Burnham MST396, MST288, MST629 manual Section Ix Maintenance and Service Instructions, Steam Boilers

SECTION Ix: MAINTENANCE AND SERVICE INSTRUCTIONS

A.MAINTENANCE OF LOW WATER CUT- OFF DEVICES

WARNING

Probe and float type low water cut-off devices require annual inspection and maintenance.

1.PROBE TYPE LOW WATER CUT-OFF Although these devices are solid state in their operation, the probe is exposed to possible contamination in the boiler water and subject to fouling.

It is important to physically remove the probe from the boiler tapping annually and inspect that probe for accumulation of scale or sediment.

Follow these steps to inspect, clean and/or replace the probe:

a.Turn off electric service to the boiler.

b.Drain boiler water to a level below the tapping for the probe.

c.Disconnect wiring connections between the low water cut-off control and the probe.

d.Remove the low water cut-off control from the probe.

DANGER

Assure that the boiler is at zero pressure before removing the LWCO probe. Do not rely on the pressure gauge to indicate that the boiler is at zero pressure. Open the safety valve to relieve all internal pressure prior to proceeding. Safety valve discharge piping must be piped such that the potential for burns is eliminated.

e.Unscrew the probe from the boiler tapping.

f.Inspect that portion of the probe that is exposed to the boiler water for a scale or sediment buildup.

g.Light deposits may be removed by wiping the probe with a damp cloth. Wiping the probe with a cloth soaked in vinegar will remove more tenacious lime deposits. The most stubborn deposits may be removed from the probe by using a diluted amount, 3 parts of water to 1 part of phosphoric acid (H2PO4).

CAUTION

Exercise caution when handling phosphoric acid and follow the instruction label on its container.

h.Clean the pipe threads of the probe to remove old, hardened pipe dope and other foreign matter.

i.Apply a moderate amount of good quality pipe dope to the pipe threads on the probe, leaving the two end threads bare. Do not use PTFE (Teflon) tape.

j.Screw the probe into the boiler tapping.

k.Mount the low water cut-off control on the probe.

l.Reconnect the control to probe wiring.

m.Fill the boiler to its normal waterline.

n.Add boiler water treatment compound as needed

(refer to Paragraph B.).

o.Restore electric service to the boiler.

p.Fire burner to bring the water in the boiler to a boil to drive off free oxygen.

q.WARNING — BEFORE RETURNING

BOILER TO SERVICE: Follow the low water cut-off check out procedure in Section VIII, Paragraph I, No. 4.

2.FLOAT TYPE LOW WATER CUT-OFF During the heating season, if an external low water cut-off is on the boiler, the blow off valve should be opened once a month (use greater frequency where conditions warrant), to flush out the sediment chamber so the device will be free to function properly.

Low water cut-offs and water feeders should be dismantled annually by qualified personnel, to the extent necessary to insure freedom from obstructions and proper functioning of the working parts. Inspect connecting lines to boiler for accumulation of mud, scale, etc., and clean as required. Examine all visible wiring for brittle or worn insulation and make sure electrical contacts are clean and that they function properly. Give special attention to solder joints on bellows and float when this type of control is used. Check float for evidence of collapse and check mercury bulb (where applicable) for mercury separation or discoloration. Do not attempt to repair mechanisms in the field.

Complete replacement mechanisms, including necessary gaskets and installation instructions are available from the manufacturer.

B.BOILER AND SYSTEM CLEANING INSTRUCTIONS FOR TROUBLE FREE OPERATION

1.STEAM BOILERS

a.Oil, greases & sediments which accumulate in a new boiler and piping must be removed in order to prevent an unsteady water line and carry over of the water into the supply main above boiler.

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