Back to Air Compressors
Return to Main Equipment Page
|D-R 5C-VIP2 Compressor (Pic1)
||D-R 5C-VIP2 Compressor (Pic2)
||D-R 5C-VIP2 Compressor (Pic3)
||D-R 5C-VIP2 Compressor (Pic4)|
|D-R 5C-VIP2 Compressor (Pic5)
||D-R 5C-VIP2 Compressor (Pic6)
||D-R 5C-VIP2 Compressor (Pic7)
||D-R 5C-VIP2 Compressor (Pic8)|
|D-R 5C-VIP2 Compressor (Pic9)||D-R 5C-VIP2 Compressor (Pic10)|
Qty 1: Dresser-Rand Model: 5C-VIP2 Compressor
Cylinder Size: 12.50"
Number of Cylinders: 2
Nominal rated: 1200 HP
Max. Rod Load: 33,000 LB
Rated RPM: 1,500
Rated Discharge: 450 PSIG
Max. Pressure: 495 PSIG
Hydro Test: 743 PSIG
Max. Allow Discharge Gas Temp: 350 F
The Recip - a State of the Art Compressor
High Speed Compressors offer opportunities for clients to lower total installed cost by having a smaller compressor in physical size, but equal the flow (MMSCFD) of larger, slower speed reciprocating compressors. While lower total installed cost cannot be disputed with high-speed compressors, there is an overriding concern of lifetime costs and maintenance due to the high rotative speed. It is clear that development of a true high speed, reliable, reciprocating compressor is needed to provide consumers with the opportunity to compress gas at lower cost. This paper will identify the Dresser-Rand "VIP" compressor as a solution to the need to compress gas reliably at very low cost.
Dresser-Rand Company has a long history in providing equipment for the oil and gas, and petrochemical markets. In the areas of gas compression many years of design and operating experience are brought to bear in the development of new solutions to meet specific needs of the client. Specific compression solutions include: non-lubricated service, high pressure, gas transmission, gas gathering, sour gas service, and hazardous gas compression. To specifically address the need for a solution to reliably compress gas at higher rotative speeds, Dresser-Rand embarked on the design of the "VIP - (Valve-In-Piston)" compressor. After nearly five years of applying this cylinder design in a variety of compression applications, clients have experienced increased reliability and lower operating costs than other high speed units in similar service.
Until the introduction of the "VIP" cylinder there were basically two types of compressor cylinder designs: Barrel and Valve-in-Head. The "Barrel" cylinder configuration is designed with the compressor valves radially around the cylinder bore. These cylinders typically have the highest percent of clearance due to the need to feed the valves via scallops or cylinder liner port cuts. Piston design is conventional, cylindrical in shape, and attached to a piston rod with collars and a piston nut.
The Valve-In-Head cylinder configuration has the compressor valves at each end of the cylinder. This cylinder configuration generally provides lower percent of clearance over a "barrel" type cylinder offering a performance advantage. However, an inherent maintenance concern exists with an unusually large outer head, which must be removed for routine service of the piston and compression rings. Sealing gas pressure is also a concern. Large numbers of bolts on the outer head are required to contain the gas pressure. As a result, this configuration of cylinder is usually restricted to lower pressure applications.
The VIP (Valve - In - Piston) cylinder configuration is different than either the "barrel" and Valve-In-Head" configuration and must be understood to make a comparison. The VIP has two stationary suction valves mounted within the cylinder bore. These valves serve two purposes: The first is to act as a suction valve allowing gas to enter the compressor cylinder during the expansion stroke. The second is to act as frame and outer heads containing the gas for compression during the compression stroke. The discharge valves are in motion and are attached to the piston rod and serve two purposes. The first is to act as discharge valves allowing compressed gas to exit the compressor after compression. The second is the discharge valve assembly serves as the piston providing the structure to support compression rings and being a robust component utilized to compress the gas to the required higher pressure. Percent of "unswept" volume or clearance affect the performance of any cylinder. Clearance is at a minimum when compared to the "barrel" or "Valve-In-Head" design.
The only volumes that are unswept by the piston are: the frame
and outer end "bump" clearances and the clearance in the valve assembly.
Note also that the amount of seals required to contain the gas within the
cylinder are at a minimum. Valve covers have been completely eliminated, removing
them as a potential source of gas leakage as well as a maintenance concern.
Designing the VIP for Reliability
The Compressor Valve
Without a doubt the heart of any compressor cylinder and the continued ability of the cylinder to compress gas is served by the compressor valve. The VIP valve is a derivative of the proven, "PF" valve design, which has been utilized in Dresser-Rand high-speed compressor applications since 1985. The VIP valve is a ported plate design, which uses a non-metallic, Hi-Temp, plate, trochoidal in shape for optimum reliability
Finite element analysis, life cycle testing have demonstrated that the shape of this plate in combination with the material used optimizes the reliability of the valve by forcing the valve plate to impact on the area of the compressor valve plate with the most material.
The VIP is different in that the discharge valve is in motion. Recognizing this, the discharge valves were first analyzed utilizing Finite Element Analysis in a static condition with 3-D, 20 node, structural solid elements. The analysis was verified with strain gage work and finally the entire assembly run and loaded dynamically on the Dresser-Rand closed loop.
