quote:Originally posted by paulu:
To maintain phosphate ester properly you need to the acid numbers by fluid conditioning (Selexsorb GT is recommended for this), water removal and particle filtration.Ion exchange may help with the acid numbers but it may cause water contamination as a by product thereby causing more problems. As a filtration person who works with many people in the power industry, I have seen many such complaints. I would recommend that you speak with the people at Supresta to discuss your situation. Carlos Martinez or Paul Hartsuch may be good people to start with.
Paul
Supresta is in a unique position, aren't they? They have the majority market share in the EHC market, supply an acid scavenging technology and also provide free fluid analysis. This appears like a high-value service offering to customers.
Until one looks a little deeper.
The selexsorb data sheet warns against using selexsorb on “older fluids”. What exactly is an older fluid? Selexsorb can have several negative consequences on the operation of the EHC system and the quality of the fluid including air release properties, foaming issues and gel which is referred by end-users as Vaseline, fish-eyes or black goup. This is due to the reaction of Y-Zeolite with phosphate ester. An ingredient of Y-zeolite is sodium silicate. It is possible for Na to leach from the filters into the phosphate ester to react. The presence of Na in phosphate esters forms metal soaps and deposits on servo-valves. This causes unit trips. Elevated Na and other dissolved metals causes the acid number to increase at a faster rate and Supresta recommends more frequent Selexsorb filter changes. Eventually, this results in escalating acid numbers and the need for a bleed & feed or dump & recharge. Not entirely inconvenient for Supresta.
Selexsorb has a wide particle size distribution. It's zeolitic nucleation center is less than 0.1 microns. Prolonged use of selexsorb may cause a high distribution of extremely small particles (smaller than mechanical filters can remove) which can cause valve silting.
Now look at their fluid analysis program. They are the only lab that I’m aware of that does not provide spectrochemical analysis. Even the cheapest analytical package includes spectro. The EPRI EHC Maintenance Guide recommends running metals every 6-months to identify by-products from acid scavenging medias. Why does Supresta not report metals? Could it be because of the possible increases of Na in fluids that use selexsorb?
One thing is certain...just because a fluid supplier provides free analysis and recommends acid scavenging media, doesn't necessarily mean that these services are in the best interest of the customer.