Explosion Hazards of Explosives due to Pumps and Pumping during Manufacture of Explosives

 

No explosive is safe. In the scale of measurement, one type may be safer than the other types. But hazards and explosions move side by side during manufacture, storage, transportation, and uses of explosives for rock blasting. Out of the different factors that incite fire, and explosions are the pumps and the pumping systems used for explosives.

The explosives commonly used for rock blasting are emulsion, watergel, slurry, ANFO, and Heavy ANFO. All of these are equally unsafe because all of these pose explosion hazards if these are not handled properly.

There have been many incidents where pumping of in-process and finished materials are required in explosives manufacturing operations. Improper and non-diligent pumping give rise to incidents of explosions resulting in losses of life. This is partly because the processes of pumping are thought to be “safe” and therefore (a) more people can be exposed in a single building because the risk of explosion is much smaller than with conventional explosives and (b) less process safety control is necessary. Even those explosions that have not resulted in major losses have very often had fatal or at least serious consequences. This perception of pumping explosives being “safe” is not just incorrect – it is also extremely dangerous for those involved in working with them.

The pumping process is at the heart of factory cartridging and field loading operations, and experience has shown that the degree of hazard depends on the type of pumping system chosen, of which there is a considerable variety. Each pumping application can be reviewed and an appropriate safety system can be designed with the information presented in this document used as a guide to help in the process. To the extent that these guidelines are used, their strengths, weaknesses, and errors will be uncovered. They are not intended to stifle innovation in the selection of suitable pumps and their safe operation.

The following is a list of those explosive properties that have been considered to be relevant to the hazard of pumping. It is intended as a checklist only for engineers designing pumping systems to lessen the risk of overlooking one or more explosive properties and conditions that may be important in a particular system.

1. Rheological properties including pseudo-plasticity or thixotropy.
2. Minimum ignition energy
3. Minimum burning pressure
4. Critical diameter confined
5. Impact and friction sensitivity under confinement and pressure
6. Thermal stability under pressure
7. Minimum practical temperature for pumping
8. Presence or absence of suspended solids
9. Nature of suspended solids such as brittle, friable, explosive, abrasive.
10. Water content
11. Presence or absence of sensitizers, such as self sensitizer like TNT, and not-self-explosive like perchlorates.
12. Nature of continuous phases, such as water or oil.
13. Thermal conductivity
14. Presence or absence of gas bubbles
15. Gas encapsulated or not
16. The pressure of a gas in encapsulation
17. Chemical nature of capsules (micro balloons)
18. Presence or absence of flammable volatiles
19. Degree of homogeneity (droplet or particle size)

 Three important conditions of use related to hazards are:

1. Rate of pressurization or pressure differential

Pumping can go from a vacuum to high pressure in a short time. Conversely, a vacuum pump can cause bubbles quickly.

2.               2.Cavitation through starvation of feed.

3. Foreign objects – assume they will occur.

We leave the chapter here, and take this as a learning step to get answers from the learned group of explosive manufacturers and users to know which type of pump is perceived as the best type of explosive pumping?

       Diaphragm Pumps

       Peristaltic Pumps

       Progressive Cavity or Helical Screw Pumps

       Gear Pumps

       Piston Pumps

       Love Pumps or Three Leaf Clover Pumps

       Centrifugal Pumps

       Positive Displacement Pumps

       Any Other