2000kVA Silent Self Start Electric Auto Spare Parts Muffler Oil Pump Genset with Alternator Power Engine Generation Set Diesel Generator Price List

• After-sales Service: Video Guided Installation, Commissioning, etc.
• Warranty: 1 Year or 1000 Running Hours
• Type: Self-Starting Diesel Generator
• Installation Method: Fixed
• Stroke: Four Stroke
• Cooling Method: Water Cooling
• Model NO.: DB-1800GF
• Output Type: AC Three Phase
• Speed: 1500(R/Min)
• Conditions of Use: Land Use
• Usage: Common Units, Standby Unit, Emergency Crew
• Landuse Type of Unit: Automation Type
• Excitation Mode: Brushless and Self- Exciting
• Genset Type: Open/Silent/Containerized /Trailer Type
• Rated Frequency: 50Hz/60Hz
• Rated Voltage: 230/400V or as Your Required
• Generator Warranty: 1 Year or 1000 Running Hours
• Alternator: Engga, Marathon, Leroy-Somer etc.
• Control Panel: Smartgen, Deep Sea etc.
• Certificates: CE, ISO
• Transport Package: Plastic Film
• Specification: 6200*2200*2966(mm)
• Trademark: Dingbo Power
• Origin: China
• HS Code: 8502131000
• Production Capacity: 7000 Sets/Year

Product Description

Product Description

 

Dingbo Power diesel generators are meticulously crafted to be both rugged and durable, ensuring not only high efficiency but also a stellar reputation for stable performance and extended service life. Our versatile products come in a variety of sizes and configurations, tailored to meet the diverse needs of our valued customers. We offer reliable and efficient backup power solutions, ideal for homes, businesses, and industrial facilities. Dingbo Power generators serve as the backbone for primary power sources, backup power, and emergency power solutions. They are extensively utilized across various sectors including factories, construction sites, supermarkets, shopping malls, hospitals, hotels, animal husbandry, mechanical engineering, chemical mines, real estate ventures, petroleum industries, metallurgy, transportation railways, and remote regions such as mountainous areas and deserts.

Our Advantages

 

Dingbo Power collaborates with an array of prestigious diesel engine manufacturers, including industry giants such as Cummins, Deutz, Yuchai, Shangchai, Weichai, Ricardo, MTU, Doosan, and more. We pride ourselves on delivering diesel generator sets ranging from 25kVA to a robust 3725KVA, ensuring reliability and excellence in every unit.

Extended service life coupled with minimal maintenance requirements.
Experience seamless operation, exceptional efficiency, low noise levels, and minimal vibration.
Boasting remarkable sudden loading capacity and formidable power output.
Enhanced low emission technology and eco-friendly economic performance.
Innovatively designed, our diesel generator sets come in various configurations including open type, silent canopy type, containerized type, mobile trailer type, and mobile car power stations, blending beauty with practicality.
Adherence to all major standards, such as GB/T2820, ISO9001, ISO14001, ISO45001, CE, Euro Stage II, Euro Stage III, and EPA Tier 2, Tier 3, Tier 4 standards.
Seamless remote operation, troubleshooting, and maintenance are achievable through the Dingbo cloud service platform.
Comprehensive after-sales network and global warranty service to ensure peace of mind.

Product Parameters

Applicable Standards: Designed in accordance with international quality and safety benchmarks to guarantee top-notch operational efficiency.I
Factory Inspection: Each generator undergoes rigorous testing to ensure flawless functionality and durability.
ISO9001: Adherence to the global standard for quality management systems.
Complete Design and Quality Inspection: Thorough checks conducted at every stage to maintain the highest quality.
ISO14001: Compliance with the international standard for effective environmental management systems.
0%, 25%, 50%, 75%, 100%, 110% Load Test: Comprehensive testing at various load capacities to ensure consistent performance.
ISO45001: Certification for occupational health and safety management systems.
Function Test: Ensuring all operational functionalities meet the required standards.
CE: Conformance with European health, safety, and environmental protection standards.

Environmental Conditions: Built to perform optimally across a range of environmental settings.
Ambient Temperature: +5°C~+40°C: The generator set functions efficiently within this temperature range.
Altitude: ≤1000m: Designed to operate effectively at altitudes up to 1000 meters.
Remark: For varied environmental conditions, please consult our sales team to customize your generator set.

