Filters and Strainers

Question 1

Why is differential pressure monitored across filters and demineralizers

Answer 1

The pressure drop across the demineralizer is a function of flow rate. Higher than normal DP indicates flow is too high or clogging due to buildup of corrosion products and suspended solids.

A sudden lowering of DP can be a symptom of channeling

Question 2

Types of strainers and filters

Answer 2

Cartridge filters- perforated metal cylinders with fiber yarn wound around them. Another type uses wafer or disk filters

Precoat filter- septums inside housing, which are coated in medium

Deep Bed filters- large cylindrical tanks, used to filter water. Have 2-4 feet of charcoal or granular anthracite

Metal edged filters- used in lubrication systems, has a series of metal plates or disks. Turning the handle on top moves the plates or disks across each other to remove any collected particles

Y strainer-water flows thru basket and particles are trapped in basket

Question 3

Application and operation of backwash

Answer 3

Flow liquid in the opposite direction, creating a pressure that pushes the debris off of the strainer or filter.

Question 4

Purpose of ion exchangers

Answer 4

Reversible exchange of ions used to remove undesirable ions from a liquid and substitute acceptable ions

When the undesirable ions are minerals such as calcium or magnesium, it is called demineralization.

2 types of demineralizers: deep-bed and powdered resin filters

Deep bed
Adv- large ionic capacity that allows time for orderly shutdown
Disadvantage- large amount of regenerate solutions and channeling

Powdered resin
Adv-waste requirements are lower, more effficient at mechanical filtering
Disadvantage- lower ionic capacity, sloughing