When pressure matters DCM Group releases the burden

The machine shop of the DCM Group has been manufacturing components and products for pressure and vacuum relief on storage tanks as well as for transferring and measuring a wide variety of fluids such as fuels, acids and bases, cement, bitumen, paints, distillates, oil, wine, milk, juices, and water for nearly 50 years.

Lecore, a company within the DCM Group and of which the machine shop forms part of, was founded in 1968 for the purpose of manufacturing and developing a South African product range of pressure vacuum breather valves, flame arrestors, emergency vent valves and dip hatches.

When the founder of Lecore decided to retire 20 years ago Darryl Massey, CEO of the DCM Group, jumped at the opportunity to acquire the business of Lecore as he saw the potential and the synergies with his own company. Massey had started his own company – the DCM Group – 10 years prior and was mainly operating in the petrochemical space supplying the multinationals and others with instrumentation.

Workshop Manager Peter Steytler and Darryl Massey, CEO of the DCM Group

“The fit was perfect for us as we had already built up relationships in the industry and Lecore was manufacturing and supplying products for the same industry that we were operating in but not exclusively to the petrochemical industry,” said Massey.

“What was also attractive to us was that Lecore were designing, manufacturing and supplying some unique and niche products that are essential for pressure and vacuum relief of storage tank equipment. No matter what fluid is stored under a pressurised environment there is the chance of volatility and there needs to be a relief mechanism in place,” added Massey.

“Accurately specified and appropriately maintained pressure relief valves (PRVs) and emergency pressure vents (EPVs) are critical to protect plant personnel and equipment against unexpected overpressure events. Effective lifecycle management of PRVs and EPVs can significantly improve operational efficiency ensuring safety, reducing maintenance costs, and increasing plant reliability,” explains Massey.

“The term pressure relief valve is used as a generic all-encompassing term including relief, safety and safety relief valves. However, there are specific definitions associated with the opening action of specific styles of valves. It is important that the correct style of valve be applied to the specific process needs. This is especially significant in the case of liquids and multi-phase applications,” continued Massey.

Product on the shelf waiting for final assembly

“The most important appurtenances on any pressurised system are the pressure relief devices provided for overpressure protection of that system. They may never be called upon to operate, but when needed, must operate in a very specific manner. They are the last line of defence in an over-pressure event and protect employees and equipment.”

“Because of their importance to safety, PRVs are a diverse range of solutions found in several facets of a single operation, from steam boilers to low-pressure tanks, that can quickly add up in maintenance costs.”

“PRVs are mostly self-operated mechanical equipment that do not depend on any control system or electrical instrumented system to function. Therefore, it is not possible to monitor relief event history or access online diagnostic information. Preventive maintenance with pre-scheduled inspection and testing is mandated to ensure functionality on demand.”

Design and specification
“PRVs are designed based on the general construction rules and operating conditions of the vessel or system which they protect. For instance, in most cases the PRV is set to open (within a defined tolerance) at the maximum allowable working pressure (MAWP) of the vessel. In addition, the PRV must flow its fully rated capacity before the pressure reaches the allowable accumulation of the vessel and must re-close (blow-down) before the pressure degrades below the normal operating pressure of the system.”

A GSM 2473 CNC bed mill machining center with a coolant through spindle was supplied by Craft Machine Tools three years ago

“In certain scenarios, such as multiple PRV installations and fire sizing, valves can be set higher than MAWP and may also be sized for full flow above the maximum accumulation.”

“Some of the common dimensional characteristics of a PRV include the size and pressure rating of the inlet and outlet as well as the size of the nozzle bore. For some styles of valves, these bore sizes carry a letter designation symbolising minimum bore size adhering to industry standards. The combination of the area of the valve bore plus the dimensional lift of the valve when open, determines the amount of process fluid the valve will flow.”

“These standards may also standardise center-to-face dimensions, which allow end users to interchange PRVs from different manufacturers. Although overall height is not normally addressed by standards or recommended practices, it may be an important consideration in piping design and in replacement valve applications.”

“PRVs are designed, sized, selected and manufactured to meet requirements of specific codes and standards and are of special interest to the many jurisdictions charged with enforcement of local laws and regulations.”

