To install a manhole or handhole plate, first center the fitting in the opening. Make sure the shoulder does not bind on the edges of the opening. Then slip the yoke on and start the stud nut. Run the nut on the stud until it is hand tight; then give the nut one-quarter of a turn with a wrench. Do NOT tighten the nut enough to compress the gasket.
When the boiler is given a hydrostatic test, the pressure of the water usually forces the manhole and handhole gaskets into place and thus ensures proper seating. The plates are first set up lightly. When the boiler is ready for testing, the pressure should be pumped up to within 50 psi of the hydrostatic test pressure, regardless of any leakage from the manhole or handhole plates. Leakage is likely to be general at first, but it decreases as the pressure is increased. When the pressure is within 50 psi of the test pressure, most of the leakage stops although the nuts are still loose.
If some plates are leaking badly, the trouble is probably caused by improper seating of the gaskets. As a rule, the gasket is caught on the outer edge between the edge of the plate and the edge of the counterbore for the seat. A light blow with a hammer on the outside of the plate usually relieves the tension on the gasket and allows it to seat properly.
After leaky gaskets have been adjusted and while full test pressure is on the boiler, tighten up all plates firmly. Use only the wrenches specified for this purpose.
Some economizer headers and a few superheater headers are fitted with handhole plugs instead of handhole plates. Also, some economizers have bayonet types of cleanout plugs on the front ends of the tube loops to allow access to the tubes at the return bend end. Detailed instructions for installing and removing the plug type of manhole fittings and the return bend cleanout fittings are given in appropriate manufacturer's technical manuals.
The boiler should be given a hydrostatic test annually or whenever the operator doubts the boiler strength. The purpose of the test is to prove the TIGHTNESS of all the parts of the boiler or the STRENGTH of the boiler and its parts.
In preparing the boiler for a test, rinse it out with fresh water. Then check carefully to see that no loose scale or tools are left in any part of the boiler.
The procedures for making boiler hydrostatic tests are as follows:
1. Close all openings and "gag" (clamp down) all safety valves. Gags should be only hand tight and straight. Do NOT use a wrench; it will bend the valve stem and possibly damage the seat. Remember that valves are easily damaged if lifted by water pressure. Close all connections on the boiler except air cocks, test pressure gauge, and valves of the line through which pressure is to be applied.
2. Reduce the water level in the boiler by opening an air cock, and blow down the boiler until the water level is below the feedwater inlet connection. Clear the blowdown area before blowdown.
3. Connect a hydrostatic pump between the boiler and water service connection. Install all pipe and fittings between the pump and the boiler. Remember, the pipe and fittings must be able to withstand test pressures. Install a hose between the pump and the chosen water service. Ensure the chosen water service supplies ample water pressure to conduct the test.
4. Remove the plug from the feedwater inlet cross by turning it in a counterclockwise direction.
5. Open the boiler casing access doors or plates, so tube ends can be inspected during the test.
6. Install a wedge between the control switch and the pressure-actuating platform. Also, install a stop valve before the control switch to protect the control, so hydrostatic pressure will not actuate or damage the control. The range of the pressure control is usually less than the hydrostatic pressure being applied. Do NOT bend or damage the actuating parts.
7. Fill the boiler with water until water discharges out of the air cock; then close the air cock. Ensure all the air is expelled from the boiler before closing the air cock. Turn on the water service valve. The water temperature should be the same as the surrounding atmosphere. The minimum water temperature must be 70F.
8. Check the boiler steam pressure gauge in-line cock to ensure that it is open. Ensure the butterfly handle is in-line (parallel) with the tubing. 2-6Continue Reading