A pump lifts fluid

Process diaphragm pumps convey toxic and corrosive liquids on a delivery platform

The conveying or pump technology required for this must exclude any risk to personnel and the environment. It is therefore necessary, for example, that these pumps are hermetically sealed - i.e. leak-proof - and that the pump material is as resistant as possible to corrosion from sulfur compounds and also chlorides. For technical reasons, a low minimum suction flange pressure of the pump (NPSH required) is also very important for this pumped medium in order to keep construction costs low.

The materials and the type of construction are decisive

After it has been separated, the condensate is fed into a connected container (tank), from where it is pumped to the flare and burned. Process diaphragm pumps are very well suited for this task: They have no dynamically acting seals and are therefore hermetically sealed. In addition, pumps with dynamic seals of conventional design are usually made of low-alloy or at most stainless ss316 steels. These materials are susceptible to corrosion and cracking from compounds containing sulfur and hydrogen sulfide, such as those present in the condensate. Pump manufacturers such as Lewa therefore use either duplex, superduplex or nickel-based materials, depending on the composition of the respective pumped medium. These materials are more resistant to corrosion and cracking caused by compounds containing sulfur and hydrogen sulfide. This prevents possible leaks in the long term; this also ensures uninterrupted operation of the oil production.

In addition to the right choice of material, the safe handling of the condensate also depends on the design of the pump. It is therefore of great importance that there are no moving sealing surfaces between the pumped medium and the environment, because these always lead to minimal system-related leakage. The frequently used API-674 constructions do not meet this requirement, however, because the piston and packing come into contact with the fluid and are therefore not hermetically sealed. Although a barrier system on the packing can catch any leaks that may occur, the sand and particle contamination that is often carried along with the pumped medium shortens the service life considerably. In addition, this pump technology is associated with additional costs for installation and maintenance: The system must be regularly serviced and monitored by additional instruments in order to ensure that it functions over the long term.

The process diaphragm pumps from Lewa, on the other hand, comply with the API 675 standard for the process-safe pumping of flammable, toxic, solids-laden or highly viscous fluids. They have no dynamic seals with relative movements between the seal and the sealing surface. As a result, such a system-related leakage of the fluid is excluded.

The spring integrated in the M9 diaphragm pump head also supports the suction stroke of the pump through the return movement of the diaphragm. For this reason, such pumps can suck in liquids with up to 1 bar. In addition, this type of pump has a low minimum suction flange pressure (NPSH required).

In the M9 pump head, a spring-assisted return movement of the diaphragm increases the suction stroke: This means that these pump heads have a particularly advantageous suction behavior (low NPSH value, also known as the holding pressure level): They work cavitation-free at low suction flange pressures. This property is also important from an economic point of view for pumping such media: As a rule, the condensate tanks are on the same level as the pump, and the condensate has a high vapor pressure.

Without the increased suction stroke of the M9 pump heads, the liquid pressure at the suction flange would have to be higher, i.e. the tank would have to be higher than the pump or the construction of the tank itself would have to be changed. But that would be very costly.

Simulations for the reliable construction of the pipeline system

In order to coordinate diaphragm pumps and pipeline systems with one another, it makes sense to simulate possible vibrations in the pipeline due to the pulsating mode of operation of the pump. With the help of these pulsation studies - taking into account the system complexity, the number of cylinders in the pump and the fluid properties - recommendations can be made on pulsation dampers, resonators, orifices and, under certain circumstances, additionally required pipe fastenings.

For example, pipe sizes for pulsation dampers and resonators are calculated for the suction side. This is always done taking into account the reaction of the pump system to the safety valve response pressure, simultaneous operation of several pumps and different speeds.

Lewa is the only pump manufacturer to have verified these calculation programs through tests in practice and on its own test bench and can offer such simulations. This know-how enables the correct dimensioning and positioning of the components. This ensures the smooth running of the system and thus its long-lasting, operationally reliable functionality. Subsequent changes to the construction are also avoided.