Engine Specifications: Powerhouse components engineered for high performance and durability.

SHANGCHAI Series Diesel Generator Set
Set Type	Genset Prime Power  (KW/KVA)	Engine Model	Engine Prime/Standby  (KW)	Bore-stroke  (mm)	Number of Cylinder	Machine oil capacity (L)	Fuel consumption g/kw·h	Open type Overall Size (L*W*H)(mm)	Open type Weight (kg)
DB-55GF	50/55	SC4H95D2	62/68	105X124	4	13	200	1900*750*1300	960
DB-55GF-1	50/55	4HTAA4.3-G32	62/68	105X124	4	13	192	1900*850*1300	980
DB-83GF	75/83	SC4H115D2	78/86	105X124	4	13	200	1950*900*1300	1050
DB-88GF	80/88	4HTAA4.3-G34	95/105	105X124	4	13	192	1950*920*1300	1080
DB-110GF	100/110	SC4H160D2	105/116	105X124	4	13	195	2000*900*1300	1150
DB-110GF-1	100/110	4HTAA4.3-G35	106/117	105X124	4	13	192	2000*900*1300	1150
DB-132GF	120/132	SC4H180D2	120/132	105X124	4	13	195	2100*900*1300	1300
DB-132GF-1	120/132	4HTAA4.3-G36	120/132	105X124	4	13	192	2100*900*1300	1300
DB-165GF	150/165	SC7H230D2	154/170	105X124	6	17.5	195	2500*900*1630	1600
DB-165GF-1	150/165	SC7H250D2	168/185	105X124	6	17.5	195	2500*900*1630	1600
DB-165GF-2	150/165	6HTAA6.5-G34	180/198	105X124	6	17.5	195	2500*900*1630	1600
DB-198GF	180/198	SC8D280D2	185/204	114X135	6	19	200	2500*900*1630	1600
DB-198GF-1	180/198	SC13G280D2	187/206	135X150	6	41	205	2500*900*1630	1600
DB-220GF	200/220	SC9D310D2	208/228	114X144	6	19	197	3100*1020*1780	1950
DB-220GF-1	200/220	SC9D355D2	228/255	114X144	6	25	195	3100*1020*1780	1950
DB-220GF-2	200/220	SC13G355D2	236/260	135X150	6	41	200	3100*1020*1780	1950
DB-220GF-3	200/220	6DTAA8.9-G33	230/253	114X144	6	25	192	3100*1020*1780	1950
DB-242GF	220/242	6DTAA8.9-G34	245/253	114X144	6	25	192	3100*1020*1780	1950
DB-275GF	250/275	SC13G420D2	280/308	135X150	6	41	200	3100*1020*1780	1950
DB-275GF	250/275	6ETAA11.8-G32	280/308	128X153	6	41	190	3100*1020*1780	950
DB-330GF	300/330	SC12E500D2	339/373	128X153	6	41	195	3100*1020*1780	2700
DB-330GF-1	300/330	SC15G500D2	330/373	135X150	6	41	202	3100*1020*1780	2700
DB-330GF-2	300/330	6ETAA11.8-G33	340/380	128X153	6	41	190	3100*1020*1780	2700
DB-330GF-3	300/330	6ETAA11.8-G31	307/338	128X153	6	41	190	3100*1020*1780	2700
DB-385GF	350/385	SC25G610D2	405/445	135X150	12	65	202	3300*1400*1780	2850
DB-440GF	400/440	SC25G690D2	459/505	135X150	12	65	202	3500*1400*1850	4000
DB-550GF	500/550	SC27G755D2	505/561	135X155	12	65	202	3600*1400*1850	4500
DB-550GF-1	500/550	SC27G830D2	565/610	135X155	12	65	202	4350*1750*2189	4460
DB-605GF	550/605	SC27G900D2	600/662	135X155	12	65	202	4350*1750*2180	4650
DB-660GF	600/660	SC33W990D2	660/726	180X215	6	75	205	4550*1750*2189	5860
DB-825GF	750/825	SC33W1150D2	782/860	180X215	6	75	205	4850*1850*2200	6500
DB-880GF	800/880	SC33W1150D2	782/860	180X215	6	75	205	4850*1850*2200	6500
DB-1000GF	1000/1250	6WTAA35-G311	1118/1230	186X215	6	100	195	4590*2200*2515	10800
DB-1100GF	1000/1375	12KTA58-G36	1280/1410	170X210	12	313	188	4590*2200*2515	11250
DB-1200GF	1200/1500	12KTA58-G35	1420/1560	170X210	12	313	188	5110*2200*2740	12000
DB-1350GF	1350/1687.5	12KTA58-G34	1560/1720	170X210	12	313	188	5540*2200*2565	14200
DB-1500GF	1500/1875	12KTA58-G33	1720/1890	170X210	12	313	188	5540*2200*2890	14800
DB-1600GF	1600/2000	12KTA58-G32	1850/2035	170X210	12	313	188	5870*2200*2890	15500
DB-1800GF	1800/2250	12KTA58-G31	2010/2210	170X210	12	313	188	6200*2200*2966	17620

