Primers and its working | Rising Mains.

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Primers:

Primers used to exhaust air from the suction and the casing. Various types of the primers are discussed here. devices. After the pump is primed the at morphemic pressures able to force the water to reach the pump entry.

Various types of the primers are:-

Reciprocating Primers:

These are reciprocating pumps which develop higher-pressure by the direct action of plunger on the fluid (liquid or gas) confined in a cylinder and forcing the fluid out from the discharge.

Working of Reciprocating Primers:

The piston is driven from the main pump drive shaft by its engagement with the help of a crank shaft & a lever. The priming pump inlet is connected to the delivery side of the main pump h a priming value (air value). The priming value is normally kept closed by means of spring. thus isolating the priming pump from the main pump. During down stroke the air moves above the piston though the value in the piston. Again in the up stroke; the air above the piston is forced out though the outlet drain pipe. By the up & down movement of the piston in the cylinder entire amount of air Is first pushed out, followed by water.

Exhaust Gas Ejector Primers:

These primers find the maximum usage in fire service pumps mounted on vehicles like Fire Tenders.

Principle:

When a fluid liquid or gas under high velocity passes through a throw at into a chamber of large dia meter a negative pressures created around the throat.

Construction of Primers:

The essential parts of a jet pump are

  • The nozzle.
  • The diffuser.

The purpose of nozzle is to convert pressure energy to. Velocity energy. The purpose of diffuser, a mixing chamber of motive gases and the entrained fluid, is’ to convert the’ velocity energy back to pressure energy- Jet pumps have no moving parts and thus practice all no maintenance is required.

But they do need high pressure motive fluid which is usually expensive to supply.

Working of Gas Ejector Primers:

When the pump is to be primed the priming value is opened and the exhaust valve closed. The purpose of closing the exhaust ve is to divert the exhaust gases from their normal passage r the exhaust pipe to the silencer. And conduct them to the nozzle of the jet pump which is connected to the casing of the pump.

Rotary Primers (Water Ring Primer):

A water ring primer may be automatic in action boing driven directly room the main pump shaft. This is the primer widely use in the fire service as this can be arranged either automatic or hand operated.

The rotating parts move in relation to the casing so as to create a space which first enlarges drawing in the fluid in the suction line is sealed and then reduces in volume, forcing the automatic or hand operated. through the discharge ports at a higher pressure.

Construction:

  • Mounted on the casing of the main pump it is constructed with the following parts.
  • A rotor or impeller with radial vanes. This has two suction and two discharge ports
  • Oval shaped casing.
  • Stationary boss having two suction and two discharge ports.
  • A waste pipe connected with discharge pipes of two outlet ports.

Working:

As the rotor revolves, a small quantity of water which is kept in the casing is thrown by centrifugal force thus leaving a vacuum between the boss of the rotor and the water. When the inlet ports in the casing and those in the rotor coincide, air is drawn in by the vacuum and carried around until the outlet ports are reached. Here as the casing narrows, the fluid is forced out. Thus driving out the air through these outlet ports.

The inlet and outlet ports being duplicated, extremely rapid. And effective priming is achieved. Since the impeller is located centrally in the oval shaped casing there are two pumping actions in one revolution?

Advantages of Rotary Primers:

  • It has large exhausting capacity.
  • It gives extremely large rapid and effective priming.
  • This is suitable for low water levels.
  • No skills is required in operating.

 

S. No. Symptom Causes Remedial Measures
1 Pump does not prime

1. Air leak in the primer pump or hose.

2. Delivery valve open.

3. Defective Primer.

1. Check all joints for leaks.

2. Close delivery valve.

3. Examine and rectify.

2

Failure after disengaging

the primer

1. Air leak in pump or suction hose.

2. Air leak through gland packing: or 

Mechanical seal of the pump.

1. Check all joints.

2. Adjust ‘gland’ packing repairer

replace mechanical seal. 

3 Low Output Chocked suction strainer. Clean the suction strainer
4 Broken or crackling jet

1. Suction hose insufficiently submerged.

2. Small leak on suction side of pump.

1. Submerge until vortex disappears.

2. Check pump joints for leaks and rectify.

 

ADVANTAGES/DISADVANTAGES OF VARIOUS TYPES OF PRIMERS:

S. No. Primers Type Advantages Disadvantages
1 Reciprocating

1. Simple to operate.

2. High efficiency at low RPM.

1. Too heavy/bulky.

2. Too many movable parts more

wear and tear.

