Sealing problems encountered when using diaphragm pumps to pump bromine

Bromine has high permeability. PTFE diaphragms are used to pump concentrated sulfuric acid, and they work fine even with nitric acid; however, they are not suitable for pumping bromine. Initially, it was planned to use integrated diaphragms that had no leakage points. Later, fluororubber diaphragms were found to be compatible with bromine, so we decided to give them a try

I’ve attached pictures of the pressure plate and diaphragm; the black one is fluororubber, while the white one is PTFE diaphragm

We analyzed the possible reasons. PTFE material has poor elasticity and low compressibility, which results in a poor fit with the sealing surface; this leads to problems with materials that are highly permeable to bromine or highly corrosive. In addition, there is a planar seal between the pressure plate and the diaphragm. Fluororubber is soft and elastic, which ensures that both the first and second seals function properly. We are waiting for the results of the tests conducted by the customer. Someone suggested placing an O-ring on the flat surface within the groove of the pressure plate; however, the compressible height of this O-ring cannot be too large, otherwise it will affect the fit between the pressure plate and the diaphragm, impact the friction force, and cause the pressure plate to loosen. It is also necessary to ensure the effectiveness of the second seal

The customer has replaced the diaphragm pump with one that uses fluororubber diaphragms, and is now waiting to see the results of its use. PTFE is relatively hard, and both sealing surfaces are made of hard materials; please refer to the sealing diagram. As long as fluororubber can withstand bromine (relevant information indicates that it is compatible, but it’s still necessary to test this), the sealing performance will be better than that of Teflon diaphragms. Fluororubber has good elasticity, recovers well under pressure, and fits well with the sealing surfaces. PTFE diaphragms, on the other hand, tend to develop gaps

The pump with a fluororubber diaphragm has been in use for 10 days now. The outlet of the pump is at a height of 10 meters; the pump has stopped working, but there is no pressure release at the outlet. The interior of the pump has to withstand a pressure of 3 kilograms. It remains submerged in bromine, and further observation is needed. After one month of use, we will have a better idea of the diaphragm’s compatibility and whether there is any leakage into the pneumatic motor

Not bad. Please continue to provide updates; thank you, the original poster.

The diaphragm pump that used a fluororubber diaphragm did not last long – less than 20 days – before the diaphragm broke. However, the rubber remained soft and elastic; it’s possible that bromine has a corrosive effect on fluororubber. We have now opted for the second method: we created grooves for seals on the pressure plate and installed a fluororubber O-ring. The diaphragm still consists of PTFE. It has been in use for 18 days now, and we will see how it performs over the course of a month

The diaphragm pump that used a fluororubber diaphragm did not last long – less than 20 days – before the diaphragm broke. However, the rubber remained soft and elastic; it’s possible that bromine has a corrosive effect on fluororubber. We have now opted for the second method: we created grooves for seals on the pressure plate and installed a fluororubber O-ring. The diaphragm still consists of PTFE. It has been in use for 18 days now, and we will see how it performs over the course of a month