This design work under laboratory conditions clearly demonstrated the reliability of the valve assemblies. The VIP Cylinder The VIP Cylinder is simple in design. It is a single wall casting and resembles little more than a "cast tube." This makes the cylinder easy to cast by having the foundry difficulties attributed to double wall and water-cooled cylinder designs, eliminated.
However, as simple as the cylinder is, the reliability and
soundness of the design needed to be verified. Cylinder design takes on the
following steps: hand calculations to determine wall thickness etc., Finite
Element Analysis (FEA) to verify stress levels and utilization of metal in
areas where it is most useful, and finally a strain gage test or burst test
of the cylinder to verify and correlate the design work. The FEA indicates
the area of higher stress. Note that the burst test of the same cylinder shows
the failed area in identical location to what was predicted utilizing FEA.
This is excellent correlation. Note that from the burst tests conducted, VIP
cylinders have withstood pressures in excess of four times the design pressure.
The VIP - Application
The VIP has been and is applied at a variety of speeds, heavy and light mole weight gases, sour and sweet gas service, low and high-pressure.
The VIP is designed for speeds up to 1800 revolutions per minute. All of the internal components are suitable for sour gas service to National Association of Corrosion Engineers (NACE) MR0175-94 "Sulfide Stress Cracking Resistant Metallic Materials for Oilfield Equipment." Clearance is easily added to the VIP cylinder to "tune" the performance to the specific client operating condition.
This is accomplished by easily adjusting the outer end inlet valve outward from the moving discharge assembly much the same way as clearance outer heads are done on conventional "barrel" type cylinders. In addition, side mounted fixed clearance heads as well as bypasses to inlet mechanisms are also available.
The VIP Frame and Running Gear
The solution that Dresser-Rand was addressing in the development of the VIP was directed toward the cylinder end. This is primarily due to existing Dresser-Rand running gear designs that are very reliable for high-speed operation. Therefore, the VIP cylinder was adapted to proven, reliable Dresser-Rand running gears such as: Dresser-Rand CUB, KOA, and HOS.
The final verification of any design is to test. Dresser-Rand has a closed loop test facility, which has the capability of running a given compressor at various pressures and speeds. It is on this closed loop that performance measurements are taken to verify the performance prediction. In addition, this closed loop serves as a full-scale endurance test apparatus. Problems in design, should they arise, are addressed here before any equipment is placed in the field.
Dresser-Rand Company owns a large rental compression fleet.
Part of the design verification is to place newly designed and laboratory
tested equipment in the field, utilizing Dresser-Rand's rental fleet, to gain
"real life" operational data. This fleet typically serves the "gas
patch" where adverse operating conditions including wind, weather, and
unattended operation is the norm. Successful testing using both lab endurance
testing combined with field-testing equates to a more reliable compressor
when it is sold to our clients.
The "VIP" - Cost Effective
Comparing a VIP with other cylinder designs, one can observe that fewer parts are utilized on a VIP versus a "barrel" or "Valve-in-Head" design cylinder. This can be seen in the preceding figures. Fewer parts means lower cost. In addition, a part commonality between cylinder bore sizes is a plus when considering inventory for common wearing or replacement parts. This design has an overall effect of lower installed cost due to fewer parts and lower long term operating costs because of parts commonality.
The "VIP" - A Reliable Compressor
One of the main concerns is the reliability of high-speed compression equipment. Dresser-Rand sought to develop a compressor to address this concern. Successful designs, laboratory testing, and field-testing provide a sound basis on which to introduce a new compressor to the market. However, the variation of applications, and the environments in which a compressor must run are more typically encountered when more units are placed in the field either through rental compression or sale to clients.
Since 1994, Dresser-Rand has placed more than 400 VIP cylinders into services ranging in speeds up to 1800 rpm, bore sizes up to 23 inches, gases ranging from hydrogen to carbon dioxide, and sweet and sour (H2S) gas service. These cylinders, along with their running gear, have an average running time well over 17,000 hours. Some units have more that 50,000 hours of service with no more than routine wear parts replacement. Even with routine wear parts replacement, down time is minimised due to the ease at which parts are removed from the cylinder.
Durability of the compressor valve design is key. VIP valves have been known to function without damage even with harmful debris entering the cylinder and being lodged in the valve. This is due to the ability of the valve plate material to be embedded and the robust design of the seat and guard. This VIP Compressor has been proven to be extremely robust even in more than difficult services.
By identifying a need by the client for a cost effective and more reliable high-speed compressor, Dresser-Rand embarked on the design of the VIP. Through proper design methods, and laboratory and field-testing, Dresser-Rand has sold more than 400 VIP cylinders flanged to proven Dresser-Rand frame and running gear. The VIP compressor has been proven reliable in many applications and various conditions of service.
The success of the VIP is now demonstrated. It is clear that the VIP compressor cylinder design contributes greatly toward improved compressor reliability and lower maintenance costs.
VIP cylinders can be applied at various speeds, strokes, piston rod diameters, and operating conditions without significant changes to proven frame and running gear. This includes Dresser-Rand running gear, as well as other compressor running gear.
SML RESOURCES INTERNATIONAL
FOR INQUIRIES CONTACT