2 Exhaust Ejector

1. Simple to operate.

2. Less damage. By mishandling.

Less efficient.
3 Water Ring (Rotary)

1. Large exhausting capacity.

2. Rapid priming.

3. No skills required.

4. Suitable for lower water levels.

None.

Fixed Installations:

Dry and Wet Rising Mains:

  • Dry Rising Mains.
  • Wet Rising Mains.

Dry Rising Mains:

A vertical pipe installed in a building for fire fighting purposes, fitted with inlet connections at fire brigade access level and landing valves at specified points, which is normally dry but is capable of being charged with water usually by pumping from Fire Service appliances or form other pressurized sources.

General:

  • Risers shall be installed in buildings where any floor is at a height of more than (18) meters above ground level.
  • For building where the upper floor is less than (30) meters above ground level, dry risers can be provided.
  • For buildings where the upper floor is more than (30) meters above ground level w risers shall be provided.
  • The Fire Prevention Officer should be consulted in each case.

Siting:

Each rising main shall be provided with landing valves (hydrant outlets) at various floos levels sited:

  • Within a ventilated lobby or a lobby approach, where this is provided.
  • In a stairway enclosure.
  • In such other positions as may be agreed upon with the Fire Authority.

On selection of positions for inlet connections for a dry rising main, attention shall be paid to the position of fire hydrants available near the building, the possibility of damage resulting from falling parts from windows and other possible occurrences during a fire.

Inlet connections for dry rising main should be installed in an external wall or in a boundary wall of the buildings as close as possible to the position of the main which they serve, and any rim between the inlet and the vertical rim of the main should be given fall towards the drain valve. Easy access shall be provided for the fire brigade to the inlets,

The number and positions of rising mains normally should be such that:

  • one is provided for each (900) m2
  • Rising mains are not more than (50) meters apart in horizontal direction.
  • No part of the floor area is more than (60) meters distant from a landing valve. The distance is to be measured along a route suitable for hose lines, including any distance up or down a stairway.

Construction:

  • Dry and wet risers shall be designed in accordance with the approved standards.
  • The riser should be of galvanized wrought steel piping, heavy quality to BS (1387/1967), screwed and socketed. The fittings to be malleable iron or wrought iron, galvanized and of steam quality. 

Diameter of Riser:

  • The internal diameter of a riser main which has two outlets at any level should be not less than(152) mm and, in case of one outlet the diameter should be not less than (102) mm.

Air Valve:

  • An automatic air valve will be required, this should be fitted at the topmost point of the riser.

Inlets:

  • A (102) mm riser should be fitted with two inlets and a (152) mm riser with four iniets, each iniet consisting of a 63 mm instantaneous male coupling and a non-return valve as the type used by the General Directorate of Civil Defence ( BS 5041Part : 1975).
  • Inlets should be protected by a cap secured by a suitable length of chain, the coupling to conform to BS (336/1965).

Inlet Boxes:

  • The inlets to a dry rising fire main should be housed in a glass fronted box, so sited that access for a pumping appliance can be obtained to within (18) meters and within sight of the inlet.
  • The door of the box containing the inlets should be:
  • Glazed with wired glass and conspicuously indicated by words (Fire Service Dry Main Inlet) in block letters on” the inner face of the glass in English and Arabic.
  • Fastened only by means of a spring lock which can also be operated from the inside without the aid of a key after the glass has been broken.
  • Made large enough for hose to be connected to the inlets even if the door cannot be opened and the only means of access is by breaking the glass. The minimum external length, height and depth of box containing the inlet connections should be in accordance with BS (5041/Part 5/1974) namely:

102 mm diameter riser:

  • 609 mm x 405 mm x 304 mm or
  • 405 mm x 609 mm x 304 mm x 152 mm diameter riser:
  • 609 mm x 609 mm x 304 mm.

All boxes should have a fall of one in twelve towards the front at the base.

Drain Valves:

A (25) mm drain valve should be fitted to the riser, normally in the inlet box. Where any part of the pipework falls below the inlet box level, a similar valve should also be provided at the lowest point of the pipework, together with facilities to conduct water from the valve to a suitable drain. Where a low level drain valve is fitted a permanent notice should be provided in the inlet box reading (Low level Drain Valve in…… Room). The low level valve should be kept strapped and padlocked closed except when in use.

Provision of Outlets:

Outlets should be provided on each riser at each level above first floor and where appropriate, on the roof. Where not with standing conformity with the distance factor, prescribed at paragraph (2 Siting d), it is deemed necessary lord the purpose of adequate coverage, to provide more than one outlet of any floor, two outlets at a floor level may be allowed on one riser. In buildings with basements of unusual depth, it may be advisable to extend the installation to serve outlets at levels below ground.

