- A boiler designed to operate at 125 psi. is now operating at 15 psi. what changes will be made to the safety valve? SPO 6-7-8
If the change is permanent, a safety valve with a larger disk and lower pressure rating will need to be installed.
- On an Ashton type safety valve, a screw type adjustment is labeled “0” and “S”, what do these letters stand for and what adjustments can you make?
O pen & S hut. I am not certified to make adjustments
- On an Ashton type safety valve, a screw type adjustment is labeled “0” and “S”, what do these letters stand for and what adjustments can you make?
A surface blowoff is used to remove contaminants from the surface of the boiler water. The take-off is located in the top 3 to 4 inches of boiler water. It controls the total dissolved solids. (TDS)
- What is a continuous blowdown system, and where is it installed? SPO 6-7-8 LPB 2-3 BOW 2-3-4
Based on water analysis, the surface blowdown is metered for continuous flow. The take-off is located just below the NOWL (normal operating water level)in the steam and water drum (Mud).
- How should a continuous blowdown be piped as it leaves the boiler. Why? SPO 6-7-8 BOW 2-3-4
It will be piped through a heat exchanger or flash tank to recover the heat, then on to the blow-down tank.
- When is the best time to blow down a boiler? How long do you bottom blow the boiler? What important safety procedure is observed when using a bottom blowdown? SPO 7-8 LPB 2-3 BOW 2-3
During light loads because more of the sludge has settled to the bottom.
For about 10 seconds, depending on the type of the boiler,
Once you have opened the valve, DO NOT take your hand off of it until you have closed it!
- Where is the bottom blowdown pipe connected on an HRT boiler? SPO 6-7-8
The underside of the shell at the rear end of the boiler.
- What type valves are used in the bottom blowdown and in what order are they placed? How should you blowdown a boiler using those valves? What size piping is used in the blowdown line? SPO 6-7-8 LPB 2-3 BOW 2-3-4
Two slow opening or one quick and one Slow operating valve, The quick operating valve is installed next to the boiler and opened first and closed last.
The piping must be at least 1” and not greater than 2-1/2” In. in diameter. ¾” is allowed on boilers of less than 100 sf. Heating surface.
- What is a slow opening valve? SPO 6-7-8 BOW 2*4
It is a screw type valve that requires at least 5 full turns from closed to open position.
- What is a plug valve and why is it used on blowdown lines? SPO 6-7-8 BOW 2-3-4
A plug valve has a circular tapered plug ground to fit in the valve body. There is a hole through the plug that aligns with the hole in the valve body when open. When turned closed, the holes are out of line. It’s shearing action cuts through scale and it will not fail open.
- How is a blowdown tank piped, how does it work and why isn’t any blowdown connected directly to the sewer? SPO 6-7-8 LPB 2-3 BOW 2-3-4
The blow down enters the tank above the water line maintained in the tank against a splash guard. There is a vent in the top of the tank to prevent backpressure. The tank discharge line is also vented to prevent siphoning. The tank has a drain valve and a manhole for cleaning.
The discharge line is opposite the inlet, resulting in the cooler water being discharged first.
- What is a non-return valve? Where is it located? Why does it have a drain? SPO 6-7-8 LPB 3 BOW 2-3-4
It is an automatic stop check valve to prevent a back-flow of steam when the boiler pressure falls below that of the header.
It is as close to the boiler as possible, snd between the boiler and the header valve.
It has a drain to remove condensate.
- Draw three boilers in battery showing the header with valve types and locations in the piping.
picture
- What is a soot blower? How does it work? Name two types. SPO 6-7-8 BOW 3-4
It is a device using jets of steam, compressed air or both to remove the ash and slag from the fire side of the tubes.
It is a revolving blow-arm equipped with properly spaced nozzles.
The arm is operated by a chain and a wheel while the boiler is in service.
Two types are automatic and manual.
- How do you operate a manual soot blower? What happens if the condensate isn’t drained from the soot blower steam supply prior to using the soot blower? SPO 6-7-8
Always operate a soot blower with the boiler on high fire. Slowly opening the main steam supply to the soot-blower. Open drains on the main steam supply until the piping is good and hot. Close the drains and start a slow rotation of the hand wheel, which will open the steam to the soot-blower.
Rotate the element 360 degrees without stopping and make sure the steam to the soot-blower stops. Close the steam supply and open the drain valve.
Condensation in the steam supply will warp and break the elements, and when it is discharged into the fire box it will form sulfuric acid, it will pack the soot onto the tubes and will cut into the tubes.
- How can you tell if the soot blowing had any effect on the boiler? SPO 6-7-8
You will notice a decrease in stack temperature and draft.
- Describe a globe valve and where is it used most often? How do you pipe a globe valve? Name 6 places for a bypass. SPO 6-7-8 BOW 2-3-
It consists of a plug or a disk that is forced into a tapered hole called as seat. It ca be plugged or damaged easily and has more resistance to flow. It is used most for throttling such as in a bypass. The supply comes in under the disk.
Bypasses are common around strainers, pumps, PRV’s, traps, header valves, check valves and control valves
- Describe a gate valve and where is it used most often. SPO 6-7-8 LPB 3 BOW 2-3-4
A valve with a wedged shaped gate which is raised or lowered into a passageway. The wedge shape tightens against the sides of the slot when closed, It offers little resistance when open and should not be used to throttle. It is used most for isolating devices for repair.
- What are rising stem valves and non-rising stem valves? SPO 6-7-8 BOW 2-3-4
A rising stem valve has a stem that rises as the valve opens.
A non-rising stem valve has a stem that stays stationary.
- Explain the letters SWP and WOG found on the side of a valve. BOW 2-3-4
SWP – is the MAXIMUM STEAM WORKING PRESSURE rating.
WOG – is the maximum WATER< OIL or GAS pressure the valve may be used
