above the start up pressure of main firewater pumps. In some cases a cross-over from the utility water system can be used in place of a jockey pump, however a check valve is installed to prevent drain down of the firewater by the utility water system. Jockey pumps do not require the... 

When more than one pump is installed, they should be coordinated to start in sequence, since immediate startup of all pumps may not be necessary and could cause damage to the system. Depending on the number of pumps available they can be set up on sequentially decreasing fire main pressure set points. All firewater pumps should be able to be started from remote activation switches located in manned control rooms, but shutdown should only be accomplished at the pump itself. 

Firewater pumps should be solely dedicated to fire protection. They may be used to feed into a backup system for emergency process cooling but not as the primary supply. If such backup is allowed, it should be tightly controlled and easily accessible for prompt shutdown in case of a real emergency. 

In some cases, the proximity of a local fire station or provision of a dedicated fire station within a large industrial complex can be relied upon to provide backup firewater pumping capabiHty to the fire protection system. In fact, historical evidence indicates that when the fixed firewater pumps have been impacted by a major fire or explosion incident, mobile fire apparatus has to be heavily relied upon as a backup mechanism. Previous coordination with the fire station as to their capabilities, mobile apparatus accessibility, connection points, drafting sites, emergency admittance, and manpower should be evaluated and incorporated into emergency pre-fire plans for the facility. 

Process facilities susceptible to earthquakes should be provided with suitable restraints for fire protection systems. The extent of these restraints are normally dictated by local ordinances and primarily concern the bracing of pipework and adequate securing of firewater pump base plates and controller panels for earthquake forces. Pump houses should be adequately constructed and braced so they will not collapse onto the firewater pump or distribution piping. 

Start the fire pump to be tested and let it run for a minimum of 30 min, for stabilization of the mechanical systems. The firewater pump can be started manually from the controller, but it is typically preferred that a local fire water device is opened (i.e., fire hydrant(s)) to simulate firewater pump auto-start on low fire main pressure detection. If several fire pumps are arranged to start in sequence, the sequence startup should be verified to confirm programming logic arrangements. Adjust the driver (i.e., engine) rpm to operate the pump as close as possible to the rated rpm performance curve. 

Verification of fire pump startup and flow and pressure indications in the plant DCS should be confirmed if such indications are provided as part of the plant monitoring system. Remote stopping of the firewater pump should not be allowed. 

Figure 9.1 shows the use of fire zones. A ring main goes around the entire facility. It is filled with water whose pressure is maintained with a jockey pump. Connected to the ring main are multiple zones. The firewater headers in each zone are normally dry. In this example, there are two firewater pumps, each of which has sufficient capacity on its own to handle the design fire case. These pumps are placed in different locations at the facility so that, if one is destroyed, the other will provide a full flow of firewater. It is common for them to have different power supplies—in particular, one of them will be driven by a stand-alone diesel motor that operates independently of the facility s utility systems. 

Firewater Systems. These systems are best laid out by contractors or other specialists. National Fire Protection Association (NFPA) rules will spell out required coverage, typical pump size, and other standard items. A small jockey pump will maintain system pressure at all times. 

Some licensees have a switch to bypass RCIC high steam tunnel temperature trips. Some licensees are evaluating improvements to prevent seal LOCAs from loss of seal cooling which are most important for W plants, but B W licensees identified improvements related to alternate seal flow capability under loss of power conditions. The use of high temperature seals is noted for some W plants. Many PWR IPEs identify AFWS improvements. These include additional backup water supplies such as the firewater system and redundant pump cooling capability. Other reliability... 

Safety systems should not be segregated together. Each safety system should be diversified as much as possible to avoid the possibility of a single point failure. A prime example is the firewater supply which should be pumped into a facility firemain at several separate and remote locations. 

Firewater supply sources can be the city public water main, a dedicated storage tank and pumps, or the most convenient lake, river or if an offshore installation the open sea. Brackish or salt water supplies can be used if suitable corrosion protection measures are applied to the entire firewater system if it is planned to be used for an extended life (i.e., grater than five years). If a short life span of the facility is expected, short corrosion resistant materials may be used (i.e., carbon steel, galvanized steel, etc.), provided periodic testing indicates their integrity is still adequate and scale or corrosion particles do not affect operational efficiency. 

Firewater systems - tanks, pumps, underground pipe. 

Safety Systems. Major expenditures here include the flare system (the flare structures and large lines extending throughout the plant) and the firewater system (high-capacity pumps and extensive piping). Safety systems, fortunately, are usually given particular attention. At this study phase, the main thrust should be to check the completeness of licensor equipment lists for cost estimation purposes. 

Step 10 How will any firewater run-off be dealt with Hose and pumps will be necessary to transfer firewater run-off from the bund to another bund or catchment area. Alternatives include purpose-built bund overflows to a remote tertiary containment system, or increasing the capacity of an existing bund. Transfer could be by pumps or via gravity flow. 

On-plant equipment/ facilities (excluding emergency response equipment) Tank deluge and foam systems. Firewater storage 70 000 litres, pumps 3000 litres, min, pressure 10 bar. 

Identify watercourses, separators and plant drainage systems with the aim of minimising environmental pollution. Include areas where firewater run off can be contained. Identify equipment required to assist in this, eg drain sealing equipment, booms and fire service New dimensions pumping equipment. Consideration should be made of the resources held by Fire and Rescue Service (FRS) and how on-site resources will be used by FRS personnel. 

When pump A was restarted at 2200 hours, the temporary cover on the open flange (where the pressure relief valve would normally have been) failed, and a large quantity of light hydrocarbon hquid and vapor spewed out. Shortly afterward it found a source of ignition and the initial explosion and fire occurred. The tire then escalated with more explosions at 2220 hours, 2250 hours and a final huge explosion happened at 2320 hours. There were also other factors which made control of the tire difficult or impossible - e.g., the switches to start the firewater system were located too near... 

A jockey pump maintains pressure on the firewater system at all times. The set pressure will typically be in the range 8—lObarg. Generally, the jockey pump will mm itself on and off depending on the header pressure. If the pump mns continuously its discharge should recirculate through a minimum flow bypass. 

An underground firewater system is any part of a firewater system that is underground, including storage, piping, pumps, valves, hydrants, and monitors. The underground firewater system should be a loop with branches off it. This means that, if the underground line is broken or blocked at any point, firewater can still reach the point where it is needed. 

Capabilities and limitations of the firewater system and its components Fire-pump operation and water deliverability Hose handling techniques PPE... 

During the night the hydrocarbon header was pressured up by a pump about a mile away. Its pressure was greater than that of the firewater header so hydrocarbon liquid flowed into the firewater system. Through a series of underground... 

---