Figure 2-3. - Low water plate.
additional feedwater treatment that might not otherwise be necessary. Since the boiler and system arrangements usually make it impractical to perform daily and monthly maintenance of the low water cutoff devices, it is essential to remove the operating mechanism from the bowl annually, or more frequently if possible, to check and clean the float ball, the internal moving parts, and the bowl housing. Also, check the cross-connecting piping to make certain that it is clean and free of obstructions.
A broken or discolored gauge glass should be replaced at once. Always use new gaskets when replacing a gauge glass. Use the proper size rubber packing. Do not use "loose packing" that could be forced below the glass and possibly plug the valve opening.
Close the valves when replacing the glass. Slip a packing nut, a packing washer, and a packing ring onto each end of the glass. Insert one end of the glass into the upper gauge valve body far enough to allow the lower end to be dropped into the lower body. Slide the packing nuts onto each valve and tighten.
If the glass is replaced while the boiler is in service, open the blowdown valve and slowly bring the glass to operating temperature by cracking the gauge valves slightly. After the glass is warmed up, close the blowdown valve and open the gauge valves completely. Check the try cocks and gauge cocks for freedom of operation and clean them as required. It is imperative for the gauge cocks to be mounted in exact alignment. If they are not, the glass will be strained and may fail prematurely.
Proper control of the water level requires that the feedwater regulator be maintained. Here are a few pointers for regulators.
If the water level changes from its normal position, make sure you adjust the bypass to manual operation and check promptly for the source failure. If leaks develop around the packed stems, see that they are stopped immediately. If the boiler is off line, close the hand valve in the feed line. Bear in mind that the regulator is not designed for use as a stop valve. About once every 3 months, you will probably be called on to assist in blowing down the steam and water connections separately.
Valves deserve special care and attention if they are to work as intended. There may be variations among activities in the type and frequency of valve inspection and servicing requirements. Therefore, follow instructions issued by your activity when they differ from those outlined here.
Types of valves that you may be responsible for helping service and maintain at regular intervals include (1) stop valves of the globe or gate type and (2) stop-and-check valves, which combine in one tray and angle or stop valve of the globe type and a check valve. At least once every 3 months, valves that have not been operated for some time should be operated to prevent sticking. Make sure that you also check for leaks, bent stems, a missing or broken handle, and lubricate the exposed threads and gearing of the valve stem.
Loosen and lift the packing follower about once every 3 months or more often if possible. Lubricate the packing with graphite bearing oil or graphite bearing grease. Replace the packing followers and tighten sufficiently to ensure against leaks.
BLOWOFF or BLOWDOWN VALVES should be opened at least once a day. There are four reasons for using these valves:
1. Controlling high water
2. Removing sludge and sediment
3. Controlling chemical concentrations in the water
4. Dumping a boiler for cleaning or inspection
The amount and frequency of blowing down depends on a chemical analysis of the water in the boiler and operating conditions.
On a quarterly basis, inspect the blowoff valves when the boiler is washed out and an internal inspection is made. Check the valves for leaks, and inspect the pipe and fittings between the blowoff 2-3Continue Reading