External Inspection

(i) Make sure valve mountings or head supports are secure. Loose mounting permits head and element to move in and out of the wall sleeve, undoing all the careful internal alignment.

(ii) Check the operating head and valve to make sure it is functioning properly, mechanically and that it can rotate without undue binding.

(iii) See that mechanical parts are clean and free from rust. Dirt and rust act as an abrasive, causing moving parts to wear.

(iv) Remove immediately any and all water pockets in the supply piping system. PROPER DRAINING OF PIPING IS OF PRIME IMPORTANCE. When the blowing medium is steam the supply pipe should have an independent direct connection to the boiler drum, to obtain the direct possible steam at maximum pressure. Stem supply piping should be insulated for safety, and to reduce condensate in the soot blowing system.

(v) Make sure piping connections to soot blowers are flexible enough that no leakage to abnormal stresses will develop. Proper hangers should be provided for the pipe.

Pipe risers should never depend on the soot blower head for any support. This always causes binding when the unit is operated.

(vi) If condensate traps are used on steam systems, dis-assemble them and clean the screens during outages to make sure they operate properly.If a drain valve with 4mm hole in the seat be used instead of a trap, make sure it is in place and in operating condition.

(vii) Make sure condensate is drained to atmosphere. If drains are led to blow-down tanks, check valves should be used. If drain systems are connected in series to two or more boilers, check valves should be used to prevent steam from backing up on unused equipment.

5.3 Maintenance

Things listed so far have been inspection points to check during boiler outages. There are other points that can be checked while the boiler is in service.

(i) Operation personnel should be instructed to report immediately to the maintenance personnel any difficulty encountered in operating.

(ii) Competent maintenance personnel should be required to follow and observe each and every soot blower through its operating cycle on certain definite dates. These inspection periods should be bi-weekly or monthly, depending on the size and importance of the soot blower installation to proper boiler operation.

(iii) All steam leaks should be corrected immediately.

(iv) All valves should seat tightly to prevent wire drawing.

(v) All packing glands should be drawn just tight enough to prevent leakage without binding or breaking down packing fibre by excessive pressure.

(vi) All cams and moving parts should be cleaned and properly lubricated.

(vii) Gear boxes should be filled to proper levels with correct gear oils or grease. Greases should be checked regularly to see if they have hardened or separated from their bases because of high ambient temperatures. On outdoor installations, they should be checked when temperatures drop to see if hardening or channelling occurs.

(viii) Lubrications in air lines to air motors should be checked at least once a week to make sure oil reservoirs are full and feed is correct.

(ix) With electric motors, insulation, brushes and commutators should be clean and free from oils. General rules for care of electrical equipment and industrial controls should be followed.

(x) Where drive chains are used, the chain should be kept as dry as possible.Only enough oil to prevent rust should be applied. Excess oil picks up fly ash and grit to form a cutting abrasive between link connections.

(xi) With any lubricants, manufacturer’s specifications for correct types, amounts and frequency of application should be closely followed.

5.4 Preparing for outages

Where boilers are subject to extended outages, as in heating plants, maintenance can be reduced by giving proper attention to the equipment before and during the down period.

(i) Moving cams, etc., should be well coated with rust-preventive lubricants.

(ii) Mechanical units should be covered with canvas, oil cloth or paper for protection against moisture or excessive dust.

(iii) If operating valves or pistons have rings or parts not made of rust-resistant alloys these parts should be removed. They can be protected by a rust inhibitor by a rust inhibitor or stored until the equipment is required.

(iv) Where feed lines or telescope tubes are of carbon steel, the units should be extended and rust preventive applied to these parts.

(v) Inspections and repairs should be made immediately when the boiler is shut down to assure proper operation when the boiler is put back into service.

Care, adjustment and maintenance of automatic control, panels for automatic-sequentital systems are properly entrusted to the instrument personnel. Such systems usually require little care after being placed in service, except to keep all parts thoroughly clean.

Generally speaking, they require the same maintenance as any industrial control system except that the loads on relays, indicator lamps and switches are comparatively light, therefore, requiring less attention. Little maintenance trouble is met, if this equipment is kept clean and free from dust and oil.

5.5 Operation

Correct operating procedure will help to minimize maintenance problems. These are important check points.

(i) Drain valve should be fully open, and supply valve opened slowly, during warm-up period. Drain valve should not be closed until the steam leaving the drain is absolutely dry. Drain valves should remain open when units are not operated. These precautions prevent condensate from entering elements to warp or distort them.

(ii) Rotation of elements should be slow, even and continuous from the time steam flow starts until it is shut off. Should the automatic valve-in-head unit fail to shut off, the entire system should be shut down immediately, and the offending unit be corrected or blanked off before proceeding with the other units in the cleaning cycle. To proceed with the other units after one operating head has failed to shut off would cause tube damage. In addition, there would be reduced blowing pressures to the other elements which would prevent proper boiler cleaning.

(iii) All units should be kept in operating condition as far as possible. Loss of one unit could cause plugging and thus divert hot gases over an adjacent unit to destroy that element.

(iv) Blowers should be operated in proper sequence along the gas flow lanes with dampers fully open. This moves soot out, rather than blowing it from one place to another.

Boiler load should be ¾ to full, if possible to prevent puffs or possible explosions.

(v) Blowers should be operated at proper intervals to reduce temperatures and prevent loss of elements and nozzles. Operating intervals should not be set for certain hours of the day or shift, unless the boiler steams vary evenly and neither soot nor slag conditions are of much concern. Blowing intervals should be adjusted to load, firing and fuel conditions. The guiding rule is that flue gas temperature should not rise more then 20 Deg. C between soot blower operating periods.

Soot blowers should also be operated after any abnormal fuel burner operation resulting in heavy smoke while burning oil. This is especially true if there is an economiser or air heater.

Soot blowers are expected to clean efficiently and safely. They are intended to operate on low power and labour cost, and to give long life with minimum maintenance expense. This is possible, even if the equipment be subjected to high temperatures and adverse operating conditions.

Soot blowing engineering takes these points into consideration and uses the highest possible engineering standard in design and construction. As a result, blower equipment properly installed and cared for is as trouble-free as possible. To maintain this standard of operation requires only a regular programme of inspection and preventive maintenance.

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