Purpose of a Stuffing Box:
A stuffing box is used to maintain or seal the pressure of fluid during unit operation. The pumping unit moves around the rod to pull whatever you are trying to access — such as oil — to the surface. The stuffing box helps maintain the correct pressure inside the unit during use. It prevents leakage around a piston, rod and other moving parts that work inside a cylinder or other vessel.

Measure a Stuffing Box:
You will want to measure your stuffing box if you are unsure about the exact dimensions. Follow these steps:
Measure the diameter of the shaft.
Measure the stuffing box bore.
Check the depth of the stuffing box.
Calculate the diameter of the flush hole.
Measure the length between the edge of the flush hole and the bottom of the box.
Calculate the distance from the stuffing box to the nearest obstruction.

Main Parts of a Stuffing Box?
The stuffing box comprises several main components, including:
Stuffing box casing
Packing rings
Stuffing box bushing
Packing gland
Lantern ring

Fix a Leaking Stuffing Box:
Your first step should be to tighten the cap nut and backing nut. If this stops the fluid from coming through, you probably don’t need to replace your stuffing box rubbers yet. If the problem keeps recurring, you will want to replace your rubbers rather than continuing to tighten the nuts because you could create scoring damage.

If your stuffing box is dripping a little bit while the system is running, that means it’s working correctly. You need some lubrication to prevent the shaft from overheating. However, if you are getting a more consistent fluid flow, it is time to replace your stuffing box rubbers.

How to Change Stuffing Box Rubbers and Address Stuffing Box Leaks
If you need to service your stuffing box, start by measuring the inside diameter of the packing nut. Before you can repack the stuffing box rubbers, you’ll need to remove the old packing with a hooked tool. Once that is done, take your packing, ensure you have the correct type of packing and the proper size, and get ready to insert it into the shaft.

Then, use a blunt tool to get the new packing into the stuffing box. Thread the nut on to push the packing into the shaft. You can use a mirror to ensure you are getting the packing in sufficiently. Once your rubber is in the shaft, tighten the nuts to finish the replacement. After completing the process, run the pump to make sure you have resolved your leaking problem. Assuming you get only the small drip, your stuffing box should be functioning optimally.

How Much Should a Stuffing Box Drip

A stuffing box should be watertight when you turn it. However, there must be a drip when you move it. Two to three drops per minute is the ideal stuffing box drip rate.