 

*Heavy Duty Diesel Engine: Delivers robust and reliable power output.*Starter Battery: Equipped with a maintenance-free, lead-acid battery for reliable start-up.
*Anti-Vibration Mount: Minimizes operational vibrations for smoother performance.*Flexible Fuel Connection Hoses: Ensures secure and adaptable fuel connectivity.
*Replaceable Fuel Filter, Oil Filter & Air Filter: Easy maintenance for prolonged engine life.*Exhaust Silencer and Bellows: Reduces noise and exhaust emissions efficiently.
*Cooling Radiator and Fan: Maintains optimal engine temperature for continuous operation.*Operation Manuals and Circuit Diagram Documents: Comprehensive guides for easy operation and troubleshooting.

Alternator Specifications: Designed for superior electrical performance and reliability.

Alternator brand optional	Leroy Somer/Marathon/ENGGA
Rated Voltage(V)	400/230
Output way	3 phase 4 wire
Rated power factor	0.8
Exciter	Brushless, Self-exciter
Wire connecting method	Y type, 3 phase 4 wire
Max voltage regulation	±1%
Protection class	IP23
Insulation class	H
Rotor:	Single/double bearing
Efficiency:	95%
Regulator:	AVR
Recovery time(Tr)	1s
Waveform : TIF	<50
Waveform : THF	<2%
Overload	110% rated load for 2 hour per 24 hour

 

Engine: Robust, fuel-efficient, and engineered for longevity.
Heavy Duty Diesel Engine: Built to withstand demanding conditions and deliver consistent power.
Four Stroke, Water Cooled: Ensures efficient and smooth operation.
12V and 24V Starter and Charge Alternator: Dual voltage system for versatile power requirements.
Cooling Radiator and Fan: Effective cooling system to maintain optimal engine performance.
Maintenance-Free Battery Including Rack and Cable: Provides stable power supply and easy installation.
Flexible Fuel Connection Hoses and Manual Oil Sump Drain Valve: Enhances ease of maintenance and fuel management.
Exhaust Silencer: Reduces operational noise for a quieter environment.

Alternator: High-performance alternator designed for reliability and efficiency.
Brushless, Single Bearing, Flexible Disc: Ensures smooth and reliable electrical output.
Insulation Class: H: High-grade insulation for superior safety and performance.
Protection Class: IP23: Protects against solid objects and water spray.
Self-Exciting and Self-Regulation: Automatic system for maintaining consistent voltage.

Canopy: Engineered for Protection, Durability, and Ease of Use.
All Canopy Designed with Modular Principles: Simple and efficient assembly.
All Metal Canopy Parts Painted by Electrostatic Polyester Power Paint: Long-lasting and resistant to environmental wear.
Soundproof Design: Keeps operational noise within safe and manageable levels.
Convenient to Lift and Move: Designed for easy transportation and repositioning.
Easy to Maintain and Operate: User-friendly design for hassle-free maintenance and operation.

Base Frame: Robust foundation for stability and longevity.
Base Frame Including Position for Forklift and Crane: Simplifies handling and installation.
Integral Fuel Tank: Built-in tank for uninterrupted operation.
Daily Fuel Tank Continuously Supply for 8-24 Hours: Ensures long hours of continuous operation.
Fuel Tank Easy to Maintain and Clean: Simplifies routine maintenance.
Anti-Vibration Pads are Flexed Between Engine and Alternator: Reduce operational vibrations for smoother performance.

