Pro tips for repacking a pump
Repacking a pump can seem like a fairly straightforward process, but there are a few subtleties that are often overlooked by novice and experienced pump packers alike. Overlooking these details can make a repacking job harder than it really is, consuming more time and increasing the risk of a poor start-up.
Repacking a pump can be viewed as a four-part process. The process consists of the following steps:
Removal
Inspection
Installation
Start-up
For each step of the repacking process, we present some tips for successfully repacking a pump and obtaining a trouble-free start-up and operation.
Tip #1: Be prepared!
Before commencing a repacking job, it is wise to ensure that all the needed tools and supplies are on-hand. A good idea is to create a repacking kit which contains everything necessary to carry out the repacking. A well-stocked kit contains the following:
Proper sized wrenches for the pump gland nuts
A flashlight and an inspection mirror
Correctly sized packing pullers
A tamping tool to seat the new packing
Correctly sized replacement compression packing
A sharp knife
A ring packing cutter (optional)
A new shaft sleeve (in case the old sleeve is badly worn)
Safety equipment
Tip #2: Use correctly sized packing pullers
Removal of the old packing is best done with the use of correctly sized packing pullers. This ensures that the old packing is completely removed from the stuffing box. If any residual packing is left in the stuffing box, it could interfere with the seating of the new packing.
Tip #3: Don’t overlook inspection!
Sometimes, due to the need to meet tight maintenance schedules, inspection of the pump shaft and stuffing box is overlooked. Inspection is a key part of every repacking job! Only by fully inspecting the pump shaft and stuffing box can one detect abnormal wear and tear – wear and tear that could be a signal of a potential future problem or failure. Performing a thorough inspection when repacking can lead to effective preventive actions – an ounce of prevention is worth a pound of cure!
Tip # 4: Learn the secrets of a good installation
Key points to achieving a good compression packing install:
Choose the right size packing. To determine the correct packing size, measure the diameter (ID) of the pump shaft inside the stuffing box and then measure the diameter of the stuffing box to obtain the OD of the ring. Subtract the ID measurement from the OD measurement and divide by two. The result is the required packing size.
Cut the packing rings, don’t wind! Packing leakage will be affected by the ring “end gaps.” Wrap each ring around a shaft and cut individually. Do not lay packing flat for cutting. Wrap packing in the same direction that the packing was “spooled” and avoid “over-handling” the rings as this can cause the ends to fray.
Always seat each packing ring using a tamping tool. To make a simple tamping tool, cut a piece of PVC pipe to fit around the stem of the valve, drill two holes in one end, and put a piece of wire in each hole. Cut the pipe to the length you require, and then cut it in half lengthwise to seat each ring of packing. Take care to stagger the packing ring joints every 90 degrees.
Tip #5: Learn the secrets of a trouble-free start-up
Achieving a trouble-free start-up should be the objective of every repacking job. Key points to observe include the following:
First, bring the packing gland up to the packing and tighten the gland nuts only finger tight. Start the flush fluid then start the pump. Allow generous leakage for 15 minutes to allow the packing to seat properly in the stuffing box.
If excessive leakage continues, tighten the gland nuts 1 flat at a time. Do not allow heat to build up.
Continue to tighten gland nuts 1 flat every 15 minutes until leakage is controlled. Use caution when tightening gland nuts as too much tightening will cause the compression packing to glaze or burn, shortening its useful life.
Acceptable leakage is a function of shaft size. A good rule of thumb states that you should have leakage of 8 to 10 drops per minute per inch of shaft size.
Following these pro tips can help you streamline the repacking process and achieve a trouble-free start-up every time. At Canada Rubber Group Inc. (CRGI), we are always available to help customers with their compression packing needs. We can supply a wide range of high quality Teadit compression packing styles, including aramid yarn, carbon graphite, ePTFE and PTFE, ramie, and synthetic yarn.
To find out more about the Teadit compression packing styles we can supply, please contact our sales department directly at crg@canadarubbergroup.com.