Mechanical Seal Protection In Non Operating Pumps

Mechanical Seal Protection In Non-Operating Pumps

Around 20 to 30% of mechanical seal failure occurs in the process industries are due to the improper storage of mechanical seals in non-operating pumps.

It is always essential for mechanical engineers in the maintenance field to ensure the protection of mechanical seals in non-operating pumps.

When a non-operating pump has come into the service during some emergency condition. During that time the seal failure will happen may lead to pump failure and in some cases, it may lead to a plant shut down.

we will the various recommendations / general guidelines for mechanical seal protection.

1. Storage

It is always recommended to remove the mechanical seal from the pump if it is stored in the storage room or in the field. In most of the plant conditions, both internal as well as external contaminants, such as airborne dust, in some case rust in the stuffing box can accumulate in the critical sealing areas. This will cause leakage or damage to the seal during the pump start up time.

It is good engineering practice; the seal should be labeled to identify the materials of construction, then packaged and stored in an air-conditioned room. This is to avoid the secondary seal (o-rings) to lose its elasticity property.

2. Intermediate Operating Pumps

Intermediate operating pumps refers to the pumps only used during the starting/shutdown times of plant operation.

Also applicable for the pumps which are operating only for the particular time it may per occur 3 to 6 months of an interval. Emergency or Autostart pumps are not to be considered as Intermediate Operating Pumps

The procedure as follows

1. Make sure all the pumping fluids are drain properly. By open the pump casing drains.
2. Then open the mechanical seal drain plug and buffer or barrier fluid drain valve (if applicable). After ensuring proper drainage of pumping fluid and barrier/buffer fluid.
3. Clean seal chamber with a solvent compatible with the seal materials to remove all possible residues and drain from the pump and seal.
4. Rotate shaft by hand during this process, and make sure the pump rotates smoothly.
5. Plug all seal ports with metal plugs (As per API 682, metal plugs prefer than the plastic plugs.
6. Mask the opening between the shaft or seal sleeve and the gland to protect the seal from environmental contamination

3. Pumps in Erection Phase

The below points are only applicable to the pumps that are erected and prepared for commissioning. If plant commissioning is delayed or plant commission is expected after 3 months. The below way is used to protect the mechanical seals.

1. First, remove seal environmental controls.
2. Plug all seal ports.
3. Mask the opening between the shaft or seal sleeve and the gland to protect the seal from environmental contamination.
4. Tag the equipment with the date of storage. (It is for periodic check-up)

4. Restarting equipment

1. Check with the seal manufacturer to assure the date of storage in conjunction with the materials of construction (mostly o-ring) does not exceed the shelf life. If shelf life will exceed then it shall be renewed.
2. Remove masking from the opening between the shaft or seal sleeve and the gland.
3. Remove all plugs (except drain plug) from seal ports and flush with a solvent. Make sure the solvent is compatible with the seal materials to remove all possible residues.
4. Rotate shaft by hand during this process and ensure free rotation of the shaft.
5. Drain the fluid from the pump casing and external flushing lines. To prevent dust or rust enter into the seal.
6. Reconnect seal environmental controls and/or plug seal ports.
7. Open suction and crack open discharge valves.
8. Vent the seal chamber to permit the seal to become surrounded by liquid.
9. Start the pump, using the checklist/procedure of Appendix 1 of this text.

If the seal has previously been in operation or has been in contact with fluids, it should be returned to the manufacturer for inspection and/or repair.