Control, Monitor and Protect the Generator Set Including: Comprehensive system for optimal performance and safety.
High Water Temperature: Monitors and prevents overheating.
Low Oil Pressure: Ensures the engine operates within safe oil pressure levels.
Over and Under Speed: Regulates engine speed to prevent damage.
Over Current: Protects the generator from damage due to excessive current.
Under/Over Generator Voltage: Maintains voltage within safe limits.
Start and Stop Failure: Ensures reliable operation during start-up and shutdown.
Low and High Battery Voltage: Monitors battery health for consistent performance.
Charge Fail: Alerts for any issues with the charging system.
Emergency Stop: Immediate shutdown capability for safety.
24h Online Customer Service: Dedicated support available around the clock to assist with any inquiries or issues.

Genset Models-50Hz

 

Genset Model	Diesel Generator Set				Engine Model	Size
	Prime Power		Standby Power			Dimension ( L x W x H:mm )	Weight (KG)
	KW	KVA	KW	KVA
Powered by DCEC Cummins engine, 50Hz/1500rpm
DB-17GF	17	20	19	24	4B3.9-G11	1650×800×1300	760
DB-22GF	22	27	24	30	4B3.9-G1	1650×800×1300	760
DB-25GF	25	31	28	35	4B3.9-G12	1650×800×1300	780
DB-32GF	32	40	35	44	4BT3.9-G1	1650×800×1300	800
DB-45GF	45	56	50	62	4BTA3.9-G2	1850×850×1300	820
DB-52GF	52	65	56	70	4BTA3.9-G2	1850×850×1300	820
DB-64GF	64	80	72	90	4BTA3.9-G11	1850×850×1300	900
DB-80GF	80	100	88	110	6BT5.9-G1	2200×850×1600	1060
DB-84GF	84	105	92	115	6BT5.9-G2	2200×850×1600	1060
DB-92GF	92	115	100	125	6BTA5.9-G2	2300×850×1600	1080
DB-110GF	110	138	120	150	6BTAA5.9-G2	2450×850×1600	1150
DB-120GF	120	150	132	165	6BTAA5.9-G12	2450×850×1600	1150
DB-150GF	150	188	165	206	6CTA8.3-G1	2450×850×1800	1450
DB-150GF	150	188	165	206	6CTA8.3-G2	2450×850×1800	1450
DB-160GF	160	200	176	220	6CTAA8.3-G2	2600×950×1800	1860
DB-200GF	200	250	220	275	6LTAA8.9-G2	2800×1000×1800	2000
DB-220GF	220	275	242	303	6LTAA9.5-G3	2800×1000×1800	2300
DB-250GF	250	313	275	344	6LTAA9.5-G1	2800×1000×1800	2500
DB-310GF	310	388	340	425	6ZTAA13-G3	3200×1200×1950	3000
DB-350GF	350	438	385	481	6ZTAA13-G2	3250×1360×2100	2700
DB-360GF	360	450	396	495	QSZ13-G5	3250×1360×2100	3200
DB-400GF	400	500	440	550	QSZ13-G3	3250×1360×2100	3200
Powered by CCEC Cummins engine, 50Hz/1500rpm
DB--200GF	200	250	220	275	NT855-GA	2900×1000×1800	2300
DB--240GF	250	313	275	344	NTA855-G1A	3000×1040×1655	2600
DB--260GF	260	325	290	363	NTA855-G1B	3000×1060×1800	2550
DB-280GF	280	350	310	388	NTA855-G2A	3000×1060×1900	2600
DB-300GF	300	375	330	413	NTAA855-G7	3200×1200×1900	2850
DB-300GF	300	375	330	413	KTA19-G2	3200×1200×1900	2850
DB-320GF	320	400	350	438	QSNT-G3	3200×1200×1900	3000
DB-360GF	/	/	360	450	NTAA855-G7A	3200×1200×2000	3250
DB-360GF	360	450	400	500	KTA19-G3	3600×1550×2200	3400
DB-400GF	400	500	440	550	KTA19-G3A	3450×1400×2000	3550
DB-400GF	400	500	440	550	KTA19-G4	3450×1400×2000	3750
DB-430GF	430	538	470	588	KTAA19-G5	3450×1500×2200	3900
DB-480GF	480	600	528	660	KTAA19-G6	3450×1500×2200	4300
DB-520GF	/	/	520	650	KTA19-G8	3450×1500×2200	4400
DB-550GF	550	688	600	750	KTA19-G9A	3500×1600×2200	4580
DB-600GF	580	725	640	800	KTA38-GA	4500×2000×2300	6100
DB-600GF	600	750	660	825	KTA38-G2	4500×2000×2300	6350
DB-650GF	650	813	720	900	KTA38-G2B	4300×2060×2430	6900
DB-740GF	728	910	800	1000	KTA38-G2A	4500×2000×2300	6800
DB-800GF	800	1000	880	1100	KTA38-G5	4500×2000×2300	6900
DB-900GF	900	1125	1000	1250	KTA38-G9	4500×2000×2300	8600
DB-1000GF	1000	1250	1100	1375	KTA50-G3	5200×2250×2500	10000
DB-1100GF	1100	1375	1320	1650	KTA50-G8	5200×2250×2500	10000
DB-1200GF	1200	1500	1320	1650	KTA50-GS8	5200×2250×2500	11000
DB-1340GF	1340	1675	1500	1875	KTA50-G15X	5200×2250×2500	12000
DB-1500GF	1500	1875	1600	2000	KTA50-G16A	5200×2250×2500	12000

