Sludge precipitated in HP Dosing (TSP) stainer

Hello,

Today we found some kind of slurry sludge in the HP dosing pump stainer.

What can be the issue related to this?

Attached few photos.

COMMENT BY WATER NETWORK ADMIN (In HP Dosing Phosphate especially Tri sodium phosphate is added at the  boiler  drum which is operating at high pressure (so called  HP dosing  system) through  HP dosing  system. If it is  dosed  at feed pipe, it may react with impurities and sludge may be deposited at the feed line.)