Lecore Series EPV Emergency Pressure Vents for tanks
The Lecore Series EPV emergency pressure vents are designed to provide emergency relief capacity beyond that furnished by the operating vent on the tanks. The Series EPV vents do not provide vacuum relief. Vacuum relief must be supplied by independent operating vents. Under normal operating conditions, the vent pallet assembly is closed providing an effective vapour seal. In the event of an emergency (fire involvement of the tank), the pallet lifts in response to the increased pressure in the tank’s vapour space. Vapour is expelled, thereby protecting the tank from dangerous over-pressurisation. Pallet assembly automatically closes and reseals when the pressure is reduced.”

Components that have been machined

“The pressure and vacuum breather valve minimises losses from storage tanks during operations, whilst preventing internal pressure and vacuum conditions from exceeding the tanks limits. Hence both product and vessel are protected, as well as the tank environmental conditions.”

The Lecore machine shop, which is situated in Briardene, Durban and run by Peter Steytler, is a relatively small machine shop. At this stage the company only has two CNC machines on the floor and three conventional lathes and one drill. The staff compliment is only 11.

“We have only just purchased our second CNC machine – a Headman T35A CNC turning center from MJH Machine Tools. The machine is a relatively small machine but it suits our current needs. It has a maximum swing diameter over the bed of 350mm, a maximum swing diameter over the slide of 160mm, a maximum length of work-piece of 250mm, a spindle bore of 45mm with a 5kW spindle and a maximum spindle speed of 5 000rpm. The bar capacity is 45mm,” said Steytler.

“This is also our first CNC lathe as previously we could cope with our conventional lathes and primarily our work revolves around milling operations. For this work we purchased a GSM 2473 CNC bed mill machining center with a coolant through spindle from Craft Machine Tools three years ago. The machine has a XYZ travel of 1 520mm x 700mm x 700mm, a table size of 610mm x 1 854mm and a spindle speed of 50rpm to 6 000rpm.”

Components are made of aluminium, brass and stainless steel

“On the Headman we are mainly machining rods, pins and guide tubes. We are very self sufficient on all of our machining requirements and as we are an in house machine shop it is not necessary to think production runs. The key is to clearly define your business, have a single purpose, and not try to be everything to everyone. Sometimes you will have to say no and walk away from an opportunity. By keeping it simple you can focus all your efforts into being the best at what you do. I believe that it is always better to be the very best at one thing, rather than mediocre at a dozen,” said Steytler.

“All materials are outsourced of course, as are our bodies, which are aluminium castings. The various materials used are cast iron, stainless steel and brass and aluminium for certain components. 316 stainless is used on all the working components of our products. Certain components have to be laser cut so we outsource this as well.”

“Besides the emergency pressure vents we also manufacture vapour recovery units and to date we have installed more than 300 units worldwide.”

“The Lecore flame arrestor is designed specifically to meet the requirements of the petro-chemical, oil and chemical industries to prevent propagation of an external flame into the storage tank vapor space.”

The DCM Group have only have just purchased their second CNC machine – a Headman T35A CNC turning center from MJH Machine Tools

“Another product is the DCM lockable gauge hatches. A dip hatch’s main function is to allow easy access to storage tanks while controlling vapour losses. Lecore dip hatches are supplied with “O” ring seats in nitrile rubber for easy maintenance.”

“Then there are the slot dipping devices. These devices have been designed to provide convenient and safe methods for dipping and sampling of storage tanks containing volatile and hazardous products.”

“Another facet of the machine shop is to refurbish existing products. We had an interesting one that came in recently. Sasol had been using one of our valves for 30 years and it was still in very good working condition. Although some of the products that we manufacture and supply could be regarded as safety critical products they do not have to hold tight tolerances like certain industries.”

“However, we do have a calibration unit and all products are tested before we send them out.”

“Currently we have close to 3 000 units of our devices installed on storage tank equipment, both here in South Africa and internationally. The downside is that because they last so long it will take years before a replacement takes place.”

“Our products are very unique in more ways than one. Worldwide very few companies manufacture similar products.”

For further details contact DCM Group on TEL 031 312 6258 or visit www.lecore.co.za or www.dcm.co.za