 

Genset Models-60Hz

 

Genset Model	Diesel Generator Set				DCEC Cummins Engine Model	Size
	Prime Power		Standby Power			Dimension ( L x W x H: mm )	Weight ( kg )
	KW	KVA	KW	KVA
Powered by DCEC Cummins engine, 60Hz, 1800rpm
DB-20GF	20	25	22	28	4B3.9-G11	1650×800×1300	760
DB-24GF	24	30	27	34	4B3.9-G2	1650×800×1300	760
DB-28GF	28	35	30	38	4B3.9-G12	1650×800×1300	760
DB-36GF	36	45	40	50	4BT3.9-G2	1850×850×1300	820
DB-51GF	51	64	56	70	4BTA3.9-G2	1850×850×1300	820
DB-60GF	60	75	60	75	4BTA3.9-G2	1850×850×1300	820
DB-72GF	72	90	75	94	4BTA3.9-G11	1850×850×1300	900
DB-91GF	91	114	100	125	6BT5.9-G2	2200×850×1600	1060
DB-100GF	100	125	110	138	6BT5.9-G2	2200×850×1600	1060
DB-109GF	110	137.5	120	150	6BTA5.9-G2	2300×850×1600	1080
DB-114GF	120	150	132	165	6BTAA5.9-G2	2450×850×1600	1150
DB-136GF	136	170	150	188	6BTAA5.9-G12	2450×850×1600	1150
DB-159GF	159	199	175	219	6CTA8.3-G2	2450×850×1800	1450
DB-173GF	173	216	190	238	6CTAA8.3-G2	2600×950×1800	1860
DB-208GF	208	260	228	286	6LTAA8.9-G2	2800×1000×1800	2000
DB-227GF	227	284	250	313	6LTAA8.9-G3	2800×1000×1800	2300
DB-240GF	240	300	264	330	6LTAA9.5-G3	2800×1000×1800	2300
DB-250GF	256	320	280	350	6LTAA9.5-G1	2800×1000×1800	2500
DB-318GF	318	398	350	438	6ZTAA13-G3	3250×1360×2100	2700
DB-355GF	355	443	390	488	6ZTAA13-G2	3250×1360×2100	2700
DB-364GF	364	455	400	500	QSZ13-G2	3250×1360×2100	3200
DB-360GF	360	450	396	495	6ZTAA13-G4	3250×1360×2100	3200
DB-382GF	382	477	420	525	QSZ13-G5	3250×1360×2100	3200
DB-400GF	400	500	440	550	QSZ13-G3	3250×1360×2100	3200
DB-440GF	440	550	480	600	QSZ13-G11	3250×1360×2100	3200
Powered by CCEC Cummins engine, 60Hz, 1800rpm
DB-220GF	-	-	220	275	NT855-GA	2900×1000×1800	2300
DB-320GF	320	400	350	438	QSNT-G3	3200×1200×1900	2400
DB-250GF	250	313	275	344	NTA855-G1	3000×1060×1800	2550
DB-275GF	275	344	300	375	NTA855-G1B	3000×1060×1900	2600
DB-275GF	275	344	300	375	NTA855-G2	3000×1060×1900	2600
DB-315GF	315	394	350	438	NTA855-G3	3200×1200×1900	2850
DB-350GF	350	438	400	500	KTA19-G2	3450×1400×2000	3550
DB-410GF	410	513	450	563	KTA19-G3	3450×1400×2000	3550
DB-450GF	450	563	500	625	KTA19-G3A	3450×1400×2000	3550
DB-450GF	450	563	500	625	KTA19-G4	3450×1400×2000	3750
DB-470GF	470	588	550	688	KTAA19-G5	3450×1500×2200	3900
DB-500GF	500	625	570	713	QSK19-G4	3500×1600×2200	4580
DB-550GF	550	688	600	750	QSK19-G5	3500×1600×2200	4580
DB-620GF	620	775	680	850	KT38-G	4200×1820×2200	4700
DB-700GF	700	875	770	963	KTA38-G1	4500×2000×2300	6100
DB-600GF	725	906	800	1000	KTA38-G2	4500×2000×2300	6350
DB-800GF	800	1000	880	1100	KTA38-G2A	4500×2000×2300	6800
DB-750GF	750	938	830	1038	KTA38-G2B	4500×2000×2300	6800
DB-900GF	900	1125	1000	1250	KTA38-G4	4500×2000×2300	6900
DB-1100GF	-	-	1100	1375	KTA38-G9	4500×2000×2300	8600
DB-1100GF	1100	1375	1260	1575	KTA50-G3	5200×2250×2500	11300
DB-1130GF	1130	1413	1180	1475	KTA50-G12	5200×2250×2500	11300
DB-1220GF	1220	1525	1430	1788	KTA50-G12A	5200×2250×2500	11300
DB-1260GF	1260	1575	1500	1875	KTA50-G9	5200×2250×2500	11300

