The potential danger and volatility of certain fluids make safety a primary concern within the chemical industry. Diaphragm pump technology offers many benefits in such applications and the latest technology's design ensures efficiency and high performance, as well as virtually leak-free operation.
Image 1. This type of metering pump comprises diaphragm and plunger pumps, with drives to accommodate single or multi-stream applications using horizontal or vertical configurations. (Courtesy of SPX)The chemical industry faces many challenges due to the nature of the fluids processed. Fluids may be abrasive, hazardous, toxic or volatile when they mix with other compounds such as water. These chemicals must be handled carefully and any leaks or ingress of moisture involving substances such as Triethylaluminium (TEAL) can cause serious health and safety risks.
Slurries or suspensions containing particulates can be abrasive and have detrimental effects on rotating parts of pumps and their seals.
In addition to concerns about damage creating leakages, machinery may require increased maintenance and greater system downtime with such fluids. Special materials and sophisticated seal systems can be used to improve pump performances, but keeping the liquid separate from the pump internals may offer a more secure, efficient and reliable solution.
Examining the Pumps
When using a hydraulic diaphragm pump head, the diaphragm separates and protects the pump's moving parts from the pumped liquid. Hydraulic fluid pushes the diaphragm backward and forward and, as it moves backward, it increases the volume inside the pump chamber. This creates suction that opens an inlet valve and allows fluid into the chamber. As it pushes forward again, the chamber volume reduces, opening the outlet valve and pushing the fluid out again. The lack of spinning parts carries benefits that include preventing leaks that may be harmful to personnel or the environment and providing quiet, energy-efficient operation.
Compared with a diaphragm pump, plunger pump technology can seem appealing because of its simple maintenance, ease of use and lower initial cost outlay. Operating costs associated with plunger pump technology, however, rise considerably with age. Diaphragm technology in many applications may offer significant savings in total ownership cost throughout a pump's lifetime while providing improved safety and reliability in critical chemical installations.
Once a diaphragm pump is set to a given flow rate and pressure, operation is simple with no further adjustments required. Fewer parts are exposed to the pumped fluid, leading to overall increased reliability and uptime that may further negate the need for a duty/standby configuration depending on how critical the process is. The benefits these pumps offer can increase with the latest developments, including double-acting, double-diaphragm technology and triple-diaphragm head configurations.
The latest diaphragm pump designs can increase pumping efficiency and reduce maintenance in several ways.
Reciprocating Diaphragm Pump
Reciprocating diaphragm pump technology offers the potential to maximize process uptime. The technology offers reduced wear compared with pumps with more internal parts in contact with fluids, particularly if those fluids are abrasive. Using a double diaphragm offers increased protection against leaks and produces a sealless design that reduces maintenance needs.
Pump configurations that use a double-acting head where the displacer suction and discharge stroke operate simultaneously, effectively doubling the pumping capacity, are also available. This means the pump offers the reliable performance of proven diaphragm pump head technology with the capacity of equivalent duplex pumps. Using a single gear, the double-acting pump heads further reduce maintenance time and cost compared with a duplex system. It also creates a more compact solution with reduced footprint and weight ideal for achieving required pumping duty where space comes at a premium.
Diaphragm Process Pumps
Modern diaphragm process pumps offer additional benefits besides the safe and reliable operation associated with using diaphragm technology. Models such as one manufacturer's triple diaphragm pump use pump heads arranged in three dimensions. The design reduces the number of crankshaft bearings from six to two. This simplified form increases reliability and reduces maintenance overheads. These process pumps can also be manufactured using the double-acting head design to further increase flow transfer capacity.
Digital Communications
Diaphragm pumps are available with all modern digital communication protocols for easy integration into wider plant supervisory control and data acquisition (SCADA) systems. Pump controls are designed to maximize efficiency and improve quality. The pumps' accuracy optimizes the use of raw materials that can further reduce production costs. Pumps are available with ATEX certification for use in hazardous areas up to Zone 1 IIC T4 (Zone 22 also available), Pressure Equipment Directive (PED) certification as required, CE and American Petroleum Institute (API) standards.
Chemical Applications
Diaphragm pumps have been proven in a variety of applications such as the pumping of caustics, ammonia, methanol, sodium cyanide and all types of acids including sulphuric, hydrochloric or hydrofluoric, and hydrazine. One major chemical manufacturer in the Middle East used the technology for the safe pumping of TEAL. This particular chemical combusts on contact with moisture, so pump designs were adapted to incorporate nitrogen seals to prevent leakage paths from being exposed to air.
Diaphragm pumps can operate under high pressure and high-flow transfer conditions, and they can handle a wide range of temperatures. Gear sizes can be combined to achieve required flow rate and pressure parameters. Pumps can also be constructed from various materials to handle different fluid properties, making them an adaptable solution. Various manufacturers offer configurable products to meet specific installation needs, as well as the capability to provide complete pump packages in a framework with all pipework, valves, controls and instrumentation. This gives users a fully tested solution that requires little on-site work and, with the supplier taking total ownership for the overall package, greater peace of mind for a smooth-running project.
Conclusion
The latest developments in diaphragm pump technology combine safety and accuracy with pump configurations that can increase capacity and reduce maintenance, offering an even faster return on investment. These pumps can safely handle a wide variety of harsh, dangerous chemicals including slurries and high-temperature liquids. The pumps' accuracy optimizes the use of raw materials and increases efficiency in high-flow, high-pressure applications.
Steve Digby is the commercial manager at the SPX Brixworth plant in the UK. He is responsible for all commercial activity from this facility. Digby also manages the UK external sales team that works with customers across SPX Bran+Luebbe, Johnson Pump and Plenty Pump brands.