For transportation and pumping of acids and to handle corrosive. As well as abrasive slurry & sludge transfers, whose pH value is less than seven. Unique designed pumps called Acid Pumps are generally used. In particular, these pumps are made and designed in such a way that they are resistive to the corrosive nature of the acid. Acid pumps are perfectly sealed without any leak from its glands.
A unique model of acid pumps
One the famous type is the magnetic type acid pump. Its working principle is similar to a normal centrifugal pump. Only the material of construction is varied. It is made of materials like polypropylene thermoplastic, fibreglass reinforced polyesters or DuPont tefzel linings. The lining in the sense is that a polypropylene layer is coated on the inner side of the pump that is exposed to the acid. A pump with polypropylene coating can handle sulphuric acid with concentration 93-98% for a lifetime without maintenance. The wetted parts of an acid pump are the impeller, inner casing, shaft and the bearing box. These components are made with Teflon PTFE (polytetrafluoroethylene), ETFE, PFA and packing with carbon graphite or glass filled Teflon is used.
The best model of acid pump would a vapour proof design because almost all acids produce fumes. The harmful fumes escape through gland and sealant even they are protected with non-corrosive fitting. This happens because of the long run the pump will make some of the acids get heated at a point in the casing. The liquid acids convert into the fume and so the pressure built-up more than the designed. The fumes puncture through the gland and leaks into the surrounding.
Application of mechanical seal in acid pumps:
A typical type of mechanical seal should be used for an acid pump. If the pump is shaft driven. After the stuffing box, the gap between the casing lock and shaft will make the acid leak. It flows as film and reach out drop by drop near the sleeve. Nitrogen Gas barrier is used as mech seal in controlled or close rooms. Instead, if the pump is installed or used in open atmosphere it sufficient that a mechanical seal with double stuff box could provide enough leaks proof.
Acid pumps for safety operations:
For safety concern, an industry process or a person who will be transporting acid should prefer acid pump only for the job. In case of handling small quantity of acid materials that are stored in drums or barrels. A portable thermoplastic design acid pump is sufficient to complete the job. For experimental purposes a pump with little maintenance along with pressure control should be selected which is manufactured based on centrifugal pump design.
Features of acid pumps:
One of the important features of acid pump is that
- It should have very low pulsation
- It must be able to handle the solid liquid mixture.
- It should not coagulate the salts formed in the spent acid.
In small-scale process, hydrochloric acid vapours produced by adding liquid sulfuric acid to liquid hydrochloric acid. This operation is carried in a treatment vessel. The adding procedure is done using acid pump. Mostly operated by the magnetic assembly. Impeller of the pump is fitted with fluoroplastic built it with a magnet. The impeller and casing is totally sealed. Another magnet on outside of the pump rotates with help of a motor. The impeller rotates due to the magnetic effect caused due to pole attraction of a magnet present inside it. These types of acid pumps are called as zero emission pumps.
Benefits of acid pumps:
Can handle and pump concentrated inorganic acids like sulphuric acid, nitric acid (above 50%), phosphoric acid and organic acids in large quantities. It is beneficial to handling corrosive liquids in efficient way under continuous operations than other type of pumps. This capability ranks it and makes it stand front in the buyer selection line.
Monoblock centrifugal pumps mostly used to handle acid hazards and harmful chemicals during transportations. These pumps frequently suffers break down due to high wear and tear and occurrence of erosion and corrosion due fluids flow. By monitoring, the working condition simulation of the parameters gives out the approximate breakdown period of the pump. One of the best methods is using neural network algorithm to perform the period fault in the mechanical and transportation system. Every component of the monoblock centrifugal pump has definite signal value that gives information about its conditions and how they alter the characteristics of pumping. Fuzzy logics use such vibration signals and diagnosis by altering various operation parameters. These signals can be measured by electronic transducers.
Procedure to perform monoblock centrifugal pump fault diagnosis:
- Pump is fitted with sensors like seismic or piezoelectric transducers.
- Data acquirement and signal monitoring
- Feature values extraction-using wavelets
- Classification using support vector machine algorithm
- Generating and analysis of results.
This procedure helps to improve the running lifetime of the selected acid pump. All important faults condition namely cavitation, bearing and impeller can predicted.