Type of Outlets:

  • The outlets should be of a type approved by the General Directorate of Civil Defence (BS5041/Part 1 and 2/1975) and should comprise a gate pattern valve (63) mm bore, constructed in gunmetal, screwed or flanged for attachment to the riser and fitted with a (63) mm bore. Fitted with (63) mm instantaneous female coupling to conform to the requirements of the General Directorate of Civil Defence, and a blank cap secured by a suitable length of chain.
  • The valve spindle should not be less than (22) mm in diameter and fitted with a gun meta hand wheel, about (152) mm in diameter, which should be marked with Open and Shut directions.
  • Sound constructions and hydraulically tested to a pressure of (20) bars before being connected to the rising main.
  • Where outlets are required to be recessed into the wall in a duct or valve, the opening should give not less than (152) mm clearance on both sides and below the valve and pot less than (203) mm clearance above the hand wheel. The depth of the opening should not be greater than is necessary and in no case should the front edge of the female coupling be more than (76) mm behind the face of the wall. 
  • If this is not practicable, each outlet should be kept strapped shut, the strap being secured by a padlock.
  • Outlets should be installed about (760) mm above floor level.

Earthling:

Dry rising mains should be electrically earthed.

Telephone System:

In some cases, a simple single cable and plug telephone may be required by the Fire Service to assist communication between the ground floor and the floor at the a landing valve is in use.

Test on Dry Rising Mains:

Notification to interested parties:

No test shall be carried out without prior notification to the interested parties (i. e. water undertakings, owners or occupiers of the building, and a representative of the installers).

Joint Inspection:

On the arrival of the Civil Defence officer who is responsible to carry out the test at the premises he should make contact with a suitable representative of those responsible for the site. Both these representatives should then carry out in company a physical check of the installation. The inspection should verify that earthling requirements have been carried out satisfactorily or certified by the electrical contractor.

Static pressure test:

On being satisfied that the system is in order, water should be allowed to flow through it discharging via the topmost outlet to flush out any debris that may be present. This procedure is of particular importance at acceptance tests when quantities of foreign matter may be lodged in the nine work. The system should then be completely charged with water to a pressure of (10) bar measured at the inlet for a period of at least (15) minutes. During this period, an inspection of the system should be made to check that no leakage of water is taking place at any of the points or landing valves.

Flow test:

After the test in accordance with (c) completed, a flow test should be carried out if this is considered to be necessary. For this test, water should be passed through the system under pressure and the flow gauge readings recorded. Inability to sustain an effective fire-fighting jet from the topmost outlet, or any undue pressure loss in the rising main (after allowing for the height involved) should be investigated.

Remedial action and retesting:

If as a result of these tests any defects are found, these should be remedied as necessary and a retest of the system should be carried out. When the pressure has been released at the pumping appliance of the coupling to the rising main inlet should be disconnected and the action of the non-return valves checked. The sister should then be drained and left ready for use.

Indemnities:

Before testing any system a signed indemnity should be sought from the person at that time responsible for the work site or premises. This may be required by the Civil Defense Authority in respect of liability for damage caused to persons or property arising out of, or in connection with any test.

Maintenance of Dry Rising Mains:

  • The service of a competent person should be obtained to carry out maintenance and repairs as under.
  • Inlets landing valves, drains valves, door hinges and locking arrangements to the inlet and landing valve boxes should be inspected every three months.
  • Special attention should be given to all valves, spindles, glands and washers to ensure that they are in satisfactory condition, so that all equipment is ready for immediate use.
  • In addition, it is recommended that wet tests be carried out annually when the main can be checked for leaks.

Rectification of defects:

It is essential that all defects are rectified in the shortest possible time to ensure that the fixed fire fighting equipment restored to satisfactory condition in as short a time as possible. Where, due to unforeseen difficulties, it is necessary to leave an installation not available for use, the fire brigade should be informed immediately in order that alterative arrangements may be made to Cover this deficiency should the need arise. In addition a suitable notice to indicate that the installation is not available for use should be placed in a prominent position. The notice should be in a inlet box. 

Test Records:

A permanent record of all initial inspections and acceptance tests should be kept by the o or occupier. This should record are- date and time for inspection or test. Person carrying out re-test. Test results noted any external factors significantly affecting the results (eg weather conditions). Work carried out as result of (e) with the date and result of retest.

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