 

Company Profile

 

Guangxi Dingbo Power Equipment Manufacturing Co., Ltd., established in 2006, stands at the forefront of diesel generator set manufacturing in Guangxi, China. With over 15 years of expertise, Dingbo Power seamlessly integrates design, supply, commissioning, and maintenance of diesel generator sets. As an esteemed authorized OEM supplier, we offer top-tier diesel engines including Cummins, Deutz, Weichai, Yuchai, SDEC, MTU, Ricardo, Wuxi, and premium AC generators like Leroy Somer, Marathon, Siemens, and Engga. Catering to diverse power needs, we provide diesel generator sets ranging from 20kw to 3000kw, ensuring unmatched quality and reliability.

Dingbo Power stands as a premier power generation one-stop solution provider in China, driven by a commitment to cutting-edge technology and superior products. We deliver cost-efficient, turn-key system solutions tailored for specialized generating set investors. Our products excel in performance, pricing, after-sales service, and swift delivery times, establishing strong comparative advantages in the market.

Through relentless dedication, our team has crafted exceptional products that earn high praise from global customers. Our offerings have reached diverse regions, including Africa, South America, North America, the Middle East, Southeast Asia, and Europe, consistently receiving favorable feedback.

At Dingbo Power, we prioritize our customers' needs, leveraging our robust R&D capabilities, advanced manufacturing, modern production facilities, comprehensive quality management, and reliable after-sales service. We ensure safe, stable power solutions for industries such as mechanical engineering, chemical mining, real estate, hospitality, education, healthcare, manufacturing, and other sectors facing power constraints.

From R&D to production, each phase-from raw material procurement and assembly to processing, final debugging, and testing-is meticulously executed. Our processes adhere strictly to national and industrial quality, specification, and performance standards, as well as contract provisions, guaranteeing excellence at every stage.

♦ Management strictly complies with ISO9001 Quality Management and ISO14001 Environmental Management Systems.
♦ All products boast ISO and CE certifications.
♦ Each product undergoes rigorous factory testing to ensure exceptional quality prior to shipping.
♦ Product warranty terms are rigorously implemented.
♦ High-efficiency assembly and production lines assure timely delivery.
♦ We provide professional, timely, thoughtful, and dedicated services.
♦ We supply favorable and complete original accessories.
♦ Regular technical training sessions are conducted year-round.
♦ Our 24/7/365 Customer Service Center ensures rapid and effective responses to all service needs.

Client Cases

Certifications