Description:

One of the largest Petrochemicals Facilities in Alberta, NOVA Chemicals in Joffre, was dealing with high operational costs of their single cartridge seals in Caustic Service. The seals required an API Plan 32 Boiler Feed Water flush at 3.5 gpm into the process, which presented the flush utility costs and in addition diluted the caustic and required costly caustic make‐up and blow down. Overall, these costs were estimated at ~$250,000 Annually.

 

The recommended solution was an Up‐Stream Pumping seal which is essentially a dual un‐pressurized seal which is supported by a simple and inexpensive, atmospheric supply tank, which provides water to the seal's intermediate cavity (the cavity between it inboard and outboard seals).

 

The inboard seal incorporates spiral grooves technology which creates a mini, high pressure, low flow pump, which pumps a small amount of water from its intermediate cavity into the seal chamber, against the seal chamber's process pressure. This pumping action consumes and dilutes the process at a very low rate of 50ml/hr (0.31 gallons per day) as opposed to 3.5 gallons per minute (5,040 gallons per day) with previous, Plan 32 flushed single seal. The pumping action provides a thick and stable fluid film for the inboard seal faces. This stable and thick fluid film minimizes friction and power consumption, it provides a self‐cleaning mechanism for the inboard seal, which prevents caustic solids build up at the seal faces.

 

This translated to a MTBR of 4+ years. Utilizing this Up‐Stream Pumping technology, NOVA was able to save the cost of water and the cost of the caustic make‐up due to the previous seal's process dilution, while maintaining high seal reliability. In addition, using the Up‐Stream Pumping technology, NOVA was able to practically apply a dual seal which acts as a true zero‐emission dual pressurized seal without the associated costs of dual pressurized seal support systems such as Plan 53A/B/C or Plan 54, since the seal does not require a pressurized barrier fluid, given its internal "mini‐pump".